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The scientific names of all kinds of organisms are composed of two parts: • the genus (group) name,
and • the species (particular organism) name.
Family:A group of two more genera (plural of genus)
Order:A group of related families. For example, the family of cats (Fel
Class:Related orders make a class.
Phylum:A phylum is the largest category with related classes g
Kingdom:Kingdom is the largest group of organisms differentiated on very general
The bacteria have cell walls (as found in all plant cells) but they have no chlorophyll.
(bacteria) It includes bacteria and blue green ‘algae’ (not really algae). • Monera are single-celled. •
Their chromosome material is not enclosed within a nuclear membrane. It means that they have no
compact nucleus. The Monera are described as prokaryotes
Shapes:Spherical (cocci), rod-like (bacilli), or spiral (spirilli)
Some are used in making antibiotics. And, many are beneficial in nature as in the carbon and the
nitrogen cycles. Fig. 23.4 Common types of bacteria – spherical, spiral and
Protozoa
are single-celled(unicellular) organisms, and have a well-defined membrane-bound nucleus. Their
modes of nutrition may be quite varied.
Some of the protists are pathogenic, such as Entamoeba histolyticathat causes dysentery and
Plasmodium vivaxthat causes malaria.
Fungi
Multicellular in nature. • Absorb nutrients from dead or living organisms. • Produce spores in special
rounded bodies called spore heads (sporangia) as in the common bread mould
Yeasts (Saccharomyces) are widely used in baking bread and in winemaking, etc. Some fungi produce
diseases, such as ringworm.
plants that produce seeds openly (not contained inside the fruit) (Gymnosperms), and • plants that
produce seeds contained inside the fruit (Angiosperms).
The heterotrophic unicellular Protistans like Amoeba used to be described as Protozoans under the
animals. But according to the new five-kingdom classification. They to no longer belong the animal
kingdom.
Ascaris(Fig. 23.15) is found in human intestine.
tapeworm (Taenia sp.) which is a parasite of the human intestine
Snails, slugs, oysters, and octopuses and cuttlefish
Starfish, brittle star, sea urchin, sea cucumber, etc.
Mollusca (snails, oysters)
Echinodermata (starfishes)
Chordata (animals with backbone and some others)
Vertebratais the largest group in Chordata. It is divided into five very distinct classes. a) Pisces
(fishes) b) Amphibia (frogs) c) Reptilia (lizards) d) Aves (birds) e) Mammalia (animals with milk
glands)
Pisces
• 2-chambered heart Fishes are mainly of two types – cartilaginous fishes and bony fishes
Amphibia (frogs, toads) • Live both in water and on
Aquatic respiration by skin (when under water) as well as by lungs (when on land) • All larval stages
as well as some adults breathe by gills. • Heart 3-chambered • Cold blooded (body te
Reptilia (lizards, crocodiles)
Cold blooded (therefore live in warmer regions only) • Eggs with a leathery (non-calcareous) shell •
Breathe by lungs right from birth • Rough horny scales on the skin • 3-chambered heart,
but the ventricle is partially divided in crocodiles
Aves (birds) • Body covered with feathers • Only the two hindlegs present, forelegs are modified
into wings. • Scaly legs • 4-chambered heart
Nucleus:The nucleus is a small ovoid or spherical mass located somewhat in the centre of the
cytoplasm. • This is the largest organelle.
Centrosome(in animal cells only):It is located near the nucleus and contains 1 or 2 centrioles. • It
initiates and regulates cell division.
Plastids(in plant cells only):These are of various shapes – oval, spherical or disc-like. The most
common ones are chloroplasts that contain chlorophyll
Parts other than the organelles The vacuoles and granules are the non-living parts of a cell.
(special features not found in plant cells) Centrioles:
Mitosis:Cell division leading to growth and repair • Meiosis:Cell division leading to the production of
sex cells
chromosomes (the number specific for the species, e.g. 46 in humans)
Two main differences in mitosis in a plant cell and an animal cell • In plant cells, there is no
centrosome and no centrioles inside it. However, the spindle is formed. • Upon the completion of
mitosis, the cytoplasm in plant cell does not constrict (furrow is not formed). Instead, a cell plateor a
new cell wall is laid down in the cytoplasm at the middle of the cell. It divides the original cell into
two daughter cells.
During meiosis the number of the chromosomes is halved in the resulting sex cells so that when the
male cell and the female cell combine during fertilization, the normal number of chromosomes in
the species is restored.
Broadly, meiosis is completed in two phases or stages (Fig. 24.4). Stage I:A reduction division that
involves production of two cells with half the number of chromosomes in each. Stage II:The
immediately following second division is mitotic and produces four cells at the end. Characteristic
features
Thus, each pair of chromosomes is now a group of four chromatids.
Thus, each pair of chromosomes is now a group of four chromatids.
Meiosis in a human cell • The 46 chromosomes organise in homologous pairs (23 pairs). • Each pair
breaks, but each separated chromosome is already split into two chromatids that are still held
together. • The cell divides into two daughter cells (this is the first meiotic division which actually is a
reduction division) and now each of the two resulting cells has only 23 single chromosomes. • Each
of the two resulting cells undergoes the second (mitotic) type of division in which the two
chromatids of each of the 23 chromosomes separate apart (just as in mitosis) and the two cells
divide to form four cells (these are the sex cells).
Plant tissues are basically of two types – meristematicand permanent.
Permanent tissue:It is made up of cells, which have lost their ability to multiply.
i. Protective tissue:
ii. Supporting tissue:
cells that fill upthe interior of potatoes, which store food, • cells that provide temporary supportto
the plant, such as in the pith (central region)
iii. Conducting tissue: It is also called the vascular tissue. It provides passage for the fluids to move
up and down in the plant. It is of two types–xylemand phloem(Fig. 24.9). Xylem is located more
towards the centre of the stem. It allows water and minerals absorbed from the soil to travel
upwards in the plant. Phloemis located outward of the xylem and serves to conduct the food (sugar)
synthesized in the leaves to flow downward and upward so as to reach all other regions.
Meristematic tissue: It is found at the growing points of a plant such as at the tips of the roots, stems
and branches.
Millets Sorghum (Jowar), Ragi (finger millet) and Bajra (pearl millet)
Tuber crops Potato, Tapioca, Ginger and Turmeric
The branch of agriculture that deals with growing and production of vegetables, fruits, ornamental
plants and management of orchards is called horticulture.
Leguminous crops include pea, beans, grams and pulses.
Beans Peas, Soyabean, Cowpea, Lentil
Table 32.2 Improved high-yielding varieties of crops Crop Variety Rice I R-8, Jaya, Padma, Bala Wheat
Sarbati sonara, Sonalika, Kalyan sona, Hira-moti, RR-21 and UP 301 Maize Ganga 101, Rankit and
Deccan hybrid Lady’s finger (Bhindi) Pusa savani Brinjal Pusa purple, Pusa kranti and Muktabeshi
Weeds must be removed as they use up the nutrients in the soil and thereby make them unavailable
for the crop itself. Weeds can be divided into two groups: (i) graminaceous (Monocotyledonous),
and (ii) non-graminaceous (Dicotyledonous). Hariali or Doobgrass is a graminaceous weed, while
Choulaiis a non-graminaceous weed
Generally plant diseases are caused by fungi, bacteria, and viruses.
Rust of wheat and Blast of rice are two common fungal diseases of plants.
Dr. M. S. Swaminathan. He is the recipient of World Food prize for fighting against hunger.
Viral diseases: Pox in cattle, goats, sheeps, and fowls; dermatitis in goats and sheep; foot and mouth
disease in cattle. Bacterial diseases:Tuberculosis in cattle and poultry birds; cholera in fowls;
diphtheria in calf; diarrhea in chicks; foot rot in sheep.
Capillaries:Thin vessels between the artery and the vein. The capillaries allow the exchange of
materials between blood and tissues.
You must have noticed that veins bring impure blood to the heart and the arteries take the pure
blood away from the heart. But here are two exceptions – the pulmonary artery carries impure
blood and the pulmonary vein carries pure blood.
Blood is a connective tissue that circulates throughout the body. It is made up of a fluid medium
called plasmain which float three types of blood cells, called red blood cells, white blood cells and
blood platelets. Blood cells are manufactured in the bone marrow.
No nucleus is present in RBCs
Blood platelets (Thrombocytes) • These are very small fragments of cells • They have no nuclei
LYMPHATIC SYSTEM Lymph is also a circulatory fluid and flows in the lymph vessels. • It is light
yellow in colour. • It always flows only in one direction from tissues to heart. • Cells called
lymphocytes present in lymph eat up germs and prevent body from infections. • Lymph carries
digested fats from intestine to other parts. • It returns proteins and fluid from circulation to tissues.
Normal blood pressure is 120/80.
The process by which, organisms obtain and utilise food for their growth and development (from
their environment) is called nutrition.
The process of photosynthesis is completed in two steps – light reaction and dark reaction.
i) Light reaction: The first step of photosynthesis occurs in the presence of light. During this step,
chlorophyll contained in the chloroplast of plant cells absorbs light energ y. This energy is converted
into another form, which can be supplied for the completion of the dark reaction. ii) Dark reaction:
This second step of photosynthesis does not require light, and is called dark reaction. It can also
carry on in the presence of light. During this step, energy generated during light reaction is used to
combine carbon dioxide and water molecules to form energy rich compounds, such as glucose.
Oxygen is also released in this process.
Chlorophyll is the most important internal factor. The rate of photosynthesis decreases with an
increase in the age of leaf.
Carbohydrates may be in the form of sugars, starch or cellulose.
Type of nutrient Carbohydrates l Glucose l Fructose l Sucrose l Cellulose l Starch Proteins Oil and fats
Food source ( some examples ) Grapes All fruits that taste sweet Sugarcane and beet root, common
sugar Peels of fruits and vegetables, whole grains (bran – good source of roughage) Cereals (wheat,
rice, maize, barley), and vegetables (potato, sweet potato, tapioca, onion, banana, water chestnut or
singhara) Pulses (soyabean, beans, peas, lentils, gram), nuts Groundnut, mustard seeds, coconut
VITAMINS W ater-soluble Fat-soluble Vitamins B-complex Vitamins A, D, E and K (B 1 , B 2 , B 4 , B 12
) and C
All enzymes are complex proteins and remain unchanged during the reaction. They can be used
repeatedly. Since they speed up the rate of chemical reactions in the body they are also known as
biocatalysts. Enzymes may help in joining or splitting of biomolecules.
The entire process of nutrition includes the following steps: ingestion, digestion, absorption,
assimilation and egestion.
The food is ingested through the mouth. Carbohydrates, such as starch, are broken down or digested
to form sugar. The saliva contains an enzyme salivary amylase that helps in the digestion of starch
into sugar.
HCl creates an acidic medium for the activation of enzymes and kills bacteria. These enzymes break
down the proteins into smaller fragments called peptones.
The food moves from the stomach to duodenum, which is the upper part of the small intestine. Here
the emulsification of fat (fat is broken in to fat droplets)
Pancreas secretes trypsin, amylase and lipase(pancreatic juices) which are poured into the
duodenum.
The food moves to ileum, which is the lower part of the small intestine. The inner surface of the
ileum contains thin finger-like projections called villi.
Deficiency diseases caused due to malnutrition are of three types: • Protein Energy Malnutrition
(PEM) • Mineral deficiency diseases • Vitamin deficiency diseases
Two diseases caused due to PEM are – marasmus and kwashiorkor.
a) Marasmus It affects children up to one year of age. This occurs in deprived children of mother’s
milk. T
b) Kwashiorkor Amongst children of age group 1-5 years protein deficiency causes kwashiorkor.
Xerophthalmia Lack of Vitamin A leads to Xerophthalmia,
Rickets Milk and liver are good sources of vitamin D
Phosphorus is also in bajra, green leafy vegetables and nuts.
Beri-beri Deficiency of Vitamin B 1 in the diet leads to beri-beri. It is a disease of heart and nerves
Pellagra Deficiency of vitamin B 4 results in pellagra. This disease causes: • reddening and drying of
skin (eczema)
at metaphase chromosomes are clearly seen lying at the equator.
By now you know that genes are bearers of hereditary characters and they are present on
chromosomes. From the work of many scientists, today we know that genes are segments of
chemical molecules called DNA
One chromosome contains one molecule of DNA and genes are fragments of this DNA molecule.
Three common hereditary disorders are Thallasemia, Haemophilia and colour blindness.
Patients suffering from this disorder are unable to manufacture haemoglobin
Those persons suffering from haemophilia have either a defective gene or lack genes, which control
production of substances responsible for blood clotting.