Class 7 Science Chapter 1 Nutrition in plants Oxford Book Solutions

Class 7 Ch 1 Nutrition in Plants

1. Objective type questions

A. Fill in the blanks with the correct words.

1. The mode of nutrition in which an organism makes its own food is called (autotrophic/heterotrophic) nutrition.

2. The green pigment found in leaves is present in structures called (chloroplasts/chlorophyll).

3. Water and other nutrients absorbed by the roots are transported from the roots to other parts of the plant through structures called the (xylem/ phloem).

4. The roots of saprophytic plants contain convert dead and decaying matter into (fungi/bacteria) that (nutrients/oxygen).

5. The (symbiotic/parasitic) association between Rhizobium and leguminous plants replenishes the soil with (oxygen/nitrogen).

Ans:

The mode of nutrition in which an organism makes its own food is called autotrophic nutrition.

The green pigment found in leaves is present in structures called chloroplasts.

Water and other nutrients absorbed by the roots are transported from the roots to other parts of the plant through structures called the xylem.

The roots of saprophytic plants convert dead and decaying matter into nutrients with the help of fungi.

The symbiotic association between Rhizobium and leguminous plants replenishes the soil with nitrogen.

B. Write T for the True and F for the False statements. Correct the false statements.

1. All plants are autotrophic in nature.

2. Plants make food in the form of starch as a result of photosynthesis.

3. The leaf of the pitcher plant is modified into a tubular pitcher to trap insects.

4. Lichens are a parasitic relationship between a fungus and a bacteria.

5. Farmers grow leguminous plants alternately with other crops to restore potassium and phosphorus content of the soil.

Ans:

False – All plants are not autotrophic. Some are heterotrophic (e.g., Cuscuta).

True

True

False – Lichens are a symbiotic relationship between a fungus and an alga.

False – Leguminous plants restore nitrogen, not potassium and phosphorus.

C. Choose the correct option.

1. Which of these absorbs light energy?

a. Chlorophyll

b. Stomata

c. Guard cells

d. Veins

2. Which of these increases the surface area to absorb water and minerals through the roots?

a. Rootlets

b. Secondary roots

c. Root hair

d. Primary root

3. Which of these is the reason for heterotrophic nutrition in certain plants?

a. They do not contain chlorophyll.

b. They grow in places where there isn’t enough light.

c. They depend on other organisms for certain specific nutrients.

d. All of these

4. Which of these plants live in association with other organisms in such a way that both gain from each other?

a. Insectivorous plants

c. Symbiotic plants

b. Saprophytic plants

d. Parasitic plants

5. Which of these does a sundew plant have for trapping and digesting insects?

a. Tentacles and mucilage

c. Short, stiff hair and leaves that snap shut

d. Bladder structures that snap shut

b. Pitcher and digestive fluid

6. Which of these is needed for photosynthesis?

a. Chlorophyll

c. Carbon dioxide

b. Sunlight and water

d. All of these

7. Which of these helps leaves to get carbon dioxide for photosynthesis?

a. Xylem

b. Phloem

c. Stomata

d. Thylakoid

8. Which of these tissues help in conducting prepared food from leaves to the roots?

a. Xylem

b. Phloem

c. Guard cells

d. Both a and b

9. Which of these plants live off dead and rotting material?

a. Parasitic

b. Saprophytic

c. Insectivorous

d. Symbiotic

10. Which of the following do pea plants get into a symbiotic relationship with?

a. Fungus

b. Algae

Ans:

a. Chlorophyll

c. Root hair

d. All of these

c. Symbiotic plants

a. Tentacles and mucilage

d. All of these

c. Stomata

b. Phloem

b. Saprophytic

c. Rhizobium

II. Very short answer type questions

Give two examples for the following.

1. Plants that have autotrophic mode of nutrition

2. Plants that have heterotrophic mode of nutrition

3. Plants that grow in nitrogen-deficient soil

4. Plants that harm their host plant

5. Symbiotic plants

Ans:

Autotrophic plants: Mango, Neem

Heterotrophic plants: Cuscuta, Pitcher plant

Plants in nitrogen-deficient soil: Venus flytrap, Sundew

Plants that harm hosts: Cuscuta, Mistletoe

Symbiotic plants: Lichen, Pea plant with Rhizobium

III. Short answer type questions

1. Define heterotrophic mode of nutrition. Name the four types of heterotrophic nutrition in plants.

2. How do parasitic plants benefit from their host plants?

3. What is the symbiotic association in lichens?

Ans:

  1. Heterotrophic nutrition is the mode where plants depend on other organisms for food.
    Four types: Parasitic, Insectivorous, Saprophytic, Symbiotic.
  2. Parasitic plants get water and nutrients from the host plant by attaching themselves and absorbing directly through structures like haustoria.
  3. Lichens are a symbiotic association between a fungus (which absorbs water and minerals) and an alga (which performs photosynthesis and prepares food).

IV. Long answer type questions

1.With the help of a labelled diagram, describe the process of photosynthesis in autotrophs.

Ans: Photosynthesis Process (with diagram)

Plants use chlorophyll, sunlight, carbon dioxide, and water to produce glucose and oxygen.

Equation: 6CO2+6H2O→C6H12O6+6O2

(Include a diagram with leaf, sunlight, water from roots, CO₂ from air, glucose production, and oxygen release.)

2.Describe how insectivorous plants trap and digest insects for nutrition. Support your answer with examples.

Ans: Insectivorous plants grow in nitrogen-deficient soil and trap insects for nutrition:

Pitcher Plant: Leaf forms a tube to trap insects.

Sundew: Sticky tentacles catch insects.

Venus Flytrap: Snap-shut leaves with trigger hairs.

They secrete digestive juices and absorb nutrients.

Insectivorous plants grow in soil that is poor in nitrogen. To fulfill their nitrogen requirements, they trap and digest insects. These plants have specially modified leaves that act as traps. For example, the pitcher plant has a tube-shaped leaf with a lid. Insects are attracted to its color and scent, fall into the pitcher, and are digested by digestive juices. The sundew plant has sticky tentacles on its leaves that trap insects. Once an insect is stuck, the tentacles curl around it and secrete enzymes to digest it. The Venus flytrap has leaves with sensitive trigger hairs. When an insect touches these hairs, the leaves snap shut, trapping the insect inside. The plant then secretes digestive fluids to break down the insect and absorb the nutrients. These adaptations help insectivorous plants survive in nutrient-deficient environments by supplementing their food through animal protein.

3. Discuss the different ways in which nutrients are replenished into the soil

Ans: Nutrients replenished in soil by:

Growing leguminous plants with Rhizobium bacteria to fix nitrogen.

Decomposition of dead plants and animals.

Fertilizers and manure add nutrients like nitrogen, phosphorus, and potassium.

Plants absorb essential nutrients like nitrogen, phosphorus, and potassium from the soil to grow and carry out various life processes. Over time, continuous farming depletes these nutrients, making it necessary to replenish them for healthy plant growth and good crop yield. One natural way to restore nutrients is through the decay of organic matter. Dead plants, animals, and animal waste decompose with the help of microbes and fungi, releasing nutrients back into the soil.

Another effective method is the use of manure and fertilizers. Manure, made from animal dung and organic waste, is rich in nutrients and improves soil texture. Chemical fertilizers contain specific nutrients like urea (rich in nitrogen), superphosphate, and potash, which directly boost soil fertility.

Crop rotation is also a common practice. Farmers grow leguminous plants like peas and beans in between other crops. These plants have a symbiotic relationship with Rhizobium bacteria, which live in their root nodules and fix atmospheric nitrogen into the soil.

Additionally, green manure involves growing certain crops and ploughing them back into the soil to enrich it. These sustainable practices help maintain soil health, reduce dependency on chemicals, and ensure long-term agricultural productivity.

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