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Nutrients in Plants
Nutrition
Nutrition is the mode of intake of food by the organism and its utilisation by the body. All
organisms need food to perform their life processes. Food comprises of different nutrients which
include carbohydrates, proteins, fats, vitamins and minerals. Food provides us energy to grow,
repair the damaged parts in our body. Living organisms include microorganisms, plants and
animals.
Plants obtain their nutrition by various modes. The mode of nutrition in plants can be autotrophic
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mode or heterotrophic mode. Plants can be classified into autotrophs and heterotrophs.
Autotrophic plants can synthesise their own food by the process of photosynthesis.
Heterotrophic plants cannot synthesise food on their own but depend on other organisms for their
nutrition. Heterotrophic plants can be further classified into parasites, saprophytes and symbiotic
plants.
Autotrophic mode of nutrition - Photosynthesis
It is an autotrophic mode of nutrition. Photosynthesis is a process by which green plants can
synthesise glucose from raw materials like carbon dioxide and water in the presence of sunlight
and chlorophyll. Photosynthesis involves the conversion of solar energy into chemical energy to
synthesise starch.
Requirements for photosynthesis
Facts about photosynthesis
All chlorophyll-containing plants, including algae, and some plants with red, brown or other
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dominant pigments, make their food by photosynthesis.
Leaves are considered as food factories of a plant.
Roots absorb water and minerals from the soil and are transported to different parts of the plant.
Stomata present in the lower epidermis of the leaf take in carbon dioxide from the air.
Leaves have special structures called as chloroplasts. Chloroplasts possess chlorophyll, a green
colour pigment present in the leaf captures energy from sunlight. Sun is the ultimate source of
sunlight for all the living organisms on earth.
Plants synthesise glucose using carbon dioxide and water in the presence of sunlight.
Oxygen and water are released as by-products through the stomata during daytime.
The food synthesised is transported to other parts of the plant for utilisation and storage.
Glucose is a carbohydrate. Glucose synthesised by the process of photosynthesis is converted
into complex compounds like starch and cellulose. Starch is stored in different parts of the plant.
Plants also prepare proteins with the help of nitrogen which is obtained from the soil.
Thus, the minerals dissolved in water are used to convert sugar synthesised into carbohydrates,
proteins and fats.
These food components stored are the source of energy for other heterotrophic plants and
animals.
Activity 1
Aim: To prove the essentiality of green colour pigment chlorophyll for photosynthesis.
Procedure: Following steps are performed in a sequential order.
Step-1: Take a beaker with boiling water and drop a leaf into it. Let it boil for 2 minutes.
Step-2: Take the leaf out of the beaker and place it in a test tube with alcohol. Place this test tube
in a hot water bath for 10 minutes. Alcohol decolourises the leaf by removing chlorophyll from it
by the process of bleaching.
Step-3: Remove the leaf from alcohol and wash it with warm water. Place it on a tile for further
test.
Step-4: Add 2 drops of iodine on to the leaf. The portions which contained chlorophyll turn into
bluish-black colour. The portions which did not contain chlorophyll and did not participate in
photosynthesis remain the same.
Inference: From the experiment we can infer that green parts of the leaves synthesised starch
and non-green parts did not perform photosynthesis to form starch.
Activity 2
Aim: To explain the essentiality of light in photosynthesis
Procedure: Following steps are performed in a sequential order.
Step-1: A leaf is selected on a plant and is covered with black paper.
Step-2: Plant is destarched by keeping it in atmost darkness for 3 days. Pick a leaf and test it to
confirm that the plant is starch free. i.e. It did not perform photosynthesis in the darkness.
Step-3: Expose the same plant to sunlight for a day.
Step-4: Test the leaf covered with black paper using iodine. It does not turn blue-black as it has
not synthesised starch. Starch synthesis did not happen as it is not exposed to sunlight.
Inference: Photosynthesis did not occur in the leaf covered with black paper confirming the
essentiality of light for the synthesis of starch.
Activity 3
Aim: To prove the requirement of carbon dioxide for photosynthesis
Procedure: Following steps are performed in a sequential order.
Step-1: A potted plant is taken and placed in complete darkness for few hours.
Step-2: Take potassium hydroxide in a conical flask rubber stoppered with a cork. Insert one leaf
( still attached to parent plant) into through a hole in the rubber cork. Potassium hydroxide
absorbs all the left-over carbon dioxide from the flask.
Step-3: Entire arrangement is exposed to sunlightfor 6 hours.
Step-4: The leaf placed in the conical flask with potassium hydroxide solution is tested with
iodine solution. This does not turn into bluish-black colour.
Inference: The leaf trapped inside the conical flask did not perform photosynthesis as it did not
receive any carbon dioxide.
Heterotrophic mode of nutrition
Heterotrophic plants do not possess chlorophyll. Therefore, they cannot produce their own food
using the process of photosynthesis. Heterotrophic plants obtain food from other plants by
following either a parasitic, saprophytic or symbiotic mode.
a) Parasitic mode:
The organisms which exhibit parasitic mode of nutrition are called as parasites. Parasites obtain
their nourishment from other living organisms. In parasitic mode of nutrition, plants depend on
other plants or animals for their nourishment. Such plants are called as parasites and the ones on
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which parasites depend are called as hosts.
e.g.Mistletoe is another parasitic plant which depends on other organisms for its nourishment.
e.g.Cuscuta is a parasitic plant which develops special roots called haustoria. Haustoria penetrate
deep into host plant tissues and just absorb the nutrients from them.
b) Insectivorous mode:
These are the plants with special leaves that are modified into special structures. These structures
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have the ability to trap the organisms.
e.g. Nepenthes is otherwise called as pitcher plant has its leaves modified into pitchers closed
with leaves. These have a network of fibres which entangle the trapped organism and later digest
it by secreting some hydrolysing enzymes to digest them.
e.g. Venus fly trap feeds on small animals and insects to obtain their nourishment. These plants
especially obtain the nitrogen they require from insects and small animals.
c) Saprophytic mode:
The plants which exhibit saprotrophic mode of nutrition are called as saprotrophs. Saprotrophs
are the plants that obtain their nutrition from dead and decaying organic matter. Saprotrophs
secrete digestive juices onto dead and decaying matter to dissolve it and then absorb nutrients
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from it.
e.g. Indian pipe which is found on dead and rotting material, inhabits fungus in its roots. These
extend their mycelium and secrete enzymes to digest the decaying matter.
e.g. Coral roots are another type of plants exhibiting saprophytic nutrition.
d) Symbiotic mode:
Symbiosis is the phenomenon by which two organisms maintain relationship with each other to
be mutually benefitted. In symbiotic mode, organisms develop a special relationship with certain
other organisms to obtain nourishment. Organisms involved in this type of relationship are called
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as symbionts.
e.g. Rhizobium bacteria and Leguminous plants are symbionts exhibiting symbiosis. Plants
cannot utilise atmospheric nitrogen directly. Hence, leguminous plants establish a symbiotic
relationship with bacteria like Rhizobium. Both the organisms of symbiotic relationship are
mutually benefited. Leguminous plant provides shelter and nourishment for the bacteria and in
turn bacteria fix atmospheric nitrogen to the plant.
e.g. Digestion in ruminants is a good example of symbiosis. A large sac-like structure called the
caecum lies between the small and large intestines. The symbiotic bacteria present in the caecum
help in complete digestion of cellulose. Microorganisms present in the stomach of ruminants
help in digesting cellulose and in turn obtain shelter and nourishment form the animal. A
symbiotic relationship exists between microorganisms and the ruminants.
e.g. Lichens form a very good example of symbiotic relationship. Lichens are formed by the
symbiotic relationship between algae and fungi sharing a single colony. Fungus provides water,
nutrients and shelter in the form of network formed by mycelium. Algae synthesises the food for
entire colony by the process of photosynthesis.
Differences between a parasite and a saprotroph
PARASITE
SAPROTROPH
An organism that depends on other
An organism that obtains its nourishment
organisms for its food and
from dead and decaying.
nourishment.
It develops special organs like
It is capable of secreting some enzymes
suckers, hooks or haustoria to
which can digest complex molecules of
obtain nourishment from the host. into simpler forms.
e.g. Cuscuta, Nephenthes etc.
e.g. Fungi, Bacteria.
HD12:26
Activities & Simulations
Activity 1
Mbdalchemie.com has created a virtual lab to make the activity of 'Stomata' understandable.
Click on the 'Teacher's Desk' button. Under that 'Experiment' option has to be selected. It gives
the student a clear-cut idea about the experiment, materials required and mainly the procedure in
which experiment has to be performed. It explains each and every equipment in a systematic
way. It allows the user to regulate experimental conditions by chosing different equipment. By
getting equipped with information, user can understand the concept.
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Activity 2
Tc.pbs.org has designed an interactive activity to explain the concept of 'Photosynthesis'. The
template exhibits three buttons. 'The cycle' button allows us to provide the plant with water,
carbon dioxide and sunlight. Just by touching the can, water is poured. By touching the raiser,
sunlight is allowed to fall on the plant. 'Atomic shuffle button allows the user to know about the
formation of glucose molecule, release of oxygen by combining carbon dioxide with water
molecules. 'Three puzzlers' allow the user to answer certain questions after getting clear
explanantion on the topic.
Go to Activity
Questions & Answers
View Unanswered Questions
Ask a Question
1 . How are nutrients replenished in the soil?
Nutrients are replenished by certain different microorganism that are found in the soil or also by
the death of certain plants such as the r...
2 . Is insectivores plants heterotrophs or autotrophs?
insectivores olants which trap insects and digest nutrients.it is not a heterotrophic or autotrophic
3 . Why does paddy field grow well in clayey soil?
It grows well in clayey soil as it has a lower percolating rate. That means it's water holding
capacity is very high.
4 . Can u explain me in heterotrophic nutrition ,parasitic ,saprophytic ,insectivorous , symbiotic
plants
Hello Ashok, heterotrophs are orgnisms which cannot prepare their own food due to lackof
chlorophyll and hence depende upon other organisms...
5 . We make our own food in the kitchen. This means that humans are also autotrophs. Do you
agree? Give reasons.
No humans are not autotrophs , they are heterotrophs because we humans depend on animals
and plants for our nourishment . Humans cannot ..
Digestion in Humans
H
Nutrition in animals
Animals exhibit heterotrophic mode of nutrition. As animals cannot synthesise their own food,
they depend on plants or other smaller animals for food.
Types of animals
Based on the food they consume, animals are classified into herbivores, carnivores and
omnivores.
Holozoic nutrition: It is a process by which animals take in their food. It involves different steps
namely, ingestion, digestion, absorption, assimilation and egestion. Human beings exhibit
holozoic mode of nutrition involving five basic steps.
Digestion: Digestion is the process by which food is broken down into simple absorbable
substances. Digestion of food takes place in the digestive system. Digestive system is made up of
alimentary canal and associated glands. Digestion in man is an extracellular process.
Digestive system in human beings: Digestive system in human beings is formed by alimentary
canal and digestive glands.
Parts of alimentary canal: It is also called as digestive tract. It comprises different parts like
mouth, oesophagus, stomach, small intestine and large intestine. It starts with mouth and ends
with anus.
Mouth is guarded by upper lip and lower lip. The process of taking in food through mouth is
called as ingestion.
Buccal cavity is the inner region of the mouth. It encloses teeth and tongue. The buccal cavity
leads into pharynx.
a) Teeth are of different types namely, incisors, canines, premolars and molars.
• Incisors are used for cutting and biting food. There are 4 incisors in each jaw. They are also
called as biting teeth.
• Canines are sharp and pointed and are used to pierce or tear food. There are 2 canines in each
jaw.
• Premolars have broad grinding surfaces. Hence they help in chewing and grinding the food.
There are 4 premolars in each jaw.
• Molars are the principal grinders which help to chew and grind the food. There are 6 molars in
each jaw.
Teeth help in the process of mastication.
• Mastication involves proper chewing of food and mixing it with saliva.
• Food is broken into small pieces by biting, grinding and crushing.
• Digestion of food starts in the mouth with the help of salivary amylase present in the saliva.
• Salivary amylase is the enzyme which digests starch, a form of carbohydrate present in the
food.
Structure of a tooth
Dental care
b) Tongue is a muscular organ attached to the floor of the buccal cavity at the back.
• It is free at one end and helps in pushing the food inside while chewing.
• It helps in mixing of food with saliva and swallowing it.
• It has many taste buds on it which can taste different types of food. Taste buds are sensory
receptors which give a sense of taste.
• Taste receptors can taste sugar, salt, sour, bitter and one another taste called as umami.
• Tongue also helps in speech.
Pharynx is at the back of buccal cavity.
• The pharynx is the common channel for food and air.
• When you swallow food, a flap-like valve called the epiglottis closes the windpipe.
• Epiglottis prevents the entry of food particles into respiratory tract.
Oesophagus also called as food pipe helps in conveying the food from buccal cavity to stomach.
The oesophagus is also known as the gullet. It is about 25 centimetres long.
• Food inside the oesophagus reaches the stomach by peristalsis movements.
• Peristaltic movements are the alternate contractions and relaxations of oesophageal wall which
bring about movement of food from buccal cavity to the stomach.
• Food conveyed to the stomach is called as bolus as it is round in shape.
Stomach is the widest part of the alimentary canal. It is a J-shaped muscular organ divided into
three parts namely, cardia, fundus and pylorus regions.
• Stomach as a whole can hold at about two litres of food.
• Stomach secretes a fluid called as digestive juice. Digestive juice is made up of hydrochloric
acid, mucous and some enzymes.
• Hydrochloric acid kills the bacteria present in the food and softens the molecules of food.
• Mucous protects inner lining of the stomach from the action of hydrochloric acid.
• Digestive enzymes partially digest some nutrients like proteins and fats. Stomach churns the
food into a milky paste.
• This partially digested food is called as chyme.
• Chyme is conveyed to small intestine for further digestion. Chyme is acidic in nature.
Small intestine is made up of three regions namely duodenum, jejunum and ileum.
• Acidic chyme from the stomach is received by the duodenum for further digestion.
• Duodenum also receives bile form the liver. Bile reduces the acidity of chyme.
• Bile also provides alkaline environment to activate some enzymes which bring about digestion
of certain nutrients in the food.
• Duodenum also receives pancreatic secretions which help in the digestion of food.
• Duodenum also secretes some enzymes on its own.
• All these substances bring about digestion of food in the intestine.
• The inner walls of small intestine are thrown into many folds which have millions of small
finger like projections called villi.
• Villi increase the surface area for digestion as well as absorption of digested food by eight
times. Small intestine also helps in the process of absorption and assimilation.
• Undigested food is sent into large intestine.
Large intestine comprises of colon and rectum. Large intestine receives undigested food from
small intestine.
• Water from the food is reabsorbed to a great extent in the large intestine.
• Semi-solid undigested waste is stored in the rectum for defecation.
• Anus is the opening of the alimentary canal to the exterior. This helps in the elimination of
faeces by the process of egestion.
Digestive glands: These glands are also called as associated glands. These are also considered to
be exocrine glands which have ducts to drop their secretions into the target organ directly. The
secretions of the digestive glands help in the process of digestion. These glands include salivary
glands, gastric glands, intestinal glands, liver and pancreas.
Salivary glands are present inside the buccal cavity. They secrete saliva. Saliva helps in
lubrication of food . This saliva plays an important role in breaking down complex components
like starch into simple sugars. It brings about partial digestion of starch.
Gastric glands are microscopic glandular cells present in the inner lining of the stomach. Gastric
glands secrete gastric juice comprising HCl, pepsin and prorennin. Gastric juice helps in the
digestion of proteins. Gastric juice helps in emulsification of fats.
Intestinal glands are present in the inner lining of small intestine. These secrete various enzymes
which aid in the process of digestion of all the components of food.
Liver is the largest gland in our body. The liver secretes a yellowish green watery fluid called
bile. It is temporarily stored in a sac called the gall bladder. Bile provides an alkaline
environment for many enzymes to get active. It also reduces the acidity of chyme. Bile plays an
important role in the digestion of fats. Bile is sent into duodenum through a narrow tube-like
structure called the bile duct. Bile breaks the larger fat molecules into tiny droplets, thereby
increasing their surface area, which helps in the digestion of fats easily.
Pancreas is the mixed gland. It acts as both endocrine and exocrine gland. The pancreas secretes
the pancreatic juice that helps to digest carbohydrates, proteins and fats. The pancreatic juice
converts carbohydrates into simple sugars and glucose, proteins into amino acids, and the lipids
into fatty acids and glycerol.
Absorption: The process of allowing simple absorbable nutrients into blood capillaries through
surface of the villi is called as absorption. Inner wall of small intestine comprises many finger
like projections called as villi. Villi increase the surface area for absorption of food.
Each villus is made up of central structure called as lacteal which mainly absorbs simple fats and
transports them into lymphatic system. Lacteal is surrounded by a network of fine blood
capillaries. Blood capillaries absorb glucose molecules and amino acids and transport them in the
blood. Vitamins and minerals get readily absorbed into the blood.
Assimilation: The process of utilisation of absorbed food, such as glucose, amino acids, fatty
acids and glycerol is called as assimilation. Energy needed for various activities is obtained from
glucose. Glucose is broken in the cells in the presence of oxygen to syntheise energy in the form
of ATP. Amino acids are used for building and repairing body parts. Fatty acids and glycerol are
stored in the adipose tissue and under the skin for future use.
Egestion: It is the process by which undigested food is passed to exterior through an opening
called as anus. Rectum stores undigested waste in the form of faeces. Faeces are sent out through
anus.
Activities & Simulations
Activity 1
Sheppardsoftware.com has displayed a group of activities in a single page under the topics '
Digestion Game level-1', ' Digestion Game level-2' and 'Digestion quiz'. Student has to select the
activity and play the game as per the instructions or answer the quiz. Student is given the score
while playing. Additional information is also given about different parts of the digestive
system.You have a tutorial providing information about digestion.
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Activity 2
Ehc.com has created an interactive video which brings the attention of students with different
options on the template.Student has to select 'Digestive tract'. This module is divided into Guided
tour, Zoom in and Organize your organs. Once we click on the organise your button, organs of
the digestive system are displayed. Student needs to put them into proper place as instructed by
the video.You can also know information about digestive system under the 'Guided tour'. Zoom
in helps in to see what happens to the food consumed in different parts of the digestive system.
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Questions & Answers
View Unanswered Questions
Ask a Question
1 . Why do we get instant energy from glucose?
Sol:
Glucose is the simple form of carbohydrate which is readily used up by our body cells to provide
energy. Glucose (dextrose) is...
2 . mention 5 steps in the process of animal nutrition
Following are the five steps in the process of animal nutrition.
1. Procurement of food
2. Ingestion
3. Digestion <...
3 . Name the glands associated with the alimentary canal in man.Mention their secretions.
1. Salivary glands: These produce saliva 2. Gastric glands: These secrete gastric juice 3.
Intestinal glands: These secrete intestinal juice...
4 . WHAT IS VILLI ? WHAT IS IT'S FUNCTION AND LOCATION?
The inner walls of small intestine have thousand of finger like out growth these are called villi
Function The villi increase the surface ar...
5 . Why are mushrooms considered to be saprotrophs?
Sol:
Mushrooms are considered to be saprotrophs as they grow on dead and decaying matter
and obtain nourishment from it by ...
Summary
HD4:12
Animals which feed on plants are called as herbivorous animals. Plant cells contain rich content
of cellulose. Cellulose is an important component in the diet of herbivorous animals. Humans
cannot digest cellulose.
Ruminants: These are also called as grass-eating animals. These are hoofed animals whose body
stands on four limbs. Ruminants include, cows, buffaloes, sheep, giraffe, camel, deer etc. They
also possess special type of digestive tract which extracts nutrition from the food they eat.
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Dentition in ruminants: Dentition is quite different in rumination.
Incisors are absent on the upper jaw.
Canines are absent in both the jaws.
Molars are very strong as these animal chew the cud.
Rumination: Ruminants swallow the food without chewing. After feeding, they bring the food
from the stomach back into the mouth and chew it leisurely. This process is called rumination
and such animals are called as ruminants. Rumination is also called second chewing.
Ruminant stomach: The stomach of a ruminant is divided into four chambers – the rumen,
reticulum, omasum and abomasum. Rumen is the largest part of the stomach.
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Process of digestion: Grass-eating animals swallow the food quickly and store it in the
rumen. Rumen also inhabits cellulose digestic bacteria which establish a symbiotic relationship
with the animal stomach.
Digestion in ruminants is a good example of symbiosis.Microorganisms present in the stomach
of ruminants help in digesting cellulose and in turn obtain shelter and nourishment form the
animal. A symbiotic relationship exists between microorganisms and the ruminants.
As rumen is full, the food is taken into second part of the stomach, the reticulum.
Digestive juices of the reticulum partially digest the food. The partially digested food in the
reticulum is called as cud.
While resting, cow brings back the cud into the mouth for regurgitation.
Food is chewed completely and swallowed into omasum for further digestion.
Then the food moves into abomasum for digestion brought about by digestive juices.
A large sac-like structure called the caecum lies between the small and large intestines.
The symbiotic bacteria present in the caecum help in complete digestion of cellulose. Digestion
of food is completed in the intestine.
As the symbiotic bacteria are not present in the human digestive system, humans cannot digest
cellulose.
Activities & Simulations
Activity 1
Csus.edu has formulated a small interactive module to make the user understand the concept
of 'Digestion in ruminants'. Though it is a simple module, it makes the concept clear for the
student. User needs to follow the instructions and click on the respective parts of the ruminant
stomach. Clearcut animation is shown along with the text to explain the role of that part of the
stomach in the process of digestion.
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Activity 2
Razeghi.ir has devised a template on the concept 'Ruminant digestion'. Click on continue button
to enter the interaction. Student has to answer some questions in order to obtain information on
the concept. After each step user has to click on the 'Play' button to resume the next step.
Ruminant digestion is explained clearly in different steps represented by the slides.
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Questions & Answers
View Unanswered Questions
Ask a Question
1 . Why do we get instant energy from glucose?
Sol:
Glucose is the simple form of carbohydrate which is readily used up by our body cells to provide
energy. Glucose (dextrose) is...
2 . mention 5 steps in the process of animal nutrition
Following are the five steps in the process of animal nutrition.
1. Procurement of food
2. Ingestion
3. Digestion <...
3 . Name the glands associated with the alimentary canal in man.Mention their secretions.
1. Salivary glands: These produce saliva 2. Gastric glands: These secrete gastric juice 3.
Intestinal glands: These secrete intestinal juice...
4 . WHAT IS VILLI ? WHAT IS IT'S FUNCTION AND LOCATION?
The inner walls of small intestine have thousand of finger like out growth these are called villi
Function The villi increase the surface ar...
5 . Why are mushrooms considered to be saprotrophs?
Sol:
Mushrooms are considered to be saprotrophs as they grow on dead and decaying matter
and obtain nourishment from it by ..
Digestion in Amoeba
Summary
HD5:07
Amoeba
The amoeba is a microscopic unicellular, eukaryotic organism. It belongs to the group protozoa.
The name comes from the Greek word ‘amoibe’ meaning ‘change’.
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General characteristics of amoeba
Amoebae are found at the bottom of fresh water bodies like ponds and lakes, even in a gutter or
muddy water. Some of them are also found in damp soil and food.
An amoeba contains jelly-like cytoplasm. In the cytoplasm are present the cell organelles like
nucleus, food vacuoles and contractile vacuole.
An amoeba takes in oxygen, gives off carbon dioxide through the cell membrane by the
mechanism of diffusion. It takes in dissolved oxygen from water.
Amoeba possesses false feet called as pseudopodia. Pseudopodia are used to capture food as well
as for locomotion.
An amoeba can move in all directions using temporary feet-like structures called pseudopodia. It
can change its shape with the help of these pseudopodia to exhibit locomotion.
Amoeba is a simple, unicellular organismwhich reproduces by binary fission. The division
begins with the division of the nucleus.
Amoeba forms a cyst in unfavourable conditions.
Amoeba either lives as a free-living organism or as a parasite.
Parasite causes a disease amoebiasis. This is the intestinal disease caused by the parasite
Entamoeba histolytica. It is symptomatic during excess infection percentage. The patients
experience blood motions with mucus. It is advised to wash hands with soap after using toilet.
Some species of amoeba living in the mouth and intestine are not dangerous to human beings.
Nutrition in amoeba
Amoeba is omnivorous organism. It feeds on plants, microorganisms, smaller organisms etc.
Nutrition is holozoic.
Amoeba does not possess any mouth. It can ingest through any place on the surface of cell
membrane.
Amoeba has a sense of ability to accept food molecules and reject non-food particles.
Amoeba extends its pseudopodia when the food is found.
Pseudopodium just wraps around the food molecule and forms a food vacuole around it.
An amoeba engulfs its prey along with a droplet of water in the food vacuole inside the
cytoplasm.
Food vacuoles circulate in the cytoplasm by streaming movements.
The prey can be killed and digested with the help of the digestive enzymes secreted by the food
vacuole.
Digestion is intracellular in amoeba.
The diffusible substances resulting from the process of digestion are uilised in synthesisng more
protoplasm. They are also stored as reserved food. They are also used to generate energy by the
process of respiration.
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The undigested food is sent out through an opening appearing on the vacuole by changing the
shape of the body. This process is called as egestion.
Activities & Simulations
Activity 1
Stem.org.uk has designed a template with many activities. Click on 'Amoeba' button on the
template. Inside this, students are provided with instructions. When the student selects the 'Play
the movie' button, amoeba is displayed along with the formation of the food vacuole,
pseudopodia, contractile vacuole etc. Depending on the selected option, animlation is shown.
Hotspots are also highlighted to explain the paths. There is also another button 'Explore the
science'. This is an additional information provided to the student about digestion in amoeba.
There are some features provided on the template. These include Inform, Question, Challenge,
Hypothesise.
Go to Activity
Activity 2
lcmrschooldistrict.com has provided a clear animation about the 'Digestion in amoeba'.Student
has to click on the different parts of amoeba to know the information about it. When the student
clicks on the food vacuole, the digestion of food in it can be observed clearly. All the parts of
amoeba are labelled and represented in a diagram.
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Questions & Answers
View Unanswered Questions
Ask a Question
1 . Why do we get instant energy from glucose?
Sol:
Glucose is the simple form of carbohydrate which is readily used up by our body cells to provide
energy. Glucose (dextrose) is...
2 . mention 5 steps in the process of animal nutrition
Following are the five steps in the process of animal nutrition.
1. Procurement of food
2. Ingestion
3. Digestion <...
3 . Name the glands associated with the alimentary canal in man.Mention their secretions.
1. Salivary glands: These produce saliva 2. Gastric glands: These secrete gastric juice 3.
Intestinal glands: These secrete intestinal juice...
4 . WHAT IS VILLI ? WHAT IS IT'S FUNCTION AND LOCATION?
The inner walls of small intestine have thousand of finger like out growth these are called villi
Function The villi increase the surface ar...
5 . Why are mushrooms considered to be saprotrophs?
Sol:
Mushrooms are considered to be saprotrophs as they grow on dead and decaying matter
and obtain nourishment from it by ...
Animal Fibre - Wool
Summary
Fibres obtained from animals are - wool and silk.
Let us discuss about wool. Wool is the animal fibre. Wool comes mostly from sheep. It was the
first fibre to be spun into yarn, and it provides more warmth than other animal fibres.
Animals that Yield Wool
Apart from sheep, wool also comes from the angora goat, yak, llama, alpaca, and even camels.
All these animals have a thick coat of hair or fleece, which keeps them warm. Wool is obtained
from this fleece.
Sheep wool is more commonly available in India. In Tibet and Ladakh, yak wool is more
common, whereas in Jammu and Kashmir, it is the angora wool. The famous Pashmina shawls
come from the soft under fur of the Kashmiri goat.
In South America, the llama and the alpaca yield wool.
Wool from sheep
Sheep hair is formed by two types of fibres – the coarse beard hair and the fine soft under-hair,
which is close to the skin. This fine hair provides the fibre to make wool.
Sheep Rearing
Sheep rearing is a branch of animal husbandry. Sheep are reared mainly for their meat, wool, and
milk.
You must have seen the flocks of grazing sheep in the fields. Sheep are herbivores and prefer
grass and leaves. However, shepherds also feed them mixtures of pulses, corn, jowar, oil cakes
and minerals. In winter, they are fed leaves, grain and dry fodder.
In India sheep are reared in the hills of Himachal Pradesh and Arunachal Pradesh, and in the
plains of Haryana, Punjab, Rajasthan and Gujarat.
Selective Breeding
Selective breeding is a process of selecting the parents for obtaining special characters in the
offspring. Selective breeding is done to have sheep with soft hair.
The Nali and Lohi breeds are found in Rajasthan and Punjab, the Rampur bushair in Uttar
Pradesh and Himachal Pradesh, and the Bakharwal in Jammu and Kashmir. Gujarat breeds the
Marwari and Patanwadi sheep.
Each breed yields wool used for different purposes.
• Nali breed wool is used to make carpet wool.
• Patanwadi wool is used for hosiery.
• Lohi wool is of very good quality, and is used for making clothes.
• Bakharwal wool is used for shawls.
Processing Fibres into Wool
The process of making fibre into wool follows – shearing, scouring, sorting, cleaning of burrs,
dyeing, straightening, combing and finally rolling into yarn.
Shearing
Shearing is the first step in processing fibre into wool. It is the removal of the fleece of the sheep
along with a thin layer of the skin.
Generally sheep are sheared in warm weather, usually spring, as they don’t require their woolly
coats to keep them warm.
Shearing is done with the help of mechanical shears and is usually done by hand. Shearing
doesn’t hurt the sheep as the uppermost layer of the skin is dead.
Scouring
Scouring is the process of washing the sheared hair. The woollen fibres are thoroughly washed in
big tanks to remove grease, dust and dirt by fully mechanized machines.
Sorting
Sorting is done after scouring to separate hair of different textures and types. This is to separate
the low and good quality fibres.
Some parts of the sheep’s coat have better hair than others. This good quality wool from the
shoulders and sides of the sheep is used for clothing, while the more inferior quality comes from
the lower legs, and is used to make rugs. The fleece is sorted according to its texture and type.
Dyeing
Picking out of any remaining burrs (small fluffy fibres) is followed by the dyeing of fibres in
various colours.
Since the natural fibres are mostly black, brown or white in color they can be dyed in various
colours.
Straightening, Combing and Rolling
Once the dyeing process is complete, the fibres are straightened, combed and rolled into
yarn. Longer fibres are made into wool for sweaters, while the shorter fibres are spun and woven
into woollen cloth.
Occupational Hazards
Workers in wool industry face occupational hazards. Risks that can be life threatening to workers
due to their occupation are called occupational hazards. They get infected by a bacterium called
anthrax, which causes a fatal blood disease called sorter’s disease.
Practice Test
Activities & Simulations
Activity1:
Ideares.net has developed an interactive simulation regarding fibre obtained from Alpaka animal.
This simulation also helps you to learn different products formed from alpaka fibre.
Go to Activity
Activity2:
Victoriacarpets.com has developed an interactive simulation regarding the properties of wool, its
nature and uses through interesting images to help you in understand the concept in easy way.
Go to Activity
Questions & Answers
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1 . Life cycle of silk moth
Ans: Sericulture, or silk farming, is the rearing of silkworms for the production of raw silk.
Life cycle of a silk moth: <...
2 . Explain the life cycle of silk moth?
Life Cycle ? Silk Moth: Actually silkworms are not worms, but the larvae or caterpillars
hatched from the eggs of the silk...
3 . RAYON IS KNOWN AS REGENERATED FIBRE . WHY ?
Rayon is known as regenerated fibre because it is manufactured from natural resources like
cellulose present in wood pulp.
4 . Wool production.
there are six steps by which wool is obtained form sheep. Step 1: shearing The process of
removing hair from the body of a sheep is called s...
5 . fibre to fabric
Ans: The hairs on the skin help to control body temperature. The hairs trap a layer of air above
the skin, which helps to i...
Animal Fibre - Silk
Summary
What is cool in summer and warm in winter? The Chinese guarded the making of this fabric with
their life What fabric are we talking about?
Yes! We are talking about silk, the queen of textiles. Silk is a type of an animal fibre produced
by the silkworm.
Discovery of silk
Chinese legend has it that empress Si-lung-Chi was worried about the damaged mulberry leaves
in her garden. Emperor Huang-ti found out that the white worms were eating up the mulberry
leaves and spinning shiny cocoons. A cocoon accidentally dropped into the empress’s cup of hot
tea, and the delicate tangle of threads separated from the cocoon, thus leading to the discovery of
silk.
Thus, the silk industry was born in China. This was kept secret for hundreds of years. later this
was introduced in other countries by traders and travelers much later. The route they travelled
was called the silk route.
Properties of Silk
Silk is an elastic, lustrous protein fibre. The soft silk thread is as strong as a comparable steel
thread.
Types of Silk
Different types of silk moths yield different types of silk yarn, such as mulberry silk, tassar silk,
eri silk and moonga silk.The most common silk moth is the mulberry silk moth. It’s Latin name
is Bombyx mori.
Let us discuss about the life cycle of silk moth.
Life Cycle – Silk Moth
Actually silkworms are not worms, but the larvae or caterpillars hatched from the eggs of the silk
moth. The life history of a silk moth starts when a female silk moth lays eggs.
The larvae or caterpillars hatched from the eggs of the silk moth. These silkworms feed on fresh
mulberry leaves the silkworm grows in size and then becomes a pupa.
In the pupa stage, it weaves a net to hold itself. It then swings its head from side to side,
secreting a fibre that hardens on contact with air. This fibre is made of a protein and becomes the
silk fibre.
The caterpillar covers itself completely with silk fibre and turns into a pupa, this covering is
known as the cocoon. The moth continues to develop within the cocoon. The silk thread or yarn
is obtained from the silk moth’s cocoon.
Rearing Silkworms
Sericulture
Sericulture, or silk farming, is the rearing of silkworms for the production of raw silk. Silkworms
are reared under suitable conditions of temperature and humidity to obtain silk threads from their
cocoons. The female silk moth lays hundreds of eggs.
These are stored on strips of cloth or paper. Mulberry leaves are the staple diet of silkworms.
When the mulberry tree bears a fresh crop of leaves, the eggs are warmed suitably so that the
larvae hatch from them.
The larvae, caterpillars or silkworms are then stored in clean bamboo trays and are fed freshly
chopped mulberry leaves. They eat day and night, and grow to enormous sizes.
The bamboo trays are provided with small racks or twigs to which the cocoons can be attached.
This happens usually after 25 to 30 days when the caterpillars stop feeding and move to the twigs
to spin cocoons. The silk moth develops inside these cocoons.
Interesting fact about Caterpillar
As the caterpillars grow bigger, they shed their skin. The skin of the caterpillar does not grow
along with it. So, it sheds its skin, and underneath the old one is a new skin. Caterpillars may
shed skin four or five times!
Processing Silk
Extracting silk from the cocoon is called processing silk.
The first step is to separate the silk fibre from the cocoon. For this, they need to be exposed to
warmth.
Piles of cocoons are kept under the sun, boiled or exposed to steam. The warmth causes the silk
fibre to separate from the rest of the cocoon.
The next step is called reeling the silk, which is the process of delicately unwinding the fibre
from the cocoon.
Reeling is also done in special machines.
The silk thread is then bleached and dyed into many shades.
The silk fibre is then spun into silk thread, which is then woven into silk cloth by weavers.
HD8:46
Activities & Simulations
Activity1:
Pem.org has developed an about silkworm life cycle, silk cultivation and fashioned in silk with
interseting images from the ancient times. The simulation is based on images. You can learn the
concept through images which excelently desingned in understanding the concept.
Go to Activity
Activity2:
Kji.iitm.ac has developed an interactive simulation regarding the life cycle of silkworm. The
simulation is totally image based about each stage of silkworm.
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Activity3:
Springer.com has developed an interesting simulation regarding life cycle of silkworm through
intersingf images and explanation for the each stage of silkworm life cycle. The simulation
containes interesting question through the quiz.
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Questions & Answers
View Unanswered Questions
Ask a Question
1 . Life cycle of silk moth
Ans: Sericulture, or silk farming, is the rearing of silkworms for the production of raw silk.
Life cycle of a silk moth: <...
2 . Explain the life cycle of silk moth?
Life Cycle ? Silk Moth: Actually silkworms are not worms, but the larvae or caterpillars
hatched from the eggs of the silk...
3 . RAYON IS KNOWN AS REGENERATED FIBRE . WHY ?
Rayon is known as regenerated fibre because it is manufactured from natural resources like
cellulose present in wood pulp.
4 . Wool production.
there are six steps by which wool is obtained form sheep. Step 1: shearing The process of
removing hair from the body of a sheep is called s...
5 . fibre to fabric
Ans: The hairs on the skin help to control body temperature. The hairs trap a layer of air above
the skin, which helps to i...
Temperature and Its Measurement
Summary
Temperature
Temperature is a measure of the degree of hotness of a body. The SI unit of temperature is
kelvin (K). But temperature is also measured in celcius (°C) or fahrenheit (°F) scales. The
instrument used to measure temperature is called a thermometer.
Thermometer
A thermometer is used to measure the temperature of an object. Galileo invented a rudimentary
water thermometer in 1593. He called this device a thermoscope. However, this form was
ineffective as water freezed at low temperatures. In 1714, Gabriel Fahrenheit invented the
modern mercury thermometer. A thermometer consists of a long, narrow, uniform glass tube
called the stem. The scales in which the temperature is measured are marked on the stem. At the
end of the stem there is a small bulb which contains mercury in it. A capillary tube is inside the
glass stem in which mercury expands when the bulb is kept in contact with a hot body. Mercury
is toxic, and it is very difficult to dispose it when the thermometer breaks. So, nowadays digital
thermometers are used to measure the temperature, as they do not contain mercury.
Types of Thermometers
There are different types of thermometers for measuring the temperatures of different things like
air, our bodies, food and many other things. There are clinical thermometers, laboratory
thermometers, Galileo thermometers, maximum-minimum thermometers and digital remote
thermometers. Among these, the commonly used thermometers are clinical thermometers and
laboratory thermometers.
Clinical Thermometer
These thermometers are used to measure the temperature of the human body, at home, clinics
and hospitals. All clinical thermometers have a kink that prevents the mercury from flowing back
into the bulb when the thermometer is taken out of the patien's mouth, so that the temperature
can be noted conveniently. There are temperature scales on either side of the mercury thread, one
in Celsius scale and the other in Fahrenheit scale. Since the Fahrenheit scale is more sensitive
than the Celsius scale, body temperature is measured in °F only. A clinical thermometer indicates
temperatures from a minimum of 35 °C or 94 °F to a maximum of 42 °C or 108 °F.
Precautions to be Followed While Using a Clinical Thermometer
• The thermometer should be washed before and after use, preferably with an antiseptic
solution.
• Jerk the thermometer a few times to bring the level of the mercury down.
• Before use, the mercury level should be below 35 °C or 94 °F.
• Do not hold the thermometer by its bulb.
• Keep the mercury level along your line of sight and then take the reading.
• Handle the thermometer with care. If it hits against some hard object, it may break.
• Do not place the thermometer in a hot flame or in the hot sun.
Laboratory Thermometers
Lab thermometers are used to measure the temperature in school and other laboratories for
scientific research. They are also used in the industry as they can measure temperatures higher
than what clinical thermometers can record. The stem and the bulb of a lab thermometer are
longer when compared to that of a clinical thermometer and there is no kink in the lab
thermometer. A laboratory thermometer has only the Celsius scale ranging from −10 °C to 110
°C.
Precautions to be Followed While Using a Laboratory Thermometer
• Do not tilt the thermometer while measuring the temperature. Place it upright.
• Note the reading only when the bulb has been surrounded by the substance from all sides.
Conversion between Celcius and Fahrenheit Temperatures
The Celsius and Fahrenheit scales are related as follows.
C5=F - 329C5=F - 329 where C and F are the temperatures measured in Celcius and Fahrenheit
scales, respectively. The relation between Celcius and Kelvin temperatures is given by
K = C + 273, where K is the temperature in kelvin.
Activities & Simulations
Activity 1
Goalfinder.com has created flash animation to describe the working ot the thermometer. Using
this animation we can understand the construction of the mercury thermometer and working of
the thermometer. We can also understand how the expansion of liquid ( mercury) is useful to
measure the temperature of the bodies using a thermometer.
Go to Activity
Activity 2
Poodwaddle.com has created an excellent simulation that is very useful to convert the
temperatures among Celsius, Fahrenheight and kelvin. It can be used as the temperature
converstion calculator
Go to Activity
Activity 3
Etech.cz has created a java applet to simulate the working of a liquid thermometer i.e. mercury
thermometer. Using this simmulation we can understand the working of a liquid thermo meter
like a mercury thermo meter.
Questions & Answers
View Unanswered Questions
Ask a Question
1 . What is the difference between clinical and labratory thermometer?
Clinical thermo meter: This thermometer is used in Clinics to measure the temperature of
human body.
A clinical t...
2 . What is the fastest and slowest mode of heat transfer ?
Answer: R adiation is the fastest mode of transfer of heat, because...
3 . Why can't sun's heat reach the earth through conduction or convection
Because space is a vacuum and conduction annd convection doesn't work in vacuum and the
only way is Radiation
4 . In places of hot climate it is advised that outer wall of houses should be painted white? Exlain
In places of hot climate the outer walls of the house are painted white as we know that the white
colour reflects the rays of the sun where...
5 . Why mercury is used as a thermometric fluid ?
The reasons for using mercury as a thermometric liquid are the following:
1. It expands uniformly when heated.
Transfer of Heat
Heat flows from hotter objects to colder objects. When an object is at a temperature different
from its surroundings, heat transfer takes place such that the body and the surroundings reach the
same temperature. For example, when milk is boiled and the flame is off, the milk slowly
transfers heat to the surroundings and becomes cooler. There are three modes of heat transfer:
Conduction, convection and radiation.
Conduction
Conduction is the process of transfer of heat from the hotter part to the colder part of an object
without the movement of its particles. Also, in conduction, heat gets transferred between
substances that are in direct contact with each other. In solids heat transfer takes place by
conduction. For example, when you pop corn in a cooker on a flame, heat is transferred from the
flame to the corn by conduction.
Based on their ability to conduct heat, materials are classified into conductors and insulators.
Materials that allow heat to flow through them are called conductors. Examples: copper, steel,
silver, iron and mercury. Materials that do not allow heat to flow through them are called
insulators. Examples: wood, paper, rubber, cork, glass, bakelite and ceramic.
Convection
Convection is the process of transfer of heat by the movement of particles of a medium from one
place to another. It takes place only in liquids and gases. Occurrence of wind currents, sea
breeze, land breeze, the lower floor of a building being cooler than the upper floor, water being
warmer at the surface of a swimming pool or lake, and the pleasant atmosphere at the sea shore
are due to convection.
Radiation
The process in which heat flows from one object to another either through a medium or through
vacuum, without heating up the space in between, is called radiation. The heat absorbed from the
surroundings by a body increases its temperature. The sun warms up the earth through radiation.
A camp fire, a microwave oven and a light bulb are a few examples of objects that transfer heat
by radiation.
HD15:23
Activities & Simulations
Activity 1
Openhighschoolcourses.org has developed an interactive tutorial which explores the transfer of
heat by the three modes i.e., Heat transmission by conduction, Heat transmission by convection
and Heat transmission by radiation. Using this vitual activity we can understand the processes of
heat tansfer with the suitable examples.
Go to Activity
Activity 2
Hk-phy.org has developed an interactive tutorial which explores the transfer of heat by the three
modes i.e., Heat transmission by conduction, Heat transmission by convection and Heat
transmission by radiation. Using this vitual activity we can understand the processes of heat
tansfer with the suitable examples.
Go to Activity
Activity 3
sciencekids.co.nz has created an interactive activity to explore the heating and rise in temperture
of the bodies with respect to the time.
Go to Activity
Questions & Answers
View Unanswered Questions
Ask a Question
1 . What is the difference between clinical and labratory thermometer?
Clinical thermo meter: This thermometer is used in Clinics to measure the temperature of
human body.
A clinical t...
2 . What is the fastest and slowest mode of heat transfer ?
Answer: R adiation is the fastest mode of transfer of heat, because...
3 . Why can't sun's heat reach the earth through conduction or convection
Because space is a vacuum and conduction annd convection doesn't work in vacuum and the
only way is Radiation
4 . In places of hot climate it is advised that outer wall of houses should be painted white? Exlain
In places of hot climate the outer walls of the house are painted white as we know that the white
colour reflects the rays of the sun where...
5 . Why mercury is used as a thermometric fluid ?
The reasons for using mercury as a thermometric liquid are the following:
1. It expands uniformly when heated.
Seasons and Clothes
Summary
HD8:34
LearnNext Lesson Video
Summer Clothes
In hot weather, white or light coloured clothes suit better, because they reflect the heat away and
keep the body cool, whereas black clothes retain heat. During summer, clothes made
of cotton are preferred as they absorb the sweat and their air spaces allow the circulation of air
which helps faster evaporation of the sweat. This keeps the body cool and comfortable. Also
loose clothes allow air to circulate below the fabric. Thus, loose clothes are more suited during
summer than tight fitting clothes. Hence summer wear should be breathable, light-coloured and
loose fitting rather than dark and tight fitting.
Winter Clothes
In cold weather, dark coloured clothes have to be worn as they are good absorbers of heat.
Also woollen garments are suitable for cold weather. As wool is a very good insulator and a poor
conductor of heat, woollen clothes keep the body warm and protect it from the cold winds. Also,
the air trapped between the woollen fibres prevents the flow of heat from the body to the cold
surroundings. It also prevents the cold air from coming in contact with the body. Woollen
garments have excellent shape retention because of the crimp in the fibres. The crimp creates
many tiny air pockets that trap the warm air of the body or form a sort of insulation from the
external air. This insulating barrier of air pockets protects the body from cold winds. Sweaters,
mufflers, cardigans and woollen garments give protection from cold weather. Thus dark, thick,
woollen garments are suitable during winter.
Questions & Answers
View Unanswered Questions
Ask a Question
1 . What is the difference between clinical and labratory thermometer?
Clinical thermo meter: This thermometer is used in Clinics to measure the temperature of
human body.
A clinical t...
2 . What is the fastest and slowest mode of heat transfer ?
Answer: R adiation is the fastest mode of transfer of heat, because...
3 . Why can't sun's heat reach the earth through conduction or convection
Because space is a vacuum and conduction annd convection doesn't work in vacuum and the
only way is Radiation
4 . In places of hot climate it is advised that outer wall of houses should be painted white? Exlain
In places of hot climate the outer walls of the house are painted white as we know that the white
colour reflects the rays of the sun where...
5 . Why mercury is used as a thermometric fluid ?
The reasons for using mercury as a thermometric liquid are the following:
1. It expands uniformly when heated.
Indicators
Substances can be classified as acidic, basic or neutral.
Acidic Substances (Acids)
The word acid is derived from the Latin word acere meaning sour.Substances that taste sour
contain acids. The chemical nature of such substances is acidic.
Example: Curd, lemon juice, tamarind, spinach and vinegar.
Properties of Acids
• Acids have corrosive action on skin.
• Acids are good conductors of electricity.
• Acids neutralize bases to form salt and water.
Classification of Acids
Acids can be classified as natural and mineral acids
Natural acids are present in food.
Example: Lactic acid, citric acid, acetic acid and tartaric acid.
Common laboratory acids like hydrochloric acid, sulphuric acid and nitric acids are mineral acids
or inorganic acids.
Examples of some organic acids along with their sources
Organic acid
Sources of Organic acid
Acetic acid
Vinegar
Citric acid
Oranges, Lemons
Formic acid
Ant sting, Nettle sting
Tartaric acid
Tamarind
Oxalic acid
Tomatoes
Lactic acid
Curd
Basic Substances (Bases)
Basic substances taste bitter. The chemical nature of such substances is basic.
Bases are slippery to touch.
Example: Milk of magnesia, Soaps, Lime water, Household cleaners.
Properties of bases
• Bases are bitter to taste, soapy to touch.
• Bases are good conductors of electricity in aqueous solution. In aqueous solution, they
release ions, which conduct electricity.
• Bases liberate heat on dilution.
Neutral substance: Substance that does not show acid or base properties is called neutral
substance.
Example: Water.
You have learnt about acidic, basic and neutral substances. But how would you find out whether
a substance is acidic or basic?
One way of doing it is tasting the substance. But it is not a safe method. Certain chemicals are
used to identify the substances called indicators.
Indicators
Indicators are substances that are used to test whether a substance is acidic or basic ot neutral in
nature. They change their color when added to a solution containing an acidic or a basic
substance.
Indicators are of two types - natural and artificial.
Naturally occurring indicators are turmeric, litmus, china rose and red cabbage.
Litmus
Litmus is a natural dye extracted from lichens. It is the most commonly used natural indicator.
Litmus turns acidic solutions red and basic solutions blue. Neutral solutions do not change the
color of either red or blue litmus.
Turmeric
Turmeric gives brownish red color in basic medium and yellow in acidic medium.
China Rose
A solution of china rose turns green in a basic solution, and bright pink or magenta in an acidic
solution.
Identification of Basic Substances
Soap, milk of magnesia and limewater turn red litmus paper blue. This indicates the basic nature
of these solutions.
Soap, milk of magnesia and limewater turn turmeric red and the china rose green.
Identification of Acidic Substances
Red litmus paper when dipped in lemon juice and vinegar remains red. But they turn blue litmus
paper red. This indicates the acidic nature of these solutions.
Lemon juice and vinegar turn turmeric yellow and china rose pink.
Activities & Simulations
Activity 1
Iitm.ac has created an educational animation on “Acids, Bases and Salts”. From this students
learn about properties of acids and bases. Students will explore indicators of acids and bases.
Students can also learn more about salts, preparation and their properties.
Go To Activity
Activity 2
Kidsknowit.com has created an interactive learning animation on “Acids and Bases”. From this
animation students learn about acids and bases and how they are measured classified. Student
can also learn more about discovery of acids and bases, pH scale, behavior of acids and bases in
water, etc.
Go To Activity
Activity 3
Unnes.ac has created an activity on “Acids and Bases”. This is quiz based activity. The questions
are appropriate and stimulate the concept in student's mind. This activity will also help to
improve application knowledge of students.
Go To Activity
Questions & Answers
View Unanswered Questions
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1 . Differences between acids and bases
Acid is sour in taste while base are bitter in taste and fee l soapy on running it Acids turn Blue
litmus to red , turmeric solution to blue...
2 . All alkalies are bases but all bases are not alkalies. Explain this statement
A base is a substance that reacts with acids and neutrlize them. Some bases are soluble in water
some are insoluble. Soluble bases are calle...
3 . blue litmus is dipped in a solution .it remains blue . what is the nature of the solution ? explain
It can be either a base or the solution is neutral.For checking whether it is base or neutral you
have to dip a red litmus paper to the solu...
4 . acids,bases and salts
we need to take a lab test. classification depends upon the result
5 . Lime Water turns Milky white
Because when carbon dioxide reacts with lime water, ithe turns milky
Neutralisation
Summary
LearnNext Lesson Video
Neutralisation
The reaction of an acid with a base to give salt, water and heat is called neutralisation.
Example: Hydrochloric Acid + Sodium Hydroxide → Sodium Chloride + Water + Heat
HCl + NaOH → NaCl + H2O + Heat
The heat evolved in the neutralisation reaction raises the temperature of the reaction mixture.
Example: During the mixing of dilute sulphuric acid with potassium hydroxide, the test tube
heats up.
Indicator
The neutralisation reaction between an acid and a base can be identified by an indicator.
Example: For the reaction between hydrochloric acid and sodium hydroxide, phenolphthalein is
added as an indicator. Phenolphthalein is pink in sodium hydroxide. When hydrochloric acid is
added to it, the color slowly fades to pale pink and then colorless. This change in color indicates
neutralisation.
Classification of simple salts
Salts can be classified into acidic, basic and neutral salts.
When a strong acid reacts with a weak base acidic salts are formed.
Example: Ammonium chloride.
When a strong base reacts with a weak acid basic salts are formed.
Example: Sodium acetate.
When a strong acid reacts with a strong base neutral salts are formed.
Example: NaCl, KNO3, CaBr2.
Properties of salts
Melting and boiling points
Most of the salts are solids. And they have high melting and boiling points.
Solubility in water
Generally salts are soluble in water.
Examples: Sodium chloride, Potassium sulphate, Ammonium carbonate and aluminium nitrate
are soluble in water.
Silver chloride, lead chloride, copper carbonate, etc., are the examples for water insoluble salts.
Water of crystallization
Some salts have a fixed number of water molecules as an essential part of their crystal. These
water molecules which form the part of the crystal are called water of crystallization and such
salts are called hydrated salts. These water molecules are responsible for the crystal its shape
and color of some crystals. In general they exist as dry in pure form. These salts on heating lose
water molecules in them and forms anhydrous salts.
For example, in your laboratory, the blue coloured copper sulphate is copper sulphate penta
hydrate. When heated, this salt loses its water molecules as a result the copper sulphate crystal
lose its shape and color and changed to a powdery substance.
CuSO4.5H2O (On heating) → CuSO4 + 5H2O
Neutralisation in Daily Life
Neutralisation in Digestion
The stomach contains hydrochloric acid, which helps in the digestion of food. If this acid is
produced in excess, it causes indigestion, which is painful.
An antacid such as milk of magnesia neutralises the excessive acid in the stomach, and
provides relief from the pain due to indigestion.
Neutralisation- Ant Sting
Ant sting contains formic acid. When an ant bites, it injects this formic acid into the skin. This
causes pain.
It can be neutralised by rubbing the ant bite with moist baking soda, which contains sodium
hydrogen carbonate (NaHCO3), or with a solution of calamine, which contains zinc carbonate
(ZnCO3).
Neutralisation - Acidic Soil
Excessive use of fertilisers makes soil acidic. As a result, plants cannot grow properly, and the
yield decreases. Adding a base like quick lime, (calcium oxide) or slaked lime (calcium
hydroxide) neutralises the soil and makes it suitable for plants.
Similarly, when soil is basic in nature, organic matter is added to release acid and make it
neutral, and thus, suitable for plants.
Neutralisation - Factory Wastes
Factory waste contains acids. This waste must be treated with bases for neutralisation before it is
released into a water source. Otherwise, it can cause damage to living organisms in the water
source.
Uses of some salts
Name of the salt
Sodium chloride NaCl (Common salt)
Uses
To preserve pickles, fish and meat.
As a raw material for the manufacture of other
compounds.
Sodium carbonate -
Used to manufacture of glass, cleansing
Na2CO3.10H2O (Washing
agents, soap, glass and paper, sodium
soda)
compounds like borax.
Sodium bicarbonateNaHCO3(Baking soda)
Used in bakery and antacids
Ammonium nitrate - NH4NO3 Used in fertilizers
Potash alum K2SO4.Al2(SO4)3.24H2O
Silver nitrate
YouTube Video
Used in purification of water
Used in photography
Activities & Simulations
Activity 1
Intel.co has created a wonderful activity on “Neutralisation Reactions”. In this activity Students
learn about everyday neutralisation reactions with help of examples. There are many daily life
examples of neutralisation reactions. These examples are explained with a beautiful animation.
At the end of the animation students can also get test paper to test their knowledge.
Go To Activity
Activity 2
Taskermilward.org has created an animation on “Neutralisation Reactions”. This animation will
help to students to visualise the changes that are taking place during neutralisation reaction. This
animation is very helpful to the students because it is showing the neutralisation reactions at the
ionic level.
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Questions & Answers
View Unanswered Questions
Ask a Question
1 . Differences between acids and bases
Acid is sour in taste while base are bitter in taste and fee l soapy on running it Acids turn Blue
litmus to red , turmeric solution to blue...
2 . All alkalies are bases but all bases are not alkalies. Explain this statement
A base is a substance that reacts with acids and neutrlize them. Some bases are soluble in water
some are insoluble. Soluble bases are calle...
3 . blue litmus is dipped in a solution .it remains blue . what is the nature of the solution ? explain
It can be either a base or the solution is neutral.For checking whether it is base or neutral you
have to dip a red litmus paper to the solu...
4 . acids,bases and salts
we need to take a lab test. classification depends upon the result
5 . Lime Water turns Milky white
Because when carbon dioxide reacts with lime water, ithe turns milky
Physical and Chemical Changes
Summary
HD14:59
LearnNext Lesson Video
Change is all around us and happening constantly. Some changes are physical and some are
chemical.
Physical change: A change in the physical properties such as shape, size, color and state of a
substance is a physical change.
Examples of physical changes are melting of ice, boiling of water, freezing of water,
Condensation, Crystallization and heating of metalsto red hot, etc.
Characteristics of a physical change:
• Physical changes are generally reversible.
• Temporary in nature.
• No new substances are formed when a physical change takes place.
• Energy in the form of heat, light and temperature is not emitted.
Chemical Change: A chemical change occurs when one or more substances are converted into
one or more new substances.
Examples: Formation of rust on the iron bench or articles of iron kept in the open for a long time,
Digestion of food, burning of magnesium ribbon, the reaction between vinegar and baking soda,
etc.
Characteristics of a Chemical change:
• A chemical change is permanent.
• A new substance is formed.
• Forms of energy, such as heat, light or electricity, may be emitted or absorbed during a
chemical reaction.
• A chemical change is generally irreversible.
Rusting: If articles made of iron are left in open air for some time, they get coated with a brown
powdery substance, called rust. This process of iron changing into rust is called rusting.
Rusting of iron occurs only if iron comes in contact with moist air.
The process of rusting can be represented as:
Fe + O2 (from air) +H2O (water) → Fe2O3 (rust)
Prevention of Rusting: Rusting can be prevented by adopting any of these methods.
• Galvanisation - It is the process of depositing a layer of zinc on iron.
• Alloy formation - Stainless steel is an alloy.
• Painting an iron surface.
Some chemical changes in laboratory
Burning of magnesium ribbon
When magnesium ribbon burns in oxygen it forms magnesium oxide.
2Mg + O2 → 2MgO
If water is added to magnesium oxide magnesium hydroxide is produced.
MgO + H2O → Mg(OH)2
The change from magnesium to magnesium oxide and then to magnesium hydroxide is an
example of a chemical change
Reaction between vinegar and baking soda
Add a pinch of baking soda to this test tube which contains vinegar. You would observe a strong
effervescence along with a hissing sound. This is due to the evolution of carbon dioxide gas.
Vinegar (acetic acid) + Baking soda (sodium hydrogen carbonate) → Carbon dioxide + water +
Other substances
This reaction between vinegar and baking soda is a chemical change.
When carbon dioxide gas is passed through freshly prepared limewater turns it milky.
Carbon dioxide (CO2) + Lime water [Ca(OH)2] → Calcium Carbonate (CaCO3) + Water (H2O)
This reaction between carbon dioxide and lime water is a chemical change.
Reaction between copper sulphate solution & iron nail
Put an iron nail in blue colour copper sulphate solution and wait for half an hour. The solution
turns light green and the iron nail acquires a brown colour deposit on it, which is of copper.
Copper sulphate solution (blue) + Iron → Iron sulphate solution (green) + Copper (brown
deposit)
This change in colour of the solution is a chemical change.
Activities & Simulations
Activity 1
Ohiou.edu has created an interactive animation on "Physical and Chemical changes". This
module teaches the physical and chemical changes with the help of examples. Each example
contains a beautiful animation. Student has to identify and mark the type of change. After
marking on the type of change student will get answer along with clear explanation.
Go To Activity
Activity 2
Mheducation.com has created student friendly animation on “Physical and Chemical Changes”.
Students learn different types of changes with proper demonstration. Students can also learn
more about properties of physical and chemical changes and differences between physical and
changes.
Go To Activity
Activity 3
Elearning.cmu has created an interactive educational video on “Physical and Chemical
Changes”. This video teaches different types of changes with real life examples. This is a student
friendly animation which reflects the concept into student's mind.
Go To Activity
Questions & Answers
View Unanswered Questions
Ask a Question
1 . what is the difference between 2O and O2?
20 means twenty because if we add 0s to the right it has value but in the left it doesn't so 20
means twenty and 02 is two ( zero doesn't ha...
2 . advantage and disadvantage
Ans: Some chemical reactions produce useful products that can be very helpful and at the same
time they may produce by-prod...
3 . Explain why rusting of iron object is faster in coastal area than desert?
Because in coastal regions humidity and moisture is more in air than in deserts and rusting only
takes place when iron come in contact with...
4 . Symbols
'C' represents only Carbon element. Remember that if one symbol represents particular element,
it cannot be used to represent other element...
5 . Why is burning of paper chemical change and tearing of paper doesnot?
Tearing paper is a physical change. Because tearing paper changes its shape and size but not its
chemical composition,Still it is paper
Weather and Climate
Summary
The day-to-day conditions of the atmosphere at a place with respect to elements like temperature,
humidity, rainfall, wind speed, etc. is called the weather of that place.
Changes in weather are observed in the atmosphere. The atmosphere is all around us – we cannot
see it, but it keeps us warm. Without it, the earth would be a lifeless ice ball. In addition, the
atmosphere absorbs or deflects the incoming ultraviolet rays and other charged particles.
Constituents of weather
Weather is made up of elements like rainfall, temperature, humidity, wind speed, snow, thunder
and lightning.
Factors effecting weather
The sun is responsible for all the changes in the weather. We know that the sun is a huge sphere
of hot gases and has a very high temperature. The distance between the sun and us is very large.
The sun is the chief source of light and heat for the earth. It is also the primary source of energy,
and causes changes in the weather.
The energy absorbed and reflected by the earth’s surface, the oceans and the atmosphere play an
important role in determining the weather at any place. Also, gases like carbon dioxide, methane
and water vapor play a role in determining the weather.
Place and weather
The weather in coastal areas is very different than that in a desert or hilly areas. The maximum
and the minimum temperatures of a place are recording using a special type of thermometer
every day. Special thermometers called maximum and minimum thermometers are used to
determine the maximum and the minimum temperatures in a day.
The maximum temperature of the day is recorded during the afternoon, while the minimum
temperature is recorded early in the morning.
Measuring the components of weather
Different types of measuring instruments are available to measure different weather components
like temperature, rainfall, windspeed, humidity etc.
Measuring temperature of a place
The change in the temperature of the day. The temperature is low early in the morning, and
increases by noon. It decreases again towards the evening, and the cycle continues.
The instrument useful to measure the temperature of a place is thermometer. Inorder to measure
the highest and lowest temperature of a place is maximum minimum thermometer (MMT).
Measuring rainfall
In general meterologists measures the rainfall by using a "Rain gauge" also called as
Ombrometer or Puliometer expressed in centimeters or millimeters.
Measuring the direction of wind
The direction of wind and speed by using Anemometer.
Measuring humidity of a place
" Quantity of moisture in the air is the humidity of the place". It feels more sweaty when
humidity is high and high temperature.
Climate of a place
In winters, it gets dark early. Meteorologists record the weather every day. The records of the
weather are preserved for several decades. These records helpful to determine the pattern of the
weather at a place. The average weather pattern taken over a longer time is called the climate of
the place.
The mean temperature for a given month is found in two steps. First, we find the average of the
temperatures recorded during the month. Next, we calculate the average of such temperatures
over many years. The result is the mean temperature.
Mean temperature helps compare the weather at two different places. For example, if we
compare the temperatures of Thiruvananthapuram in Kerala and Srinagar in Jammu and
Kashmir, we can conclude that Thiruvananthapuram is very hot and wet than Srinagar, which
is moderately hot and wet for some parts of the year.
Consider another place like Rajasthan, which has high temperatures during most parts of the
year, but very low temperatures in winter, which lasts for a few months. This region receives
scanty rainfall. Therefore, it is known as typical desert climate.
North-eastern India receives rain for a major part of the year. Hence, we can say that the climate
of the region is wet.
Activities & Simulations
Activity1:
Oceanservice.noaa.gov has developed an interactive simulation to guide the knowledge of
weather and climate of a different places of the world. The difference in colours will give you
basic information of a particular place.
Go to Activity
Activity2:
Lessons.e-learningforkids.org has developed an interactive simulation regarding weather and
climate starting from the basic levels of understanding the concept. Followed by questions which
involves drag and drop of images in respective places of weather conditions, this enables you to
move into next level.
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Activity3:
Cotf.edu has developed an interactive quiz and questions are based weather and climate. Each
question is followed by explanation.
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Questions & Answers
View Unanswered Questions
Ask a Question
1 . How do elephants living in the tropical rainforest adapt themselves?
They have large ears for hearing very low voices and for cooling themselves.
2 . list three adaptation in animals to prevent heat loss from the body giving one example for
each case?
Ans: Adaptation of the animals lived in Polar Regions:
1. They have thick layers of fur which keeps them warm in
...
3 . Explain, with examples, why we find animals of certain kind living in particular climatic
conditions.
Q1 Explain, with examples, why we find animals of certain kind living in particular climatic
conditions.
Answer: Climate has...
4 . what are adaptations of fish , red frog ,monkeys ,whale ,camel?
Fishes have developed streamlined shape to move easily in water Red frogs have developed
sticky pads on feet to climb easily on trees Monkey...
5 . list three adaptions in animals which keep their body cool giving one example for each case?
Ans: Adaptations of animals living in hot climate:
They have thin layer of fur under their bellies so that lesser
Climate and Adaptations
Summary
time is called the climate of the place.
Different parts of the earth have different types of climate. The sun is responsible for this
difference in climatic conditions.
Climate is described in terms of overall temperature distributions and air pressure. Based on the
precipitation and the temperature five major types of climates are recognised. They are,
• Moist tropical climate
• Dry climate
• Humid middle latitude climate
• Continental climate
• Cold climate
Moist Tropical Climates are known for their high temperatures and large amount of rain around
the year.
Dry Climates are characterised by little rain and a high daily temperature range.
In Humid Middle Latitude Climates, land or water differences play a key part. These climates
have warm, dry summers, and cool, wet winters.
Continental Climate is characterised by winter temperatures low enough to support a fixed
period of snow cover every year, a relatively moderate precipitation occurring mostly in summer,
and an even distribution of precipitation.
Polar areas have cold climates as they are covered by ice almost all the year round. Most areas
are covered by glaciers or by a semi-permanent layer of ice.
Climate has an intense effect on all living organisms. Animals adapt themselves to survive
various conditions in which they live. Animals that live in extreme climates acquire some special
features to protect themselves from it. Animals evolve to acquire these features and habits to
adapt to their environment.
Example: The camel has a hump to store food in the form of fat, and hooves to tread on the
desert sand with ease.
Adaptation of animals in Polar region
Regions like, Canada, Greenland, Iceland, Norway, Sweden, Finland, Alaska in the United States
and Siberia in Russia are in the northern polar region.
The temperature in the polar areas may go down to -370C during winters.
Animals like polar bears, penguins and many types of fish, musk oxen, reindeer, foxes, seals,
whales and birds are found in the polar regions.
Adaptation in Polar bears - Camouflage
• Polar bears protect themselves with the thick fur on their bodies.
• They have two layers of fur for protection from the extreme climate.
• They also have a layer of fat under the skin, and are very well insulated. In fact, they often
take rest to avoid getting overheated.
• The polar bear often goes for a swim to cool off on warm days. Its wide and large paws are
useful for swimming as well as for walking on the snow.
Adaptation in Penguin
The bodies of penguins are white, and merge into the background. They have a thick layer
of skin and move around in groups to keep warm.
Their streamlined bodies and webbed feet make penguins swift swimmers.
Fish survival in Polar region
Water retains its warmth under the icy layer. Fish go deeper in the water to stay warm.
Migration of Siberian cranes
Birds have to stay warm to survive. Hence, at the onset of winter, these birds migrate to warmer
areas. They come back again in the summer.
Siberian cranes migrate to far-off places like Bharatpur in Rajasthan, Sultanpur in Haryana and
also to some wetlands of north-eastern India. They fly here all the way from Siberia. Birds travel
thousands of kilometers to migrate. During the day, the sun guides them, and the stars do so in
the night.
Tropical rain forests
Tropical rain forests spread around the equator. Temperatures like 15°C in winter and 40 ° C in
summer are characteristic features of this region. Day and night are of equal duration through
year. The Western Ghats and Assam in India, South East Asia, Central Africa and the Amazon in
Central America experience this type of climate.
These regions receive abundant rainfall. A significant feature about this region is
the tropical forest.
A wide variety of plants and animals are found in these regions due to the continuous
warmth and rain.
The major types of animals living in this type of rainforests are monkeys, apes, gorillas, lions,
tigers, elephants, leopards, lizards, snakes, birds and insects.
Adaptation in Tropical Rain Forests
• Most of the tropical animals have sensitive hearing, sharp eyesight and thick skin. They
also have skin colour that helps them to disguise and protect themselves from predators.
• All animals have some special feature, like good eyesight, sharp claws, long beaks,
sensitive hearing or long trunks, to protect themselves.
• Some animals of the rainforest have special features that help them to find food and live on
trees.
For example, a toucan has a long, large beak. This helps it to reach the fruits on branches that are
otherwise too weak to support its body weight.
• Red-eyed frogs have sticky pads on their feet to help climb trees. Monkeys also have long
tails that help them to hold on to branches. This is how they adapt to find food and live on trees.
• A lion-tailed macaque stands out for the silver-white mane that covers the head from the
cheeks to the chin. It is also known as a Beard ape and can climb very well. It survives mainly on
fruits, seeds, stems, young leaves, flowers and buds. Macaques spend the maximum time of life
on trees as they get sufficient food on the tree itself.
• The elephant has such large ears and tusks. The tusks are modified teeth and are used to tear
the bark of trees for food. The large ears help it hear even very soft sounds. They also keep it
cool in this hot and humid climate.
Activities & Simulations
Activity1:
Hyperstaffs.info has developed to help you in learning climate and factors affecting climate. This
simulation gives valuable information about climate of a different places of the world. It also
includes activities, quizes regarding different places of world.
Go to Activity
Activity2:
Ecokids.ca has developed an interactive quiz based on climate and adaptations of animals for the
climate. Each explanation has followed by interesting questions.
Go to Activity
Activity3:
Sutton.gov has developed an interactive simulation based factors affecting climate and global
warming. This explains about the factors polluting our climate and causing global warming and
also shown that how these further damages the climate of different places.
Go to Activity
Questions & Answers
View Unanswered Questions
Ask a Question
1 . How do elephants living in the tropical rainforest adapt themselves?
They have large ears for hearing very low voices and for cooling themselves.
2 . list three adaptation in animals to prevent heat loss from the body giving one example for
each case?
Ans: Adaptation of the animals lived in Polar Regions:
1. They have thick layers of fur which keeps them warm in
...
3 . Explain, with examples, why we find animals of certain kind living in particular climatic
conditions.
Q1 Explain, with examples, why we find animals of certain kind living in particular climatic
conditions.
Answer: Climate has...
4 . what are adaptations of fish , red frog ,monkeys ,whale ,camel?
Fishes have developed streamlined shape to move easily in water Red frogs have developed
sticky pads on feet to climb easily on trees Monkey...
5 . list three adaptions in animals which keep their body cool giving one example for each case?
Ans: Adaptations of animals living in hot climate:
They have thin layer of fur under their bellies so that lesser
Air Pressure
Summary
Air Pressure
Air exerts pressure in all directions. The pressure exerted by air is called the air pressure, which
is the thrust exerted by air per unit area. The weight of the air acting on a unit surface area is
called the atmospheric pressure.
To show that air exerts pressure, take a glass and fill it with water. Cover the mouth of the glass
with an index card. Now hold the card in place and invert the glass over a sink and remove your
hand from the card. The card sticks to the glass. This is because air exerts pressure on the
card from below to keep the card in place. Here the pressure exerted by air upwards is more than
the pressure exerted by water downwards.
Winds
Air expands on heating and contracts on cooling. Warm air, being lighter than cool air, rises up,
whereas relatively cooler air, being heavier than the warm air, sinks towards the earth's surface.
This is due to convection, a mode of transfer of heat. As warm air rises up, reducing air pressure
at that place, cool air moves in to take the place of warm air. Moving air is called wind. Winds
are caused by variations in air pressure. A wind blows from a region of high pressure to a region
of low pressure. The speed of the wind mainly depends on the difference between the pressures
of the air in the two regions. When air moves at high speeds, it creates a low pressure area. High
speed winds are known to blow away thatched and tiled roofs in rural and semi-urban areas.
Strong winds can uproot trees and electric poles, and even snap cables.
Anemometer
The instrument used to measure the speed of wind is called an anemometer. It is usually fixed on
top of a building.
Winds
Summary
Air expands on heating and contracts on cooling. To prove this we can perform the following
activity. Take two deep pans - one filled with hot water and the other with cold water. Stretch a
balloon across the mouth of a milk bottle and seal it with tape. Keep this bottle in the hot water
pan. The balloon gets slowly inflated. This is because the heat from the hot water in the pan heats
up the air inside the bottle, which makes the air inside the bottle expand. Now place the bottle in
the pan containing cold water. The balloon deflates and shrinks. This is because the air inside the
bottle gets cooled and hence contracts.
Warm air, being lighter than cool air, rises up, whereas relatively cooler air, being heavier than
the warm air, sinks towards the earth's surface. As warm air rises up, air pressure at that place
reduces and cool air moves in to take the place of warm air. Moving air is called wind. Air
moves from the region of high air pressure to the region of low air pressure. The greater the
difference in air pressure, the faster the air moves. The increased wind speed is accompanied by
a reduced air pressure.
Wind Currents
Wind currents occur due to (a) uneven heating between the regions near the equator and the
poles and the rotation of the earth and (b) uneven heating of land and water in coastal areas. The
equatorial and tropical regions get hotter than the polar regions as they get maximum heat from
the sun. The warm air at the equator rises, and the cold air moves in from the polar regions. The
air moves due to uneven heating of the earth’s surface between the equator and poles, which
results in the circulation of wind across the globe. But the wind flow is not in the exact northsouth direction because a change in direction is caused by the rotation of the earth.
Monsoon Winds
The word monsoon is derived from the Arabic word "mausam," which means season. The winds
from the ocean carry water in the form of water vapours, resulting in rains over land. These are
called monsoon winds.
Thunderstorms and Cyclones
Summary
Thunderstorms
Storms are severe atmospheric disturbances accompanied by very strong, high-speed winds.
Thunderstorms are whether conditions characterised by thunder, lightning and heavy rain. They
occur due to the convection of air in hot and humid tropical areas. As the air near the earth's
surface warms up, it rises. This results in strong upward rising winds which carry moisture with
them. The moisture condenses into water droplets in the cooler, upper regions of the atmosphere.
The water droplets fall down as rain or freeze and fall as hail. The rising air and the
rapidly falling water droplets and ice crystals collide with each other and produce static electric
charges. As a result the clouds get charged. When electric discharge occurs between the clouds
or between a cloud and the ground, lightning occurs. The lightning heats up the air in its path
very quickly and this results in a loud sound which we hear as thunder.
Precautions During a Thunderstorm
• Move away from open garages, metal sheds and water bodies.
• You may sit inside a car, a bus or a closed vehicle, or inside a building.
• Do not take shelter under an isolated tree. If in a forest, take shelter under a small tree.
• Do not take shelter under an umbrella with a metallic end.
• Do not sit near an open window.
• If you are in water (swimming pool, river, etc.) get out and go inside a building.
Cyclone
A cyclone is a natural calamity caused by difference in air pressure in the atmosphere. It is a
violently rotating wind storm. It develops over the sea and may move over the land causing great
damage. Cyclones begin as thunderstorms and later develop into cyclones. They are associated
with strong winds, heavy rains and tidal waves. In tropical regions like India, thunderstorms are
common, but very few thunderstorms become cyclones. In India, the eastern coast is more
vulnerable to cyclones than the western coast.
In different parts of the world, cyclones are known differently. For example, in America, a
cyclone is referred to as a hurricane, while in Philippines and Japan it is called a typhoon.The
largest tropical cyclone recorded was Typhoon Tip that struck Japan in 1979. At its peak
strength, the diameter of its eye wall was 2220 kilometres. The wind speeds were recorded at 305
kilometres per hour.
Formation of Cyclones
The formation of a cyclone depends on the speed and direction of the wind, temperature and
humidity. Humidity is the amount of water vapour in the atmosphere. As the humidity in a region
increases, the difference in temperature also increases. A cyclone arises due to the difference in
the temperatures between two regions. A low pressure is created as the air in the high
temperature region becomes warm and rises. The gap in the low pressure area is filled by cold air
rushing in from the surrounding areas. When the warm air rises, it cools, condenses and forms
clouds. When the water vapour in the clouds turns into rain drops, the heat possessed by the
water vapour is released into the atmosphere. The process repeats and the release of heat from
the water vapour continues. Falling water droplets and rising air move vigourously to produce
thunderstorm, which develops into a cyclone under certain weather conditions. The calm and
clear area at the centre of a cyclone is called the eye of the cyclone.
Tornado
A rotating column of high speed winds that appears as a dark funnel-shaped cloud reaching from
the ground to the sky is called a tornado. A tornado may form within a cyclone. A tornado forms
due to the effect of low pressure in the eye of a cyclone. Objects near the base of a tornado, such
as cars, dust, debris and even houses, are sucked into its funnel and thrown out at the top.
More than a thousand tornadoes occur every year across the world. Most occur in the United
States of America. Tornadoes occur regularly in the regions around the Atlantic Ocean. Weak
tornadoes travel with wind speeds of 50 to 60 km/h, while a violent tornado can travel at a speed
of about 400 km/h. A tornado is a natural disaster, but not as dangerous as a cyclone.
A tornado shelter is a room situated underground or in the interior of a building with no
windows. If tornado shelter is not available, it is advisable to shut the windows and take shelter
under a table.
Protection from Cyclones
Destruction Caused by Cyclones
Cyclones cause a lot of damage to land, people and property, and create a lot of havoc in the
lives of the people. When a cyclone hits an agricultural field, it makes the land infertile and
useless for agriculture. A cyclone spares nothing. It worsens the flood situation. There are
indirect impacts of a cyclone as well, such as flooding in coastal areas. Flooding not only
damages land, but also pollutes drinking water sources. This can cause epidemics. High-speed
winds during a cyclone can cause major damage to houses, human beings, animals, trees, power
supply, and even communication systems such as telephones.
High waves several kilometres away from the shore indicate an upcoming storm. As a cyclone
strikes the coast, the intense winds raise the water into a gigantic wave that is pushed towards the
shore. A high wall of water moving towards the shore from the ocean is called a storm surge.
The combination of a storm surge and a tide is known as a storm tide. The most dangerous
storms are the ones where the storm surge arrives on top of a high tide, and then the storm
reaches an area that might otherwise have been safe.
Names of Tropical Cyclones
Tropical cyclones are given names. The names are selected from a list decided by the national
meteorological organisation of a country, or by a committee of the World Meteorological
Organisation. The names of tropical cyclones that cause major death or destruction are not used
again, as a tribute to the people who lose their lives in the disaster.
Safety Measures Taken by the Government
To keep people safe and secure during a cyclone, the government takes certain measures, such
as:
• Constructing cyclone centres in the cyclone prone areas
• Making arrangements to relocate people during cyclones
• Providing information about a cyclone, and warning people, fishermen, ships, ports, airlines
and various government
agencies
• Delivering accurate and effective cyclone forecasts and warnings
Cyclone Forecasting and Warning
The development and movement of cyclones is studied with the help of INSAT satellite and a
series of Cyclone Detection Radars installed along the coastal belt of India. With the help of
modern technology, a cyclone alert or cyclone watch is issued 48 hours in advance of any
expected storm and a cyclone warning is issued 24 hours in advance. The message is broadcast
every hour with the help of TV and Radio.
Safety Measures to Follow before and during a Cyclone
• Do not move out unless and until required.
• Keep a note of all the warnings given by the Meteorological Department.
• Keep emergency phone numbers of police, ambulance and fire brigade handy.
• Move people and valuable items to a safe place.
• Store hygienic drinking water.
• Help neighbours and friends.
• Avoid contact with wet electric lines and switches.
• Store enough food items in waterproof bags.
• Avoid going in flood water and be careful of snake bites.
Soil Profile
Summary
Soil is the upper layer of earth in which plants grow and is usually composed of a mixture of
organic remains, clay, and rock particles.
(or)
Soil is the upper layer of earth in which plants grow and is usually composed a mixture of rock
particles and humus.
Soil is a natural resource that is essential for life. Soil is used as a source for food, clothing,
shelter, minerals, coal, bricks, mortar, pottery and porcelain. Soil provides water and minerals to
plants for their growth. Thus all living organisms depend on soil.
Soil Formation - Weathering:
Soil is formed when rocks are broken down by the action of wind, water and climate. This
process is called weathering. The characteristic features of a soil depend upon the rocks from
which it has been formed and the kind of plants that grow in it.
Weathering Types: Weathering is of two types
• Physical Weathering
• Chemical Weathering
Physical Weathering: Physical weathering is also termed as mechanical weathering, in which
the composition of the original rock is unaffected. In this process the rocks and landforms are
broken down into smaller pieces by physical forces like wind, frost, ice and temperature changes.
Chemical Weathering: In this process the mineral composition of the rock get changed due to
the action of chemical agents like water, oxygen, carbon dioxide, etc. This is caused when
chemical agents like water reacts with minerals in rocks to form new minerals and soluble salts.
Soil Profile: If you examine the sides of a ditch that has recently been dug up or the sides of a
road on a hill, you will find that the soil forms layers of particles of different sizes. You will
notice that each layer is different from the other in texture, colour and chemical composition.
Even the thickness of each layer is not the same.
A vertical section that shows different layers of soil is called a soil profile. Each layer is called
a horizon.
Horizons are classified into 4-types. They are,
• Top soil or Horizon-A
• Middle layer or Horizon-B
• Horizon-C
• Bed rock
Horizon-A: The topmost layer is dark in color, and contains the remains of dead plants and
animals. This rotting matter is called humus.
This layer of soil is called topsoil or A-horizon.
It is made up of humus and minerals, and makes the soil fertile.
It is soft and porous, and can retain more water than the other layers.
Many tiny organisms, such as beetles, worms and rodents, live in the topsoil. The roots of small
plants do not go down very deep and can be found in the topsoil.
Horizon-B: The layer below the topsoil is called B-horizon or the middle layer.
The middle layer is less porous than the topsoil, and is, therefore, harder.
It contains more minerals as compared to the topsoil, but less quantity of humus.
Horizon-C: It is not as compact as the two layers above it. This layer is called C-horizon.
It has cracks running through it.
It is mostly made up of rocks.
Bedrock: The bottom-most layer in the soil profile is called bedrock.
This is far more solid in composition than the other layers and is very hard. This layer consists of
the parent rock.
Soil erosion: Soil erosion is removal of land surface by agents like floods, wind and ice. Plant
roots firmly bind to the soil. When trees are removed soil become loose and it easily carried
away by wind or flowing water. Soil erosion is severe in areas of little or no surface vegetation,
such as deserts and barren lands. Therefore, cutting of trees and deforestation should be
prevented and efforts should be made to increase greenery.
Due to soil erosion the fertile soil is washed away. This causes a decrease in the net fertile land
available for cultivation.
The major causes of soil erosion:
• Deforestation
• Overgrazing
• Floods and heavy rain fall
• Improper farming
Prevention of soil erosion:
• Afforestation – Planting large number of trees.
• Constructing dams - Floods can be controlled by constructing dams.
• Construction of embankment or mud walls around hill slopes to prevent flow of water.
• Adopting terrace farming in hilly areas - In this method the ground is cut into large steps
called terraces. On each level suitable crops are grown. This reduces the speed with which water
flows down, water stops at each level. In this way higher terrace will get enough water and soil
erosion is reduced.
Soil Types and its Properties
Soil has some characteristics that form the basis for its classification into various types, and also
the types of crops that are grown in it.
These properties are,
• Absorption of water
• Moisture in the soil
• Percolation rate of water in soil
Absorption of water: The capacity of the soil to hold water before it starts dripping is called its
water absorption capacity. All types of soil do not absorb water in the same way.
This property of soil can be understood by performing an activity using plastic funnel with filter
paper. A dry powdered soil is poured in the funnel. Now pour water drop by drop on the soil.
Pour water evenly over the soil; continue pouring till the water starts dripping.
The percentage of water absorbed is calculated by using the following formula
= U - VSolid Weight×100U - VSolid Weight×100
Where,
U= Initial weight of water
V = Final weight of water
Moisture in the soil: Soil moisture is the water content present inside it as moisture and it is
available for evaporation.
Moisture content of the soil is mainly depends on the type of soil. Soil moisture plays a major
role in the plant growth because plants always depend on the moisture content available at roots.
The moisture content in the soil can be observed by heating a little bit of soil in a boiling tube.
Percolation rate of water in soil: The phenomenon of absorption of water by soil is termed
as percolation. The rate of absorption is different for different types of soils. The rate of
absorption of a soil depends on its composition. A soil with more percolation rate can hold water
for longer time. On the other hand a soil with poor percolation rate will hold water for
shorter time. Percolation rate helps in selection of suitable soil for crop growth.
Percolation rate =Amount of water (ml)Percolation time (min)Percolation rate =Amount of water
(ml)Percolation time (min)
Types of soil: Soil is not similar everywhere. Soil is classified into various types based on the
appearance and proportion of particles.
• Sandy soil
• Clay soil
• Loamy soil
Sandy soil: Sandy soil is made of greater proportion of big particles like sand. They cannot fit
closely together. So, there are large spaces between them. These places are filled with air.
Therefore, in this type of soil, water absorption is very high as the water passes quickly through
these spaces. These soils are light, well aerated and dry.
Clayey soil: Clayey soil is made of a relatively higher proportion of fine particles. Unlike sandy
soils, these soils have very less space between particles. Because the particles are smaller in size,
water can be trapped in the tiny gaps between them. Clay soils are heavy and hold more water.
Loamy soil: Loamy soil is a mixture of sand, soil and silt. Silt particles are present between
sand and soil particles. It also contains humus, and is, therefore, considered the best for the
growth of plants. The percolation rate is between that of sandy soil and clay soil.
Soil and crops: Climatic factors as well as the components of the soil determine the types of
vegetation and crops that grow in a particular area.
• Cereals like wheat and gram are grown in clay and loamy soils, because these soils have
better water retention capacity.
• Soils rich in clay and organic matter with good water retention capacity are ideal for paddy.
• Loamy soils, which drain water easily, are suitable for lentils and other pulses.
• For cotton, loamy or sandy soils are more suitable, because of their water draining and air
logging capacity.
• Clay soils are rich in humus and fertile. These soils are very good for wheat.
Respiration
Human body is made up of cells. Cells perform different functions like growth, excretion,
reproduction, etc. A cell
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needs energy to perform all these functions.
The digestive system converts the food we eat into glucose. Blood absorbs glucose and
transports it to the cells. In the cells, this glucose is broken down to release energy.
Respiratory system helps in taking in oxygen by the body. When we inhale air, oxygen enters the
lungs. From the lungs, the oxygen is absorbed by the red blood cells and is supplied to all the
cells in the body. This oxygen is utilised in breaking down glucose to release energy in the form
of ATP.
Respiration
Respiration is the process of taking in oxygen, using it in oxidation of glucose, releasing energy
and eliminating waste products like carbon dioxide and water in the presence of respiratory
enzymes. Respiration is brought about in two steps namely external respiration and internal
respiration.
a) External respiration is also called as breathing.
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It involves inhalation and exhalation. Inhalation is the process of taking in air rich in oxygen.
Exhalation is the process of releasing out air rich in carbon dioxide.
b) Internal respiration is also called as cellular respiration.
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Cellular respiration is a chemical reaction which involves oxidation of food.
It is the breakdown of glucose in a cell to release energy.
Cellular respiration is a slow process which occurs at body temperature.
Cellular respiration is observed only in living cells.
Cellular respiration involves release of energy at various steps.
The energy released will be stored in the form of ATP molecules.
Chemical reaction of respiration
C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy
Types of respiration
Respiration can be of two types namely, aerobic respiration or anaerobic respiration. Aerobic
and anaerobic respiration are the processes which involve release of energy by exchange of
gases. Both these reactions occur inside the cell.
a) Aerobic respiration is the process of breaking up of glucose into carbon dioxide and water in
the presence of oxygen with release of energy. Aerobic respiration takes place in almost all the
animals.
b) Anaerobic respiration is the breakdown of glucose in the cell in the absence of oxygen.
Glucose is converted into alcohol and carbon dioxide with release of little amount of energy.
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Anaerobic respiration can also be seen in yeast. The breakdown of glucose in the absence of
oxygen in yeast forms alcohol, energy and carbon dioxide. Yeasts and other organisms that
respire in the absence of oxygen are also known as anaerobes. As yeast is a unicellular organism
that respires anaerobically to yield alcohol, it is used in the production of beer and wine. Yeast is
used in beverage industries to produce beer and wine by the process of fermentation.
Fermentation is the process of breaking down glucose into alcohol and carbon dioxide releasing
little amount of energy. Fermentation is otherwise called as anaerobic respiration.
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Anaerobic respiration is observed in muscle cells. Accumulation of lactic acid inside the cells
leads to muscle cramps. Supply of oxygen will break down lactic acid into carbon dioxide and
water. Hot water bath relieves muscles from cramps by converting lactic acid into carbon dioxide
and water.
Differences between aerobic and anaerobic respiration
AEROBIC RESPIRATION
Glucose is completely oxidised into
carbon dioxide and water.
ANAEROBIC RESPIRATION
Glucose is incompletely oxidised into
alcohol and carbon dioxide.
This type of respiration takes place in This reaction takes place in the
the oxygen rich environment.
insufficiency of lack of oxygen.
It takes place in the mitochondria of
cellular environment.
It takes place in the cytoplasm of the
cell.
It is harmless to the organisms.
It shows side-effects and is toxic to
plants.
Respiration in plants
During day time, plants utilise carbon dioxide to perform photosynthesis and release out oxygen.
During night, plants respire taking in oxygen and releasing carbon dioxide. Exchange of gases in
plants takes place through special structures called the stomata.
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Stomata are the small structures present in the epidermal cells located on the surface of the
leaves. Stomata with its guard cells is called as stomatal apparatus.Opening and closing of
stomata is brought about by special structures called as guard cells under the influence of amount
of moisture and sunlight. Gases are just exchanged between the leaves and outside environment
through stomata.
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Roots also respire during which they utilise oxygen stored in the air spaces between the soil
particles. Over watering of potted plants should be avoided as water molecules displace the air
spaces in the soil. In this case, roots cannot breathe affecting the growth of plants.
Significance of respiration in plants
During respiration, plants convert glucose molecules into carbon dioxide and water with release
of energy.
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This energy released is utilised by the plant to sustain its life.
The energy released from food is useful for different processes like growth, excretion,
reproduction, nutrition etc.
The carbon dioxide released into the environment is again used by the plant in the process of
photosynthesis.
Breathing
Summary
The cells of living organisms require a constant supply of oxygen to release energy. The energy
released is used to carry out cellular processes.
Breathing
It is the process by which organism takes in oxygen continuously and releases carbon dioxide
into the environment.
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Breathing is a part of respiration and it is also referred to as external respiration.
Breathing merely involves exchange of gases between the organism and the environment.
Breathing is purely a physical process.
Breathing is brought about by coordination between lungs, ribs and the diaphragm. Diaphragm is
a thin sheet of skeletal muscle that separates the thoraciccavity from the abdominal cavity.
It is a mechanical process that involves two steps – inhalation and exhalation.
a) Inhalation is the action of taking in air rich in oxygen. During inhalation, the rib cage moves
outwards and the diaphragm contracts to move downwards. As the rib cage expands, the space in
the chest cavity increases allowing air rich in oxygen enter the lungs.
b) Exhalation is the action of giving out air rich in carbon dioxide to the environment. During
exhalation, the ribs move inwards and the diaphragm relaxes to return to its normal position. The
contraction of rib cage reduces the size of the chest cavity. Now air rich in carbon dioxide is
driven out of the lungs.
RESPIRATION
BREATHING
Respiration involves both physical and
Breathing is purely physical process.
chemical processes.
Breathing is the action of taking in
Respiration involves oxidation of food
oxygen and giving out carbon
to release energy.
dioxide.
Respiration is the sum of external and Breathing is the sum of inhalation and
internal respiration.
exhalation.
Respiration releases energy.
Breathing does not release any
energy.
Respiration takes place in all the cells Breathing takes place only in the
of the body.
organs involved in the process.
Respiration involves breathing and and
Breathing is a part of respiration.
oxidation of food in side the cell.
Breath and breathing rate
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One complete breath accounts for the sum of one inhalation and one exhalation.
Breathing rate is the number of times a person breathes in one minute. Normal breathing rate in
an individual during rest is 15 – 18 breaths per minute. Breathing rate increases drastically
during exercise and running.
Respiratory system in human beings
Different organs of respiratory system include nostrils, larynx,trachea, bronchi, a pair of lungs,
bronchioles and alveoli.
Mechanism of breathing
a) During inhalation, nostrils take in the air which is moistened by the mucous secreted by the
inner lining of the nose.
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The mucous lining present in the respiratory tract keeps the passage moist from the nasal cavity
to the lungs.
Mucous and the hair in the nose entangle the dirt, pollen and other dust particles and prevent
them from entering our nose.
b) Air passes through the pharnyx and enter the trachea made up of rings of cartilage. Trachea is
also called as wind pipe.
c)Trachea bifurcates into two stems called as bronchi (singular: bronchus).
d) Lungs are situated inside the chest cavity and they rest on a large muscular sheet called the
diaphragm.
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Diaphragm forms the floor of the chest cavity. When you breathe in, your diaphragm and rib
cage get into action.
The diaphragm is protected by the rib cage.
The diaphragm plays an important role in inhalation and exhalation. Movement of diaphragm is
brought about by special musculature.
e) Each bronchus enters the lung on either side and gives out repeated branches named as
bronchioles inside the lung.
f) Bronchioles supply individual cells of the lung named as alveoli (singular: alveolus). Each
lung is made up of 300 million alveoli.
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A group of alveolar cells are surrounded by blood vessels.
Oxygen that enters the lungs is exchanged with carbon dioxide from the tissues at this alveolar
region.
Carbon dioxide is taken out in the same path through which oxygen entered inside.
g) Carbon dioxide is released through nostrils by the process of exhalation.
h) During exercise, breathing rate increases so as to obtain more amount of oxygen which in turn
oxidises more food to release more energy required.
Respiration in lower animals
Respiration is a vital life process of all the cells in found in animals.
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Different animals possess different structures for respiration.
Lower organisms respire through their cell membrane which helps in diffusion of gases.
Organisms like insects respire through air holes called as spiracles.
Types of respiration based on structures
Different types of respiration based on the structures used for the process are cutaneous
respiration, branchial respiration and pulmonary respiration.
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The organisms exhibiting cutaneous respiration respire through skin. e.g. Earthworms, Frogs,
Toads .
The organisms exhibiting branchial respiration respire through gills. e.g. Fish, Aquatic
organisms.
The organisms which exhibit pulmonary respiration respire through lungs. e.g. Frogs,
Reptiles,Birds and Mammals.
Respiration in lower organisms
Unicellular organisms like amoeba and paramecium respire through their cell membrane.
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Cell membrane is thin and permeable to gases.
They take in oxygen through entire body surface and give out carbon dioxide.
Exchange of gases takes place through the cell membrane by the process of diffusion.
Hydra respires through its moist outer surface by the process of diffusion.
Respiration in earthworms
Earthworms exhibit cutaneous respiration i.e. respiration by skin.
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Earthworms do not possess special organs for respiration.
They always secrete slimy secretion on to the skin which keeps it moist.
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The skin in these animals is moist and slimy which makes it permeable for oxygen to diffuse in
and carbon dioxide to diffuse out of the body.
As the earthworms cannot breathe in waterlogged conditions, they come out on to the soil during
rainy season to obtain oxygen required for respiration.
Respiration in insects
An insect body is covered with air holes called as spiracles.
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Air enters through these air holes on the body and finally reaches the trachea.
Trachea are a network of fine air tubes extending through out the body.
Trachea help in circulating the oxygen throughout the body.
The oxygen in the air diffuses into the tissues and is ultimately absorbed by the cells.
The carbon dioxide released by the cells is carried by the trachea and given out through the
spiracles.
Respiration in fishes
Fish are the aquatic vertebrates which respire through structures called as gills. This is called as
branchial respiration.
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Gills are present on either side of the head and are supplied by rich blood vessels.
Fish obtain oxygen dissolved in water.
During respiration, water enters the body through mouth, passes through gills and comes out of
the operculum.
Exchange of gases takes place in the gills of fish supplied by numerous blood vessels.
They accept oxygen into the body and expel out carbon dioxide.
Respiration in frogs
Frog is an amphibian having two lives, one in water and one on land.
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Frogs are the only organisms which exhibit cutaneous, branchial and pulmonary respiration in
during different stages of their life cycle.
Adult frogs can breathe through their skin. Skin is moist and slimy helping the animal to respire
through skin under water as well as on land. This is termed to be cutaneous respiration.
Adult frogs while on land respire through lungs. Lungs are the respiratory organs which help in
exchange of gases. This is termed to be pulmonary respiration.
Tadpoles, the larval stages of frog live in water. They respire through their gills as they do not
possess well developed lungs. This is termed to be branchial respiration.
Transportation in Humans
Summary
All livings beings require food, water and oxygen for their survival and to perform various
activities. Food we consume is digested in to simple absorbable substances called as nutrients in
the digestive system.
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The circulatory system helps in the transport of nutrients in the glucose, amino acids and fats to
different parts of the body. Every cell receives absorbed nutrients through the circulating fluid
tissue called as blood.
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Excretory system is responsible for the removal of waste from different parts of the body. Every
cell releases its waste material into the blood to be carried over to excretory organs for expulsion.
Circulation in lower animals
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In unicellular organisms like amoeba and paramecium, circulation is brought about by the
process of diffusion. Nutrients are delivered to all parts of the cell by diffusion.
In multicellular organisms like hydra and jelly fish, nutrients are circulated in the body by water
vascular system.
Circulatory System in human beings
The circulatory system is also known as the cardiovascular system. The circulatory system
comprises blood, blood vessels and the heart.
Blood: Blood is a fluid tissue that flows in special tubes called as blood vessels. Different
functions of blood are elucidated.
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Blood maintains constant body temperature.
Blood helps in transportation of food and water from the digestive system in the body to all the
cells in the body.
Blood helps in transportation of oxygen from the respiratory system to the cells present in all
parts of the body.
Blood helps in transportation of harmful and unwanted wastes from the cells to the excretory
organs. Blood is made up of plasma and formed elements.
Blood provides resistance to the body against pathogens and infections they cause in different
parts of the body.
a) Plasma is the fluid part of blood which contains 90% water. It is pale yellow in colour. It
carries nutrients, enzymes and waste materials in it.
b) Formed elements are made up of three different types of blood cells. These include red blood
cells, white blood cells and platelets. Each of these cells performs a specific function.
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Red blood cells - RBCs are disc-shaped cells which transport oxygen to different parts of the
body. The presence of haemoglobin gives blood its red colour. Haemoglobin is an iron
containing pigment that combines with oxygen to form oxyhaemoglobin. As the blood reaches
the cells, oxyhaemoglobin dissociates to release oxygen which is supplied to cells. In the cells,
carbon dioxide binds with haemoglobin to form carboxy-haemoglobin. In the lungs, carboxyhaemoglobin dissociates to release carbon dioxide which is expelled out.
White blood cells - These cells are also called as WBCs. These cells are larger than RBCs.
White blood cells help in defending the body against infections. White blood cells have the
capability of destroying foreign cells. WBCs can move on their own and can enter the areas of
infection by passing through the membranes of blood vessels. These are of many kinds Leucocytes, basophils, neutrophils, eosinophils etc.
Platelets - Platelets are the non nucleated irregularly shaped blood cells which bring about
clotting of the blood. These are also called as thrombocytes as they release thromboplastin which
brings about clotting of blood. Platelets immediately come to the place of injury and lyse
themselves to release thromboplastin. The remnants aggregate in large amounts to form a plug
on the injury preventing the blood loss.
Blood vessels: Blood flows through narrow pipe-like structures in the body known as blood
vessels. These blood vessels transport food, oxygen and waste throughout the body. Blood
vessels are of three types namely, arteries, veins and capillaries.
Arteries are the blood vessels which carry fresh oxygenated blood to all parts of the body.
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Arteries carry blood away from the heart. All the arteries except for pulmonary artery, carry
fresh oxygenated blood.
Oxygenated blood is pumped by the heart with a great pressure into arteries, hence they have
thick elastic walls.
Arteries transport bright red oxygen rich blood from the heart to the other parts of the body.
Arteries on reaching the tissues divide into fine vessels or tubes known as capillaries
Pulmonary artery carries impure blood to the lungs from heart.
Veins are the blood vessels which carry deoxygenated blood from all parts of the body to tissues
to the heart.
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Veins carry blood to the heart. They carry carbon dioxide rich blood to the heart from different
parts of the body.
Veins have valves on their inner lining that allow blood to flow only in one direction.
In the tissues, number of capillaries join together to form a vein.
Pulmonary veins carry pure blood from lungs to the heart.
Blood capillaries are the thinnest blood vesels which are in direct contact with the cells.
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Capillaries nourish the cells of the tissue with oxygenated blood.
They have thin membranes through which oxygen and nutrients get into the cells.
Veins inturn receive carbon dioxide and waste products from the cells.
Later, all these capillaries of that tissue at another end combine to form a vein.
This vein carries deoxygenated blood to the heart.
Deoxygenated blood is sent to lungs for purification.
Heart: The heart is the central organ for pumping the blood throughout the body. Heart is made
up of strong cardiac muscles.
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It is located in the chest cavity with its lower part pointing towards the left. Its size is that of the
person’s fist.
It pumps blood rich in carbon dioxide to the lungs and oxygen-rich blood to other parts of the
body.
The heart consists of four chambers namely auricles and ventricles. The two upper chambers of
the heart are known as the auricles.The two lower chambers of the heart are the ventricles.
Left and right parts of the heart are separated by a muscular partition called as septum.
Heart has number of valves which allow the blood to flow in one direction. These valves prevent
the oxygenated blood mixing with de-oxygenated blood.
Purification of blood is a stepwise procedure happening in a sequence. Double circulation is
observed in human beings. Blood passes twice through the heart.
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Step 1 - Pure oxygenated blood from the lungs is carried to the left auricle through pulmonary
veins. Left auricle contracts to push the pure blood into left ventricle.
Step 2 – Blood from left ventricle is carried to all parts of the body through arteries. Blood gets
purified in the lungs.
Step 3 – Deoxygenated blood from the tissues is collected by veins and transported to right
auricle. Right auricle contracts to send this impure blood into right ventricle.
Step 4 - Right ventricle pumps deoxygenated blood into the lungs through pulmonary arteries.
Heart beat is the combined effect of contractions and relaxations of the cardiac muscles
occurring in two batches.
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Two auricles contract first to force the blood into two ventricles on either side. This produces a
'lub' sound.
Later, two ventricles contract to send the blood into arteries moving towards the body and
pulmonary artery moving towards the lungs producing a 'dub' sound.
The rhythmic contraction and relaxation of the heart constitutes heartbeat.
Heartbeat can be felt by placing the palm on the left side of the chest.
Stethoscope is a device that amplifies the sound of your heartbeat.
Pulse is the throbbing sensation in the wrist region signifying the blood rushing through the
arteries.
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It is the pressure applied by blood on the walls of an artery at a particular part of the body.
The number of times the heart beats in a minute is the same as the pulse rate.
The ideal pulse rate is 70 to 80 per minute.
Excretion
The process of the removal of waste produced in the cells in living organisms is called excretion.
The organs that help in the process of excretion constitute the excretory system.
Functions of excretory system
Excretion helps in eliminating different types of wastes.
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Nitrogeneous wastes are the wastes formed in the body as a result of protein metabolism.These
can be in the form of ammonia, urea or uric acid. All these nitrogeneous wastes should be
eliminated from the body due to their toxic nature. Nitrogeneous wastes mix with water in the
body to form urine. Urine is expelled out in periodic intervals.
Excess sugar from the blood is filtered and sent out through urine in case of diabetic patients.
Undigested wastes are passed out through anus by the process of egestion.
Carbon dioxide, an excretory product from every cell is expelled out through lungs.
Excess salts from the body are eliminated through sweat.
Excretion in lower animals
Lower organisms like amoeba, paramecium, hydra do not possess special organs for excretion.
They eliminate waste products to the environment by the process of diffusion occurring through
cell membrane.
Excretory system in human beings
The excretory system in human beings includes a pair of kidneys, a pair of ureters, a urinary
bladder, and a urethra. This is also known as the urinary system.
a) Kidneys - The kidneys are located in the abdominal region, one on either side of the
backbone.
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Kidneys mainly act as excretory organs and also control the balance of water and mineral ions in
the body.
Kidneys filter out nitrogenous wastes from the blood producing urine.
They absorb minerals into the blood. they also produce hormones to some extent.
Kidney is divided into two regions namely, cortex and renal medulla.
Kidney is made up of tiny tubules called as nephrons. Nephrons are the functional units of the
kidney.
Each nephron consists of a corpuscle and a renal tubule. It filters out excess water, salts and urea
from the blood.
b) Ureter - Ureters are tubular structures which arise from each kidney. Ureter opens into the
urinary bladder.
c) Urinary bladder - Urinary bladder is a muscular bag which has high elasting capacity to
accumulate urine in it .Urinary bladder opens out to the exterior through an opening called as
urethra.
d) Urethra - The urethra passes urine to the outside of the body. The urethra emerges through
the penis in males and close to the vagina in females.
Urine is the liquid formed by the combination of urea with water. Urine formation occurs in
three steps. A healthy human being passes out 1.5 to 2.5 litres of urine every day.
Dialysis is the treatment primarily used to provide an artificial replacement for of a kidney which
has become non-functional. Kidney does not function properly due to renal failure. Dialysis is
eliminating nitrogenous waste and unwanted water from the blood. The material used in this
technique is the dialyzing fluid which actually filters the blood to separate the wastes.
Transportation in Plants
Summary
Plants are the organisms exhibiting autotrophic mode of nutrition. They synthesise their food by
a physico-chemical process known as photosynthesis occurring in the leaves. Leaves are
considered to be food factories.
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Raw materials for the process of photosynthesis should be transported to leaves.
Starch synthesised in the leaves should be sent to different parts of the plant where it can be
utilised or stored for future use.
Transportation – An essential process
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Transportation in plants is a vital process to circulate water, essential nutrients, excretory
products and gases within the plant for various purposes.
Transportation in plants is mainly brought about by vascular tissues.
Vascular tissues are the conducting tissues formed by xylem and phloem in plants.
Water and minerals are transported to various parts of a plant by a suction force.
Xylem: It is the vascular tissue extending from top to bottom of the plant.
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Xylem helps in the transport of water molecules and dissolved substances from the root hairs to
aerial parts of the plant.
Xylem transports water in one direction. Xylem mostly occupies the centre of the vascular
bundle.
Xylem mainly comprises different types of cells namely, tracheids, vessels, xylem parenchyma
and xylem fibres.
Phloem: It is the vascular tissue which transports food molecules to the place of necessity in
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the plant.
The elements in the phloem are sieve elements, fibres, phloem parenchyma and companion cells.
The transport in the phloem tissue is bidirectional.
It forms vascular bundles in association with xylem.
Phloem occupies the edges of the vascular bundle.
Absorption of water
Plants absorb water from the soil through roots.
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The tips of the roots are protected by root caps.
Roots have single-celled root hairs to absorb water and minerals from the soil.
The amount of water absorbed is proportionate to the number of root hairs.
The process of absorption of water in plants takes place through these root hairs.
These are highly permeable to water.
These root hairs also have lot of vacuoles to store absorbed water.
The old root hairs are periodically replaced by the new ones.
Transpiration
Transpiration is the process by which plants release excess water into the atmosphere.
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Transpiration occurs in leaves through special structures present on them called as stomata.
Excess water is lost in the form of water vapour.
Transpiration increases the moisture content of the atmosphere, thus bringing about a cooling
effect in the immediate surroundings.
Significance of transpiration
Transpiration is the process which helps the plant in many ways.
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Transpiration removes excess water from the cells of the plant to prevent plant decay.
Transpiration maintains salt -water balance in the plant .
Transpiration cools down all parts of the plant.
Transpiration helps in the distribution of dissolved substances to all parts of the plant.
Transpiration pull is used to absorb more water and minerals. It is strong enough to draw water
even in tall trees.
Translocation
It involves the transportation of synthesised food molecules to different parts of the plant.
Phloem is responsible for the process of translocation.
Food is translocated to different organs for its utilisation.
Excess food syntheised is translocated to storage organs of the plant.
Differences between transpiration and translocation
TRANSPIRATION
TRANSLOCATION
Transpiration is the evaporation of water
Translocation is the transportation
from the leaves in the form of water
of synthesised products in a plant.
vapour.
Transpiration always occurs against the Translocation does not always occur
gravity.
against gravity.
Transpiration involves mainly the xylem Translocation involves both xylem
cells.
and phloem cells
...
Electric Components
Circuit Diagram
A simplified conventional pictorial representation of an electrical circuit, using standard symbols
for electric components, is called a circuit diagram. A circuit diagram is also known as an
electrical diagram, wiring diagram, elementary diagram or electronic schematic.
Electrical Circuit
A closed path formed by the interconnection of electrical components through which electric
current flows is called an electrical circuit. A simple electrical circuit consists of a battery, a light
bulb and a switch connected using connecting wires. If current does not flow through a circuit,
then it is said to be an open or an incomplete circuit. Its switch is in ‘off’ position. A circuit is
said to be a closed or a complete circuit when current flows through it. Its switch is in ‘on’
position. A combination of two or more cells connected together is called a battery. Batteries are
used in many devices, such as torch lights, mobile phones, calculators and even automobiles.
Symbols for Electrical Components
Different symbols are used to represent different components of electrical circuits, but the
symbols used must be standardised. These symbols are easy to understand, remember and draw.
Component
Wire
Symbol
________
Function of the Component
It allows current to flow from one
part of the circuit to another.
Switch
When the switch is ON position,
current will flow.
When the switch is in OFF
position, current will not flow.
Cell
It supplies electric current. The
positive terminal (+) of a cell is
represented by a vertical long
line, while the negative terminal
(-) is shown as a parallel, shorter
line.
Bulb
The bulb glows if the switch is
ON, and doesn’t glow if it is in
OFF position.
Battery
It supplies electric current. A
battery is a combination of two or
more cells connected together.
]
The Heating Effect of Electric Current
When an electric current flows through a wire, the wire gets hot. This is known as the
heating effect of electric current. The factors that affect the production of heat in a wire
through which an electric current flows are the length and thickness of the wire, the
duration of flow of current, and the material of the wire.
Some appliances that work on the property of the heating effect of electric current are
electric room heater, electric roti maker, electric iron, toaster, hair dryer, electric stove,
immersion water heater, food warmer, electric coffee maker, electric rice cooker and
geyser. These appliances have coils of wire known as heating elements which produce heat.
As current flows through these electrical appliances, the heating elements turn bright
orange red in colour. This is because a huge amount of heat is produced. An electric bulb
also works on the heating effect of electric current. The filament of an electric bulb gets
heated to such a high temperature that it starts glowing. Different appliances have different
types of heating elements. The type of heating element depends on the function of the
appliance. Some appliances are required to produce more heat than others.
Electric Fuse
An electric fuse is a safety device used to prevent damage to an electrical circuit when
excessive current flows through it.The electric fuse works on the principle of the heating
effect of electric current. It consists of a piece of wire made of a metal or an alloy of low
melting point. As the current increases beyond a limit, the wire in the electric fuse melts
and breaks off. The fuse is then said to have blown off. The circuit is broken and current
stops flowing through it. Thus a fuse prevents fires. There are various types of fuses. Some
fuses are used only in buildings, while others are used in appliances.
Reasons for Excessive Current
When all the appliances are connected to the same socket, they draw more current, and so
the load increases. When the insulation on the wires is torn, two wires carrying current
may touch each other directly. This causes a spark, which leads to fire. This is termed as a
short circuit. If a fuse is not used, overloading and short circuits occur which results in fire.
Compact Fluorescent Lamp (CFL)
We use electric bulbs to obtain light but it also gives heat. This is not desirable. This results
in the wastage of energy. CFL’s do not depend on the heating effect of electricity to
produce light, since they do not use filaments. Using CFL’s instead of ordinary bulbs
minimises wastage of electricity. In CFL’s, light is generated using two electrodes. The
fluorescent coating inside each tube makes the light brighter.
ISI Mark
We should purchase only appliances that bear an ISI mark. ISI stands for Indian
Standards Institute. If an appliance bears the ISI mark, it means that it is safe and will not
waste electrical energy. Moreover, it is a mark of quality.
Miniature Circuit Breakers (MCBs)
The problem with the fuses is that whenever overloading occurs the fuse wire melts and it
has to be replaced to complete the circuit. This problem is overcome in miniature circuit
breakers (MCBs) which are widely used nowadays. MCBs are switches that turn off
automatically when there is an overload or a short circuit. After solving the problem in the
circuit, the switch can be turned back on, and then the current flows as usual.
Magnetic Effect of Electric Current
When an electric current flows through a wire, the wire behaves like a magnet. This is known as
the magnetic effect of electric current. This was discovered by Hans Christian Oersted. Once,
while preparing for a lecture, he noticed that there was a deflection in the needle of a magnetic
compass kept near a wire that was connected to a battery. This deflection occurred every time the
battery was switched on and off. He realised that a magnetic field is created around a currentcarrying wire in a circuit.
Electromagnet
When electric current flows through a wire wound around an iron bar, the bar behaves like a
magnet. This magnet is called an electromagnet. An electromagnet is formed due to the magnetic
effect of electric current. Electromagnets are used in toys, iron industries, electric bells, cranes
and Maglev trains. Cranes are used for separating magnetic materials from junk and to lift cars
and other heavy objects. Eye doctors use electromagnets to remove tiny pieces of
magnetic material that have accidentally fallen in the eye.
Construction of an Electromagnet
The components required to create an electromagnet are two pieces of insulated copper wire, a
nail, a battery containing two cells, a bulb with a holder, and some paper clips made of iron. The
bulb serves as a resistance to the current in the circuit and it prevents the battery from quick
discharge. The circuit to make an electromagnet is shown here. When you switch on the current,
the paper clips will cling to the nail. This is because the nail becomes an electromagnet. When
the battery is disconnected, the nail is no longer an electromagnet. The paper clips will detach
from the nail.
Construction and Working of an Electric Bell
Circuit: An electric bell consists of an iron core, on which is wound a wire as a coil. One end of
the coil is connected to one terminal of a battery, and the other end to a steel rod that acts like a
spring for the hammer touching the screw contact. The other terminal of the battery is connected
to the screw contact with a switch in the middle.
Working: Electric current flows through the coil when the switch is ON, and the iron core acts as
an electromagnet. The iron core attracts the hammer towards it. The hammer hits the bell and
produces a sound. The circuit breaks at the screw contact when the hammer moves towards the
iron core. At this point, the iron core ceases to be an electromagnet. The hammer is pulled back
to its original position due to the spring action of the steel rod, and then touches the contact again
to complete the circuit. The circuit is completed and current flows through the coil again, and the
hammer strikes the bell again. The process repeats itself and you hear a ringing sound since the
hammer keeps hitting the bell, until the switch is released.
Reflection of Light
The path of light is always straight and never curved. Examples to show that light travels
in a straight line are light emitted by a torch light and light emitted from the headlights of a
vehicle. The direction of light can be changed only by reflection. The bouncing of light by
any surface is called reflection of light.
Image Formed by a Plane Mirror
Due to the reflection of light, the impression of an object formed in a mirror is called the
image of the object. As the distance of the object from the mirror increases, the distance of
the image from the mirror also increases. The concept that images in a plane mirror are
located at the same distance behind the mirror as the object in front of it is mainly used in
interior decoration and in architecture to make rooms appear brighter and bigger.
Moreover, placing a mirror near lights, chandeliers and table lamps reflects the light over a
larger area, and makes the room appear brighter. Images that cannot be captured on a
screen are called virtual images.
Left–Right Inversion
As the name suggests, images are laterally inverted, i.e. the right part of an object appears
on the left in its image, and the left part of the object appears on the right. For example, the
word AMBULANCE is painted left-right inverted on the ambulance so that when the
driver of a vehicle in front looks into his rear-view mirror, he can make out the word
AMBULANCE quickly and give way.
Characteristics of Image Formed in a Plane Mirror
The image formed by a plane mirror is:
• of the same size as that of the object
• left-right inverted
• erect and virtual
• as far behind the mirror as the object is in front of it.
A mirror maze is created based on the principle of reflection in plane mirrors. The maze
has several plane mirrors placed at fixed angles to each other. When a person enters a
mirror maze, he finds several images of himself and several passages. There is only one
passage that is real, while all the others are just images.
Spherical Mirror
Mirrors are the basic means of viewing our own beauty. There are two types of mirrors – plane
mirrors and curved mirrors. If the curved mirror is a part of a huge sphere, then the mirror is a
spherical mirror. Spherical mirrors can be further classified into two types – concave mirrors and
convex mirrors. Like plane mirrors, spherical mirrors also follow the laws of reflection.
Terms Associated with Spherical Mirrors
• Centre of curvature (C) is the centre of the sphere, of which the mirror is a part.
• Radius of curvature (R) is the radius of the sphere, of which the mirror is a part.
• Pole (P) is the geometric centre of the spherical mirror.
• Principal axis is the line joining the pole and the centre of curvature.
• Principal focus (F) is the point on the principal axis, where a parallel beam of light, parallel
to the principal axis after reflection converges in the case of a concave mirror and appears to
diverge from in the case of a convex mirror.
• Focal length (f) is the distance of the principal focus from the pole of the mirror.
There are two types of images: real and virtual. Real images are those that can be caught on a
screen while virtual images are those that cannot be caught on a screen.
Concave Mirror
If a part of a hollow glass sphere is cut and the cut part of the sphere is coated outside with silver
or similar material, then its inner surface reflects the entire light incident on it, and thus, forms a
mirror. Since the inner surface is a concave surface, the mirror so formed is called a concave
mirror.
Concave mirrors converge the light incident on them and hence are called converging mirrors.
You can observe yourself magnified when the mirror is placed close to your face. This is due the
position of the object between the focus and the pole. As the object moves away from the mirror,
the size of its image reduces along with its distance from the mirror. If an object is placed close
to a concave mirror such that the distance between the mirror and the object is less than its focal
length, then a magnified and virtual image is formed. Due to this property, concave mirrors are
used as shaving mirrors, and by dentists to view clearly the inner parts of the mouth.
Convex Mirror
If the cut part of the glass sphere is coated from inside with silver or a similar material, then its
outer surface reflects the entire light incident on it, and thus forms a mirror. Since the outer
surface is a convex surface, the mirror so formed is called a convex mirror.
Convex mirrors diverge the light incident on them and hence they are called the diverging
mirrors. Due to this they always form diminished, virtual and erect images irrespective of the
position of the object in front of them. Thus, the magnification produced by these mirrors is
always less than one. The field of view for a convex mirror is greater than that for a plane mirror,
the aperture being the same. Hence, convex mirrors are used as rear-view mirrors in vehicles. It
is also installed behind automated teller machines as a security measure.
Mirror Formula and Sign Conventions
The relation between the focal length (f), object distance (u) and the image distance (v) is given
by 1f1f = 1u1u + 1v1v. This is called the mirror formula.
All the distances are measured from the pole of the mirror. If we measure the distances in the
direction of the incident light, then they are taken positive or else they are taken negative. These
constitute the sign conventions.
Concave Lens
A concave lens is thinner at its centre than at its edges, and is used to correct short sightedness.
When light rays are incident on a concave lens, they bend outwards or diverge. Thus, a concave
lens is also called a diverging lens. The image formed by a concave lens is upright, virtual and
smaller than the object. For example, the images seen through a peep hole are different from
those seen through normal holes, because these peep holes contain concave lenses.
Convex Lens
A convex lens makes the object magnified, when viewed through it. A convex lens is thick in the
middle and thin at its edge. When light rays pass through a convex lens, they bend inwards and
converge at a common point to form an image of the source of light. Rays from the sun converge
to form its image as a bright spot. A convex lens converges light rays. Therefore, it is also called
a converging lens. The image formed when the object is placed close to a convex lens is virtual,
erect and magnified. Virtual images cannot be caught on a screen. Images that are caught on a
screen are called real images. When the object is placed at a distance from a convex lens, the
image formed is real, inverted and diminished.
Applications of Lenses
Lenses are used in magnifying glasses, peep holes, cameras, bioscopes, binoculars, telescopes,
microscopes and projectors. A refracting telescope uses a concave mirror and a convex lens.
Rainbow
A band of colours extending from violet to red is a rainbow. A rainbow is formed by the
refraction and reflection of the sun’s rays through raindrops. When it is raining in one part of the
sky and sunny in another, a rainbow appears. An observer can therefore see a rainbow only when
his back is towards the sun. It is believed that in the past, Norsemen saw rainbows as bridges for
gods to come to the earth from their home in the sky. Norsemen were the inhabitants of Norway.
Although sunlight appears white, it is composed of seven colours. The colours in a rainbow are
the colours of sunlight.
Newton's Disc
A Newton's disc can be created by painting a disc with the seven different colours: violet, indigo,
blue, green, yellow, orange and red. When the disc is rotated, it appears white. This explains that
white light consists of seven colours. The colours of a rainbow can be represented by the
acronym: VIBGYOR: V – Violet, I - Indigo, B – Blue, G – Green, Y - Yellow, O - Orange and R
- Red.
Dispersion of Light Through a Prism
When a narrow beam of light is incident on one face of a glass prism, light bends when it passes
through the prism. Now the light coming out of the other face of the prism is made to fall on a
white sheet of paper or a white wall. Different component colours of white light bend differently,
and so the constituent colours can be seen separately. Thus, the colours are said to have dispersed
after passing through the prism.
Water : A Precious Resource
Availability of water
Nearly 71% of the earth is covered by water in the form of oceans, seas, lakes, rivers, ice, ground
water and moisture in the air. But most of it is not fit for human consumption.
Water that is fit for human consumption is called freshwater. Only 0.006% of the water on the
earth is actually available for our use.
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In nature, water exists in three forms
As a solid, it exists as icecaps at the poles, snow-covered mountains and glaciers.
As a liquid, it is in the form of water in oceans, lakes and rivers, and underground water.
Its gaseous form is the water vapor in the air around us.
Water cycle or hydrological cycle
The continuous cycling of water in nature that keeps the total amount of water on the earth
constant is called water cycle.
Processes involved in water cycle
The processes involved in the water cycle are, evaporation, condensation ,precipitation and
infiltration.
Evaporation
The process of conversion of water molecules into vapor is called evaporation. water vapor
collects in the sky in the form of clouds.
Condensation
The process of conversion of water vapor into water by cooling is called condensation.
Precipitation
Water falls from the sky in the form of rain, snow, hail, or sleet, this process is called
precipitation.
Infiltration
The process of seeping of water into the ground is known as infiltration.
Aquifer
Sometimes, ground water accumulates between layers of hard rock. This is known as an aquifer.
Water in aquifers can be drawn with tube wells and hand pumps.
Water table
The level below which the ground is saturated with water is called water table.
Ground water
Ground water is the water found below the water table.
Depletion of water table
As long as the water drawn from the ground is replenished by seepage of rain water, the water
table remains unaffected. The problem starts when we take more water from the ground than is
replenished by natural means. Then the water table goes down, and it is said to have been
depleted.
Reasons for depletion of the water table
Increasing population that creates more demand for water.
More wells are dug and water is drawn from them.
Industrial activities are increasing the demand for water. For example, the construction industry
uses tube wells to draw ground water.
An increase in agricultural activities demands more water. In areas where there are no streams
and lakes, ground water is used for irrigation.
Scanty rainfall is another reason for depletion of the water table.
Water table depletion can be a result of deforestation.
Water management
Water management is the continuous matching of water resources with the water requirements of
a place.
Water management essentially involves activities that identify sources of water, prevent wastage
of water, and implement recycling of water.
It may also include treatment of water to make it suitable for human consumption.
Prevent wastage of water
Water leaking from pipes
Fixing Leaking taps.
Water over-flowing from buckets while clothes are being washed alongside
Using water wisely while brushing the teeth, shaving, bathing, washing and during many other
activities, practising rainwater harvesting.
Conservation of water
Instead of letting rainwater runoff into the sea, it can be used to recharge ground water. This is
known as rainwater harvesting.
Rainwater harvesting can be used to raise the water table in arid areas. It can also be used to
create water storage areas.
Farming, which typically requires huge quantities of water, can also benefit from good water
management.
Bawris
This is the old method of rain water storage and recharge. In olden days people built deep step
wells into the ground. These deep step wells are called bawris. During rainy season these wells
are filled with water. The water is stored in these wells for longer time because they are very
deep the evaporation of water is less. During shortage people use this water.
Drip irrigation
Drip irrigation is an economical way of using water. This technique involves the use of tubes to
deliver water straight to the base of a plant, where it is taken up by the roots.
Effects of water scarcity
Plants need water to absorb nutrients from the soil and make their food. Without water, plants
would die, and greenery would be lost. This, in turn, would mean the end of all life on the earth,
because without plants, there would be no food, oxygen or rainfall. There would also be many
other problems.