Download Biological Classification of Mustard Plant

Glossary
Balanced Diet
A diet containing essential dietary components in the correct proportion, which helps to
maintain health and fulfills the body requirements of organisms, is known as balanced
diet. The degree to which any particular meal is adequate in providing energy from food
depends on the nature of the job of a person.
A common man’s diet is said to be suitable if it provides 50% calories from
carbohydrates, 40% from fats, and 10% from proteins. Carbohydrates are abundantly
used foods because they are readily available and cheaper as compared to fats and
proteins. We can live without carbohydrates it our diet has all the components of food
and is capable to provide total calories required by the body. Fats are taken in our diet to
obtain energy. Our daily food requirement varies with sex, age and occupation e.g.
children need more food because they are growing. Youth need more food than elderly
people due to physical exertion. Men need more food than women. Pregnant women,
lactating mother’s convalescents need more food as compared to others.
Carbohydrates
Carbohydrates
They are organic compounds. They are found in all organisms. They are commonly
known as sugars. They contain three elements carbon, hydrogen and oxygen in which
hydrogen and oxygen exists in 2:1 ratio that is why they are called hydrates of carbon or
carbohydrates. One gram of carbohydrates provides 3800 calories of energy.
Forms of Carbohydrates
Carbohydrates occur in three forms.
1. Monosaccharide
2. Disaccharides
3. Polysaccharides
1. Monosaccharides
Monosaccharides are simple sugars. Their common example is glucose. Glucose is main
source of energy in our body cells.
2. Disaccharides
Disaccharides are formed by condensation of two monosaccharide units e.g. sucrose is
formed by the combination of glucose and fructose. Maltose is another disaccharide.
3. Polysaccharides
Why many monosaccharides link together, they form polysaccharides. A single
polyusaccharide may have many hundred units of monosaccharides. The common
examples of polysaccharides are glycogen and starch. Glycogen occurs in animals and
starch in plants. Another polysaccharide is cellulose, present in the cell walls of plants. It
is the most abundantly occurring carbohydrate.
Sources of Carbohydrates
Carbohydrates containing starch are obtained from cereals and their products like wheat,
rice, maize, oats and barley. They are also obtained from carrots, radish, turnip, beet, beet
root and potatoes. Simple sugar called glucose is obtained from grapes. The sugar derived
from fruit is called fructose. Then from beet and sugar cane is called sucrose and that
from milk is lactose.
Importance of Carbohydrates in Human Body
One gram carbohydrate food provides 3800 calories to our body. The Carbohydrates are
the cheapest and easy source of energy. Surplus carbohydrates are stored as glycogen in
the liver and muscles, or converted to fats and stored in the fat cells beneath the skin and
causes obesity.
Children, laborers and people, involved in physical labor need more carbohydrates in
their daily diet whereas other should avoid them because their excess in the body can
cause blood pressure, diabetes, obesity and heart diseases, therefore, carbohydrate
products should be taken with care.
Dietary Fibers
Dietary Fiber (Roughage)
These are foods which provide fibers to our body.
Sources of Dietary Fibers
All fruit and vegetables provide fibers to the body for example, citrus fruits, cereals,
spinach, cabbage and salads. The cell wall in plant cells are largely made of cellulose
which cannot be digested by man. Bacteria living in the gut of ruminants digest the
cellulose and convert it into fatty acids, which renders it absorbable.
Importance of Dietary Fibers
1. Roughage adds bulk to the food enabling the muscles of the alimentary canal to grip it
and keeps the food moving by peristalsis.
2. Absence of roughage in our diet may lead to constipation and related disorders.
3. Fibers keep the intestines in a healthy condition, thus our daily diet must contain a lot
of fruit and vegetables.
Difference between Prokaryotic Cell and Eukaryotic
Cell
Prokaryotic Cell
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The organisms made of prokaryotic cells are called prokaryotes e.g. bacteria and
cyanobacteria.
These cells lack a membrane bound nucleus. The hereditary material (DNA) is
found in cytoplasm.
These cells lack membrane bound organelles.
Ribosomes are of small size in and freely scattered cytoplasm.
Cellulose is absent in cell wall, rather it is made up of peptido-glycan or murein.
These cells are simple and of smaller size (average diameter 0.5 – 10 nm)
Eukaryotic Cell
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The organisms made of Eukaryotic cells are called Eukaryotes, e.g. animals,
plants fungi and protists.
These cells have a membrane bound nucleus; and hereditary material is found
inside the nucleus.
These cells have membrane bound organelles.
Ribosomes are of large size and are present in endoplasmic reticulum free in
cytoplasm.
Cellulose is present in cell wall of plant cells. The cell wall of most of fungi is
composed of chitin.
These cells are complex and of larger size (Average diameter 10-100nm)
Digestion of Food
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Digestion of Food
First of all food comes in the oral cavity where the teeth crush and break the food
and convert it into small particles. The tongue rolls the morsel of food and pushes
it under teeth again and again so that the food is evenly divided into fine particles
and the saliva secreted from the salivary glands gets mixed with the food. The
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saliva lubricates the food and makes the particles adhere to one another, forming a
ball of food called bolus. Now the chemical digestion of food begins. Saliva
contains an enzyme to digest starch in the food. The combined action of teeth,
tongue and saliva pushes the bolus through the throat into the oesophagus, and
then it reaches the stomach.
Definition of Digestion
Digestion is the process in which the insoluble and non-diffusible components of
food are broken down and by the action of enzymes are converted into soluble
and diffusible substance to be absorbed into the blood stream.
Types of Digestion
1. Mechanical digestion
2. Chemical Digestion
1. Mechanical Digestion
In mechanical digestion, the food consisting of large sized particle is broken into
fine pieces by cutting, grinding, chewing and churning up, so that enzymes can
act upon it efficiently and effectively. Mechanical digestion of food takes place in
the mouth and stomach.
2. Chemical Digestion
In chemical digestion, the digestive enzymes mix with the food and act upon it to
break it down further into simple and diffusible chemical forms. The enzymes act
on carbohydrates, proteins and fats separately. Chemical digestion takes place in
all the major parts of the digestive system. The digestive glands such as liver and
pancreas also play very important role in this digestion.
Digestive System
All living things require food to live and carry on their life functions. Animals are
unable to synthesize their food.
Digestion is the process in which the non-diffusible molecules of food are
changed to diffusible ones by the action of enzymes. All the organs which take
part in this process make a system which is called the digestive system.
Human Digestive System
The process of digestion takes place in the alimentary canal. It starts from the
mouth and ends at the anus. The tube assumes different shapes according to their
role in the process of digestion. It consists of the mouth, oesophagus, stomach,
small intestine, and large intestine. Besides these organs liver and pancreas, also
play important roles in digestion.
Peristalsis
The muscles of alimentary canal produce rhythmic waves of contraction which is
called peristalsis. Due to this process, food is carried through various parts of the
alimentary canal.
Ingestion
The food of animals and human is in the solid form and may be bulky. Taking in
of the food in the oral cavity and swallowing is called ingestion.
Digestion of Food in the Mouth
During mastication, the food is mixed thorougly with the saliva while the food is
in the oral cavity (buccal cavity). The saliva is secreted by three pairs of salivary
glands located in the buccal cavity. The saliva is continuously secreted by the
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salivary glands in response to the presence of food in the buccal cavity.
Saliva is alkaline and contains an enzyme ptyalin. This enzyme converts starch
into sugar (maltose). The morsel of food after being chewed and thoroughly
mixed with the saliva is called a bolus. It is rolled down by the swallowing action
into the oesophagus which conveys it to the stomach by the wave of peristalsis.
The end of stomach lined with oesophagus is called cardiac end.
Digestion of Food in the Stomach
Stomach is a thick sac like structure, in which food is stored for some time. Its
wall is strong and muscular. Its inner surface has numerous glands called gastric
glands. These glands secrete a juice called gastric juice. Human stomach secretes
about one to two liters of this juice daily; Gastric juice contains Hydrochloric acid
and two enzymes, renin and pepsin. Hydrochlroic acid changes the medium of
food to acidic. This medium kills the bacteria that may be found in the food. the
pepsin acts on proteins and breaks them down into peptones. Renin helps to
curdle milk in infants. There is no chemical action on carbohydrates and fats
present in food. the regular movements of the stomach churn up the food. the food
is changed into a thick fluid called chyme. When digestion in the stomach is
complete, the distal end of the stomach called the pyloric end relaxes, and allows
a small amount of chyme to pass into the first part of the small intestine. Food
stays in stomach for about 2-3 or 3-4 hours.
Digestion of Food in the Small Intestine
Food from stomach enters the duodenum which is the first part of the small
intestine. An alkaline pancreatic juice from the pancreas and bile juice from the
liver and poured into the duodenum by a common duct. Both the juices contain
bicarbonates which neutralize the acidic chyme and make. It rather alkaline
besides these juices other intestinal juices from the walls of the small intestine are
also poured. These entire juices act on food and help in digestion of food.
Liver
It is largest gland, in the body. Its colour is reddish brown. It lies just below the
diaphragm on the right side of the body under the ribs. It has five lobes, three on
the right side and two on the left. The cells of the liver secrete a greenish yellow
alkaline fluid which is called the bile juice. It contains bile salts and bile pigments
which give greenish yellow colour to the juice. Bile contains no digestive
enzymes, but it does contain bile salts which break down the large molecules of
fats to small fat droplets. This process is called emulsification. This process helps
in the digestion of fats. Bile juice also contains bile pigments that are by products
of red blood cells, these pigments are eliminated from the body along with the
faeces, and the colour of faeces is due to these pigments. Besides this, bile juice
also kill the germs in the food.
Functions of Liver
1. Liver stores glycogen and regulates the level of glucose in the blood.
2. It breaks down excess amino acids. this process is called deamination.
3. It is involved in detoxification.
4. It produces and secretes bile juice which is stored in the gall bladder.
5. It metabolizes carbohydrates, fats, proteins and other compounds.
6. As a result of chemical changes a lot of heat is produced, therefore liver helps
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to keep the body warm.
7. It makes fibrinogen and other blood proteins.
8. It decomposes the damaged red blood cells.
Pancreas
It is a leaf like organ. It lies below the stomach and between the two arms of
duodenum. The pancreas produces a juice which is called the pancreatic juice.
This juice flows down the pancreatic duct into the duodenum. It contains three
enzymes.
1. Pancreatic amylase which acts on undigested starches of the food and converts
them into maltose.
2. Enzyme trypsin which breaks down proteins into peptides.
3. Lipase which splits fats into fatty acids and glycerol.
If any of the constituents of food still remain undigested, enzymes secreted by the
glands in the small intestine act upon them and complete the digestion by
converting peptides to amino acids, maltose and other sugars to glucose and fats
to fatty acids and glycerol.
The enzymes secreted by the intestinal walls are amino-peptidases and
disaccharidase,(which form glucose from maltose, lactose and sucrose). In this
way food is completely digested at intestine.
Enzymes
Definition of Enzymes
Enzymes are chemical compounds. They are protein in nature. They are formed in living
cells. They are not consumed in a reaction but act as a catalyst as they only speed up the
chemical reactions.
Types of Enzymes
There are two types of enzymes:
1. Intracellular Enzymes
2. Extracellular Enzymes
1. Intracellular Enzymes
They work within a cell, in which they are produced.
2. Extracellular Enzymes
Some enzymes are secreted out of the cells where they work. They are called
extracellular enzyme. Bacteria and fungi secrete such extra cellular enzymes into the
medium in which they are growing. The higher organisms secrete extracellular enzymes
into the lumen of alimentary canal to act on the food.
The enzymes acting on the starch are known as Amylases; those acting on proteins are
known as Proteinases, while those acting on fats are known as Lipases.
Characteristics of Enzymes
The characteristics of enzymes are as follows:
1. All enzymes are protein in nature; they can be destroyed by heating.
2. They act best within a narrow, temperature range.
3. They work efficiently in narrow range of acidity or alkalinity.
4. A particular enzyme forms the same end-product, because it acts on a
particular/specific substrate.
Fats and Oils
Fats and Oils
They are also organic compounds found in plants, animals and humans. They are very
important compounds made up of carbon, hydrogen and oxygen. Fats contain more
carbon and hydrogen as compared to oxygen. A fat molecule has two parts, glycerol and
fatty acids.
Fatty Acids
Different kinds of fats contain different fatty acids. Fatty acids are basically of followin
two types:
1. Unsaturated Fatty Acids
2. Saturated Fatty Acids
Unsaturated fatty acids (molecules with one or more than one double bonds) are liquids at
room temperature and are called oils. These are good for human health. Saturated fatty
acids (molecules without double bond) are solid at room temperature and are called fat.
They are not good for human health because they increase cholesterol level in the body.
They cause narrowing of blood vessels which may result in heart attack.
Vegetable Sources
Vegetable fats are liquid and are called oils e.g. mustard oil, olive oil, coconut oil, corn
oil. etc.
Animal Sources
Animal fats are solids e.g. butter, ghee and fatty meat.
Source of Energy
Fats and oils are rich source of energy they provide double energy as compared to
carbohydrates and proteins. One gram of fat on oxidation releases 9.1 kilo cal of
energy to make A
Lipids
Lipids
Lipids are obtained from two sources:
Animal Sources
Ghee, butter, cream, animal fat and fish oil.
Plant Sources
Oils from mustard, olives, coconut, maize, soya beans, sunflower and peanuts.
Importance of Lipids
1. The use of fat rich products increase in winters because they provide double the
amount of energy as compared to carbohydrates.
2. They provide 9000 cal/gm energy to the body.
3. In plants fats are stored in seeds, and in animals, they are found beneath the skin and
around the kidneys where they are not only stored but also protect these parts.
4. They provide materials for building new protoplasm and cell membrane.
5. Some fatty acids are essential for man.
6. Saturated fats (animal fats) should be used with, great care in our diet as they lead to
rise in the cholesterol level, which accumulates in the blood vessels, and thus affects the
flow of blood in the arteries This can result in heart attack.
Electron Microscope
Electron Microscope
This is the most advanced form of microscope. Its resolving power is 250 times or more
that of a compound microscope. In this microscope, a beam of electrons under high
voltage is passed through the object and its image is reflected on to a screen through an
electro magnetic lens to make a photograph.
(Diagram)
With the help of microscope, any object an be magnified up to 250,000 its original size.
Comparison of Light Microscope and Electron Microscope
Light Microscope
The radiation source is light so it is called light microscope.
Wavelength of light is 400 – 700 nm.
Maximum resolution is 200 nm.
Maximum useful magnification is X 1500 with eye.
Lenses are used.
Electron Microscope
The radiation source is beam of electrons, so it is called Electron Microscope.
Wavelength of beam of electrons is 0.005 nm.
Maximum resolution is 0.5 nm.
Maximum useful magnification is X. 250,000 on screen as image or photograph.
Electromagnets are used.
Meiosis
Meiosis
It is that type of cell division in which cytoplasm and nucleus divides twice and as a
result of this, four daughter cells are formed and chromosome number is reduced to half.
It means that one diploid (2n) parent cell divides to form four haploid (n) daughter cells.
Meiosis consists of two sub divisions:
1. Meiosis I
2. Meiosis II
1. Meiosis I
It has following stages:
Prophase I
1. It is lengthy than prophase of mitosis. It is very important phase. It is divided into five
stages during which there is continuous condensation of chromosomes.
2. The important process of this phase is synapsis in which homologous chromosomes
pair with each other length wise.
3. Each pair consists of four chromatids or two chromosomes.
4. After synapsis, the process of crossing over takes place. In this, homologous
chromosomes exchange their chromatids parts at certain places.
5. At end of this phase, nuclear membrane breaks up. Nucleolus disappears and
chromosomes scatter over the spindle.
6. Like mitosis, mitotic apparatus is also formed here.
(Diagram)
Metaphase I
1. The chromosomes arrange on scatter of the spindle.
2. Here, homologous bivalents arrange at equatorial plate of spindle.
3. Only one spindle fiber is attached to each chromosome.
Anaphase I
1. Homologous pairs of chromosomes are separated.
2. Spindle fibers contract.
3. Chromosomes begin to move towards the opposite poles.
4. This phase is different from metaphase of mitosis because half the number of
chromosomes moves towards each pole and each chromosome still has two chromatids.
Telephase I
1. Half the number of chromosomes reach at opposite poles.
2. Chromosomes again increase their length.
3. Nucleolus reappears. Nuclear membrane is reformed and in this way two daughter
nuclei are formed.
4. Now cytoplasm divides and two daughter cells are formed. Each cell is haploid (n).
2. Meiosis II
It is similar to mitosis. The haploid cells formed in meiosis I pass through phases of
meiosis II and ultimately four haploid (n) daughter cells are formed. These cells
afterwards change into spores (in plants or gametes (animals)
Significance of Meiosis
1. Meiosis takes place only in germ mother cells which form gametes or spores.
2. It maintains the chromosome number of a species constant generation after generation.
3. If gametes had the same number of chromosomes as in somatic cells, the number of
chromosomes would have doubled after each generation in a species.
4. The number of chromosomes is constant for each species. During meiosis; gametes
(both and) formed are haploid.
5. Gametes unite to form a diploid zygote.
6. During meiosis, pairing of chromosomes takes place which is called synapsis.
7. Exchange of genetic material occurs during meiosis. In this way variations are
produced which are raw material for evolution
Frog
Frog
Frog is found in he water or near the water. It belongs to class Amphibia. it passes a
specific part of life in water and remaining life on land. Its bilogical name is Rana
Tigrina. It is a cold blooded animal i.e. blood temperature changes with that of the
environment. At the start of winter, water is decreased and temperature is lowered, the
frog lives buried in the mud to over come winter.
(Figure)
Coelom
The body cavity of frog is called Coelom. It contains many organs which form different
systems.
Digestive System of Frog
This system consists of alimentary canal and accessory glands like liver and Pancreas.
Alimentary Canal
It is a coiled tube through which food passes. It consists of buccal cavity, pharynx,
oesophagus, stomach and intestines.
Buccal Cavity and Pharynx
Mouth is present between upper and lower jaws. Upper jaw has a row of pointed
maxillary teeth. Lower jaw lacks teeth. There is a pair of set of vomerine teeth on the roof
of the buccal cavity. Frog does not chew the food with teeth. But teeth are used only to
grasp the food. The old teeth are continuously replaced by the new teeth through its life.
Near the vomerine teeth, internal nostrils are present on the roof of the buccal cavity.
These open outwards into external nostrils. Behind them, two large bulges indicate the
position of eyes. The tongue of frog is sticky. The tongue is attached at anterior end of
buccal cavity. The posterior end of tongue is free and bifid. the frog feeds on different
insects. To capture its prey, it suddenly throws its tongue on to the prey, which sticks to
the tongue and is brought to the buccal cavity, when the tongue is drawn back.
Near the maxillary joints, pair of opening of eustachian tubes are present. In male frog,
there is also, present a pair of opening of vocal, sacs on the lateral side of floor of the
buccal cavity which help the croaking. Buccal cavity narrows, posteriorly to form
pharynx. The digestive system, respiratory system and ears are linked to pharynx. In
posterior part of pharynx, there is another opening called Glottis. This leads to lungs
through tachea. It closes at the time of digestion of food but remains open when animal is
respiring.
(Diagram)
Oesophagus, Stomach and Intestine
Pharynx leads into a small but wider tube called oesophagus or gullet. The oesophagus
opens into the stomach. The anterior end of stomach is called Cardiac end while the
posterior end is called Pyloric end. The walls of stomach are muscular and glandular.
The muscles of walls of stomach contract and relax, by which food is broken down into
tiny pieces. The secretions of stomach have different enzymes which help in chemical
digestion. In stomach, digestion of protein of food is started. After stomach, first part of
intestine begins which is called duodenum. The ducts from liver and pancreas open into
the duodenum. These ducts bring juices from these glands. The second part of intestine is
Ilium are called Small intestine. The secretion of pancreas is called Pancreatic Juice.
Pancreatic juice enters the bile duct by small duct. This juice digests the food and brings
in such form which can be absorbed by the blood through intestine. Digested food is
absorbed by illium and surplus water is absorbed by recturm. Remaining undigested food
is expelled though cloacal aperture. A membrane keeps the intestine intact at a place and
prevents strangulation of small intestine. This membrane is called mesentery.
Respiratory System of Frog
There are three methods of respiration in frog.
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Pulmonary Respiration
Cutaneous respiration
Buccal Respiration
(Diagram)
Pulmonary Respiration
The exchange of gases through lungs is called pulmonary respiration. In this process, frog
keeps its mouth closed. Air reaches buccal cavity through nostrils. Nostrils are closed
floor of buccal cavity is raised; glottis opens, and air is pushed into the lungs. The intake
of air is called inspiration. In frog, there is a pair of balloon shaped lungs. Each lung
consists of small thin walled chambers called alveoli which greatly increase the surface
area of the lungs. On each alveolus, there are many blood capillaries. When lungs are
filled with air, then exchange of gases occurs between blood and air in lungs at the site of
alveoli. During this, the exchange of gases occurs between blood and air present in buccal
cavity. After this air is removed from the lungs. Frog uses its nostrils and floor of buccal
cavity for inspiration and expiration.
Oxygen present in the air is dissolved in moisture present on lining of lungs. Then
oxygen is diffused into the blood where it combines with hemoglobin to form
oxyhaemoglobin. This oxygenated blood goes to all parts of the body by means of
capillaries. Where oxygen separates from oxyhaemoglobin molecules and is absorbed by
the cells. Carbon dioxide from cells comes out into the blood, which carries it to the
lungs, and from here carbon dioxide is expelled.
Cutaneous Respiration
In frog, exchange of gases occurs through skin during hibernation and swimming. This is
called cutaneous respiration. Skin is richly supplied with capillaries. Skin is moist.
Oxygen diffuses through skin to capillaries and is carried by blood and CO2 diffuses
back to blood from cells and is discharged out.
Circulatory System of Frog
It consists of blood vascular and lymphatic systems.
Blood Vascular System
The blood vascular system of frog consists of following parts:
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Heart
Arteries
Veins
Capillaries
Structure of Heart
Heart is conical organ. It is muscular. It has three chambers. It is present in the body
cavity between the oesophagus and sternum. Like a pump, it contracts and is relaxes. As
a result of this, blood continuously circulates in the body. The heart is surrounded by a
membrane which is called pericardial which protects the heart.
(Figure)
The three chambers of heart are as follows:
1. Right Atrium
2. Left Atrium
3. Ventricle
the two atria form the broader interior part of the heart. The right atrium is larger than left
atrium. Both atria are thin walled. The posterior conical thick walled part of the heart is
called ventricle. A broad vessel, which is called truncus artenosus, arises from dorsal side
of the ventricle and then divides into two branches near the atria. A thin walled triangular
sinus venosus opens into the right atrium. Some biologists consider truncus arteriosus and
sinus venosus as chambers of the heart.
Function of Heart
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The chambers of the heart beat in a rhythmic way.
First of all sinus venosus contracts. Then, the two atria contract. After this
ventricle and finally truncus arteriosus is contracted.
The deoxygenated blood from the whole body except lungs is carried to sinus
venosus by two precavals and one post caval.
Sinus, venosus opens into the right atrium through an opening.
Oxygenated blood from the lungs is brought into the the left atrium by two
pulmonary veins.
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Both the atria open into the ventricle and push their blood collectively into the
ventricle by a common aperture, which is guarded by a valve.
This valve maintains the unidirectional flow of blood in the heart and prevents the
back flow of blood.
In the middle of ventricle some mixing of oxygenated and deoxygenated blood
takes place. On the two sides the blood remains unmixed due to rapid flow of
blood.
When ventricle contracts the blood goes to the truncus arteriosus through an
aperture. This aperture controls the speed and direction of the blood by a spiral
valve present at the start of truncus arteriosus.
Arterial System of Frog
The blood vessels which carry the blood from heart to different parts of the body are
called arteries. The system consisting of arteries is called arterial system.
(Diagram)
It starts from truncus arteriosus. It is divided into two main branches each of which
further divides to form three small branches.
Carotid Arch
It supplies blood to lower jaw, tongue, eye and brain.
Pulmocutaneous Arch
It carries blood to lungs and skin.
Systemic Arch
Right and left systemic arches joint posteriorly to form dorsal aorta. But prior to their
union, each systemic arch gives out arteries supplying blood to vertebral column,
oesophagus and fore limbs.
Dorsal Aorta
It runs along the vertebral column towards hind limbs. It gives off following branches.
Coeliacomesenteric Artery
It supplies blood to digestive system.
Renal Arteries
These supply blood to kidneys and general organs.
Posterior Mesenteric Artery
It supplies blood to rectum.
Illiac Arteries
These supply blood to hind limbs of their sides.
After reaching their specific organs, all the arteries divide and redivide to form
capillaries. The walls of capillaries are very thin. Due to this reason, the exchange of
materials take place between blood and tissues. The capillaries join to form venules.
These venules join to form veins. Then these veins carry blood back to heart.
Venous System
The blood vessels which bring the blood from different body parts, back into the heart are
called veins. The system containing of veins is called Venous system.
Following are the major veins in frog.
Pulmonary Veins
Blood from right and left lungs goes to left atrium through pair of pulmonary veins.
These have oxygenated blood.
Right and Left Precavals
Each precaval is formed by union of three veins which bring blood from tongue, lower
jaw, head, shoulders, forelimbs and skin. Both veins open in sinus venosus. From here
blood goes to right atrium.
Postcaval
It is formed by union of five or six pairs of renal veins from the kidney and the genital
veins. While passing through the liver, it receives two hepatic veins. Then it enters the
sinus venosus. Therefore, venous blood from different body parts enters the heart.
Renal Portal Vein
The veins which bring blood from the hind limbs and pelvic region combine to form
Renal portal vein. The renal portal vein enters the kidney of its side and form capillaries.
Blood from kidney goes to the post caval through renal veins. Post caval caries the blood
to the heart.
Abdominal Vein
The Pelvic veins of two sides combine to form abdominal vein. Before entering the liver,
it divides into branches. In liver, it is further divided to form capillaries. The blood from
the liver is drained into post caval by hapatic veins of both sides.
Hepatic Portal Vein
The blood vessels (veins) bringing blood form various organs of digestive system
(stomach, duodenum, illiums, rectum, pancreas and spleen etc) combine to form a large
vein. This is known as hepatic portal vein. Near the liver a branch of abdominal vein
combines with it. Then it enters the liver and divides and redivides to form capillaries.
The, blood entering the liver through hepatic portal veins goes to the post caval by means
of hepatic veins. The blood from post caval goes to heart through sinus venosus.
The blood coming back into the heart is of two types.
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Oxygenated blood which comes from lungs by pulmonary veins.
Deoxygenated blood from all parts of the body enters sinus venosus through
precavals and post caval and then enters the right atrium.
(Diagram)
Lymphatic System of Frog
In circulatory system, due to blood pressure, many components of blood plasma come out
of the capillaries and fill the inter cellular spaces. These components are also in the form
of fluid and called tissue fluid or interstitial fluid. Much of it reenters the capillaries and
some of it enters the lymph vessels where it is known as lymph. The flow of lymph is
unindirectional. Through lymph “vessels” lymph goes to big veins. Thus, lymph again
enters the blood.
1. The lymph keeps the tissues wet.
2. The lymph helps in transport of various substances from blood to tissues and vice
versa.
Excretory System of Frog
In frog, waste materials are removed in different ways e.g. through skin, lungs, liver
digestive system etc. But for removal of nitrogenous wastes, there are two kidneys.
Kidneys are attached to dorsal wall of body cavity. These are present close to vertebral
column in posterior part of body cavity. These are elongated and made up of urinary
tubules. Urinary tubules combine to form collecting ducts which open into Ureter. The
urine from kidneys comes into ureters after illustration. Both ureters which start from
edges of kidneys open into the cloaca. From here, urine is excreted directly or stored in
the urinary bladder, which on opening of cloacal aperture is expelled. The carbon dioxide
and water are excreted through lungs and skin while through liver and digestive system;
undigested food and some wastes are excreted.
(Diagram)
Reproductive System of Male Frog
The reproductive system of male frog consists of a pair of testes and reproductive ducts.
Each testis is attached to kidney by means of a membrane. At anterior end of testis, there
is present fat body. Each testis is composed of small ducts called seminiferous tubules in
which sperms are produced. Sperms enter the kidney via vesa efferentia. Sperms reach
the cloaca through ureter. From here, these are dischaged in the water through cloacal
aperture in this way, ureter in male frog does two jobs, one is removal of urine and other
is removal of sexual material, so it is called urinogenital duct and the urinary system and
genital system are collectively call urinogenital system.
Reproductive System of Female Frog
The reproductive system of female frog consists of a pair of ovaries and reproductive
ducts. Ovaries are present close to the kidneys. At their anterior ends, there are present fat
bodies. Each ovary contains many follicles in which eggs (ova) are produced. During
breeding season, ovaries are enlarged. Ova are released into the body cavity through the
coelomic fluid, these enter the oviduct. The anterior part of oviduct is funnel like called
oviducal funnel and reach the uterus. The uterus opens into the cloaca. At last, ova are
discharge in the water through cloacal aperture. In water, union of sperm with egg results
in formation of zygote. From zygotes, offsprings are formed and in this way continuity of
race is ensured.
Nervous System of Frog
It consists of three parts:
1. Central Nervous System
2. Peripheral Nervous System
3. Sympathetic Nervous System
Central Nervous System
It consists of brain and spinal cord.
(Diagram)
Brain
Brain is enclosed in protective layers and is located in cranium or brain case, which is
major part of skull.
(Diagram)
Brain is divided into three parts:
(a) Fore Brain
(b) Mid Brain
(C) Hind Brain
(a) Fore Brain
This is anterior part of brain. This is associated with sense of smell. It controls the
secretion of many hormones. It also receives messages from internal and external
environment of the body.
(b) Mid Brain
This is central part of brain. This is associated with eyes and vision.
(c) Hind Brain
This is the posterior part of brain. It controls and coordinates body movements and
maintains balance of the body. It also controls respiration, circulation, taste and digestion.
Spinal Cord
The posterior part of the brain is continuous with spinal cord. It runs through the vertebral
column. The spinal cord controls the movements of trunk region.
Peripheral Nervous System
It consists of nerves. These nerves connect the central nervous system (CNS) with
various parts of the body. Some nerves originate from brain. These are called cranial
nerves other nerves originate from spinal cord. These are called spinal nerves. In frog,
there are 10 pairs of cranial nerves and 9 or 10 pairs of spinal nerves.
Cranial
Basically, nerves are of three types:
Sensory Nerves
These take messages from sensory organs to CNS.
Motor Nerves
These take messages from CNS to glands and muscles.
Mixed Nerves
These do both above mentioned functions.
Cranial Nerves
In these nerves, first, second and eight pairs are sensory nerves which are associated with
senses of smell, sight and hearing. Third, fourth and sixth pairs are motor nerves which
carry message from brain to the eye. Nine and ten pairs are mixed nerves, which are
supplied to jaw, face, tongue and heart.
Spinal Nerves
These are all mixed nerves. These control functions of different organs.
Ear of Frog
The organ of hearing in frog is “Ear” like other vertebrates.
Structure of Ear of Frog
The ear of frog consists of following three parts.
1. External Ear
2. Middle Ear
3. Internal Ear
1. External Ear
External ear consists of a bone. The vibration is produced in external ear when sound
waves strike with it.
(Figure)
2. Middle Ear
Middle Ear consists of a tympanic membrane. On the inner side of the membrane is a
cavity known as tympanic cavity. The cavity contains small rod like bones called
ossicles. The middle ear is connected to internal ear by a tube which is called Eustachian
tube; it transfers the vibrations towards the internal ear.
3. Internal Ear
The internal ear is a very delicate organ. It consist of three semi circular canals. These
canals are filled with a fluid and sensory cells are located at special places in these canals.
Function of Ear of Frog
When sound waves strike the tympanic membrane, it is set into vibration, this is in turn
vibrates the internal ear and thus sound waves stimulate the hearing receptors in the inner
ear. The internal ear, in addition to hearing also keeps the balance of the body.
Eye of Frog
The frog has two eyes one on each side of the head. If we make vertical section of the
eye, we find that the innermost layer of the ball is the sensory retina. The retina contains
photoreceptor cells. Outside the retina is the choroid, which is richly supplied with blood
capillaries supplying nutrients to the retina. The sclerotic is the hard, outer most layer of
the eye. It provides shape to the eye ball. The anterior transparent part of the eye is called
cornea. Behind the cornea is Iris. The Iris has a window called the pupil. Behind the pupil
is the lens of the eye. The cornea, pupil and lens focus light on the retina. A watery fluid
is present in between the cornea and lens. Similarly a jelly like fluid is present between
the lens and retina, through which light passes before it strikes retina. Optic nerve takes
the sensory messages from the eye to the brain.
(Diagram)
Nutrition and Food Technology
Nutrition and Food Technology
For thousands of years, man has been making efforts to grow more food for storage so
that it can be used when needed. Modern man knows how to preserve food for use
subsequently when needed. Man has adopted modern techniques of food preservation in
which its nutritional value and taste are preserved. Foods are damaged by bacteria; fungi
and other micro-organisms, which occur everywhere. These organisms make food unsafe
for use and storage, so it is necessary to kill bacteria or other organisms as soon as they
enter food.
Early methods of preservation affected the taste of the preserved food, but modern
scientific techniques prevent contamination of food, keep the taste and make it
consumable even after a long period of storage. To achieve this, temperature plays an
important role.
Food that we take is usually made up of dead tissue and it can be spoiled for two reasons,
either the food is contaminated and destroyed by bacteria or fungi or the enzymes still
active in tissue start breaking down the cells, thus making food poisonous and tasteless to
eat.
All bacteria, fungi and micro-organisms must be killed or their growth must be retarded
in order to protect the food from spoilage. Heat is the best source, as extreme increase in
temperature retards bacterial growth and enzymes can also be denatured. Thus
temperature extreme can be useful in the preservation of food
Need for Food
Need for Food
Everything needs energy to do some job e.g. to operate machines, electricity, steam, fuels
like coal, petrol, wood etc are burned to get energy. Similarly, living organisms require
energy to carry out their diverse activities of life. They maintain the complex structure of
cells, excrete waste material, and reproduce for continuation of their race. They grow in
size during their life span as they are small when born and are large when adult. A
considerable amount of energy is required to carry out the functions of life. The
organisms, therefore, need to have some source of energy in order to maintain their life.
Organisms get their energy from food. The type of food depends upon the kind of
organism using the food. Some organisms use inorganic compounds to get their energy
requirements. Some organisms use vegetables (plants) while some others require flesh
(animals) as their food.
The organisms burn up their food (metabolize) to get a special form of energy called ATP
(Adenosine triphosphate) which is used by them to carry out their functions of life
Photosynthesis
Photosynthesis
Photosynthesis is a Latin word derived from two words photo (light) synthesis (building
up). In this process, green plants manufacture carbohydrates from carbon dioxide and
water. The energy needed for this process is obtained from sunlight, which is absorbed by
chlorophyll and oxygen is produced as by-product. Leaves are the major sites of
photosynthesis in most plants but all green parts of a plant including green stems; unripened fruit can carry out photosynthesis. Temperature also plays a very important role
in photosynthesis. Temperature affects the rate of photosynthesis. This process occurs
during day time only.
Conditions and Factors Necessary for Photosynthesis
Water
Plants need water for many functions of life. Water enters the root hair from the soil. It
passes through various cells and reaches the xylem of the root. From here it moves to the
stem and then the veins of the leaves. Finally, it reaches the mesophyll cells in the leaves.
It provides hydrogen for the synthesis of glucose and helps in opening and closing of
stomata. If leaves get less water, less stomata open, this reduces the rate of
photosynthesis. Opening of more stomata provide more carbon dioxide for
photosynthesis.
Carbon Dioxide
This is an important factor which affects photosynthesis. The amount of carbon dioxide
in the atmosphere is about 0.03% and does not vary much. Its amount differs from place
to place which may affect the rate of photosynthesis. e.g. the concentration of carbon
dioxide close to the ground in a dense forest is higher than in an open field. Although
carbon dioxide is needed in very little amount by the plants, yet photosynthesis cannot
take place without it. It diffuses from the air into the intercellular spaces through stomata
and enters the chloroplasts in the mesophyll cells. Carbon dioxide provides carbon to
build up glucose molecule. If the amount of carbon dioxide in the atmosphere increases
to 1% rate of photosynthesis also increases, and it starts decreasing if concentration of
carbon dioxide is decreased. If the concentration of carbon dioxide decreases below
0.03% the rate of photosynthesis also declines.
Chlorophyll
It is the green substance. It is found in special organelles called chloroplasts, which are
found in the green leaves and herbaceous stems. In leaves, it is present in the mesophyll
cells. Chlorophyll changes light energy into chemical energy and makes food in plants.
Plants lacking chlorophyll cannot carry out photosynthesis occurs only in those parts
where chlorophyll is present.
Sunlight
Light is very important for the process of photosynthesis. Without light the
photosynthesis cannot take place. It provides energy needed for the synthesis of glucose
molecule. Light intensity varies from day to day and from place to place. Plants
photosynthesize faster on a bright sunny day than on a cloudy day. While light consists of
seven colours. The blue and red are best for photosynthesis.
Is Chlorophyll Necessary for Photosynthesis?
Experiment
Since it is not possible to remove chlorophyll from a leaf without killing it, so it becomes
necessary to use a leaf where chlorophyll is present only in patches. Such a leaf is known
as variegated leaf and a plant with such leaves is used in this experiment.
For destarching the leaves, the pot is kept in a dark place for a couple of days and then
exposed to day light for a few hours. The leaf is then removed from plant. Its outline is
carefully drawn to note the position of presence or absence of chlorophyll on it.
Now iodine is applied to the leaf to test for the presence of starch (starch when ever
comes in contact with iodine turns blue).
This test shows that only those parts which were prevously green turned blue with iodine
while the white parts turned brown. This result indicates that starch is formed only in
those parts of the leaf where chlorophyll exists (i.e. green parts). In other words
photosynthesis is not possible without chlorophyll. If this were possible the white parts of
the laf should have also given a blue colour with iodine.
(Diagram)
Is Light Necessary for Photosynthesis
Experiment
A potted plant is destarched by keeping it in the dark room for two days. It is then
transferred to light. Two of its leaves are selected for the examination. One leaf is
wrapped completely in black paper. The other leaf is also wrapped in black paper but an
L-shaped part of the paper is cut out so that light can reach this part of the leaf through it.
The plant is placed in the sunlight for 4 to 6 hours. The two leaves are now detached from
the plant and tested for presence of starch. It would be observed that the leaf which does
not receive any light is free of starch (remains brown with iodine). However, in the
second leaf, light could pass through the L-shaped opening in the black paper. Only this
L-shaped area turns dark blue while the other parts of the leaf remain brown. This shows
that light plays a vital role in the manufacture of starch since starch is manufactured due
to photosynthesis, light is essential for this process.
(Diagram)
Is Carbon Dioxide Necessary for Photosynthesis
Experiment
Two potted plants are destarched by keeping them in a dark room they are watered
properly during this period. Each pot is enclosed in a transparent polythene bag as show
in figure. A petri dish containing soda lime (potassium hydroxide) is placed on one of the
pots to absorb any carbon dioxide present in the polythene bag. In the other pot a petri
dish is placed containing sodium bi-carbonate solution which would produce carbon
dioxide. The plants are then left in light for several hours. A leaf from each pot is
detached and tested for starch. The leaf from the pot containing soda lime does not turn
blue. soda lime had absorbed any carbon dioxide present in the bag. The leaf from the
other pot where carbon dioxide was being released by the sodium bicarbonates solution
turns blue indicating the presence of starch. These results show that carbon dioxide is
essential for photosynthesis
Proteins
Proteins
Proteins are very important organic compounds found in all organisms. Proteins contain
carbon, hydrogen, oxygen and nitrogen and sometimes some amount of sulphur. There is
no 2:1 ratio between hydrogen and oxygen. A protein molecule is composed of many
building units linked together to form a chain. A chain of amino acids is called
polypeptide. Amino acids are building units of a protein molecule. About twenty different
amino acids occur in nature that combines in different manners to make different type of
proteins. Proteins are structural part of the cell membrane. Some proteins are fibrous.
They form different structures in the body like muscles, bones and skin. They also occur
in our blood and cells. The enzymes which control different chemical reactions in the
body are also proteins in nature. As a result of protein catabolism, energy is released. One
gram of protein produces 4.3 kilo cal of energy which is used to synthesize ATP.
Amino Acids
Plants can synthesize all the amino acids they need from carbohydrates, nitrates and
sulphates but animals can not synthesize all amino acids. Amino acids are the building
units of proteins.
There are about twenty different types of amino acids which are used in the synthesis of
protein found in the human body.
Non-Essential Amino Acids
There are many amino acids which a human body can synthesize within the body. These
are called non-essential amino acids.
Essential Amino Acids
There are approximately ten amino acids, which human beings cannot make. These are
called essential amino acids and can be obtained directly from proteins in the diet.
Sources of Proteins
Following are the sources of proteins:
Animal Sources e.g. meat, fish, chicken, milk and cheese.
Plant Sources e.g. legumes, pulses, dry fruit and cereals.
Importance of Proteins in Human Body
1. Proteins are essentially required for growth and development.
2. Growing children ,pregnant women and lactating mothers need a lot of proteins.
3. An adult requires 50-100 gms of proteins daily.
4. Protein deficiency in children and cause a disease called Kwashiorkor.
5. Proteins play an important role in the building of cellular protoplasm.
6. They also play an important role in the building of muscles and connective tissues.
7. Many proteins are required for making enzymes, hormones and antibodies.
8. If proteins are eaten in excess than needed by body, the excessive amino acids are
converted into carbohydrates by the liver, which are either oxidized to release energy and
converted into glycogen and fat and stored.
Organelles in Cytoplasm
Mitochondria
They re oval or rod like in shape. Their membrane is doubled. Outer membrane is smooth
while inner membrane has enfolding in the mitochondrial matrix. These enfolding are
called cristae. The cristae bear small rounded bodies which are called particles.
There are about one million elementary particles in one mitochondrian. They are
involved in oxidative phosphorylation. They also have many respiratory enzymes.
Number of Mitochondria
Their number is different in different cells of different animals. In more active cells, their
number is more than 1000 e.g. liver cell.s The cells of ear lobes have a few number of
mitochondria.
Function
Mitochondria re very important organelles of Eukaryotic cell.s Many oxidation-reduction
reaction occur in the mitochondria. As a result energy is produced. This energy is used by
cell in various functions. This the reason that mitochondria are also called “Power house
of cell”.
Golgi Bodies
They were discovered by Camillo Golgi. They consist of set of smooth, flattened sacs
which are called cristernae. The cristemae are stacked over each other. Golgi bodies are
in the form of network in some cells or meshwork or filamentous in other cells.
Function
Golgi bodies store the secretions, convert them into finished products and pack them at
their margins into small rounded sacs called Golgi vesicles, which transport secretions
outside the cell.
Endoplasmic Reticulum
It is a network of tubules and cristemae extending throughout the cytoplasm from nuclear
membrane to cell membrane.
Types of Endoplasmic Reticulum
Following are the two types of Endoplasmic Reticulum:
Smooth Endoplasmic Reticulum
It is also called non-granular endoplasmic reticulum because ribosomes are not attached
on it.
Rough Endoplasmic Reticulum
It is also called granular endoplasmic reticulum because ribosomes are attached on it.
Functions
1. Smooth endoplasmic Reticulum plays a role in synthesis of lipids.
2. Rough endoplasmic reticulum plays an important role in synthesis of proteins. It also
transports materials from one part of cell to other.
3. Endoplasmic reticulum provides support to the cell.
Ribosomes
These are tiny granular structures. These re not bounded by any membrane. These are
formed in the nucleolus nd re freely dispersed in cytoplasm or attached with endoplasmic
reticulum.
Functions
Ribosome is involved in protein synthesis. It is the only organelle which is also found in
Prokaryotic cell.
Plastids
These are pigment containing organelles. These are found in plant cells. Many plastids
have one or more than one pigments.
Types of Plastids
Plastids are of three types which are as follows:
Chloroplasts
These are mot important plastids. These re green in colour and found in green parts of
plant. These contain chlorophyll which helps in photosynthesis. The study of ultra
structure reveals that it is bounded by a double membrane.
Inside the chloroplast there is present a semifluid matrix called called stroma, which is
made up of proteins and other chemicals. The inner membrane forms stacked membrane
system which becomes suspended in the stroma. Each membrane stack is called granum
(plural grana. The membranes of grana are the sites where photosynthesis occurs in the
presence of sun light.
Functions
In chloroplasts, photosynthesis takes place and food is prepared for plant.
Chromoplasts
These are second type of plastids. These are of various colours other than green. In
plants, colours other than green are due to chromoplasts. These are present in the petals
of the flowers and in the ripened fruit.
Functions
These help the plants in pollination. These impart various colours to petals and fruits.
Leucoplasts
These are third type of plastids. These are colourless plastids. These are triangular tubular
or of any other shape. These are found in food storage prts of the plant especially the
roots and tubers.
Centriole
In animal cells, two centrioles are present near the nucleus. There are hollow and
cylindrical. Each centriole consists of nine triplets of microtubules.
Function
Centrioles help in spindle formation during division of animal cell. Spindle is composed
of protein fibers which help the chromosomes to move. Centrioles are absent in cells of
higher plants. In some cells, centrioles help in the formation of flagella or cillia.
Vacuole
It is a fluid filled small sac which is bounded by a single membrane. In animal cells, these
are comparatively smaller in size but many in number while in plant cells; there is a large
central vacuole which is filled with water and salts.
Functions
In small organisms, extra water and wastes are excreted through contractile vacuoles,
while food is digested in food vacuole. Increase in size of vacuole results in an increase
in size of cell.
Multicellular Organism (Brassica Plant)
Multicellular Organism
The organisms consisting of many cells are called multicellular organism. e.g. Brassica
Plant, frog, man etc. diagram?
Brassica Plant (Mustard Plant)
1. This plant is sown in winter and at the end of season, it produces seeds and then dies.
2. This is an annual plant.
3. An oil is extracted from seeds of this plant which is known as mustard oil.
5. The scientific name of this plant is Brassica Campestris.
(Diagram)
Non-Reproductive Parts or Vegetative Parts
These parts do not directly take part in sexual reproduction e.g. root, stem, branches and
leaves.
Reproductive Parts
These parts directly take part in sexual reproduction e.g. flower, fruit and seed.
Root of Brassica
The root is that part plant which is present inside the soil. It is produced from radical of
seed. The first formed root is called Primary root. During its growth, it gives off
secondary and tertiary root. Each root has a root cap at its tip or apex. Behind the root
cap, root hairs are present which absorbs water and salts from the soil. Roots also anchor
the plant firmly in the soil.
(Diagram)
Internal Structure of Root of Brassica
When transverse section of root of Brassica is observed under the microscope, the
following parts are very prominent.
Epidermis
It is outermost and protective layer. It is single celled. Some cells grow outward to form
root hair.
Cortex
It is present inner to epidermis. It is made up of several layers of thin walled living cells
(parenchyma cells). There are present intercellular spaces. These cells store food.
Endodermis
it is the innermost layer of cortex. There are no intercellular spaces. There are thickenings
of special materials around the cell which check diffusion of water from xylem to cortex.
Pericycle
The layer present inner to endodermis is called pericycle. There are also no intercellular
spaces. All the branches of roots arise from pericycle.
Vascular Bundles
Xylem is present in middle of root which extends to pericycle in the form of four rays
and controls one way transport of water and salts. In between the xylem rays, phloem
bundles are present which transport food in two directions.
Stem of Brassica
The stem is that part of the plant which grows above ground. It arises from plumule of
seed. It is herbaceous and branched. It bears leaves and flowers. The part of stem or its
branch from where a leaf arises is called node. The part between two nodes is called
internode. the important function of stem is the conduction of prepared food from leaves
to other parts and that of water absorbed from roots to leaves. It supports leaves, flowers
and fruits like a pillar. It keeps the leaves in such a position that they can get light to
prepare food.
(Diagram)
Internal Structure of Stem of Brassica
When transverse section of stem of Brassica is observed under the microscope, following
parts are visible.
Epidermis
It is the outermost protective layer of stem. Outer to epidermis, there is layer of cutin
which reduces loss of water from stem. The cells are compactly arranged and there are no
intercellular spaces.
Cortex
It is inner to epidermis. It is made up of many layers of parenchyma and collenchyma
tissues. The main function of cortex is storage of water and food.
Endodermis
It is innermost layer of cortex. It is not prominent in stem. It allows suitable quantity of
waer to enter cortex from xylem.
Pericycle
It is in the form of bundles in between the endodermis and vascular bundles. It is
composed of sclerenchyma cells. It forms bundle cap.
Vascular Bundles
In stem, vascular bundles are arranged in the form of ring. Vascular bundle consists of
phloem and xylem. Phloem is towards outside and xylem is towards inside. Few layers of
cambium are present between the xylem and phloem. Cambium causes increase in
diameter of the stem with passage of time.
Medullary Rays
There are present few layers of thin walled living cells between every two layers. These
are called medullary rays. The medullary rays connect the cortex with pith for the
transport of food.
Pith
The central part of stem consists of living, rounded, thin walled parenchyma cells. This
part is called pith. Here food is stored.
Leaf of Brassica
1. Leaf is produced on node of stem or its branch.
2. Each leaf consists of two parts. The stalk of leaf is called petiole and upper broad part
is called lamina.
3. Young leaves are without petiole and their margins are entire or smooth.
4. Lower leaves are large in size. These are also without petiole but there margins are
wavy.
5. In the middle of leaf there is a thick midrib.
6. From midrib, arise veins of different thickness and form a network in leaf. This
arrangement of veins is called reticulate venation.
7. Veins are composed of xylem and phloem.
8. The angle formed between stem and leaf is called axil. In this axil, buds are present
which gwo and become branches.
9. The dorsal and ventral surfaces of leaves are different from each other. Such leaves are
called bifacial leaves.
10. The main function of leaf is the preparation of food by process of photosynthesis.
Internal Structure of Leaf
When transverse section of leaf is observed under the microscope, following structure are
visible.
(Diagram)
Epidermis
This layer of cells covers both upper and lower surfaces of leaf. Upper layer is called
upper epidermis and lower layer is called lower epidermis. There are more number of
stomata in lower epidermis than upper epidermis. This results in less transpiration and
CO2 enters according to need. Each stomata consists of two guard cells, which are bean
shaped, or kidney shaped. There is a pore between guard cells through which exchange of
gases takes place and water vapours come out of leaves.
Mesophyll
The tissue present between upper and lower epidermis is called mesophyll. It consists of
two parts.
Palisade Mesophyll
Uper part consists of elongated cells which hare lying vertical. These are double layered
closely packed cells and are called Palisade Mesophyll.
Spongy Mesophyll
The lower part is sponge like and has more intercellular spaces. This is called spongy
mesophyll.
Both types of cells have chloroplasts containing chlorophyll. So, photosynthesis takes
place here. The function of mesophyll is to manufacture food for the plant.
Vascular Tissue
It consists of midrib and veins. The midrib is bundle. Upper part of midrib is xylem and
lower part is phloem. Pericycle and endodermis surround this bundle. Besides this
Lamina has other bundle which are called veins.
Flower of Brassica
The flower is reproductive part. With the maturation of age, the plant bears yellowish
flowers. Many flowers are arranged on a branch in a special way. This branch is called
peduncle. This arrangement of flowers on the peduncle is called Inflorescence.
Parts of Flowers
Flower consists of a stalk and floral leaves. The stalk is called Pedicel. The upper part of
pedicel is comparatively swollen and flattened. This is called thalamus. On the thalamus,
floral leaves are arranged in four whorls.
(Diagram)
The details of floral leaves is as follows:
Calyx
It is the outermost whorl of floral leaves. It consists of four sepals. On maturation, its
colour changes to yellow. In young flowers sepals cover the inner parts of the flower. The
main function of calyx is to protect inner parts of the flower.
Corolla
It is the second whorl of floral leaves. It consists of four free petals. Its yellow colour is
conspicuous and can attract insects, honey bees and butterflies which help in pollination.
Androecium
It is the third whorl present inner to petals. It is the male reproductive part. It consists of
six free stamens. These are arranged in two whorls, the outer whorl has two small
stamens and inner whorl has four long stamens. Each stamen consists of two parts. Lower
stalk is called filament. Upper swollen part is called anther, Inside anther, a large number
of pollen grains are produced. When anther matures, a longitudinal slit appears in its
walls from which pollen grains escape. AT the base of filament, four nectaries are
present. These nectaries secrete nectar. To get nectar, insects visit the flowers. In this
way, pollen grains get attached to the bodies of insects and are transferred from one
flower to the other. This process is called pollination.
Gynoecium
It is the inner most part of flower. It is female reproductive part. It consists of two
carpels, which are fused. Each carpel has three parts. The basal swollen part is called
ovary. The stalk like part above the ovary is called Style. The top of style is somewhat
swollen and it is called Stigma. Overy contains many ovules. Ovules are ripened to form
seeds while ovary is ripened to form fruit. The fruit of Brassica is called Siliqua.
Role of Water
Water
Water makes approximately 70% of the body tissues. It is an essential component of the
protoplasm. One can live without food for more than a week but a person can die within
two to three days due to lack of water.
Importance of Water
1. It plays an important role in digestion.
2. It helps in transport of digested food and other materials in dissolved form.
3. All the chemical reactions inside the cell take place in the presence of water.
4. It helps in excretion of urine, removal of faeces.
5. Enzymes become more active in solution form.
6. It keeps the blood thin and so that it can be easily circulated.
7. Water regulates the body temperature.
8. Its deficiency in tbe body causes dehydration, which can prove fatal.
9. Plants cannot photosynthesize without water.
10. The people living in hot and dry places need more water. By breathing, sweating and
urination about 2-3 liters of water is lost per day.
Structure of Eukaryotic Cell
Structure of Cell
There are two types of cells:
1. Prokaryotic cell
2. Eukaryotic Cell
Prokaryotic cell lacks a membrane bound nucleus and membraned organelles e.g.
bacterial cell while eukaryotic cell has a membrane bound nucleus and membraned
organelles e.g. cells of plants and animals.
With the help of light microscope and electron microscope, a typical Eukaryotic cell
shows the following structural details.
(Diagram)
1. Cell Wall
2. Cell Membrane
3. Nucleus
4. Cytoplasm
1. Cell Wall
It is the outer most boundary of plant cells. It is rigid and non-living. It is chemically
composed of Cellulose. The cell wall of fungi is made up of Chitin. The walls of some
cells are thick and walls of some cells are thin. For example, in plants, xylem vessel
elements and tracheids (which transport water and minerals) have thick walls whereas as
parenchyma cells (which store water and food) have thin walls. The primary layer of cell
wall is known as primary walls which are further strengthened by an additional layer
called secondary wall especially in xylem vessels. Secondary wall is thicker than the
primary wall. Electron microscope studies reveal that cellulose fibers in primary and
secondary walls have a criss cross arrangement.
Functions
Cell wall provides a definite shape, rigidity, protection and support to plant cell.
2. Cell Membrane
It is a thin membrane which is also called Plasma membrane. It is present in cells of all
plants and animals. It is outer most boundary of animal cell while in plant cells; it is
present inner to cell wall. Both nucleus and cytoplasm are surrounded by cell membrane.
According to fluid mosaic model, cell membrane is composed of two layers of lipids in
which protein molecules are partially or completely embedded.
Functions
Cell membrane is selectively permeable membrane. It means that it allows some things to
pass through easily while some not. Thus, it controls the movement of material inside or
outside the cell.
3. Nucleus
It is most important and distinct part of the cell. It is present in center of the animal cell
while in plant cell it is pushed on one side due to large central vacuole. It is also
surrounded by a membrane which is called membrane. Under microscope, it to be
doubled and nuclear electron appears porous.
1. The number of chromosomes is fixed for each species. This number is called diploid
number (2n). E.g human’s cell has 46 chromosomes, cell of Radish has 18 chromosomes,
and cell of union has 16 chromosomes.
2. Chromosomes are composed of protein and DNA.
3. In the nucleolus (plural, Nucleoli) ribosomal RNA is formed which helps in the
formation of ribosome.
4. Cytoplasm
It is viscous opaque substance. It is present between nuclear membrane and cell
membrane. In a living cell, many types of organelle of different sizes and shapes are
found. It contains many insoluble granules of storage substances. There are also present
organic compounds like carbohydrates, proteins, lipids (fats), enzymes and inorganic
compounds like water and salts.
Functions
Cytoplasm provides chemicals, site and environment for different biochemical reactions.
Vitamins
Vitamins
Vitamins are very complicated compounds. When vitamins were discovered, their
chemical nature was not well known. Therefore, they were denoted with English letters
as A, B, C, D, E and K. Now it is known that vitamin B is not a single vitamin but a
group of vitamins call ed as vitamin B complex. It has eight different compounds as B1,
B2 etc although they have no energy value but they are essential in small quantities for
the normal activities of life. It has been observed that when animals were given a diet rich
in carbohydrates, fats and proteins but lacking vitamins, the growth and development of
the organisms were affected and the animal suffered from various diseases. Vitamins are
needed for healthy growth and development of the body. They also serve as enzyme.
Plants can prepare their vitamins from simple substances but animals obtain it directly or
indirectly from plants. Fifteen or more vitamins have been isolated and most of them
seem to act as essential part of coenzyme involved in chemical changes taking place in
the body.
If our diet has variety and consists of fresh fruit and vegetables, our body will receive all
those vitamins which are necessary for us.
Fat Soluble Vitamins
Some vitamins are fat-soluble and can be stored along with fat.
Water Soluble Vitamins
Some vitamins are water soluble and hence cannot be stored in the body, thus their in
take is required continuously
Unicellular Organism (Amoeba)
The organisms consisting of only one cell are called unicellular organisms e.g. Amoeba,
Paramecium etc.
Amoeba
1. It is mostly found in fresh water pond or pool.
2. In the ponds, it is found moving about around the weeds and stones. Some species are
found in the moist soil.
3. Amoeba is a large protist.
4. It does not have the permanent shape.
5. Its size is about the end of pin or it measures about 0.25mm. Therefore it is observed
under the microscope.
6. Its structure is very simple.
7. It consists of nucleus and cytoplasm, which are surrounded by a cell membrane.
8. Cell membrane protects it.
9. Cytoplasm is divided into two parts. Outer clear and transparent part is called
ectoplasm while the inner, viscous, translucent and granular part is called endplasm.
10. Endoplasm contains food vacuoles of different sizes. These food vacuoles help in the
digestion of food.
11. The food of Amoeba consists of microbes present in the water of pond.
12. Contractile vacuole maintains the concentration of water in the body. It removes
surplus water out of the cell.
13. In Amoeba, the exchange of gases and removal of waste.
14. In Amoeba, there are also present mitochondria, golgi bodies and ribosomes.
15. Nucleus changes its place with the movement of the organism.
(Diagram)
The Discovery of Cell and Cell Theory
Discovery of Cell
In 1665, an English biologist Robert Hooke invented first compound microscope and
observed the sections of corks and leaves under this microscope. He noticed in them
small box like chambers of same size which he called “cells”. After this, biologists
observed different organisms under the microscope. They found that structure of cells
was complex.
Cell Theory
In 19th century, the compound microscope was highly advanced and biologists observed
things just a micrometer apart. After this, a series of discoveries started, which provided
basic information for cell theory.
1. In 1831 – 33, Robert Brown discovered nucleus in cells of plants.
2. In 1838, a German botanist Mathias Scheiden observed that all plants were made up of
cells.
3. In 1839, Theoclor Schwann obsrved that the bodies of of animals were made up of
cells which were similar to plant cells.
4. Thus, Schleiden and Schwann formulated the “Cell Theory”. According to this, all
organisms are made up of cells.
5. In 1840, J. Purkinji gave the name “Protoplasm” to the things found inside the cells. At
that time, cell was considered as a bag of thick dense substance containing a nucleus.
Later on, resolving power and quality of microscopes were highly improved. Section
cutting of tissues and cells and their staining became easier and better. It revealed that
cell was not a simple mass of granular substance; instead it contained many sub cellular
bodies called “Organelles”. Each organelle has a definite job in the cell.
6. Human is made up of about 60 trillion cells. From Amoeba and unicellular algae to
whales and tallest red wood trees, all’ are made up of similar basic units called cell.s All
animals and plants are thus made up of cells and cell products.
Salient Features of Cell Theory
1. All animals and plants are made up of cells and cell products. Among
these some organisms are unicellular and some are multicellular.
2. Cell is structural and functional unit of living organisms.
3. New cells come
Teeth
Teeth
God has blessed animals and human beings with teeth. They help in breaking and
chewing of the food. They are present in oral cavity.Teeth are attached to the upper and
lower jaws.
Kinds of Teeth
Humans have two sets of teeth during their lives.
Milk Teeth
The first set of teeth begins to come through the gums when the baby is about six months
old. these are called the milk teeth and all twenty teeth are formed over a period of two
years.
Permanent Teeth
The milk teeth begin to drop out at the age of six years and are gradually replaced by the
second set of teeth called the permanent teeth. In man the milk teeth do not fall off
simultaneously, they fall off one by one and similarly permanent grow one by one as
well. Healthy teeth are strong and give a beautiful and lustrous look. You must brush
your teeth at least twice a day.
Structure of a Tooth
A tooth has two permanent parts, the Crown and the Root. The crown is that part of tooth
which projects out of the gum and jaws. The root the the tooth is embedded into the gums
and is therefore, hidden.
Enamel
This is the outer most part of tooth which is very hard and lustrous. It is deposited on the
outside of the crown of the tooth by cells in the gum. The enamel is a non-living
substance. It is made up of calcium salts. It imparts beauty to the tooth and protects the
tooth. If the enamel gets removed then the teeth start decaying.
Dentine
It is the part of teeth present under the enamel which is hard. But it wears off if the
enamel gets removed. Running through the dentine are strands of cytoplasm arising from
the cells in the pulp. These cells keep on adding more dentine to the inside of the tooth.
Pulp
The innermost part of the tooth is hollow and is made up of soft connective tissue which
is called the pulp. The strands of cytoplasm in the dentine derive their food and oxygen
from the pulp which enables the tooth to live and grow. The pulp contains sensory nerves
and blood capillaries. These nerve endings are sensitive to heat and cold and can produce
the sense of pain e.g. toothache.
Cement
Cement is a thin layer of very hard material which covers the dentine at the root of the
tooth. the fibers holding the tooth in the jaw are embedded in the cement at one end and
in the jaw at the other. In this way teeth remain firmly embedded in the jaws.
Protection and Cleanliness of Teeth
Teeth are a gift of nature. For a good health, presence of clean, good healthy teeth is
necessary if we wish our teeth to remain healthy; we should wash and clean them after
every meal. Our tongue helps in cleansing the upper portion of teeth to some extent. If
food particles are firmly trapped up between the teeth, or between gums and teeth, then it
becomes difficult to remove them with the tongue. The main cause of tooth decay is a
sugar coating left by sugary food on the teeth, which is converted into acid by bacteria.
The acid damages the enamel and allows the bacteria to infect the soft dentine and reach
the pulp cavity. The dentine begins to decay and causes toothache. Sugary foods such as
sweets, toffees and chocolates, the bacteria which cause decay, form a thin layer of scum
over the surface of the teeth. This layer becomes very hard with the passage of time and
becomes difficult to remove. This scum is called plaque.
The teeth should be cleansed properly and regularly with a miswaak or a tooth brush. So
that there is no formation of plaque. We should eat less sugar or sweet and sticky foods
and also cleanse the teeth afterwards. Balanced diet should be taken, especially by young
people who have growing teeth.
Tissues
Tissues
A group of cells which perform same function is known as tissue. The tissues are divided
into different types on the basis of their form and structure or function.
Plant Tissues
Following are the types of tissues in plants:
1. Simple Tissues
2. Compound Tissues
1. Simple Tissues
Simple tissues consists of only one type of cells. In plants, they are of following types:
i. Meristematic or embryonic tissues
ii. Permanent Tissues
i. Meristematic Tissues
1. Cells of this tissue have ability to divide.
2. Cytoplasm is dense nd nucleus is big in these cells.
3. Vacuoles are smaller if present other wise absent.
4. All cells are identical.
5. There are no intercellular spaces.
6. Their walls are thin and nucleus is present in centre of cell.
7. These tissues found on apex of root or shoot are called apical meristems. The cells of
these tissues divide; and redivide to add primary tissue for elongation of setm or root.
This type of growth is called primary growth.
8. Meristematic cells are also found on the lateral sides of roots and stems as
lateral(cambium) or intercalary meristem, and these add, secondary tissues. In this way,
thickness of stem or root is increased. This type of growth is called secondary growth.
ii. Permanent Tissues
The cells of this tissue lack the ability to divide and they originate from meristems. These
are given below:
a. Epidermal Tissues
b. Ground Tissues
(a) Epidermal Tissues
1. They are found as the outermost covering of leaf, stem or root.
2. There are non intercellular spaces.
3. Cells are rectangular in shape.
4. In the epidermal tissues of stem and leaves, there are small openings called stomata for
gaseous exchange.
(b) Ground Tissues
1. Most of the portion of body of herbaceous plants consists of ground tissues i.e.
parenchyma.
2. They are thin walled.
3. Cells are large in size.
4. Cells sometimes may develop the ability to divide.
5. Their main functions are to prepare and store food and water.
Supporting or Mechanical Tissues
These provide strength flexibility to the plant. They are of following two types:
a. Collenchyma Tissues
b. Sclerenchyma Tissues
(a) Collenchyma Tissues
1. These consist of living cells.
2. Their walls are not uniformly thickened.
3. Usually walls are thickened at angles.
4. These are more flexible or elastic than sclerenchyma.
5. These tissues are found in stem, in midrib of leaves and in cortex of petiole.
(b) Sclerenchyma Tissues
1. These consist of dead cells.
2. Their walls are highly thickened due to deposition of lignin.
3. Lignin provides hardness and strength to the cell.
4. These cells are without protoplasm.
5. Sclerenchyma cells are of two types,

Stone cells having uniformly thick cell walls; found in testa of seeds.

Fibrous cells which are elongated cells found in xylem and phloem for strength
and transport of water
2. Compound Tissues
These are the tissues which consists of two or more than two types of cells. But all cells
perform a common function.
These Tissues are of following types:
Xylem Tissue
1. This vascular tissue transports water in the plants and provides strength to the plant.
2. In this tissue, there are present xylem parenchyma and two types of thick walled dead
cells.
Long cells which are called vessel elements or cells. They are joined together to form
long pipe-lines. These transport water from roots to leaves.
Spindle shaped cells, which are called tracheicts. These provide strength to root and shoot
etc.
3. Xylem conducts water in one direction that is from roots towards the stem and leaves.
Phloem Tissues
1. This vascular tissue transports food in the plants.
2. It helps in two directional conduction of food material i.e. from leaves to roots and
vice-versa.
3. This tissue mostly consists of living cells. There are three types of cells
(a) Phloem Parenchyma
(b) Sieve Tube Cells
(c) Companion Cells
(a) Phloem Parenchyma
These cells store surplus water and food. They can start to divide when needed.
(b) Sieve Tube Cells
Their end walls have small pores called sieve plates. These cells join to form long
pipelines, which are called sieve tubes. There is no nucleus in these cells. Their main
function is to transport food.
(c) Companion Cells
In some plants, each sieve tube cell is accompanied by a companion cell. The companion
cell has a nucleus. The corn cell controls the movement of food through sieve tubes.
Animal Tissues
Following are four types of tissues that are found in animals:
1. Epithelial Tissues
2. Connective Tissues
3. Muscle Tissues
4. Nerve Tissues
1. Epithelial Tissues
1. these are found as outer most layers of an organ or as lining of body invaginations.
2. Their cells are long and flat.
3. These may form one or more layers of epithelial tissues of skin which is called
squamous epithelial cells.
4. Squamous Epithelium provides protection to skin.
5. Some cells are cubical in shape and known as cuboidal epithelial cells.
6. Cuboidal epithelial cells from the lining of glandular ducts and help in the production
of cell secretions.
7. Some cells are small and elongated which are found at certain places in the inner lining
of different organs and secret juice. These are called columnar epithelial cells e.g. cells of
gastric glands in stomach which secrete the gastric juice.
8. Some columnar cells have cilia at their free surface. These are called ciliated columnar
epithelial cells e.g. cells present in trachea. Due to movement of these cilia, mucous and
other materials are expelled.
2. Connective Tissues
1. This tissue is made up of semi fluid matrix.
2. These matrixes contain a variety of cells and fibers.
3. These tissues provide support to different body parts and bind them together. These
also protect the organs from germs and help in the production of blood cells.
4. These are of two types:
Soft connective tissues e.g. fatty tissues and tendons.
Hard connective tissues e.g. cartilage and bone.
5. Blood is also a special connective tissue with cells suspended in the fluid medium. It
transports materials in the body.
2. Muscular Tissues
1. This tissue is made up of special contractile cells or fibers.
2. The cells are elongated and are called muscle fibers.
3. These cells have the ability to contract and relax which results in movements of body
and the organs.
4. Following are the three types of muscles in our body.
Skeletal Muscles
These are attached to cartilage and bones. These seem to be striped fibers under the
microscope. Therefore these are striped or striated muscles. Their movements are under
our control so these are voluntary muscles e.g. muscles of arm and legs which move these
parts.
Smooth Muscles
These are found around hollow organs such as blood vessels, gut. These produce slow,
sustained contractions but do not fatigue. These re composed of spindle shaped unstriated
muscles. These are involuntary and are under the control of the autonomic nervous
system.
Cardiac Muscles
These are found in the heart. These are composed of branched fibers and are capable of
sustained contraction but do not not fatigue. These are also involuntary in action.
4. Nervous Tissues
1. These are composed of nerve cells which are called neurons.
2. Each neuron consists of a cell body, axon and dendrites.
3. These productive nerve impulse to conduct messages.
4. By this tissue, different body parts have coordination with each other.
5. This tissue also forms brain and spinal cord.
Chapter 9 - Food and Nutrition
Need for Food
Everything needs energy to do some job e.g. to operate machines, electricity, steam, fuels like
coal, petrol, wood etc are burned to get energy. Similarly, living organisms require energy to carry
out their diverse activities of life. They maintain the complex structure of cells, excrete waste
material, and reproduce for continuation of their race. They grow in size during their life span as
they are small when born and are large when adult. A considerable amount of energy is required
to carry out the functions of life. The organisms, therefore, need to have some source of energy in
order to maintain their life. Organisms get their energy from food. The type of food depends upon
the kind of organism using the food. Some organisms use inorganic compounds to get their
energy requirements. Some organisms use vegetables (plants) while some others require flesh
(animals) as their food.
The organisms burn up their food (metabolize) to get a special form of energy called ATP
(Adenosine triphosphate) which is used by them to carry out their functions of life.
Nutrients of Food and Their Importance
The food of organisms and the organic compounds, building their bodies are almost same. Their
bodies are composed of carbohydrates, proteins and fats etc. These substances are used by
organisms as their food. They get energy from these substances. They use the components of
food in growth and repairing of damaged tissues. Thus substances acquired by organisms to
obtain energy are called nutrients and the process by which they are obtained is called nutrition.
The food of all organisms which depends upon already prepared food has been found to consist
of six basic components. These are as follows:
1. Carbohydrates
2. Proteins
3. Fats, Oils
4. Vitamins
5. Minerals
6. Water
Carbohydrates
They are organic compounds. They are found in all organisms. They are commonly known as
sugars. They contain three elements carbon, hydrogen and oxygen in which hydrogen and
oxygen exists in 2:1 ratio that is why they are called hydrates of carbon or carbohydrates. One
gram of carbohydrates provides 3800 calories of energy.
Forms of Carbohydrates
Carbohydrates occur in three forms.
1. Monosaccharide
2. Disaccharides
3. Polysaccharides
Monosaccharides
Monosaccharides are simple sugars. Their common example is glucose. Glucose is main source
of energy in our body cells.
Disaccharides
Disaccharides are formed by condensation of two monosaccharide units e.g. sucrose is formed
by the combination of glucose and fructose. Maltose is another disaccharide.
Polysaccharides
Why many monosaccharides link together, they form polysaccharides. A single polyusaccharide
may have many hundred units of monosaccharides. The common examples of polysaccharides
are glycogen and starch. Glycogen occurs in animals and starch in plants. Another
polysaccharide is cellulose, present in the cell walls of plants. It is the most abundantly occurring
carbohydrate.
Sources of Carbohydrates
Carbohydrates containing starch are obtained from cereals and their products like wheat, rice,
maize, oats and barley. They are also obtained from carrots, radish, turnip, beet, beet root and
potatoes. Simple sugar called glucose is obtained from grapes. The sugar derived from fruit is
called fructose. Then from beet and sugar cane is called sucrose and that from milk is lactose.
Importance of Carbohydrates in Human Body
One gram carbohydrate food provides 3800 calories to our body. The Carbohydrates are the
cheapest and easy source of energy. Surplus carbohydrates are stored as glycogen in the liver
and muscles, or converted to fats and stored in the fat cells beneath the skin and causes obesity.
Children, laborers and people, involved in physical labor need more carbohydrates in their daily
diet whereas other should avoid them because their excess in the body can cause blood
pressure, diabetes, obesity and heart diseases, therefore, carbohydrate products should be taken
with care.
Proteins
Proteins are very important organic compounds found in all organisms. Proteins contain carbon,
hydrogen, oxygen and nitrogen and sometimes some amount of sulphur. There is no 2:1 ratio
between hydrogen and oxygen. A protein molecule is composed of many building units linked
together to form a chain. A chain of amino acids is called polypeptide. Amino acids are building
units of a protein molecule. About twenty different amino acids occur in nature that combines in
different manners to make different type of proteins. Proteins are structural part of the cell
membrane. Some proteins are fibrous. They form different structures in the body like muscles,
bones and skin. They also occur in our blood and cells. The enzymes which control different
chemical reactions in the body are also proteins in nature. As a result of protein catabolism,
energy is released. One gram of protein produces 4.3 kilo cal of energy which is used to
synthesize ATP.
Amino Acids
Plants can synthesize all the amino acids they need from carbohydrates, nitrates and sulphates
but animals can not synthesize all amino acids. Amino acids are the building units of proteins.
There are about twenty different types of amino acids which are used in the synthesis of protein
found in the human body.
Non-Essential Amino Acids
There are many amino acids which a human body can synthesize within the body. These are
called non-essential amino acids.
Essential Amino Acids
There are approximately ten amino acids, which human beings cannot make. These are called
essential amino acids and can be obtained directly from proteins in the diet.
Sources of Proteins
Following are the sources of proteins:
Animal Sources e.g. meat, fish, chicken, milk and cheese.
Plant Sources e.g. legumes, pulses, dry fruit and cereals.
Importance of Proteins in Human Body
1. Proteins are essentially required for growth and development.
2. Growing children ,pregnant women and lactating mothers need a lot of proteins.
3. An adult requires 50-100 gms of proteins daily.
4. Protein deficiency in children and cause a disease called Kwashiorkor.
5. Proteins play an important role in the building of cellular protoplasm.
6. They also play an important role in the building of muscles and connective tissues.
7. Many proteins are required for making enzymes, hormones and antibodies.
8. If proteins are eaten in excess than needed by body, the excessive amino acids are converted
into carbohydrates by the liver, which are either oxidized to release energy and converted into
glycogen and fat and stored.
Fats and Oils
They are also organic compounds found in plants, animals and humans. They are very important
compounds made up of carbon, hydrogen and oxygen. Fats contain more carbon and hydrogen
as compared to oxygen. A fat molecule has two parts, glycerol and fatty acids.
Fatty Acids
Different kinds of fats contain different fatty acids. Fatty acids are basically of followin two types:
1. Unsaturated Fatty Acids
2. Saturated Fatty Acids
Unsaturated fatty acids (molecules with one or more than one double bonds) are liquids at room
temperature and are called oils. These are good for human health. Saturated fatty acids
(molecules without double bond) are solid at room temperature and are called fat. They are not
good for human health because they increase cholesterol level in the body. They cause
narrowing of blood vessels which may result in heart attack.
Vegetable Sources
Vegetable fats are liquid and are called oils e.g. mustard oil, olive oil, coconut oil, corn oil. etc.
Animal Sources
Animal fats are solids e.g. butter, ghee and fatty meat.
Source of Energy
Fats and oils are rich source of energy they provide double energy as compared to carbohydrates
and proteins. One gram of fat on oxidation releases 9.1 kilo cal of energy to make ATP.
Photosynthesis
Photosynthesis is a Latin word derived from two words photo (light) synthesis (building up). In this
process, green plants manufacture carbohydrates from carbon dioxide and water. The energy
needed for this process is obtained from sunlight, which is absorbed by chlorophyll and oxygen is
produced as by-product. Leaves are the major sites of photosynthesis in most plants but all green
parts of a plant including green stems; un-ripened fruit can carry out photosynthesis. Temperature
also plays a very important role in photosynthesis. Temperature affects the rate of
photosynthesis. This process occurs during day time only.
Conditions and Factors Necessary for Photosynthesis
Water
Plants need water for many functions of life. Water enters the root hair from the soil. It passes
through various cells and reaches the xylem of the root. From here it moves to the stem and then
the veins of the leaves. Finally, it reaches the mesophyll cells in the leaves. It provides hydrogen
for the synthesis of glucose and helps in opening and closing of stomata. If leaves get less water,
less stomata open, this reduces the rate of photosynthesis. Opening of more stomata provide
more carbon dioxide for photosynthesis.
Carbon Dioxide
This is an important factor which affects photosynthesis. The amount of carbon dioxide in the
atmosphere is about 0.03% and does not vary much. Its amount differs from place to place which
may affect the rate of photosynthesis. e.g. the concentration of carbon dioxide close to the ground
in a dense forest is higher than in an open field. Although carbon dioxide is needed in very little
amount by the plants, yet photosynthesis cannot take place without it. It diffuses from the air into
the intercellular spaces through stomata and enters the chloroplasts in the mesophyll cells.
Carbon dioxide provides carbon to build up glucose molecule. If the amount of carbon dioxide in
the atmosphere increases to 1% rate of photosynthesis also increases, and it starts decreasing if
concentration of carbon dioxide is decreased. If the concentration of carbon dioxide decreases
below 0.03% the rate of photosynthesis also declines.
Chlorophyll
It is the green substance. It is found in special organelles called chloroplasts, which are found in
the green leaves and herbaceous stems. In leaves, it is present in the mesophyll cells.
Chlorophyll changes light energy into chemical energy and makes food in plants. Plants lacking
chlorophyll cannot carry out photosynthesis occurs only in those parts where chlorophyll is
present.
Sunlight
Light is very important for the process of photosynthesis. Without light the photosynthesis cannot
take place. It provides energy needed for the synthesis of glucose molecule. Light intensity varies
from day to day and from place to place. Plants photosynthesize faster on a bright sunny day
than on a cloudy day. While light consists of seven colours. The blue and red are best for
photosynthesis.
Is Chlorophyll Necessary for Photosynthesis?
Experiment
Since it is not possible to remove chlorophyll from a leaf without killing it, so it becomes
necessary to use a leaf where chlorophyll is present only in patches. Such a leaf is known as
variegated leaf and a plant with such leaves is used in this experiment.
For destarching the leaves, the pot is kept in a dark place for a couple of days and then exposed
to day light for a few hours. The leaf is then removed from plant. Its outline is carefully drawn to
note the position of presence or absence of chlorophyll on it.
Now iodine is applied to the leaf to test for the presence of starch (starch when ever comes in
contact with iodine turns blue).
This test shows that only those parts which were prevously green turned blue with iodine while
the white parts turned brown. This result indicates that starch is formed only in those parts of the
leaf where chlorophyll exists (i.e. green parts). In other words photosynthesis is not possible
without chlorophyll. If this were possible the white parts of the laf should have also given a blue
colour with iodine.
(Diagram)
Is Light Necessary for Photosynthesis
Experiment
A potted plant is destarched by keeping it in the dark room for two days. It is then transferred to
light. Two of its leaves are selected for the examination. One leaf is wrapped completely in black
paper. The other leaf is also wrapped in black paper but an L-shaped part of the paper is cut out
so that light can reach this part of the leaf through it. The plant is placed in the sunlight for 4 to 6
hours. The two leaves are now detached from the plant and tested for presence of starch. It
would be observed that the leaf which does not receive any light is free of starch (remains brown
with iodine). However, in the second leaf, light could pass through the L-shaped opening in the
black paper. Only this L-shaped area turns dark blue while the other parts of the leaf remain
brown. This shows that light plays a vital role in the manufacture of starch since starch is
manufactured due to photosynthesis, light is essential for this process.
(Diagram)
Is Carbon Dioxide Necessary for Photosynthesis
Experiment
Two potted plants are destarched by keeping them in a dark room they are watered properly
during this period. Each pot is enclosed in a transparent polythene bag as show in figure. A petri
dish containing soda lime (potassium hydroxide) is placed on one of the pots to absorb any
carbon dioxide present in the polythene bag. In the other pot a petri dish is placed containing
sodium bi-carbonate solution which would produce carbon dioxide. The plants are then left in light
for several hours. A leaf from each pot is detached and tested for starch. The leaf from the pot
containing soda lime does not turn blue. soda lime had absorbed any carbon dioxide present in
the bag. The leaf from the other pot where carbon dioxide was being released by the sodium
bicarbonates solution turns blue indicating the presence of starch. These results show that
carbon dioxide is essential for photosynthesis.
Nutrition in Man
Like all other animals human beings need food for following activities:
1. To get energy this may be used to carry out different activities in the body.
2. To build new protoplasm in the cells, renew and replaced damaged cells and tissues for grwoth
and reproduction.
3. To maintain health and build resistance against various diseases.
Man's diet consists of following components:
1. Carbohydrates
2. Proteins
3. Lipids
4. Vitamins
5. Mineral Salts
6. Water
Lipids
Lipids are obtained from two sources:
Animal Sources
Ghee, butter, cream, animal fat and fish oil.
Plant Sources
Oils from mustard, olives, coconut, maize, soya beans, sunflower and peanuts.
Importance of Lipids
1. The use of fat rich products increase in winters because they provide double the amount of
energy as compared to carbohydrates.
2. They provide 9000 cal/gm energy to the body.
3. In plants fats are stored in seeds, and in animals, they are found beneath the skin and around
the kidneys where they are not only stored but also protect these parts.
4. They provide materials for building new protoplasm and cell membrane.
5. Some fatty acids are essential for man.
6. Saturated fats (animal fats) should be used with, great care in our diet as they lead to rise in
the cholesterol level, which accumulates in the blood vessels, and thus affects the flow of blood in
the arteries This can result in heart attack.
Vitamins
Vitamins are very complicated compounds. When vitamins were discovered, their chemical
nature was not well known. Therefore, they were denoted with English letters as A, B, C, D, E
and K. Now it is known that vitamin B is not a single vitamin but a group of vitamins call ed as
vitamin B complex. It has eight different compounds as B1, B2 etc although they have no energy
value but they are essential in small quantities for the normal activities of life. It has been
observed that when animals were given a diet rich in carbohydrates, fats and proteins but lacking
vitamins, the growth and development of the organisms were affected and the animal suffered
from various diseases. Vitamins are needed for healthy growth and development of the body.
They also serve as enzyme.
Plants can prepare their vitamins from simple substances but animals obtain it directly or
indirectly from plants. Fifteen or more vitamins have been isolated and most of them seem to act
as essential part of coenzyme involved in chemical changes taking place in the body.
If our diet has variety and consists of fresh fruit and vegetables, our body will receive all those
vitamins which are necessary for us.
Fat Soluble Vitamins
Some vitamins are fat-soluble and can be stored along with fat.
Water Soluble Vitamins
Some vitamins are water soluble and hence cannot be stored in the body, thus their in take is
required continuously.
Water
Water makes approximately 70% of the body tissues. It is an essential component of the
protoplasm. One can live without food for more than a week but a person can die within two to
three days due to lack of water.
Importance of Water
1. It plays an important role in digestion.
2. It helps in transport of digested food and other materials in dissolved form.
3. All the chemical reactions inside the cell take place in the presence of water.
4. It helps in excretion of urine, removal of faeces.
5. Enzymes become more active in solution form.
6. It keeps the blood thin and so that it can be easily circulated.
7. Water regulates the body temperature.
8. Its deficiency in tbe body causes dehydration, which can prove fatal.
9. Plants cannot photosynthesize without water.
10. The people living in hot and dry places need more water. By breathing, sweating and
urination about 2-3 liters of water is lost per day.
Dietary Fiber (Roughage)
These are foods which provide fibers to our body.
Sources of Dietary Fibers
All fruit and vegetables provide fibers to the body for example, citrus fruits, cereals, spinach,
cabbage and salads. The cell wall in plant cells are largely made of cellulose which cannot be
digested by man. Bacteria living in the gut of ruminants digest the cellulose and convert it into
fatty acids, which renders it absorbable.
Importance of Dietary Fibers
1. Roughage adds bulk to the food enabling the muscles of the alimentary canal to grip it and
keeps the food moving by peristalsis.
2. Absence of roughage in our diet may lead to constipation and related disorders.
3. Fibers keep the intestines in a healthy condition, thus our daily diet must contain a lot of fruit
and vegetables.
Nutrition and Food Technology
For thousands of years, man has been making efforts to grow more food for storage so that it can
be used when needed. Modern man knows how to preserve food for use subsequently when
needed. Man has adopted modern techniques of food preservation in which its nutritional value
and taste are preserved. Foods are damaged by bacteria; fungi and other micro-organisms,
which occur everywhere. These organisms make food unsafe for use and storage, so it is
necessary to kill bacteria or other organisms as soon as they enter food.
Early methods of preservation affected the taste of the preserved food, but modern scientific
techniques prevent contamination of food, keep the taste and make it consumable even after a
long period of storage. To achieve this, temperature plays an important role.
Food that we take is usually made up of dead tissue and it can be spoiled for two reasons, either
the food is contaminated and destroyed by bacteria or fungi or the enzymes still active in tissue
start breaking down the cells, thus making food poisonous and tasteless to eat.
All bacteria, fungi and micro-organisms must be killed or their growth must be retarded in order to
protect the food from spoilage. Heat is the best source, as extreme increase in temperature
retards bacterial growth and enzymes can also be denatured. Thus temperature extreme can be
useful in the preservation of food.
Methods of Food Preservation
Pasteurization
This method was discovered by famous biologist, Louis Pasteur. By this method milk is prevented
from turning sour. In this process, milk is heated to 71 C for a few seconds and then cooled
rapidly. This kills most of the bacteria. The bacteria which survive this treatment may become
retarded in growth. In this way, the milk is preserved for a few days.
Refrigeration
In this methods, food is kept at very low temperature usually below freezing point. It retards the
action of enzymes and the growth of bacteria. In deep freezers food can be preserved for many
years. Quick freezing helps to maintain the taste and texture of meat, fruit and vegetables.
Dehydration
In this method food is dried. Such food can be kept safe for a long period at normal temperature.
Bacteria do not grow without water, therefore when water content is removed from meat and
vegetables, they can be preserved for long durations. Pickling of food is another common
indigenous technology in which taste and texture of pickled food is maintained for long.
Canning
In this method the food is first heated at a high temperature. This kills bacteria and destroys
enzymes. Then, the food is sealed in a metallic container. In this way; food becomes safe from
contamination. Metallic cans are usually lacquered to prevent food from chemically reacting with
metals and producing toxic substances.
Health Problems Related to Nutrition
Under Nutrition
During under nutrition a person's diet is deficient in the required calories. children are mostly
affected due to availability of less than normally required diet and they suffer from a disease
called marasmus. In this disease, children are reduced to a skeleton as the body becomes
completely depleted. Some of the countries like Ethiopia are famine stricken. Although
international community does try its best to rescue the famine inflicted areas yet it is not possible
for them to meet their complete nutritional requirements on such a large scale. The world
population is continuously and rapidly increasing each year. It has been estimated that by 2025,
the world population will rise to ten billion, whereas water and soil resources are being
continuously depleted by increasing use by the continuously growing population. The experts
therefore envisage that increasing human population if not checked will soon eat up all the food
resources of the world which may lead to destruction of human race.
Malnutrition
If malnutrition (a diet missing in one or more essential nutrients) continues for a prolonged period,
particularly under special circumstances, such as during pregnancy or immediately after
childbirth, it is found to be very harmful.
If malnutrition occurs during lactation period, it causes irreparable damage to the infant. During
the last quarter of pregnancy when foetus is rapidly developing its cerebral tissues, the protein
deficient diet of the mother results in mental retardness and nervous abnormalities in foetus,
which may prove fatal or lead to permanent disorders. These abnormalities may also occur in
infants if the lactating mother is taking a protein deficient diet during the first year of breastfeeding.
If a human diet lacks essential elements or nutrients, the body will fail to prepare vital
compounds, and thus the person will suffer from various diseases. Deficiency of a few amino
acids, vitamins, fatty acids (about thirty compounds) and 21 mineral elements, called as essential
nutrients in diet are responsible for various diseases.
In the poor countries like ours packaged or junk food(sugar coated cumin seeds, betal nuts,
chewing gums and drinks) are not prepared under proper care. The food colours scents and
flavours are added to make them commercially attractive. But these are substandard and harmful
for human health. The use of food additives may be the cause of dangerous diseases like cancer
and ulcer etc. These items should, therefore, be avoided.
Over Nutrition
It is the problem of the developed countries where people eat too much. Obesity is the most
common disorder due to over nutrition. Obesity is the cause of a large number of diseases too.
Balanced Diet
A diet containing essential dietary components in the correct proportion, which helps to maintain
health and fulfills the body requirements of organisms, is known as balanced diet. The degree to
which any particular meal is adequate in providing energy from food depends on the nature of the
job of a person.
A common man's diet is said to be suitable if it provides 50% calories from carbohydrates, 40%
from fats, and 10% from proteins. Carbohydrates are abundantly used foods because they are
readily available and cheaper as compared to fats and proteins. We can live without
carbohydrates it our diet has all the components of food and is capable to provide total calories
required by the body. Fats are taken in our diet to obtain energy. Our daily food requirement
varies with sex, age and occupation e.g. children need more food because they are growing.
Youth need more food than elderly people due to physical exertion. Men need more food than
women. Pregnant women, lactating mother's convalescents need more
Teeth
God has blessed animals and human beings with teeth. They help in breaking and chewing of the
food. They are present in oral cavity.Teeth are attached to the upper and lower jaws.
Kinds of Teeth
Humans have two sets of teeth during their lives.
Milk Teeth
The first set of teeth begins to come through the gums when the baby is about six months old.
these are called the milk teeth and all twenty teeth are formed over a period of two years.
Permanent Teeth
The milk teeth begin to drop out at the age of six years and are gradually replaced by the second
set of teeth called the permanent teeth. In man the milk teeth do not fall off simultaneously, they
fall off one by one and similarly permanent grow one by one as well. Healthy teeth are strong and
give a beautiful and lustrous look. You must brush your teeth at least twice a day.
Structure of a Tooth
A tooth has two permanent parts, the Crown and the Root. The crown is that part of tooth which
projects out of the gum and jaws. The root the the tooth is embedded into the gums and is
therefore, hidden.
Enamel
This is the outer most part of tooth which is very hard and lustrous. It is deposited on the outside
of the crown of the tooth by cells in the gum. The enamel is a non-living substance. It is made up
of calcium salts. It imparts beauty to the tooth and protects the tooth. If the enamel gets removed
then the teeth start decaying.
Dentine
It is the part of teeth present under the enamel which is hard. But it wears off if the enamel gets
removed. Running through the dentine are strands of cytoplasm arising from the cells in the pulp.
These cells keep on adding more dentine to the inside of the tooth.
Pulp
The innermost part of the tooth is hollow and is made up of soft connective tissue which is called
the pulp. The strands of cytoplasm in the dentine derive their food and oxygen from the pulp
which enables the tooth to live and grow. The pulp contains sensory nerves and blood capillaries.
These nerve endings are sensitive to heat and cold and can produce the sense of pain e.g.
toothache.
Cement
Cement is a thin layer of very hard material which covers the dentine at the root of the tooth. the
fibers holding the tooth in the jaw are embedded in the cement at one end and in the jaw at the
other. In this way teeth remain firmly embedded in the jaws.
Protection and Cleanliness of Teeth
Teeth are a gift of nature. For a good health, presence of clean, good healthy teeth is necessary if
we wish our teeth to remain healthy; we should wash and clean them after every meal. Our
tongue helps in cleansing the upper portion of teeth to some extent. If food particles are firmly
trapped up between the teeth, or between gums and teeth, then it becomes difficult to remove
them with the tongue. The main cause of tooth decay is a sugar coating left by sugary food on the
teeth, which is converted into acid by bacteria. The acid damages the enamel and allows the
bacteria to infect the soft dentine and reach the pulp cavity. The dentine begins to decay and
causes toothache. Sugary foods such as sweets, toffees and chocolates, the bacteria which
cause decay, form a thin layer of scum over the surface of the teeth. This layer becomes very
hard with the passage of time and becomes difficult to remove. This scum is called plaque.
The teeth should be cleansed properly and regularly with a miswaak or a tooth brush. So that
there is no formation of plaque. We should eat less sugar or sweet and sticky foods and also
cleanse the teeth afterwards. Balanced diet should be taken, especially by young people who
have growing teeth.
Digestion of Food
First of all food comes in the oral cavity where the teeth crush and break the food and convert it
into small particles. The tongue rolls the morsel of food and pushes it under teeth again and again
so that the food is evenly divided into fine particles and the saliva secreted from the salivary
glands gets mixed with the food. The saliva lubricates the food and makes the particles adhere to
one another, forming a ball of food called bolus. Now the chemical digestion of food begins.
Saliva contains an enzyme to digest starch in the food. The combined action of teeth, tongue and
saliva pushes the bolus through the throat into the oesophagus, and then it reaches the stomach.
Definition of Digestion
Digestion is the process in which the insoluble and non-diffusible components of food are broken
down and by the action of enzymes are converted into soluble and diffusible substance to be
absorbed into the blood stream.
Types of Digestion
1. Mechanical digestion
2. Chemical Digestion
Mechanical Digestion
In mechanical digestion, the food consisting of large sized particle is broken into fine pieces by
cutting, grinding, chewing and churning up, so that enzymes can act upon it efficiently and
effectively. Mechanical digestion of food takes place in the mouth and stomach.
Chemical Digestion
In chemical digestion, the digestive enzymes mix with the food and act upon it to break it down
further into simple and diffusible chemical forms. The enzymes act on carbohydrates, proteins
and fats separately. Chemical digestion takes place in all the major parts of the digestive system.
The digestive glands such as liver and pancreas also play very important role in this digestion.
Digestive System
All living things require food to live and carry on their life functions. Animals are unable to
synthesize their food.
Digestion is the process in which the non-diffusible molecules of food are changed to diffusible
ones by the action of enzymes. All the organs which take part in this process make a system
which is called the digestive system.
Human Digestive System
The process of digestion takes place in the alimentary canal. It starts from the mouth and ends at
the anus. The tube assumes different shapes according to their role in the process of digestion. It
consists of the mouth, oesophagus, stomach, small intestine, and large intestine. Besides these
organs liver and pancreas, also play important roles in digestion.
Peristalsis
The muscles of alimentary canal produce rhythmic waves of contraction which is called
peristalsis. Due to this process, food is carried through various parts of the alimentary canal.
Ingestion
The food of animals and human is in the solid form and may be bulky. Taking in of the food in the
oral cavity and swallowing is called ingestion.
Digestion of Food in the Mouth
During mastication, the food is mixed thorougly with the saliva while the food is in the oral cavity
(buccal cavity). The saliva is secreted by three pairs of salivary glands located in the buccal
cavity. The saliva is continuously secreted by the salivary glands in response to the presence of
food in the buccal cavity.
Saliva is alkaline and contains an enzyme ptyalin. This enzyme converts starch into sugar
(maltose). The morsel of food after being chewed and thoroughly mixed with the saliva is called a
bolus. It is rolled down by the swallowing action into the oesophagus which conveys it to the
stomach by the wave of peristalsis. The end of stomach lined with oesophagus is called cardiac
end.
Digestion of Food in the Stomach
Stomach is a thick sac like structure, in which food is stored for some time. Its wall is strong and
muscular. Its inner surface has numerous glands called gastric glands. These glands secrete a
juice called gastric juice. Human stomach secretes about one to two liters of this juice daily;
Gastric juice contains Hydrochloric acid and two enzymes, renin and pepsin. Hydrochlroic acid
changes the medium of food to acidic. This medium kills the bacteria that may be found in the
food. the pepsin acts on proteins and breaks them down into peptones. Renin helps to curdle milk
in infants. There is no chemical action on carbohydrates and fats present in food. the regular
movements of the stomach churn up the food. the food is changed into a thick fluid called chyme.
When digestion in the stomach is complete, the distal end of the stomach called the pyloric end
relaxes, and allows a small amount of chyme to pass into the first part of the small intestine. Food
stays in stomach for about 2-3 or 3-4 hours.
Digestion of Food in the Small Intestine
Food from stomach enters the duodenum which is the first part of the small intestine. An alkaline
pancreatic juice from the pancreas and bile juice from the liver and poured into the duodenum by
a common duct. Both the juices contain bicarbonates which neutralize the acidic chyme and
make. It rather alkaline besides these juices other intestinal juices from the walls of the small
intestine are also poured. These entire juices act on food and help in digestion of food.
Liver
It is largest gland, in the body. Its colour is reddish brown. It lies just below the diaphragm on the
right side of the body under the ribs. It has five lobes, three on the right side and two on the left.
The cells of the liver secrete a greenish yellow alkaline fluid which is called the bile juice. It
contains bile salts and bile pigments which give greenish yellow colour to the juice. Bile contains
no digestive enzymes, but it does contain bile salts which break down the large molecules of fats
to small fat droplets. This process is called emulsification. This process helps in the digestion of
fats. Bile juice also contains bile pigments that are by products of red blood cells, these pigments
are eliminated from the body along with the faeces, and the colour of faeces is due to these
pigments. Besides this, bile juice also kill the germs in the food.
Functions of Liver
1. Liver stores glycogen and regulates the level of glucose in the blood.
2. It breaks down excess amino acids. this process is called deamination.
3. It is involved in detoxification.
4. It produces and secretes bile juice which is stored in the gall bladder.
5. It metabolizes carbohydrates, fats, proteins and other compounds.
6. As a result of chemical changes a lot of heat is produced, therefore liver helps to keep the body
warm.
7. It makes fibrinogen and other blood proteins.
8. It decomposes the damaged red blood cells.
Pancreas
It is a leaf like organ. It lies below the stomach and between the two arms of duodenum. The
pancreas produces a juice which is called the pancreatic juice. This juice flows down the
pancreatic duct into the duodenum. It contains three enzymes.
1. Pancreatic amylase which acts on undigested starches of the food and converts them into
maltose.
2. Enzyme trypsin which breaks down proteins into peptides.
3. Lipase which splits fats into fatty acids and glycerol.
If any of the constituents of food still remain undigested, enzymes secreted by the glands in the
small intestine act upon them and complete the digestion by converting peptides to amino acids,
maltose and other sugars to glucose and fats to fatty acids and glycerol.
The enzymes secreted by the intestinal walls are amino-peptidases and disaccharidase,(which
form glucose from maltose, lactose and sucrose). In this way food is completely digested at
intestine.
Definition of Enzymes
Enzymes are chemical compounds. They are protein in nature. They are formed in living cells.
They are not consumed in a reaction but act as a catalyst as they only speed up the chemical
reactions.
Types of Enzymes
There are two types of enzymes:
1. Intracellular Enzymes
2. Extracellular Enzymes
Intracellular Enzymes
They work within a cell, in which they are produced.
Extracellular Enzymes
Some enzymes are secreted out of the cells where they work. They are called extracellular
enzyme. Bacteria and fungi secrete such extra cellular enzymes into the medium in which they
are growing. The higher organisms secrete extracellular enzymes into the lumen of alimentary
canal to act on the food.
The enzymes acting on the starch are known as Amylases; those acting on proteins are known
as Proteinases, while those acting on fats are known as Lipases.
Characteristics of Enzymes
The characteristics of enzymes are as follows:
1. All enzymes are protein in nature; they can be destroyed by heating.
2. They act best within a narrow, temperature range.
3. They work efficiently in narrow range of acidity or alkalinity.
4. A particular enzyme forms the same end-product, because it acts on a particular/specific
substrate.
Light Reactions
When light falls on the leaves, it is absorbed by chlorophyll. The solar energy is used to split
water into oxygen and hydrogen and this is called photolysis (photo means light and lysis means
to break). The oxygen is released into the atmosphere as by-product of photosynthesis. As this
process takes place only in the presence of light, it is called light reaction.
During light reaction, two compounds are formed when the solar energy is converted into
chemical energy these are:
1. NADPH (Nicotinamide Adenine Dinucleotide Phosphate)
2. ATP (Adenosine Triphosphate)
NADP, already exists in the cells of the leaf. The hydrogen released on the splitting of water
molecule is accepted by this compound and it is reduced to NADPH.
ADP (Adenosine Diphosphate) is already present in the cell; it combines with the phosphate
group using light energy to form a compound called ATP.
These compounds are energy rich compounds which are needed for the dark reactions of the
process. Light reaction is called high dependent reaction.
(Diagram)
Dark Reactions
Using the energy of ATP and the NADPH, water combines with carbon dioxide to form
carbohydrate. Thus the solar energy is now converted into chemical energy to form glucose.
Other organic compounds are also synthesized from this glucose.
This stage is completed in a series of chemical reactions with the help of enzymes. Neither light
energy nor chlorophyll is needed for dark reactions. Therefore dark reaction is also called light
independent reaction.
Various steps of the dark reactions were studied by a scientist called Melvin Calvin so the dark
reaction is also called the Calvin's Cycle.
Classification of Living Organisms
CHAPTER – 3
Classification
The arrangement of organisms into groups and subgroups on the basis of similar
characters is called classification.
Basis of Classification
The classification of organisms is based on such features or characters, which are similar
in one kind of organisms and different in different kind of organisms. These characters
may be about internal morphology, (anatomy), external morphology, physiology, cell
structure, especially the number of chromosomes and chemical composition (especially
of proteins) and embryology of the organisms. These characters help in study of intra
specific (within the same species) and intra specific (between different) species
differences.
The presence of similar characters in different organisms indicates their common
ancestory. This similarity because of common ancestral origin is called Homology e.g.
arm of a monkey, flipper of a whale and wing of a bat show homology. They are
dissimilar apparently but their internal structure (arrangement of bones and muscles) is
same. These organs are called homologous organs. Due to this homology, we can, say
that monkey, whale and bad had common ancestors and are placed in same large group
“vertebrate”. This homology is proved to be very helpful in classification.
Aims/Objectives of Classification
These are given below:
1. To determine similarities and differences between different organisms.
2. To arrange organisms on the basis of similarities and differences.
3. To identify the organisms on the basis of their structure and other prominent characters
and study them systematically and logically.
4. To find out inter-relationships of organisms.
First of all, Aristotle classified the organisms on the basis of their resemblances. After
this, Theophrastus classified the plants. Then, after a long time, Carolous Linnaeus
(1707-1778), suggested a new system of classification. In this way, he started modem
taxonomy.
Units of Classification
The basic unit of classification is specie (Plural specie). A species is a group of organisms
that can breed with one another in nature and produce fertile offspring. All members of a
species have same number of chromosomes and also have many other features in
common. All the mustard plants belong to one species. All the human beings belong to
another species. The members of one species differ from members of other species and
do not breed naturally with each other. Such different species, which are closely related,
they are grouped in large group called genus (plural; genera) e.g. Brassica is a genus. It
includes several species like mustard, cabbage and turnip. Similarly, Felis is a genus. It
includes several species like lion, tiger and cat. Similarly, many closely related genera are
placed in a bigger group called Family, families are grouped into an order, orders are
grouped into a class and classes are grouped into a phylum (plural, phyla) or division
(plural; division) in case of plants. The phyla or divisions are grouped into kingdom. All
these units are divided into subunits e.g. sub genus, sub phylum and sub kingdom etc.
The smallest the group or unit, the organisms found in this group, would be more similar,
they have more number of of similar character.
Difference between Homologous and Analogous Organisms
The fruit of all plants, whether sweet, or sour, small and dry or large and fleshy, all are
the homologous structures because they develop from ovary of flower. Their origin is
common. On the other hand, wings of an insect, and a bird, despite having same function,
are not homologous because their origin is different. Similarly green leaf of moss plant
and that of any vascular plant are not homologous. These organs are similar in function
but different in basic structure and origins are called analogous organs.
Biological Classification of Mustard Plant
Common Name —————– Mustard
Phylum or Division ———- Anthophyta
Class ———————– Dictyledonae
Order ———————– Capparales
Family ———————- Brassicaceae
Genus ———————– Brassica
Species ——————— Brassica Campestris
Classification of Human Beings
Common Name —————- Human
Kingdom ——————– Animalia
Phylum ——————— Chordata
Class ———————- Mammalia
Order ———————- Primates
Family ——————— Hominidae
Genus ———————- Homo
Species ——————– Homo sapiens
Scientific Name ———— Homo sapiens
Kingdoms of Organisms
The classification is not static, nor has only one system of classification been followed
rather it is dynamic. Whenever any new knowledge is available about organisms, it is
used in classification. Therefore, many systems of classification have been used. Living
organisms are classified into two to five kingdoms.
Two Kingdom Systems
All organisms were classified into two kingdoms before present time.
1. Plant Kingdom (Plantae) – It includes all the small and large plants.
2. Animal Kingdom (Animals) – It includes all the animals.
Important Characters of Plants and Animals
Presence of cell wall and ability to prepare their own food were considered the most
important characters of plants.
Lack of cell wall and inability to prepare food and characteristic mode of nutrition and
especially the ability to locomote were considered the most important characters of
animals.
Plant kingdom and animal kingdom were divided into large groups.
Binomial Nomenclature
The method of giving scientific names to organisms is called nomenclature. Same animal
or same plants may be known by different names. It must have one scientific name so
that there may be no confusion. To give such names to living organisms, the method was
formulated by carolous Linnaeous (1753). This method is called Binomial Nomenclature.
Because tis system is simple and comprehensive, so it is accepted and used in whole
world.
Rules of Binomial Nomenclature
1. According to this method, every species of living organisms is given a Latinized
scientific name consisting of two parts.
2. The first part is the name of genus and is called generic name. It starts with a capital
letter.
3. The second part is the name of species and is called specific name. It starts with a
small letter.
4. Both parts of scientific name of a species are either underlined separately or italicized.
The scientific name of mustard plant is Brassica campestris. The scientific name of rose
plant is Rose indica. Similarly the scientific name of frog is Rana tigrina and that of
human is Homo sapiens.
Significance of Binomial Nomenclature
Before establishment of binomial nomenclature, the names of organisms consisted of
many words. These words were based on the characters of these plants or animals. In
different countries, even in different parts of same country; local names were used for
plants and animals. The same organism may be given different names e.g. turnip,
shaljam, gongloo, thipar, and gogroon are all names of same plant. In England, there are
at least fifty names for pansy. Similarly a single common name may be used for different
kind of organisms e.g. the word “raspberry” is used for about 100 kinds of plants. This
confusion can be avoided by giving each organism a scientific name according to
binomial nomenclature proposed by Carolous Linnaeus in 1753. It is adopted by all
taxonomists.
Biological Classification of Man
Common Name —————– Man
Kingdom ——————— Animalia
Phylum ———————- Chordata
Class ———————– Mammalia
Order ———————– Primates
Family ———————- Hominidae
Genus ———————– Homo
Species ——————— Homo sapiens
Biological Classification of Frog
Common Name —————– Frog
Kingdom ——————— Animalia
Phylum ———————- Chordata
Class ———————– Amphibia
Order ———————– Salientia (Anura)
Family ———————- Ranidae
Species ——————— Rana tigrina
Respiration
CHAPTER – 10
Respiration
The oxidation of the absorbed food material in order to obtain energy is called
respiration.
There are two types of Respiration in the organisms:
1. Aerobic Respiration
2. Anaerobic Respiration
1. Aerobic Respiration
In most of the higher and larger organism, the glucose etc is oxidized by using molecular
oxygen. This type of respiration is known as Aerobic Respiration. In aerobic respiration a
mole of glucose is oxidized completely into carbon dioxide and water releasing enormous
amount of energy. One glucose molecule in this resnpiration produces 686,000 calories of
energy. Aerobic respiration thus produces 20 times more energy than the anaerobic
respiration.
In aerobic respiration food is oxidized in presence of molecular oxygen.
Stages of Aerobic Respiration
There are two stages of Aerobic Respiration:
(a) External Respiration
In this stage, the organisms take the air (containing oxygen) into their bodies. This is
called external respiration. this stage includes the transport of oxygen obtained from the
inhaled oxygen to each cell of the body.
(b) Internal Respiration
The second stage is called internal respiration. It consists of the oxidation of glucose,
amino acid and fatty acids etc, with molecular oxygen. In this stage all these reactions are
included which extract the chemical energy of glucose and other compounds and store it
in the form of ATP molecule, this respiration is also called cellular respiration as it occurs
within cells.
In the internal or cellular respiration glucose and other compounds are passed through
such enzymatic reactions which release the chemical energy gradually in small amounts
with the help of which ATP molecules are synthesized.
2. Anaerobic Respiration
Some organisms oxidize their food without using any molecular oxygen. This is known
as Anaerobic Respiration. In this type of respiration considerably less amount of energy
is released as compared with the other type of respiration.
In anaerobic respiration a glucose molecule is broken down into two molecules of lactic
acid with a release of only 47,000 calories of energy.
Glucose ——–> 2 Lactic Acid + Energy (47,000 calories)
Importance of Anaerobic Respiration
1. When earth came into being its environment was totally devoid of oxygen. The aerobic
organisms cannot lie in anaerobic environment. The early organisms started respiration in
the absence of oxygen to produce energy for survival of organisms.
2. Some existing organisms like bacteria and parasites which live in oxygen environment
have anaerobic respiration.
3. Many useful bacteria and yeasts are anaerobic.
4. Even in the aerobic respiration of the first phase is anaerobic. The glycolysis which is
the first phase of carbohydrate metabolism involves reaction which does not require the
expenditure of molecular oxygen. This proves the idea that aerobic organisms have
evolved from anaerobic organisms.
5. In our skeletal muscles, although aerobic metabolism takes place but in sustained
activity when the oxygen supply cannot keep pace with energy demand, anaerobic
respiration supplies the energy continuously by the breakdown of glucose to lactic acid.
ATP (Adenosine Triphosphate)
It is a chemical compound. ATP is an abbreviation of adenosine triphosphate. Its name
indicates that it contains adenosine and three phosphate groups. Adenosine is formed of a
nitrogenous base called adenine and a sugar called ribose. In ATP three phosphate groups
are attached to the adenosine in a series one after the other.
Significance of ATP
ATP is a big source of energy. The two terminal bonds between the phosphate groups
contain large amount of the chemical energy. When these bonds are broken in enzymatic
reaction, large amount of energy is released by which energy requiring activities are
accomplished, like synthesis of various compounds of carbohydrates, fats, proteins and
hormones etc or for carrying out any physical work like muscle contraction, heat
production or transport of substances etc.
When the terminal bond is broken the ATP is changed into ADP and phosphate 7300
calories of energy are released.
Gaseous Exchange in Plants
Plants get their energy from respiration. Plants have no special organ or system fro
exchange of gases. The gaseous exchange in plants occurs in cells, of every part of the
plant i.e. roots, stems and leaves etc according to their energy demand. The conducting
system (xylem and phloem) of plants transports water and nutrients but plays no role in
the transport of gases. The air spaces present between the cells of parenchyma of leaves,
stem and roots are involved in the gaseous exchange.
Gaseous Exchange in Leaves and Young Stems
In the leaves and young stems, gaseous exchange occurs through stomata. Some gaseous
exchange also occurs through cuticle.
Gaseous Exchange in Woody Stems and Roots
In woody stem and roots, there are present dead cells beneath the epidermis which form
cork tissue. Later on, this tissue becomes porous. The pores are called lenticels. These are
involved in gaseous exchange.
Gaseous Exchange in Leaves
The aquatic parts obtain oxygen for their respiration by diffusion from the dissolved
oxygen in water. Whereas the land plants get their oxygen from air directly through their
stomata which are more abundant on the lower surface than the upper surface of leaves.
Gaseous Exchange in Roots
The roots get their oxygen for gaseous exchange through diffusion from the air existing
in the space between soil particles.
Process of Respiration in Plants
The respiration in plants continues day and night. In this process, the oxygen from the
airspaces in the leaves and stems is diffused into tissues and cells after getting dissolved
in the film of water which is present over the cells. In the cells this oxygen oxidizes the
carbohydrates and other organic compounds into carbon dioxide and water to produce
energy. Some of the water (vapours) comes in the airspaces from where they diffuse out
to the atmosphere through lenticels and stomata. The elimination of carbon dioxide is
more evident from the parts without chlorophyll like growing seeds and buds. The water
produced in this process becomes a part of the already present water in the body of
plants. The various chemical reactions of respiration are controlled by the specific
enzymes. This process occurs at a faster rate in the parts of the plant having rapid growth
like growing seeds, buds, apical meristem of roots and shoots, because these parts require
more energy to accomplish the growth process.
Relationship between Respiration and Photosynthesis
The gaseous exchange in plant is not very evident during the day time as the products of
respiration i.e. carbon dioxide and water are used in the process of photosynthesis. In the
bright sunshine, because of high rate of photosynthesis the carbon dioxide produced in
respiration falls short and therefore, some carbon dioxide has to be taken into the plant
from outside for photosynthesis.
In the day time the plants therefore, take in carbon dioxide and expel out oxygen. The
process of photosynthesis occurs in chloroplasts whereas the process of respiration takes
place in cytoplasm and mitochondria.
Gaseous Exchange in Animals
The gaseous exchange in different animals takes place by different methods and organs.
In unicellular aquatic animals like amoeba, the dissolved oxygen in water diffuses
directly through their cell surface into the interior of the animal and the carbon dioxide
similarly diffuses out from their bodies into the external water. This is the simplest way
of gaseous exchange and it can occur only in small animals with a diameter of less than
one millimeter. These animals have greater surface area of volume ratio and have low
rate of metabolism.
During evolution, as the animals became complex and complex and grew in their size,
their skin or external body surface become impervious to water. Thus the gaseous
exchange became impossible through diffusion. In large animals certain organs were
developed for exchange of gases w.g. the moist vascular skin, gills, lungs and tracheoles.
These large animals have developed blood vascular system which transports oxygen from
the respiratory surface to the deep cells and tissues in all parts of the body. The blood in
all animals has some respiratory pigments like haemoglobin which carry large amount of
oxygen efficiently from respiratory surface to the interior cells.
Properties of a Respiratory Surface
1. Respiratory surface should have large surface area.
2. Respiratory surface should be moist.
3. Respiratory surface should be thin walled.
4. Respiratory surface should have blood supply.
Gaseous Exchange Through Skin
For the exchange of gases through the skin the skin must be moist and richly supplied
with blood. The oxygen is diffused from the external water to the blood and the carbon
dioxide is diffused from the blood to exterior water. In amphibia and fishes the gaseous
exchange occurs through the skin besides through the gills or lungs. The frogs and
tortoises breath through the skin during their hibernation period.
Gaseous Exchange by Gills
The gills are very effective for gaseous exchange in aquatic animals. Gills are of two
types:
(a) External Gills
(b) Internal Gills
(a) External Gills
Some animals have external gills which project out of body of animals. These gills have
very thin and highly vascularized surfaces e.g. the dermal papillae of star fish and
arthropods.
(b) Internal Gills
These are present inside the body inner to skin e.g. in fishes and arthropods. Have you
ever examined a fish closely? How ill you know that the fish is fresh or not? If the colour
of gills is red then it is fresh but if the colour of gills is changed, it is definitely not fresh.
The red colour of the fish gills shows the presence of oxygenated blood.
Gills of Fish
In fishes the gills are present in the branchial cavity present on lateral sides of the body
behind the head. This branchial cavity is covered over by an operculum. There is a
counter current flow of water and blood in gills which ensures maximum exchange of
oxygen and carbon dioxide between the blood and the bathing water. Water enters
through the mouth, flows over the gills and goes out of the body from the opercular
aperture.
Human Respiratory System
In humans, there is very efficient respiratory system. It consists of certain organs which
are called respiratory organs these include nose, pharynx, larynx, trachea, bronchi and
bronchioles.
Nose
The air enters through the external nostrils into the nasal cavity. This is lined with
mucous secreting epithelium and ciliated epithelium. The nostrils are lined with hairs.
The nasal cavities, located above the oral cavity and behind the nose are covered with
epithelial tissue.
The beating of cilia creates a current in the mucus that carries the trapped particles
towards the back of the nasal cavity. From here the mucus drips into the throat and is
swallowed. Mucus keeps the nasal cavities moist. Bones of the nose warm up the air.
Mucus moistens the air. Hair filter the air and stop the dust particles bacteria and any
other foreign substance from going to next part of respiratory system. In this way air is
purified and is then pushed into the pharynx.
A number of cavities called sinuses open into the nasal cavity. The sinuses are lined with
mucus secreting epithelium. The opening of sinuses into the nasal cavity is very narrow.
If these openings are closed due to cold or inflammation, the sinuses get filled up with
mucus this results in headache and changed voice.
Pharynx
The nasal cavity opens into the pharynx (throat) through two small apertures which are
called internal nares or internal nostrils. The pharynx is muscular passage which extend
from behind the nasal cavities to the opening of oesophagus and larynx. The air goes
from the pharynx into the larynx.
Larynx
The upper most part of the wind pipe (trachea) is called the larynx. The larynx is a
cartilaginous box. Two fibrous bands called vocal cords are located in this box. These
vibrate to produce sound. Larynx is, also called sound box or voice box. The air enters
the larynx through a small aperture called glottis which is guarded by a muscular flap
called epiglotis which fits into this opening while the food is being swallowed into the
oesophagus. It prevents the food from entering into the trachea and choking it. During
breathing epiglottis keeps the glottis open so that air goes to trachea.
Trachea
The air tube (wind pipe) is known as trachea. It is about 12 cm long and lies in front of
the oesophagus. It has incomplete C shaped cartilagenous rings which are regularly
placed in its wall and all along its length. These rings prevent the collapsing of the tube
nd thus keep the air passage wide open all the time. Trachea is also lined with ciliated
mucous epithelium. Any foreign particles present in the inhaling air get trapped in the
mucous that is moved out of the trachea by breathing of the cilia in the upward direction.
In trachea air is further cleansed and filtered and then moved towards the lungs.
Bronchi
The trachea while passing the chest cavity divides into two smaller tubes which are called
bronchi (single bronchus). Bronchi are similar in structure to the trachea but are smaller
in diameter and they have in their walls small irregular catilageuous plates. Each
bronchus enters into the lungs of its own side. The right bronchus divides into three
secondary bronchi and the left bronchus divides into two secondary bronchi which serve
the 3 right and 2 left lobes of the lungs respectively.
Bronchioles
the secondary bronchi further divide into very fine branches until they end in thousands
of passage ways called respiratory bronchioles. The bronchioles have not cartilaginous
plates in their walls. They have smooth muscle and elastic fibers.
Alveoli
The walls of the respiratory bronchioles have clusters of tiny branches(like bunches of
grapes) that along with the respiratory bronchioles re the sites of gaseous exchange, these
pouches or air sacs are called alveoli (singular: alveolus). The alveoli are enormous in
number. Each lung has about three hundred million alveoli.
Pulmonary artery brings deoxygenated blood from the heart into the lung. Here, it divides
and re-divides until it forms a network of fine capillaries over the wall of each alveolus.
The walls of alveoli are very thin (1/1000 mm thick) and moist. Thus, alveoli are efficient
site for gaseous exchange.
The Lungs
There is a pair of lungs present in the chest in man. Actually, the masses of alveoli
constitute lungs and their lobes. The lungs re protected by the chest box from sides and
by a doem shaped muscular diaphragm from below. Chest box or ribcage is made up of
ribs. Between the ribs, there are present inter-costal muscles. The diaphragm is a
muscular sheet which partitions the chest and abdomen.
The two lungs re covered by a double layered membrane called pleural membrane. There
is a thin film of fluid in between the two layers. This watery fluid makes the movements
of the lungs (expansion and contraction) easy. It also protects the lungs from external
injuries.
(Diagram)
Mechanism of Breathing
Breathing occurs in two phases:
1. Inspiration
2. Expiration
1. Inspiration
1. During inspiration, the dome-shaped diaphragm contracts and becomes flat some what
and thereby lowering the floor of the thoracic cavity.
2. The external inter-costal muscles contract raising the ribcage. A combined action of
these two events expands the thoracic cavity, which in turn expands the lungs.
3. The air pressure within the lungs decreases.
4. Thus air from the environment outside the body is pulled into the lungs to equalize the
pressure of both sides.
2. Expiration
1. The diaphragm relaxes and assumes dome like shape. During expiration, the external
inter-costal muscles relax and the internal inter-costal muscles contract as a result of
which ribcage drops.
2. The combined action of these two event decreases the volume of the thoracic cavity
which in turn decreases volume of lungs.
3. The air pressure with in the lungs increases.
4. The air is thus forced out of the lungs.
Bad Effects of Smoking on Heath
Smoking is injurious to human health. The smoke contains many chemical and gases.
Dried tobacco leaves are used in cigarettes. The tobacco on burning produces a number
of dangerous and toxic compounds.
Chemicals Present in Cigarette Smoke and Their Harmful Effects
(a) Nicotine
1. Man is addicted to cigarette damages brain tissues.
2. Causes blood to clot more easily.
3. Harden walls of arteries.
(b) Tar
1. Kills cells in air passages and in lungs.
2. Increases production of mucous and phlegm in lungs.
3. Causes lung cancer.
(c) Carbon Monoxide
Prevents red blood cells from combining with and transporting oxygen around the body.
(d) Carcinogens
promote the growth of cancerous cells in the body.
(e) Irritants
1. Irritate air passages and air sacs in the lungs.
2. Kill cells at the surface of air passages.
3. Causes smoker’s cough and lung cancer.
Combustion
A chemical reaction in which a substance combines with oxygen and produce heat, light
and flame is called Combustion.
Respiration
A process that liberates chemical energy from organic molecules when oxidized is called
Respiration. It occurs in all living cells. In fact respiration is a series of complex
oxidation and reduction reactions in which energy is released bit by bit.
Photosynthesis
The process in green plants by which green plants manufacture their own food by using
carbon dioxide and water with the help of energy absorbed by chlorophyll from sunlight
is called photosynthesis.
Relation of Combustion, Respiration and Photosynthesis
Combustion is the process of burning in which wood, coal, methane, gas etc are burnt in
the presence of oxygen, producing carbon dioxide and water accompanied with the
release of energy. It is an exothermic chemical reaction.
Cellular respiration can be compared to burning of fuel in which organic food
(carbohydrates, fats and proteins) rich in carbon burn in the presence of oxygen
producing carbon dioxide, water and energy.
Respiration like combustion is a catabolic exothermic chemical process. However, the
difference between the combustion and respiration is that the combustion takes place in
one go, releasing the entire energy as the heat, which may be utilized or is lost into the
environment. the respiration completes in several small steps. Each step is under the
control of a specific enzyme, releasing energy in small amounts which can be stored in
the form of ATPs. Photosynthesis, another metabolic process, is just opposite to
combustion. Combustion is a catabolic process; the photosynthesis is an anabolic process.
In photosynthesis organic substance is synthesized from carbon dioxide and water in the
presence of sunlight energy and chlorophyll. The molecular oxygen is evolved as the byproduct combustion is exothermic and releases energy, photosynthesis is endothermic
and absorbed energy.
Photosynthesis and respiration are the two metabolic reactions opposite to each other.
Photosynthesis takes place only in the gree parts of the plant body having chlorophyll,
whereas respiration takes place in all the living cells of plants and animals. Mitochondria
are the cellular organelles where respiration takes place while the organelles for
photosynthesis re chloroplasts. Photosynthesis takes place during the day time only,
whereas respiration takes place day and night. In photosynthesis body weight is increased
but in respiration weight is decreased. Respiration is an oxidation reaction whereas
photosynthesis is a reduction reaction and can be well understood by comparing their
chemical reactions.
(Diagram)
Chemical Equation in Respiration
Glucose + Oxygen ——-> Carbon dioxide + Water + Energy (In presence of
mitochondria and enzymes)
Chemical Equation In Photosynthesis
Carbon dioxide + Water ——–> Glucose + Oxygen (In presence of chloroplast and solar
energy)
Respiratory Organs of Insects
The respiratory system of insects is called the Tracheal system. It is a network of
interconnecting air filled tubes called trachea delivering air directly to the body tissue
cells. Trachea open outside through pores called spiracles.
Each trachea has chitinous cuticle lining which prevents it from collapsing.
A pair of spiracles is usually located on the sides of each segment of the thorax and
abdomen. Spiracles have valves to open or close them regulated by special muscles. This
controls water loss from internal body tissue.
(Diagram)
Trachea break up into numerous smaller tubes called tracheoles which ramify among the
body tissues ending blindly. Tracheoles lack a chitinous lining. At rest the tracheoles are
filled with watery fluid through which gaseous exchange tkes place in dissolved state.
Ventilation is brought about by contraction and relaxation of abdominal muscles which
result in a rhythmic pumping of air into and out of the trachea.
Gas exchange takes place in tracheoles which are permeable to gases and are filled with a
fluid in contact with the body tissue. Since oxygen diffuses directly into the tissue cells,
blood of insects does not have hemoglobin so it is white. However, removal of carbon
dioxide is dependent on blood plasma which takes it up for removal via spiracles.
Bryophytes and Tracheophytes
CHAPTER – 6
Bryophytes
Bryophytes are on of the two main groups of kingdom ‘Plantae’ the second being the
‘tracheophytes’. Bryophytes is a group of plants which are multicellular, photosynthetic
eukaryotes; and their reproductive organs are multicellular; their zygote develops into
small, protected embryo that develops into a complete new hence bryophytes have also
been called embryophytes. The cell of these plants is made up to cellulose.
Characteristics of Bryophytes
The important characteristics of Bryophytes are as follows:
1. Bryophytes are plants without vascular tissue (xylem a phloem), whereas
tracheophytes have vascular tissue. Therefore tracheophytes are vascular plants, whereas
bryophytes are non-vascular plants.
2. Bryophytes are the simplest land plants. Bryophytes divided into three groups.
Liverworts, hornworts, and mosses.
3. Marchantia is an example of liverworts; its plant body is a thick branched green
thallus.
4. Anthoceros is a horn wort, and Funaria is a moss.
5. All bryophytes and generally found growing in moist habitants such as damp soil and
rocks, moist brick walls, and along the banks of streams.
Life Cycle of Funaria Moss
It is a common moss found grwoing t moist places. Green leafy, moss plant of Furania, as
like all Bryophytes, Funaria is haploid gametophyte, its height is about 0.5 – 1 inch.
(Diagram)
Gamatophyte Generation
It consists of 3 parts:
1. A vertical stem like structure.
2. Leaf like photosynthetic structures arranged on the stem, which are composed of a
single layer of cells, and without stalk.
3. Numerous multicellular rhizoids, arising from the lower side of the stem and which
absorb water and salts, and anchor the plant to the soil.
Male sex organs, called antheridia (singular antheridium) are located at the tip of male
branch, and the female sex organs, called archegonia (singular archegonium) are located
at the tip of female branch.
Fertilization takes place in the presence of water within the archegonium located at the tip
of female branch. The zygote develops into the embryo (2n). The embryo forms the
sporophyte (2n). The sporophyte remains attached to the tip of female branch. The
sporophyte gets water, slts and also part of its food, from the parent gametophyte plant.
Sporophyte Generation
The sporophyte consists of three parts:
1. A foot
2. A long stalk like seta
3. Capsule
The foot is anchored to the female branch and absorbs nutrients from the gametophyte.
The seta elevates the capsule in the air. Within the capsule, haploid spores are produced
by meiosis. The spores are dispersed by wind. Each spore develops eventually into new
haploid gametophyte plant, and the life cycle continues.
Like other bryophytes, Funaria also has well defined alteration of generations; haploid
gametophyte generation is dominant, whereas diploid sporophyte is attached to and more
or less dependent on the gametophyte.
Pteridophytes
1. Unlike bryophytes the plant body in Pteridophytes is differentiated into root, stem and
leaves.
2. In contrast to other vscular plants Pteridophytes do not bear flowers, fruits and seeds.
3. Due to presence of vascular tissues, they are similar to gymnosperms and angiosperms.
4. Although the dominant generation in Pteridophytes is also the sporophyte but unlike
gymnosperms and angiosperms both sporophyte and gametophyte generations are
independent and free living. However, the gametophyte in much reduced and smaller in
size.
Spermatophytes
Seed plants or Spermatophytes are that group of vascular plants which produce seeds.
Seed is a ripened ovule. It contains a young plant with embryonic root, stem and one or
more leaves, which has stored food material and is protected by a resistant seed coat or
testa.
Spermatophytes like pteridophytes possess vascular tissues. They also have life cycles
with alternation of generations. Unlike bryophytes and pteridophytes, spermatophytes do
not have free living gametophyte; instead the gametophyte is attached to and nutritionally
dependend upon the sporophyte generation.
Main Groups of Spermatophytes
Gymnosperms
They produce seeds which are totally exposed or borne on the scales of cones.
Angiosperms
They are flowering plants which produce their seeds within a fruit.
Pinus and Thuja – The Typical Gymnosperm
Pinus is normally grows at an altitude of 5000 ft to 8000 ft. It has many types e.g. chir,
kail, chilghoza etc. However, some species are found in the plains. It is also grown as
ornamental plants. Pinus tree is a sporophyte, which is evergreen and quite tall. It consists
of an extensive root system and a strong, stout and woody stem and its branches. The
upper branches progressively become shorter in length. In this way, the tree assumes a
symmetrical conical shape.
(Diagram)
Thuja
Thuja (common known as Mor Pankh) is a short tree. It has profuse branches, which are
covered with small, dark green scale leaves. It is conical in appearance. It is grown as
ornamental plant in parks and homes.
Leaves of Thuja
Thuja has small scale like green leaves that cover the stem.
Female Cone of Thuja
In Thuja the female cones are spherical or oval in shape. These are about the size of a
bair (berry). They consist of hard, brown colour scales with triangular apices.
Pinus
Pinus has two types of shoots.
Shoots of Pinus
Long Shoots or Shoots of Unlimited Growth
They are formed on the main stem and continue growth indefinitely by buds borne at
their apices. They are covered by scale leaves.
Dwarf Shoots or Shoots of Limited Growth
These shoots originate in the axils of the scale leaves on the long shoots. They are very
short (only a few millimeters in length). Each dwarf shoot bears 1 t 5 foliage leaves in
addition to scales leaves.
Leaves of Pinus
Scale Leaves
These are small, membranous and brown in colour. They cover the stem.
Foliage Leaves or Needles
These are commonly long and narrow, tough, and leathery. In contrast to scale leaves
they are green and photosynthetic. Depending upon the type of species, a cluster of 2 to 5
needles is produced on each dwarf shoot. Each dwarf shoot with its cluster of needles is
called a spur.
Reproduction in Pinus
Pinus tree produces reproductive structures known as cones every year. Cones are of two
types, male and female c9ones. Both male and female cones are produced on the same
tree but on different branches.
Male Cone of Pinus
Male cones, usually 1 cm or less in length, are much smaller than the female cones. They
are produced in clusters. These are generally born on the lower branches of the tree. Each
male cone is composed of spirally arranged leaf-like structures called scales or
microsporophylls. Each microsporophyll has two long sacs called pollen sacs of
microsporangia on it are under surface. Asexual reproductive cells, microspores or pollen
grains are produced by meiosis in the microsporangia. Pollen grains are haploid. After
being transferred to the ovule, the pollen grain forms pollen tube. It is the male
gametophyte in which male gametes or sperms are produced.
Female Cone of Pinus
The female cones are much larger than the male cones. These are usually found on the
upper branches. Each female cone is also made of spirally arranged scales which are
called megasporophylls. These scales become woody on maturity. Two ovules are
present side by side at the base of each scale. Haploid megaspores are formed in the
ovule by meiosis. Measpores give rise to female gametophytes which produce female
gametes. Fertilization results in the formation of embryo after which the ovule is ripened
to form seed. Female cones normally remain attached for three years on the plant. On
maturity the cones open up and the seeds are set free and dispersed.
Angiosperms
Angiosperms are the flowering plants which are most successful plants. They are more
important than the gymnosperms. They have adapted to almost every type of
environment. There are about at least 235,000 species. They are dominant plants.
Angiosperms are vascular plants which bear flowers. Their seeds are produced within
fruits. The fruit protects the developing seeds and also helps in their dispersal. Seed and
fruit producing habit have helped flowering plants in their evolutionary success.
Angiosperms are found in wide variety of sizes and forms. Ensize they range from over
300 ft in height (some species of Eucalyptus) to searcely 1mm in length (duckweed,
Woiffia).
On the basis of size and woody texture, angiosperms are classified as herbs, shrubs
(bushes) and trees. Herbs are the plants which are small in size. Their stems are Herbs
which are then cut or pulled from the soil. In contrast shrubs and trees have hard woody
stems, which retain their shape even after being cut. Shrubs are shorter than trees but
have more branches. In addition to tracheids, angiosperms have efficient water
conducting structures known as vessels in their xylem.
Classes of Angiosperms
On the basis of the number of cotyledons in the seed, angiosperms are divided, into two
classes.
1. Monocotyledons or Monocots
2. Dicotyledons or Dicots
Monocots
1. Monocot seeds have only one cotyledon or embryonic leaf.
2. A nutritive tissue called “endosperm” is usually present in the mature seed.
3. Monocots are mostly herbs with long narrow leaves.
4. Leaves have parallel veins i.e. in the lamina of the leaf veins run parallel to one
another.
5. The floral parts of most flow3ers usually occur in threes or multiples of three (i.e. 3, 6,
9 …)
6. Monocots include different grasses, cereals (wheat rice, maize etc) ,palms, onions and
lilies.
Dicots
1. Dicot seeds have two cotyledons.
2. In mature seed, te endosperms is usually absent.
3. Their leaves vary in shape but usually are broader than monocot leaves.
4. Leaves have reticulate veins i.e. branched veins resembling a net. The flower parts are
four or five in number or multiples of 4 or 5.
5. Dicots include rose, peas and pulses, sheesham, Kiikar (Acacia), sarsoon (mustard),
cacti, mango, orange and sunflower etc.