Living Science 2020 2021 Solutions for Class 7 Science Chapter 1 Nutrition In Plants are provided here with simple step-by-step explanations. These solutions for Nutrition In Plants are extremely popular among Class 7 students for Science Nutrition In Plants Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Living Science 2020 2021 Book of Class 7 Science Chapter 1 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Living Science 2020 2021 Solutions. All Living Science 2020 2021 Solutions for class Class 7 Science are prepared by experts and are 100% accurate.
Page No 8:
Question 1:
If a new organism is discovered and it is found that it can make food for itself from simple non-living substances found in nature, what will you classify it as–an autotroph or a heterotroph? Give reasons.
Answer:
An organism that can prepare its food from simple non-living substances will be classified as an autotroph. This is because autotrophic organisms are those organisms which can use simple non-living substances (such as carbon dioxide and water) to produce their own food. These organism can obtain energy for this process through sunlight or chemicals.
Page No 8:
Question 2:
The absence of which of these will not affect photosynthesis–oxygen, carbon dioxide, water, chlorophyll, light? Give reasons.
Answer:
The absence of oxygen will have no effect on the process of photosynthesis. This is because the photosynthetic process utilises water and carbon dioxide to produce oxygen and carbohydrate in the presence of chlorophyll and sunlight. Thus, oxygen is a product of photosynthesis and is not required for photosynthesis.
Page No 8:
Question 3:
Do you expect the intensity of light to affect the rate of photosynthesis?
Answer:
Yes, the intensity of light has a direct affect on the rate of photosynthesis. The chlorophyll molecules that are essential for photosynthesis require a certain intensity of light to perform maximum rate of photosynthesis. Thus, light intensity will certainly affect the photosynthesis rate.
Page No 11:
Question 1:
A tiger does not eat plants, so it does not depend on plants for food. Is the statement true? Justify your answer.
Answer:
The given statement is false. Although a tiger does not eat plants, it still depends on the plants. This is because tigers feed on herbivores such as deer which obtain their food from the plants. If the plants are not available, then these herbivores will not get food and consequently, tiger will not get any food. Thus, tiger depends on plant for their food.
Page No 11:
Question 2:
All plants are autotrophic. Do you agree? Give reasons.
Answer:
No, all plants are not autotrophic. Some of the non-green plants such as dodder plants obtain their food from other plants and these plants are heterotrophic plants. Heterophic plants generally do not possess chlorophyll, which inhibits their ability to prepare their own food. Consequently, such plants are not autotrophic.
Page No 11:
Question 3:
In a forest, trees keep taking nutrients from the soil. Therefore, after sometime, the nutrient level will become so low that growth of trees will suffer. Do you agree? Give reasons.
Answer:
No, the nutrient level in a forest will not become low enough to prevent the growth of trees. This is because in forests, the decaying of dead animals and plants adds nutrients to the soil. This natural process prevents the exhaustion of nutrients and replenishes the nutrients in the soil.
Page No 11:
Question 4:
Plants need nitrogen to make proteins. Can they absorb nitrogen from the atmosphere?
Answer:
No, plants can not absorb nitrogen from the atmosphere. Plants can use nitrogen only when it is present in the soil in a soluble form. This soluble nitrogen is absorbed by the roots of the plants and is used by the plants to make proteins.
Page No 12:
Question 1:
The life porcess/processes that provides/provide energy is/are
(a) nutrition
(b) respiration
(c) both nutrition and respiration
(d) response to stimuli.
Answer:
(c) both nutrition and respiration
Nutrition is the process of obtaining food and utilising it, and respiration is the oxidation of food for obtaining energy.
Page No 12:
Question 2:
Which of these are autotrophs?
(a) all plants
(b) green plants
(c) all animals
(d) unicellular organisms
Answer:
(b) green plants
Because green plants are capable of making their own food, they are called autotrophs.
Page No 12:
Question 3:
Which of these is not necessary for photosynthesis?
(a) carbon dioxide
(b) chlorophyll
(c) light
(d) nitrogen
Answer:
(d) nitrogen
Green plants, due to the presence of chlorophyll in their leaves, can perform photosynthesis in the presence of light by using carbon dioxide as a raw material. Nitrogen is not needed for it.
Page No 12:
Question 4:
Which of these elements is needed in addition to carbon, hydrogen and oxygen to make proteins?
(a) nitrogen
(b) phosphorus
(c) potassium
(d) calcium
Answer:
(a) nitrogen
Nitrogen is an important constituent of proteins.
Page No 12:
Question 5:
Which of the following gets absorbed from the atmosphere during photosynthesis?
(a) oxygen
(b) water vapour
(c) carbon dioxide
(d) nitrogen
Answer:
(c) carbon dioxide
Green plants have tiny pores or stomata on their leaves which allow them to absorb carbon dioxide from the atmosphere during photosynthesis.
Page No 12:
Question 6:
Organisms that live in or near the host and obtain their nutrition from the host are called
(a) saprophytes
(b) atuotrophs
(c) heterotrophs
(d) parasites
Answer:
(d) parasites
Organisms that cannot make their own food and are therefore entirely dependent on their hosts for food are called parasites.
Page No 12:
Question 7:
Partial parasites are
(a) green plants
(b) non-green plants
(c) either green or non-green plants
(d) neither green nor non-green plants.
Answer:
(a) green plants
These plants obtain water and minerals from their hosts. Hence, they are called partial parasites.
Page No 12:
Question 8:
Which of these is a saprophyte?
(a) venus flytrap
(b) mushroom
(c) pitcher plant
(d) dodder
Answer:
(b) mushroom
Mushrooms live on dead and decaying plants and animals to get their food; hence, they are called saprophytes.
Page No 12:
Question 1:
Living ogranisms that cannot make their own food are called______________
Answer:
Living organisms that cannot make their own food are called heterotrophs.
Page No 12:
Question 2:
The structures in cells that contain chlorophyll are called_________
Answer:
The structures in cells that contain chlorophyll are called chloroplasts.
Page No 12:
Question 3:
What does 'photo' in photosynthesis refer to?
Answer:
'Photo' in photosynthesis refers to light.
Page No 12:
Question 4:
Which bacteria in the soil can convert atmospheric nitrogen into soluble compounds?
Answer:
Rhizobium are the bacteria which are present in the soil and convert atmospheric nitrogen into soluble compounds.
Page No 12:
Question 5:
What type of plant is Cuscuta?
Answer:
Cuscuta is a parasitic plant which obtains food from the other plants.
Page No 12:
Question 6:
What do you call a mutually beneficial relationship between two living organisms?
Answer:
Symbiosis is the mutually beneficial relationship between two living organisms.
Page No 12:
Question 7:
Name one organism that gets its food from dead and decaying matter.
Answer:
Mushroom gets its food from dead and decaying matter.
Page No 12:
Question 8:
When iodine is added to starch, it becomes __________ in colour.
Answer:
When iodine is added to starch, it becomes blue-black in colour.
Page No 12:
Question 9:
What is the ultimate source of all the energy needs of our body?
Answer:
Food is the ultimate source of all the energy needs of our body.
Note: Although sun is the ultimate source of energy for all living beings. But the energy requirements of our body is fulfilled by the food obtained from the plants.
Page No 13:
Question 10:
Saprophytes are green in colour. True or false?
Answer:
False, as saprophytes are non-green plants.
Page No 13:
Question 11:
Some green plants are also heterotrophic in nature. True or false?
Answer:
True.
Some green plants are heterotrophic in nature. For example, plants like pitcher plant feeds on insects.
Page No 13:
Question 12:
Which cells control the opening and closing of stomata?
Answer:
The guard cells control the opening and closing of stomata.
Page No 13:
Question 1:
What is nutrition?
Answer:
Nutrition is defined as the process of obtaining food and utilising it by any organism. Nutrition is one of the key processes of obtaining energy from food.
Page No 13:
Question 2:
What are 'stomata'? Where are they normally found?
Answer:
Stomata are the tiny pores on the leaves through which plants absorb atmospheric carbon dioxide. They are normally found on the underside of the leaves.
Page No 13:
Question 3:
Write down the chemical equation for manufacture of food in green plants.
Answer:
The chemical equation representing the process of manufacturing food by green plants (photosynthesis) is as follows:
Page No 13:
Question 4:
What factors are essential for photosynthesis to take place?
Answer:
Factors essential for photosynthesis are sunlight, water, carbon dioxide and chlorophyll (green pigment present in the leaves).
Page No 13:
Question 5:
How does an insectivorous plant absorb nutrients from an insect trapped by it?
Answer:
Insectivorous plants secrete digestive juices to digest the insect trapped by them. These plants then absorb the nutrients released from the digested insect.
Page No 13:
Question 6:
Why is nitrogenous fertilizer not added in soil in which leguminous plants are grown?
Answer:
Nitrogenous fertilisers are not added to the soil in which leguminous plants are grown because these plants can fix atmospheric nitrogen in the soil with the help of the bacteria Rhizobium present in their root nodules. These bacteria can fix the atmospheric nitrogen in soluble compounds which can be absorbed by the plants.
Page No 13:
Question 7:
How does a saprophyte digest its food?
Answer:
A saprophyte secretes digestive juices on the dead and decaying matter to convert the solid substances into liquid. The saprophyte then absorbs the nutrients from this liquid.
Page No 13:
Question 1:
Differentiate between autotrophs and heterotrophs, giving two examples of each.
Answer:
| Autotrophs | Heterotrophs |
| Organisms which can make their own food from simple substances are called autotrophs. | Organisms which can not make their own food and obtain it directly or indirectly from green plants are called heterotrophs. |
| They are producers. | They are consumers. |
| For example, all green plants, cynobacteria, etc. | For example, all animals like cow, lion and humans. |
Page No 13:
Question 2:
How will you test a leaf for starch? Mention any precautions you will take.
Answer:
Test for starch:
- Pluck one of the green leaves that have been exposed to sunlight.
- Boil that leaf in water for 5 minutes to soften it.
- Then put the leaf in a test tube containing alcohol. Now, gently place this test tube in a beaker of warm water till the alcohol starts boiling. The chlorophyll will slowly get dissolved in the alcohol and the leaf will start losing its green colour.
- Now, remove the alcohol by washing the leaf with warm water. Then spread the leaf over a white tile and add some iodine solution to it.
- Wash the leaf with water to remove the iodine solution and then hold it in light. The parts of leaf which have starch will turn blue-black.
- Do not allow the water in the beaker to boil.
Page No 13:
Question 3:
How do plants get nitrogen to synthesize proteins?
Answer:
Nitrogen is present in the atmosphere in large amounts, but plants can not absorb it directly. There are two ways by which plants can absorb nitrogen. They are as follows:
- The soil bacterium Rhizobium is able to fix the atmospheric nitrogen in water soluble compounds. Plants absorb these compounds along with water in order to get nitrogen.
- Plants can also get nitrogen from the nitrogen-rich fertilizers used by farmers to treat the soil.
Page No 13:
Question 4:
All animals−whether herbivores, carnivores or omnivores−depend on plants for their food. Discuss.
Answer:
Plants are capable of making their own food. All animals whether herbivores, carnivores or omnivores can not make their own food; hence, they depend on the plants for their food. Herbivores feed on plants to obtain nutrition. Again, the carnivores eat herbivores to obtain nutrition. Thus, carnivores indirectly depend on plants for their food. Omnivores, on the other hand, can directly obtain food from plants or indirectly consume animals which feed on plants. Thus, all animals ultimately depend on plants for their food.
Page No 13:
Question 5:
Explain the following with the help of an example for each:
(a) parasitic nutrition
(b) symbiosis
(c) saprotrophic nutrition
Answer:
(a) Parasitic nutrition: Parasites feed on other living organisms to obtain nutrition. This mode of nutrition is referred to as parasitic nutrition. For example, non green plants like dodder which can not synthesise their own food, grows over other plants and sucks nutrition from them using their root like structure.
(b) Symbiosis: The mutually beneficial relationship between two organisms is termed as symbiosis. For example, lichens are association between alga and fungi. Alga supplies food to its fungal partner, while fungi provides shelter to its algal partner.
(c) Saprotrophic nutrition: Organisms which feed on dead and decaying matter are called saprotrophs, and this mode of obtaining nutrition is called saprotrophic nutrition. For example, mushrooms, fungi and bacteria
Page No 13:
Question 6:
Why are manures and fertilizers added to the soil in a farm?
Answer:
Manures and fertilisers are added to the soil in order to enrich its organic composition and replenish the nutrients in it. The plants absorb most of the nutrients from the soil, leaving the soil deficient of these nutrients. Manures and fertilisers are rich in organic matter and nutrients like nitrogen, potassium and phosphorous. Thus, according to the need of the plants, farmers add manures and fertilisers in the soil.
Page No 13:
Question 7:
Distinguish between parasites and partial parasites in plants, giving one example of each.
Answer:
| Parasites | Partial Parasites |
| Parasites are non green plants which feed on other plants. | Partial parasites are green plants which can synthesis their own food but absorb water and minerals from other plants. |
| For example, dodder sucks food from other plants via its hair like structure. | For example, mistletoe plant which grows on a mango tree. |
Page No 13:
Question 1:
We make our own food in the kitchen. This means that humans are also autotrophs. Do you agree? Give reasons.
Answer:
Humans can not synthesize their own food; therefore, they are heterotrophs. We make our own food in the kitchen but the raw materials that we use to cook the food are either obtained from plants or from animals. Thus, humans, directly or indirectly, depend upon plants for their food. For example, we cook vegetables obtained from plants and meat obtained from animals.
Page No 13:
Question 2:
Why can't animals make food from carbon dioxide, water and sunlight, like plants do?
Answer:
Unlike plants, animals lack chloroplast in their body. So, animals can not prepare their food from carbon dioxide, water and sunlight. Chloroplast is an organelle which is specifically present in green plants. It has a green coloured pigment called chlorophyll. This chlorophyll traps the sunlight and enables plants to make food, which animals can not.
Page No 13:
Question 3:
The pitcher plant and Venus flytrap are green plants that can photosynthesize.
Why do they need to feed on insects?
Answer:
Even though Venus flytrap and pitcher plant are green plants, they can not perform photosynthesis because they grow in a soil which is poor in nutrients. Therefore, to obtain nutrition they feed on insects. This nutrition supplements the food prepared by them via photosynthesis.
Page No 13:
Question 4:
Plants do not have a digestive system like us. Why do they not need a digestive system?
Answer:
Plants make their food through the process of photosynthesis. Because the synthesis of food occurs within them, they do not need to digest it. Therefore, they do not have a digestive system like humans.
Page No 13:
Question 1:
Deepak carried out an experiment to see the effect of increasing the amount of carbon dioxide available to a pondweed (a submerged plant) on the rate of photosynthesis carried out by the plant. The readings of the experiment are potted in the graph.
Answer these questions.
- How do you think he measured the rate of photosynthesis?
- How do you think he increased the amount of carbon dioxide in the water?
- Since temperature causes a change in the rate of photosynthesis, he kept the temperature constant throughout the experiment. Suggest one more factor that he should have kept constant.
- Why did the graph increase initially?
- Why do you think it ultimately levelled off?
Answer:
1. The rate of photosynthesis can be measured by -
- by measuring the CO2 uptake or the O2 output or
- by measuring the gas exchange
- by measuring the amount of increase in dry weight of the photosynthesis plant or a specific plant part.
- by using Ganong’s Photosynthometer
2. The amount of CO2 can be increased the water by adding the chemical potassium hydrogencarbonate. It acts as a source of CO2. The amount of CO2 can be increased by increasing the amount of this chemical.
3. Another factor which he should keep constant is the light intensity.
4. The graph increased initially because the rate of photosynthesis increases with the increase in the amount of carbon dioxide.
5. The graph levelled off because the increase in the rate of photosynthesis with the increase in carbon dioxide, occurs only upto a point. After reaching that point, increase in the concentration of carbon dioxide has no effect on the rate of photosynthesis.
Page No 14:
Question 1:
Anwesa owns a restaurant. One day she noticed fungus growing on the bread she had bought in the morning, which had to be served for breakfast to her clients. She immediately asked her cook to throw away the bread and purchase fresh ones. In doing this, she lost some money. What value did Anwesa show?
Answer:
The above incident shows that Anwesha is a responsible, aware and an honest person who cares more about the health of her customers rather than her profits.
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