1. Nutrients And Nutrition -
ü Carbohydrates, proteins, fats, vitamins and minerals are components of food. These components of food are called nutrients and are necessary for our body.
ü Nutrition is the mode of taking food by an organism and its utilization by the body.
ü The mode of nutrition in which organisms make food themselves from simple substances is called autotrophic (auto = self; trophos = nourishment) nutrition. Therefore, plants are called autotrophs.
ü Animals and most other organisms take in food prepared by plants. They are called
heterotrophs (heteros = other).
2. Cell -
ü You have seen that buildings are made of bricks. Similarly, the bodies of living organisms are made of tiny units called cells.
ü Cells can be seen only under the microscope. Some organisms are made of only one cell.
ü The cell is enclosed by a thin outer boundary, called the cell membrane.
ü Most cells have a distinct, centrally located spherical structure called the nucleus.
ü The nucleus is surrounded by a jelly-like substance called cytoplasm.
3. Photosynthesis -
ü Leaves are the food factories of plants. Therefore, all the raw materials must
ü reach the leaf.
ü Water and minerals present in the soil are absorbed by the roots and transported to the leaves.
ü Carbon dioxide from air is taken in through the tiny pores present on the surface of leaves.
ü These pores are surrounded by ‘guard cells’. Such pores are called stomata.
ü Water and minerals are transported to the leaves by the vessels which run like pipes throughout the root, the stem, the branches and the leaves. They form a continuous path or passage for the nutrients to reach the leaf. They are called vessels.
4. Algae -
ü You often see slimy, green patches in ponds or stagnant water bodies. These are generally formed by the growth of organisms called algae.
ü They contain chlorophyll which gives them the green colour. Algae can also prepare their own food by photosynthesis.
5. Parasitic Plants -
ü A parasitic plant is one that lines inside or outside the other organism and derive their food from them.
ü The plant (non-green) which obtains their food from other organism is called a parasite and the living organism from whose body, food is obtained is called host, e.g. amarbel or Cuscuta.
ü It takes ready made food from host through special type of roots called sucking roots which penetrate into host plant and suck food material from the host.
ü The leaves have a green pigment called chlorophyll. It helps leaves to capture the energy of the sunlight.
ü This energy is used to synthesize (prepare) food from carbon dioxide and water.
ü Since the synthesis of food occurs in the presence of sunlight, it is called photosynthesis (Photo: light; synthesis : to combine).
ü We find that chlorophyll, sunlight, carbon dioxide and water are necessary to carry out the process of photosynthesis.
ü It is a unique process on the earth. The solar energy is captured by the leaves and stored in the plant in the form of food. Thus, sun is the ultimate source of energy for all living organisms.
ü During photosynthesis, chlorophyll containing cells of leaves, in the presence of sunlight, use carbon dioxide and water to synthesize carbohydrates.
ü The process can be represented in an equation-
6. Insectivorous Plants -
ü There are some plants which can trap insects and digest them for their nutrition. These plants are green in colour but lack nitrogen elements.
ü To overcome this problem, these plants eat insects. Hence they are called insectivorous plant or carnivorous plants.
ü These have specialized leaves, the apex of which forms a lid that can open and close the mouth of pitcher. There are hair inside the pitcher which are used to entangle the insects.
ü When an insect comes in contact of the lid, it gets closed and traps the insects. The insect inside the pitcher is digested by digestive juices secreted by the pitcher to obtain nitrogen compounds (amino acids) from them. e.g. pitcher plant, sundew, Venusflytrap and bladderwort.
ü Since these can synthesize their own food but fulfil their nitrogen deficiency by eating insects, therefore these are called as partial heterotrophs.
7. Saprotrophic Plants -
ü The mode of nutrition in which organisms take their nutrients from dead and decaying matter is called saprotrophic nutrition.
ü Plants which use the saprotrophic mode of nutrition are called saprotrophs, e.g. fungi like mushrooms are non-green plants that grow on the dead and decaying matter for their food. Bread moulds (fungi) and yeast are saprophytic plants.
8. Symbiotic Plants -
ü Sometimes, two plants of different species live together and help each other in obtaining food and shelter.
ü This association is called symbiosis and such plants are called symbiotic plants.
ü The relationship in which two different organisms live together and share shelter and nutrients is called symbiotic relationship, e.g. lichens and Rhizobium.
ü Lichen is an association in which algae and a fungus live together.
ü The fungus provides shelter, water and minerals to the algae and in return, the algae provide food which it prepares by photosynthesis.
NCERT PRACTICE QUESTIONS
1. Why do organisms take food?
Ans. - All organisms require energy for their life processes. Plants prepare their food and acquire nutrients from abiotic components like soil, air, water and sunlight. While, animals need to get food from either plants or other animals to obtain nutrients; hence animals need to take food to acquire nutrients and energy.
2. Distinguish between a parasite and a saprophyte.
Ans -
3. How would you test the presence of starch in leaves?
Ans. - Take two potted plants of the same kind. Keep one in the dark for up-to 72 hours and the other in sunlight. Perform the iodine test with the leaves of both the plants as -
Iodine test - Put iodine solution on the leaf Observation- Blue-black colour will be observed on the leaves of the plant kept in sunlight, which indicates the presence of starch. Blue-black colour will not be observed on the leaves of plant kept in the darkroom. This indicates the absence of starch.
3. Give a brief description of the process of synthesis of food in green plants.
Ans.-
ü Leaves are the food factories of plants. Therefore, all the raw materials must
ü reach the leaf.
ü Water and minerals present in the soil are absorbed by the roots and transported to the leaves.
ü Carbon dioxide from air is taken in through the tiny pores present on the surface of leaves.
ü These pores are surrounded by ‘guard cells’. Such pores are called stomata.
ü Water and minerals are transported to the leaves by the vessels which run
like pipes throughout the root, the stem, the branches and the leaves. They form a continuous path or passage for the nutrients to reach the leaf. They are called vessels.
ü The leaves have a green pigment called chlorophyll. It helps leaves to capture the energy of the sunlight.
ü This energy is used to synthesize (prepare) food from carbon dioxide and water.
ü Since the synthesis of food occurs in the presence of sunlight, it is called photosynthesis (Photo: light; synthesis : to combine).
ü We find that chlorophyll, sunlight, carbon dioxide and water are necessary to carry out the process of photosynthesis.
ü It is a unique process on the earth. The solar energy is captured by the leaves and stored in the plant in the form of food. Thus, sun is the ultimate source of energy for all living organisms.
ü During photosynthesis, chlorophyll containing cells of leaves, in the presence of sunlight, use carbon dioxide and water to synthesize carbohydrates.
ü The process can be represented in an equation-
5. Show with the help of a sketch that plants are the ultimate source of food.
Ans.-
6. Fill in the blanks:
(a) Green plants are called _________________ since they synthesize their own food.
(b) The food synthesised by plants is stored as _________________.
(c) In photosynthesis solar energy is absorbed by the pigment called ___________.
(d) During photosynthesis plants take in ______________________ and release __________________ gas.
Ans.- (a) autotrophs (b) starch. (c) chlorophyll. (d) Carbon dioxide and Oxygen
7. Name the following:
i) A parasitic plant with yellow, slender and branched stem.
ii) A plant that is partially autotrophic.
iii) The pores through which leaves exchange gases.
Ans. - i) Cuscuta ii) Pitcher plant iii) Stomata
8. Tick the correct answer:
(a) Cuscuta is an example of:
(i) autotroph (ii) parasite (iii) saprotroph (iv) host
(b) The plant which traps and feeds on insects is:
(i) Cuscuta (ii) china rose (iii) pitcher plant (iv) rose
Ans. - a- (ii) Parasite b- (iii) pitcher plant
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