Solutions To Text Questions Chapter 1: Nutrition in Plants Multiple Choice Questions Page No. 10 1. (d) 2. (b) 3. (c) 4. (b) 5. (c) Multiple Choice Questions Page No. 13 1. (b) 2. (c) 3. (b) 4. (c) 5. (c) SECTION A CLASS RESPONSE A. Oral Questions. 1. The process by which green plants make their own food (like glucose) from carbon dioxide and water by using sunlight in the presence of chlorophyll is called photosynthesis. 2. The leaves contain tiny, green coloured bodies called chloroplasts which contain a green pigment called chlorophyll, so, they are green in colour. 3. Non-green plants which obtain their nutrients from dead and decaying organic matter of plants and animals are called saprophytes. 4. Nutrition is the process of taking food by an organism and its digestion, absorption and utilisation by the body. 5. The mode of nutrition in which an organism cannot make its own food from the simple substances but obtains ready-made food made by green plants directly or indirectly is called heterotrophic mode of nutrition. B. Science Quiz. 1. Chlorophyll 2. Xylem 3. Phloem 4. Charles Reid Barnes WORKSHEET A. Tick (3) the correct options. 1. (d) 2. (d) 3. (b) 4. (a) B. Circle the odd ones. Give reasons for your choice. 1. Oxygen → It is produced during photosynthesis whereas others are required in photosynthesis. 2. Cuscuta → It is a parasite whereas others are autotrophs. 3. Lichens → It shows symbiotic association of algae and fungi whereas others are insectivorous plants. 4. Mistletoe → It is a parasitic plant whereas others are insectivorous plants. C. Fill in the blanks. 1. nitrogen 2. photosynthesis 3. guard 4. autotrophic Teacher’s Resource Pack SCIENCE-7 15 SECTION B A. Multiple Choice Questions (MCQs) Scientific/Practical skills. 1. (a) 2. (c) 3. (c) B. Very Short Answer Questions. 1. Cuscuta and coral root/Indian pipe 2. Pitcher plant and venus flytrap/Utricularia/Drosera 3. Stomata 4. Cactus (fleshy stem) 5. Autotrophic and heterotrophic C. Short Answer Type-I Questions. 1. Organisms that cannot make their own food but obtain ready-made food made by plants directly or indirectly are called heterotrophs. Animals and non-green plants are heterotrophs. 2. Mistletoe has green leaves which make the food for plant but it receives water and minerals from the host plant on which it grows to synthesise its food. Thus, it is called partial parasite. 3. Some plants eat insects for fulfilling their nitrogen requirements for preparing proteins. 4. The mode of nutrition in which an organism makes its own food from simple substances like carbon dioxide, water and minerals present in the surroundings is called autotrophic nutrition. 5. The mode of nutrition in which the non-green plants obtain their nutrients from dead and decaying organic matter of plants and animals is called saprotrophic nutrition. D. Short Answer Type-II Questions. 1. We can decolourise a leaf by boiling it first in water and then in alcohol. This process is called bleaching. 2. The organisms which obtain the ready-made food from the body of a plant are called plant parasites. Cuscuta and mistletoe are plant parasites. 3. When an insect lands on the pitcher of the pitcher plant, the lid gets closed and the trapped insect gets entangled into the hair. The insect is digested by the digestive juices secreted by the pitcher. 4. The plants which live in or on the body of other plants and derive ready- made food from them are called parasitic plants. For example, Cuscuta and mistletoe. The plants which feed on insects for fulfilling their nitrogen requirements are called insectivorous plants. For example, Drosera, Utricularia, pitcher plant, venus flytrap. 5. (a) Lichens show symbiotic association or symbiosis. (b) We can learn to help others and to work and live together in harmony in the society. 16 Teacher’s Resource Pack SCIENCE-7 E. Long Answer Questions. 1. To show that sunlight is necessary for photosynthesis Things needed: A potted plant, a beaker, a Bunsen burner, alcohol, iodine solution, a dropper, boiling tube, test tube holder, watch glass, wire gauze and tripod stand Method : (i) Take a healthy potted plant and keep it in a dark room for 2-3 days to destarch the leaves. (ii) Cover one of its leaves partly with a strip of black paper and put the plant in sunlight for a few hours. (iii) Pluck this covered leaf and remove the black strip. (iv) Remove the chlorophyll from the leaf by boiling it first in water and then in alcohol. In this way, you get a decolourised leaf. Wash the leaf with water again. (v) Add a few drops of iodine solution over the colourless leaf and observe. Observation : You see that the part of the leaf covered with black paper does not turn blue-black on adding iodine solution while the uncovered parts turn blue-black. Discussion: The covered part of the leaf could not get sunlight, hence, no starch is formed in this part. Conclusion: This shows that sunlight is needed for making starch, i.e., sunlight is necessary for photosynthesis. 2. Rhizobium bacteria live in the root nodules of leguminous plants and provide them nitrogen in a soluble form. In return, the leguminous plants provide food and shelter to the Rhizobium bacteria. Both organisms have mutual relationship. Thus, they help each other in survival. 3. To show that carbon dioxide is necessary for photosynthesis Things needed : A wide-mouth glass bottle, a potted plant, potassium hydroxide solution, alcohol, water, a Bunsen burner, a rubber cork, a beaker, a dropper and iodine solution Method : (i) Take a potted plant having long and narrow leaves and place it in a completely dark room for 2-3 days to destarch the leaves. (ii) Take a glass bottle having a wide mouth and put some potassium hydroxide solution in it. Potassium hydroxide solution absorbs the carbon dioxide gas present in the glass bottle. (iii) Take a rubber cork which fits tightly to the mouth of the glass bottle and cut it into two halves. (iv) Insert one destarched leaf which is still attached to the plant into this glass bottle through the split cork. The upper half of the leaf Teacher’s Resource Pack SCIENCE-7 17 should remain outside the glass bottle whereas the lower half of the leaf should be inserted in the glass bottle. (v) Keep the potted plant in the sunlight for 3 to 4 days. (vi) Pluck the leaf from the plant and take it out from the glass bottle. (vii) Remove the chlorophyll from the leaf by boiling it first in water and then in alcohol. In this way, a decolourised leaf is obtained. Wash the leaf with water again. (viii) Add a few drops of iodine over the colourless leaf and observe. Observation : You find that the lower half of the leaf (which was inside the glass bottle) does not turn blue-black on adding iodine solution. The upper half of the leaf (which was outside the glass bottle) turns blue- black. Discussion : The lower half of the leaf does not turn blue-black on adding iodine solution because starch is not formed in this part of the leaf. The lower half of the leaf was inside the glass bottle where there was no carbon dioxide. The upper half of the leaf turns blue-black on adding iodine solution because starch is present here, i.e., photosynthesis occurred here. Conclusion: This shows that carbon dioxide is necessary for photosynthesis. 4. The two types of heterotrophic nutrition in plants are saprotrophic nutrition and parasitic nutrition. (i) Saprotrophic nutrition: The mode of nutrition in which the non- green plants obtain their nutrients from dead and decaying organic matter of plants and animals is called saprotrophic nutrition. Plants which use saprotrophic mode of nutrition are called saprophytes. The roots of saprophytes contain organisms called fungi. The fungi secrete digestive juices on the dead and decaying matter and convert it into a liquid that is used as a nutrient by the non-green plants. E.g., fungi and bacteria (ii) Parasitic nutrition: The mode of nutrition in which some plants live in or on the body of other living organisms and derive their ready-made food from them is called parasitic nutrition. The plant which obtains the ready-made food is called a parasite and the organism from whose body the food is obtained is called the host. Eg. Cuscuta. F. HOTS (Higher Order Thinking Skills) Questions. 1. If plant leaves are devoid of stomata, then there will be no exchange of gases in the plants. They will not be able to make their food and give us oxygen. 2. No, only the green plants are autotrophic in nature. Non-green plants are heterotrophic in nature. 18 Teacher’s Resource Pack SCIENCE-7 3. If all the plants perish from the earth, the life will not exist on the earth. This is because all the organisms require oxygen for breathing and if plants will not be there then the process of photosynthesis will not occur and hence no oxygen will be released for breathing. 4. Photosynthesis maintains the balance between oxygen and carbon dioxide in atmosphere. During photosynthesis, plants take in carbon dioxide and release oxygen in the atmosphere. The living organisms breathe in oxygen from the atmosphere for respiration and release carbon dioxide. This carbon dioxide is again taken by plants for photosynthesis. So, the process of photosynthesis maintains a balance between oxygen and carbon dioxide. G. Application Based Questions. 1. Rohit will not get a positive starch test because keeping the plant in darkness, i.e., without sunlight, destarches the plant and thus, plant is unable to make starch.