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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