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7th Class CBSE Science NCERT Book

Nutrition in Plants: 7th Class NCERT CBSE Science Ch 01

Nutrition in Plants 7th Class NCERT CBSE Science Chapter 01

Question: Why do organisms need to take food?

Answer: All living organisms require food to survive. It gives them energy to perform various activities. All activities such as playing, running, walking, studying etc. require energy. The various components present in our food such as carbohydrates, proteins, fats, vitamins, and minerals provide energy to our body. These are also important for growth and development of the body.

Question: Distinguish between a parasite and a saprotroph.

Answer:

Parasite:

  • The organism that grows on the body of another organism and derives nutrients from it is known as a parasite.
  • Examples of parasites are Cuscuta and orchids.

Saprotroph:

  • The organism that obtains nutrients from the dead or decaying organic matter is called saprotroph.
  • Examples of saprotrophs are fungi and some bacteria.

Nutrition in Plants – Question: How would you test the presence of starch in leaves?

Answer: Experiment to test the presence of starch in leaves:

Take two healthy green potted plants of the same type. Keep one potted plant in a dark room for one or two days in order to remove all the starch from the leaves. Keep the other plant in sunlight. Now, take one leaf from each potted plant and put a few drops of iodine solution on them. Then note down the observation.

Plants kept in light and dark conditions
Plants kept in light and dark conditions

No blue black colour will be observed on the leaves of the plant kept in the dark room. This indicates the absence of starch. Blue black colour will be observed on the leaves of the plant kept in sunlight. This indicates the presence of starch.

Question: Give a brief description of the process of synthesis of food in green plants.

Answer: Photosynthesis is defined as the process in which the chlorophyll-containing plant cells synthesize food in the form of carbohydrates, using carbon dioxide and water in the presence of solar energy.

Photosynthesis

Sources of raw materials required for photosynthesis:

  1. Water is taken in from the roots of the plant and is transported to the leaves.
  2. Carbon dioxide from the air enters the leaves through the tiny pores called stomata and diffuses to the cells containing chlorophyll.
  3. Solar energy is used to break water into hydrogen and oxygen. This hydrogen is combined with carbon dioxide to form food for the plants, which is ultimately used by the animals as well.

Thus, photosynthesis can be represented by the following equation.

Photosynthesis

Question: Show with the help of a sketch that the plants are the ultimate source of food.

Answer:

Photosynthesis

Question: Fill in the blanks:

  1. Green plants are called __________ since they synthesize their own food.
  2. The food synthesized by the plants is stored as __________.
  3. In photosynthesis solar energy is captured by the pigment called ___________.
  4. During photosynthesis plants take in ___________and release ___________.

Answer:

  1. Green plants are called autotrophs  since they synthesize their own food.
  2. The food synthesized by the plants is stored as starch.
  3. In photosynthesis solar energy is captured by the pigment called chlorophyll.
  4. During photosynthesis plants take in carbon dioxide and release oxygen.

Question: Name the following:

  1. A parasitic plant with yellow, slender and tubular stem.
  2. A plant that has both autotrophic and heterotrophic mode of nutrition.
  3. The pores through which leaves exchange gases.

Answer:

  1. Cuscuta
  2. Pitcher plant
  3. Stomata

Question: Tick the correct answer:

Amarbel is an example of

  1. autotroph
  2. parasite
  3. saprotroph
  4. host

The plant which traps and feeds on insects is

  1. Cuscuta
  2. china rose
  3. pitcher plant
  4. rose

Answer:

Amarbel is an example of

  1. autotroph
  2. parasite √
  3. saprotroph
  4. host

The plant which traps and feeds on insects is

  1. Cuscuta
  2. China rose
  3. pitcher plant √
  4. rose

Question:

Match the items given in Column I with those in Column II:

Column I Column II
Chlorophyll Bacteria
Nitrogen Heterotrophs
Amarbel Pitcher plant
Animals Leaf
Insects Parasite

Answer:

Column I Column II
Chlorophyll Leaf
Nitrogen Bacteria
Amarbel Parasite
Animals Heterotrophs
Insects Pitcher plant

Question: Mark ‘T’ if the statement is true and ‘F’ if it is false:

  1. Carbon dioxide is released during photosynthesis. (T/F)
  2. Plants which synthesize their food themselves are called saprotrophs. (T/F)
  3. The product of photosynthesis is not a protein. (T/F)
  4. Solar energy is converted into chemical energy during photosynthesis. (T/F)

Answer:

  1. Carbon dioxide is released during photosynthesis. (F)
  2. Plants which synthesize their food themselves are called saprotrophs. (F)
  3. The product of photosynthesis is not a protein. (T)
  4. Solar energy is converted into chemical energy during photosynthesis. (T)

Question: Choose the correct option from the following:

Which part of the plant takes in carbon dioxide from the air for photosynthesis?

  1. Root hair
  2. Stomata
  3. Leaf veins
  4. Sepals

Answer:

2. Stomata

Question: Choose the correct option from the following:

Plants take carbon dioxide from the atmosphere mainly through their:

  1. roots
  2. stem
  3. flowers
  4. leaves

Answer:

4. leaves

Question: Potato and ginger are both underground parts that store food. Where is the food prepared in these plants?

Answer: In both the plants, shoot system and leaves are above ground. They prepare food through photosynthesis and transport it to the underground part for storage.

Question: Plants prepare their food using a different mode of nutrition than us. What is it?

Answer: The mode of nutrition in plant is autotrophic, i.e. they synthesize their own food.

Question: Photosynthesis requires chlorophyll and a few other raw materials. Add the missing raw materials to the list given below:

Water, minerals, (a) …… (b) …….

Answer:

(a) Sunlight
(b) Carbon dioxide

Question: The tiny openings present on the leaf surface. What are they called?

Answer: Stomata are the tiny pores present on the surface of leaves through which gaseous exchange takes place in plants.

Question: What is the function of guard cells of stomata?

Answer: Guard cells help in controlling the opening and closing of stomata for gaseous exchange.

Question: Which parts of the plant are called food factories of the plant?

Answer: Leaves are referred to as food factories of plants. This is because, leaves synthesize food by the process of photosynthesis.

Question: A carbohydrate is produced by plants as food source. It is constituted from which molecules?

Answer: Carbohydrates are composed of carbon, hydrogen and oxygen.

Question: Why do some plants feed on insects?

Answer: Insectivorous plants grow in soil which lack nitrogen, therefore they eat insects to fulfill their need of nitrogen.

Question: Define parasites.

Answer: Parasites they are those organisms which grow on other plants or animals for their food, e.g. Cuscuta.

Question: Name the bacteria that can fix atmospheric nitrogen.

Answer: Rhizobium is the bacterium which can fix atmospheric nitrogen.

Question: Except plants, why can’t other living organisms prepare their food using CO2, water and minerals?

Answer: Our body does not contain chlorophyll for absorbing solar energy which is necessary for preparing food using air, water etc.

Question: A leguminous plant can restore the soil’s concentration of mineral nutrients. Can you give examples of some such plants?

Answer: Plants such as gram, pulses and beans are leguminous.

Question: Algae are green in colour. Why?

Answer: Algae contain chlorophyll which imparts green colour to them.

Question: what do you understand by nutrition?

Answer: The process of utilizing nutrients like carbohydrates, proteins, fats, etc., to generate energy is called nutrition.

Question: Fungus can be harmful and useful. Give an example showing both of these traits of fungus.

Answer: Fungus produces antibiotics like penicillin used to treat diseases and fungus can also harm us by causing fungal infections on skin and hair.

Question: A unique feature in leaves allows them to prepare the food while other parts of plants cannot. Write the possible reason for this.

Answer: Leaves contain chlorophyll which is essential for food preparation and is absent in other parts of plant.

Question: Algae and fungi form a unique association sharing benefits from each other. What is the name of association between them?

Answer: Lichens.

Question: In a plant, photosynthesis occurs in a part other than leaf. Name that plant and the part where photosynthesis occurs.

Answer: Cactus, the part where photosynthesis occurs are stem and branches which are green.

Question: Why is Cuscuta categorized as a parasite?

Answer: Cuscuta derives its nutrition using an association where it deprives its host of all valuable nutrients and absorbs them itself. Hence, it is called a parasitic plant.

Question: Plant cannot use the nitrogen present in the soil directly. Why?

Answer: Plants can use nitrogen only in soluble form while in soil nitrogen is present in inorganic form.

Question: Why are insectivorous plants called partial heterotrophs?

Answer: Insectivorous plants are autotrophs, i.e. they prepare their own food. They are partial heterotrophs as they eat insects for obtaining nitrogen.

Question: What is the stored food form in sunflower seeds?

Answer: In sunflower seeds, glucose is stored in the form of oils (fats).

Question: What do you understand by saprotrophic mode of nutrition?

Answer: The mode of nutrition in which organisms take their nutrients from dead and decaying matter is called saprotrophic mode of nutrition.

Question: A mutually beneficial relationship that occurs between two plants. It is known by what name? Give an example.

Answer: Symbiosis is the mutually benefiting association between two plants, e.g. lichens.

Question: For testing the presence of starch in leaves, a boiled leaf is used. Why?

Answer: Boiling the leaf remove chlorophyll / green colour from the leaves.

Question: Mosquitoes, bed bugs, lice and leeches suck our blood. Can they be called as parasites?

Answer: Yes, these animals/insects are parasites as they harm the hosts while they suck blood.

Question: Insectivorous plants have one or the other specialized organs to catch their prey. What is that organ?

Answer: Leaves of insectivorous plants catches the prey.

Question: Farmers spread manure of fertilizers in the field or in gardens, etc. Why are these added to the soil?

Answer: Plants absorb mineral nutrients from soil. Thus, declining their concentration in soil fertilisers and manures enhance or add these essential nutrients back in soil.

Question: A cell is formed of many sub-components. Identify different constituents of the cell. Are animal and plant cells similar?

Answer: A cell contains nucleus, cytoplasm, vacuole, cell organelles like chloroplast, mitochondria, etc. No, animal cells are different from plant cells.

Question: A goat eats away all the leaves of a small plant (balsam). However, in a few days, new leaves could be seen sprouting in the plant again. How did the plant survive without leaves?

Answer: The plant of balsam survived on the food stored in the stem and roots.

Question: Different modes of nutrition has been observed in plants. What are they? Give example of each.

Answer: Plants show two major modes of nutrition, i.e.

  1. Autotrophs are those which can synthesise their own food.
  2. Heterotrophs are those which are dependent on other plants and animals for their food. They are of following types:
    (a) Parasites, e.g. Cuscuta
    (b) Saprotrophs, e.g. fungi

Question: Sunlight, chlorophyll, carbon dioxide, water and minerals are raw materials essential for photosynthesis. Do you know where they are available? Fill in the blanks with the appropriate raw materials.

  1. Available in the plant: ………
  2. Available in the soil: ………
  3. Available in the air: ………
  4. Available during day: ………

Answer:

  1. Available in the plant: chlorophyll
  2. Available in the soil: water, minerals
  3. Available in the air: carbon dioxide
  4. Available during day: sunlight

Question: Plants are considered an essential part of earth as they keep a check on lot of process occurring all over. What would happen if all the green plants are wiped from earth?

Answer: Green plants are the source of energy for all the living organisms so that they can perform their normal functions. If all green plants and trees disappear, all the organism depending on them for food and shelter will also die.

The lack of gaseous exchange will lead to increase in amount of CO2, causing death in humans and other animals also. The cycle of life will gradually disappear.

Question: Autotrophs and heterotrophs are two different organisms with distinct modes of nutrition state. How are they different from each other?

Answer: The difference between autotrophs and heterotrophs are as follows:

Autotrophs Heterotrophs
They can prepare their own food. They cannot prepare their own food.
Autotrophs take simple inorganic substances and change it into complex organic food, e.g. green plants. They take in complex food and breakdown it into simple compounds, e.g. all animals, fungi and non-green plants.

Question: Wheat dough if left in the open, after a few days, starts to emit a foul smell and becomes unfit for use. Give reason.

Answer: Carbohydrates in wheat dough encourage the growth of yeast and other saprophytic fungi which breakdown carbohydrates into simpler compounds like CO2 and alcohol and emit a foul smell.

Question: What are the various raw materials for photosynthesis?

Answer: Plants utilize carbon dioxide from air and water and minerals are derived from soil (through roots) as raw material for photosynthesis. Besides these chlorophyll present in green leaf is necessary for the process and sunlight is the source of energy which is converted into chemical energy during the process of photosynthesis.

Question: Nitrogen is an essential nutrient for plants growth. But farmers who cultivate pulses as crops like green gram, bengal gram, black gram, etc., do not apply nitrogenous fertilizers during t cultivation. Why?

Answer: Roots of pulses (leguminous plants) have a symbiotic association with a bacterium called Rhizobium. This bacteria convert gaseous nitrogen of air into water soluble nitrogen compounds and give them to the leguminous plants for their growth. Hence, farmers need not use nitrogenous fertilizers.

Question: Pooja is worried about her new shoes which she wore on special occasions that they were spoiled by fungus during rainy season. Is she right to worry, if yes, then tell why does fungi suddenly appears during the rainy season?

Answer:  Yes, the fungi reproduces by spores which are generally present in the air and grow on any article that are left in hot and humid weather for a long time. During rainy season they land on wet and warm things and begin to germinate and grow.

Question: In what unique manner does a pitcher plant derive its nutrition?

Answer: Nepenthes or pitcher plant modifies its leaf axis into a long tubular pitcher to form a pitfall trap. Inside the pitcher sticky liquid is present. When any insect comes in contact with the leaf, the lid present on it is closed and insect is trapped. The liquid contains digestive enzymes which slowly digest the trapped insects.

Question: Water and minerals are absorbed by the roots and then transported to leaves. How?

Answer: Water and minerals are transported to the leaves by the vessels which run like pipes throughout the root, stem, branches and the leaves. These vessels are xylem and phloem, forming a continuous path or passage for the nutrients to make them reach the leaf.

Question: Some plants have deep red, violet or brown colored leaves. Can these leaves perform the photosynthesis process?

Answer: Yes, plants having deep red, violet or brown colored leaves can also carry out photosynthesis because they contain chlorophyll. But their green colour of chlorophyll is masked by the large amount of all other colored pigments.

Question: If plant has a requirement for nitrogen, then from where will they obtain it?

Answer: Soil contains nitrogen in the form that is not usable by plants. Bacteria like Rhizobium converts nitrogen into soluble form that can be easily used by plants. So, if plant has a requirement for nitrogen, then it will obtain that which the help of bacteria.

Question: In the absence of photosynthesis, life would be impossible on earth. Is it true or false?

Answer: True, because photosynthesis is important for the existence of life on the earth. Photosynthesis is important process as it is provides food to all living organisms and maintains CO2 – O2 balance of nature.

Question: Describe the process by which plants prepare their food using different raw materials.

Answer: The process by which green plants can prepare their own food is called photosynthesis. Green plants possess chlorophyll in their leaf and utilizes carbon dioxide (from air) water, minerals (from soil, through root) as raw material and sunlight as source of energy and convert light energy into chemical energy. The food thus synthesized is in the form of starch (carbohydrate). The overall reaction for photosynthesis can be given as follows:

Photosynthesis

Question: Describe the method for replenishing the soils with minerals and other essential constituents used by plants growing in those soil by farmers.

Answer: Replenishment of Nutrients in Soil

Crops require a lot of nitrogen to make proteins. After the harvest, the soil becomes deficient in nitrogen. Plants cannot use the nitrogen gas available in atmosphere directly. Action of certain bacteria can convert this nitrogen into form readily used by plants. Rhizobium bacteria live in the root nodules of leguminous plants. These bacteria take nitrogen gas from the atmosphere and convert it into water soluble nitrogen compounds making it available to the leguminous plants for their growth.

In return, leguminous plants provide food and shelter to the bacteria as Rhizobium cannot prepare its food. They, thus have a symbiotic relationship. This association is very important for the farmers, as they do not need to add nitrogen fertilizers to the soil in which leguminous plants are grown.

Question: Harish went to visit his grandfather in village where he saw that his grandfather’s field of wheat are infected with fungus but no one is aware of this. Harish rushed to his grandfather’s side and told him that the field have been infected with fungi. He should use an anti-fungal agent in his fields to stop this infection.

  1. What is fungus?
  2. Can fungus only cause diseases or can it be helpful also?
  3. What values are shown by Harish?

Answer:

  1. Fungus are saprophytic organisms usually present as spores in atmosphere which can germinate on any substrate in optimal conditions.
  2. Fungus are also useful in that they produce many antibiotics which can cure different types of infections like penicillin.
  3. Harish is sincere, curious and knowledgeable with a keen sense of applying it where necessary.

Question: Wild animals like tiger, wolf, lion and leopard do not eat plants. Does this mean that they can survive without plants? Can you provide a suitable explanation?

Answer: Animals like tiger, wolf, lion and leopard are carnivores and do not eat plants. They hunt and eat herbivorous animals like deer, gaur, bison, zebra, giraffe, etc., which are dependent on plants for food.

If there are no plants, herbivorous animals will not survive and ultimately animals like tiger, wolf, lion and leopard will have nothing to eat.

Question: Asha went to visit her grandfather in his village. He was having a serious discussion with his fellow members regarding the productivity level of crops for present year. They all were worried about how to increase the productivity of crop Asha listened to this and then suggested to the group that the reason may be decreased level of minerals in soil.

She told her grandfather to plant crops like pulses, gram, beans, etc., for a year then follow with regular crops. This will increase the crop productivity?

  1. What will you name the process suggested by Asha? Why is there decrease in crop productivity?
  2. What are noted benefits of this process? Will the results be as what Asha expressed?
  3. What values are shown by Asha?

Answer:

  1. This process is known as crop rotation. All the plants/crops grown in soil use the minerals present in soil for their own use. This continuous usage depletes the concentration of mineral in soil.
  2. After growing leguminous plants, the mineral content of soil is restored and enriched to new level. Yes, the benefit of leguminous plant is the re-enrichment of soil minerals.
  3. Asha is observant, sincere and interested in applying her knowledge to situations.

True / False Question: Food is necessary for plants only.

Answer: False, food is necessary for all the living organisms as all of them grow and require maintenance from time to time

Nutrition in Plants – Question: Animals are heterotrophs.

Answer: True

Question: Cells are called building block of a body.

Answer: True

Question: Chlorophyll is present in an animal cell.

Answer: False, chlorophyll is present in leaf of plants not in animal cells.

Question: Fungi are green plants that can synthesize their own food.

Answer: False, fungi are not green and they are not classified as plants. They are saprophytic organisms which derive nutrition from dead and decaying matter.

Question: Pitcher plant eats insects.

Answer: True

Question: Lichen is a saprophytic plant.

Answer: False, lichen is a symbiotic association between an alga and a fungi. It is not a plant.

Question: Rhizobium can fix atmospheric nitrogen into nitrogen compound.

Answer: True

Nutrition in Plants – Question: Match the Column I with Column II.

Column I
Column II
(a) Saprotroph
(b) Chlorophyll
(c) Bacteria Rhizobium
(d) Cuscuta
(e) Insects
(f) Mango tree
(g) Leaf
(h) Tiny pores present on leaf
(i) CO2 and water
(j) Mushroom
(i) Pitcher plant
(ii) Food factory of plants
(iii) Green plant leaf
(iv) Fungi
(v) N2 – fixing
(vi) Stomata
(vii) Parasite
(viii) Raw material
(ix) Saprophyte
(x) Autotroph

Answer:
(a) – (iv), (b) – (iii), (c) – (v), (d) – (vii), (e) – (i), (f) – (x), (g) – (ii), (h) – (vi), (i) – (viii), (j) – (ix)

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