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class 7 nutrition in plants notes

Questions covered are:

1. What is nutrition, and why is it important for living organisms?

2. What are autotrophs and heterotrophs? Explain with examples.

3. What is photosynthesis? Describe the process in detail.

4. Why are leaves considered the food factories of plants?

5. What is the role of chlorophyll and sunlight in photosynthesis?

6. What is the significance of photosynthesis for life on Earth?

7. How do non-green plants obtain their nutrition?

8. What are insectivorous plants? How do they obtain their food?

9. What is saprotrophic nutrition? Give examples.

10. What is symbiosis? Give examples.

11. How do farmers replenish nutrients in the soil?

12. Why do insectivorous plants like pitcher plants feed on insects even though they are green?

13. What is the role of Rhizobium bacteria in agriculture?

14. What adaptations help desert plants carry out photosynthesis?

15. Explain how fungi grow and reproduce on decaying matter.

16. Why are greenhouses used for growing crops?

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1. What is nutrition, and why is it important for living organisms?

  1. Nutrition is the process of taking in food and utilizing it for various functions in the body.
  2. It provides energy for performing life processes such as respiration, growth, and reproduction.
  3. Nutrients help in building the body, repairing damaged tissues, and maintaining overall health.

2. What are autotrophs and heterotrophs? Explain with examples.

  1. Autotrophs:
    • Organisms that prepare their own food using simple substances like carbon dioxide, water, an3. What is photosynthesis? Describe the process in detail.
    • d sunlight.
    • Plants are autotrophs as they synthesize food through photosynthesis. Example: Green plants like mango and rose.
  2. Heterotrophs:
    • Organisms that depend on other organisms (plants or animals) for their food.
    • Animals and non-green plants are heterotrophs. Example: Humans and fungi like mushrooms.

3. What is photosynthesis? Describe the process in detail.

  • Photosynthesis is the process by which green plants prepare food using sunlight, carbon dioxide, water, and chlorophyll.

Steps of Photosynthesis:

  • Carbon dioxide from the air enters the leaves through stomata.
    • Water and minerals are absorbed by roots and transported to the leaves via vessels.
    • Chlorophyll in leaves traps sunlight, providing the energy required to combine water and carbon dioxide.
    • Food (glucose) is synthesized, and oxygen is released as a byproduct.
  1. Significance:
    • Photosynthesis provides food and oxygen, which are essential for the survival of all living organisms.

4. Why are leaves considered the food factories of plants?

  1. Leaves contain chlorophyll, a green pigment that traps sunlight necessary for photosynthesis.
  2. They have stomata, tiny pores that allow carbon dioxide to enter the leaf.
  3. Vascular tissues transport water and minerals to the leaves, enabling them to synthesize food.

5. What is the role of chlorophyll and sunlight in photosynthesis?

  1. Chlorophyll:
    • Chlorophyll captures solar energy and enables the synthesis of carbohydrates from carbon dioxide and water.
    • It is present in the chloroplasts of green leaves.
  2. Sunlight:
    • Sunlight acts as an energy source for the photosynthesis process.
    • The energy from sunlight is stored in the form of glucose, which serves as food for plants.

6. What is the significance of photosynthesis for life on Earth?

  1. Food Source: Photosynthesis produces food (glucose), which forms the basis of the food chain.
  2. Oxygen Production: Oxygen, essential for the survival of most organisms, is released during photosynthesis.
  3. Energy Flow: It enables plants to convert solar energy into chemical energy, making the sun the ultimate energy source for all life.

7. How do non-green plants obtain their nutrition?

  1. Non-green plants lack chlorophyll and cannot perform photosynthesis.
  2. They depend on other organisms for food and exhibit heterotrophic modes of nutrition.
  3. Example:
    • Parasites like Cuscuta obtain food from host plants.
    • Saprotrophs like fungi feed on dead and decaying matter.

8. What are insectivorous plants? How do they obtain their food?

  1. Insectivorous plants are plants that trap and digest insects to obtain nutrients.
  2. Example: Pitcher plant
    • It has a modified leaf in the shape of a pitcher with downward-directed hairs.
    • When an insect falls into the pitcher, the lid closes, and digestive juices break down the insect to absorb nutrients.
  3. These plants usually grow in nitrogen-deficient soil, and the insects provide them with nitrogen.

9. What is saprotrophic nutrition? Give examples.

  1. Saprotrophic nutrition is a mode of nutrition in which organisms feed on dead and decaying matter.
  2. Examples:
    • Fungi like mushrooms and molds absorb nutrients from organic matter such as wood or bread.
  3. These organisms secrete digestive enzymes that break down complex substances into simpler ones, which they absorb.

10. What is symbiosis? Give examples.

  1. Symbiosis is a relationship where two different organisms live together and mutually benefit each other.
  2. Examples:
    • Lichens: A partnership between an alga and a fungus. The alga prepares food, while the fungus provides shelter and water.
    • Rhizobium bacteria: These bacteria live in the roots of leguminous plants and convert atmospheric nitrogen into a usable form for the plant. In return, they receive shelter and nutrients.

11. How do farmers replenish nutrients in the soil?

  1. Farmers use fertilizers and manures rich in nutrients like nitrogen, potassium, and phosphorus to replenish soil fertility.
  2. Growing leguminous crops (like peas and beans) enhances nitrogen content in the soil due to the presence of Rhizobium bacteria in their root nodules.
  3. These practices maintain soil health and ensure better crop production.

12. Why do insectivorous plants like pitcher plants feed on insects even though they are green?

  1. Pitcher plants can perform photosynthesis but grow in nitrogen-deficient soils.
  2. To fulfill their nitrogen requirement, they trap and digest insects.
  3. The nutrients obtained from insects help them survive in such poor soil conditions.

13. What is the role of Rhizobium bacteria in agriculture?

  1. Rhizobium bacteria live in the root nodules of leguminous plants like peas, beans, and grams.
  2. They convert atmospheric nitrogen into a usable form (nitrogen fixation) for plants.
  3. This reduces the need for artificial nitrogen fertilizers and enriches soil fertility, benefitting farmers.

14. What adaptations help desert plants carry out photosynthesis?

  1. Desert plants have reduced or modified leaves (like spines) to minimize water loss through transpiration.
  2. Their green stems perform photosynthesis, storing water and energy.
  3. These adaptations enable them to survive in arid environments with scarce water availability.

15. Explain how fungi grow and reproduce on decaying matter.

  1. Fungi reproduce by spores that are present in the air.
  2. When these spores land on moist and warm organic matter, they germinate and grow.
  3. Fungi secrete digestive enzymes onto the surface of the organic matter, breaking it down into simpler substances, which they absorb as nutrients.

16. Why are greenhouses used for growing crops?

  1. Greenhouses provide a controlled environment for plants by regulating light, temperature, humidity, and carbon dioxide.
  2. They protect plants from pests, diseases, and extreme weather conditions.
  3. This ensures better crop yield and higher-quality fruits and vegetables for farmers.

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Intext Questions and Answers

Q1: How do plants prepare their own food?

Plants prepare their food through a process called photosynthesis.

  1. They use carbon dioxide from the air, water, and minerals from the soil, and sunlight as energy.
  2. Chlorophyll in leaves traps sunlight to convert these raw materials into glucose (food).
  3. Oxygen is released as a byproduct during this process.

Q2: Why are leaves called the food factories of plants?

  1. Leaves contain chlorophyll, which captures sunlight essential for photosynthesis.
  2. Stomata in leaves allow the exchange of gases (carbon dioxide intake and oxygen release).
  3. Vascular tissues transport water and minerals to the leaves, enabling the preparation of food.

Q3: Why can’t humans and animals prepare food like plants?

  1. Humans and animals lack chlorophyll, which is essential for trapping sunlight.
  2. They do not have specialized structures like stomata to absorb carbon dioxide directly from the air.
  3. Unlike plants, their bodies are not designed to convert sunlight into chemical energy for food synthesis.

Q4: How does nitrogen reach plants for protein synthesis?

  1. Certain bacteria, like Rhizobium, convert atmospheric nitrogen into a usable form and release it into the soil.
  2. Plants absorb this nitrogen along with water and minerals from the soil.
  3. Farmers also add fertilizers rich in nitrogen to the soil to meet the plant’s requirements.

Q5: How do parasitic plants like Cuscuta obtain food?

  1. Cuscuta lacks chlorophyll and cannot perform photosynthesis.
  2. It twines around the host plant and absorbs nutrients directly from it through specialized structures.
  3. This deprives the host plant of essential nutrients.

Q6: Why do some plants trap insects?

  1. Some plants grow in nitrogen-deficient soils, which do not provide sufficient nutrients.
  2. They trap insects to obtain nitrogen and other nutrients by digesting the insects with the help of digestive enzymes.
  3. Examples: Pitcher plants, Venus flytraps.

Q7: What are saprotrophs? How do they obtain food?

  1. Saprotrophs are organisms that feed on dead and decaying matter.
  2. They secrete digestive enzymes onto the organic material, breaking it down into simpler substances.
  3. The nutrients are then absorbed into their bodies. Examples: Fungi and mushrooms.

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Book-Back Questions with Answers

1. Why do organisms take food?

Organisms take food to:

  1. Obtain energy for performing various life processes such as growth, reproduction, and movement.
  2. Repair and maintain their body tissues.
  3. Carry out metabolic activities essential for survival.

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

  1. Green plants synthesize food through photosynthesis.
  2. Carbon dioxide from the air is absorbed through stomata, and water and minerals are absorbed by the roots.
  3. Chlorophyll in leaves traps sunlight, which provides energy to combine carbon dioxide and water to form glucose.
  4. Oxygen is released as a byproduct.

3. Why are Rhizobium bacteria important for farmers?

  1. Rhizobium bacteria convert atmospheric nitrogen into a usable form for plants.
  2. They live in the root nodules of leguminous plants like peas and beans.
  3. This helps farmers reduce the use of nitrogen fertilizers and enriches the soil naturally.

4. What are the different modes of nutrition in plants?

  1. Autotrophic Nutrition:
    • Green plants prepare their own food through photosynthesis.
    • Example: Mango tree.
  2. Heterotrophic Nutrition:
    • Plants depend on other organisms for food. Examples include:
      • Parasitic Plants: Cuscuta (Amarbel) obtains nutrients from a host plant.
      • Saprotrophic Plants: Fungi feed on dead and decaying matter.
      • Insectivorous Plants: Pitcher plant traps and digests insects for nutrients.

5. What is the role of chlorophyll in photosynthesis?

  1. Chlorophyll is a green pigment present in the leaves of plants.
  2. It absorbs sunlight, which provides the energy needed to convert carbon dioxide and water into glucose.
  3. Chlorophyll makes the process of photosynthesis possible, enabling plants to produce food.

6. How are nutrients replenished in the soil?

  1. Farmers add fertilizers and manures rich in nutrients like nitrogen, potassium, and phosphorus to the soil.
  2. Growing leguminous plants enriches the soil with nitrogen through their symbiotic relationship with Rhizobium bacteria.
  3. Crop rotation and natural composting also help restore soil fertility.

7. What are lichens? Explain their symbiotic relationship.

  1. Lichens are organisms that consist of a partnership between an alga and a fungus.
  2. The alga prepares food through photosynthesis, while the fungus provides shelter, water, and minerals.
  3. This mutual relationship benefits both organisms, allowing them to survive in harsh conditions.

8. How do desert plants carry out photosynthesis with reduced leaves?

  1. Desert plants like cacti have spines instead of leaves to minimize water loss through transpiration.
  2. Their green stems perform photosynthesis and store water.
  3. This adaptation allows them to survive in arid conditions.

9. Why do insectivorous plants feed on insects despite being green?

  1. Insectivorous plants grow in soils deficient in nitrogen and other nutrients.
  2. They trap and digest insects to obtain these essential nutrients.
  3. Their ability to photosynthesize allows them to fulfill their energy requirements, but they rely on insects for additional nutrients.
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