Class 7 Science Notes for Nutrition In Plants

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NUTRITION IN PLANTS
Nutrition: It is the mode of taking food by an organism and its utilization by the body.
• Nutrients: The components of food that provide nourishment to the body.
• All organisms take food and utilize it to get energy for the growth and maintenance of their
bodies.
• Autotrophs- Green plants synthesize their food themselves by the process of photosynthesis.
They are autotrophs.
• Photosynthesis: Green plants prepare their own food with the help of carbon dioxide and
water taken from the environment in presence of sunlight called chlorophyll (found in
green plants) for the manufacture of food. This process is known as photosynthesis.
• Plants use simple chemical substances like carbon dioxide, water and minerals for the
synthesis of food.
• Chlorophyll and sunlight are the essential requirements for photosynthesis.
• Complex chemical substances such as carbohydrates are the products of photosynthesis.
• Solar energy is stored in the form of food in the leaves with the help of chlorophyll.
• Oxygen is produced during photosynthesis.
• Oxygen released in photosynthesis is utilized by living organisms for their survival.
• Parasites- Fungi derive nutrition from dead, decaying matter. They are saprotrophs. Plants like
Cuscuta are parasites. They take food from the host plant.
• Heterotrophs- A few plants and all animals are dependent on others for their nutrition and are
called heterotrophs.
• Parasitic: Organisms that live on the body of other organisms.
• All parasitic plants feed on other plants as either:
(i) Partial Parasites: Obtain some of their nutrition from the host, e.g. painted cup.
(ii) Total Parasites: dependent completely on the host for nutrition, e.g. mistletoe.
• Saprophytic: Organisms that obtain nutrition from dead and decaying plant and animal
matter.
• Mushrooms, moulds and certain types of fungi and bacteria.

• Insectivorous Plants: Green plants which obtain their nourishment partly from soil and

atmosphere and partly from small insects. Example: pitcher plant, bladderwort, and venus fly
trap.
• Symbiosis: Mode of nutrition in which two different individuals associate with each other to
fulfill their requirement of food.
• Lichens found on tree trunks is the association between alga and fugus. Alga obtains water
from fungus and it in turn obtains food from alga.
Mind Map--

Some Important Questions-

Question 1. Potato and ginger are both underground parts that store food. Where is the food
prepared in these plants?
Anwer: 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 2. 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 3.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 4. 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 5. 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 synthesise
food by the process of photosynthesis.
Question 6. 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 7. 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 8. Define parasites.
Answer: Parasites they are those organisms which grow on other plants or animals for their food,
e.g. Cuscuta.
Question 9. Name the bacteria that can fix atmospheric nitrogen.
Answer: Rhizobium is the bacterium which can fix atmospheric nitrogen.

Question 10. 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 11. 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 12. Algae are green in colour. Why?
Answer: Algae contain chlorophyll which imparts green colour to them.
Question 13. What do you understand by nutrition?
Answer: The process of utilising nutrients like carbohydrates, proteins, fats, etc., to generate
energy is called nutrition.
Question 14. 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 15. 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 16. Algae and fungi form a unique association sharing benefits from each other. What
is the name of association between them?
Answer: Lichens.
Question 17. 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 18.Why is Cuscuta, categorised 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 19.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 20. Why insectivorous plants are 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 22.What is the stored food form in sunflower seeds?
Answer: In sunflower seeds, glucose is stored in the form of oils (fats).
Question 23.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 24. A mutually beneficial relationship that occurs between two plants. It is known by
what name? Give an example.
Answer: Symbiosis is the mutually benefitting association between two plants, e.g. lichens.
Question 25.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 26.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 27.Insectivorous plants have one or the other specialised organs to catch their prey.
What is that organ?
Answer: Leaves of insectivorous plants catches the prey.
Question 28.Farmers spread manure of fertilisers 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 29.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 29.
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.
(i) Autotrophs are those which can synthesise their own food.
(ii) 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 30. 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 They take in complex food and breakdown it
and change it into complex organic food, e.g. into simple compounds, e.g. all animals, fungi
green plants. and non-green plants.

Question31.
Observe the given figure and label the following terms given in the box. Stomatal opening, guard

cell

Answer: Labelled figure is given
Question32.
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 fertilisers 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 fertilisers.
Question 33. Pooja is worried about her new shoes which she wore on special occassions 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 34.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
antifungal agent in his fields to stop this infection.
(a) What is fungus?
(b) Can fungus only cause diseases or can it be helpful also?
(c) What values are shown by Harish?
Answer: (a) Fungus are saprophytic organisms usually present as spores in atmosphere which
can germinate on any substrate in optimal conditions.
(b) Fungus are also useful in that they produce many antibiotics which can cure different types of
infections like penicillin.
(c) Harish is sincere, curious and knowledgeable with a keen sense of applying it where
necessary.
Question 35. 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.

Match the Column I with Column II.

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

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