Science 7 : 1. Nutrition in Plants

[Page 1]

1. The root is the underground part of the plant body that fixes it to the soil. It takes up water and minerals from the soil. It also helps to prevent soil erosion by wind or water.
2. The stem is the main axis of the shoot system. It bears leaves, branches, and flowers. It helps to keep the plant upright.
3. A leaf is the flattened green structure which helps to prepare food for the plant by the process of photosynthesis. It requires sunlight, carbon dioxide, and water to prepare food in the presence of a green pigment called chlorophyll.
4. A flower is the reproductive part of a plant. It changes into a fruit which contains seeds.

Think and Answer [Page 2]

What will happen to the heterotrophs if plants stop producing food? Answer: If plants stop producing food, heterotrophs, including humans and animals, will not be able to survive. This is because heterotrophs depend directly or indirectly on plants for their food. Without plants, the entire food chain would collapse, leading to starvation and extinction of many species. Additionally, since plants release oxygen during photosynthesis, the oxygen level in the atmosphere would decrease, making it difficult for organisms to breathe and survive.

Think and Answer [Page 3]

How does photosynthesis maintain a balance between oxygen and carbon dioxide in the atmosphere? Answer: Photosynthesis plays a crucial role in maintaining the balance of oxygen and carbon dioxide in the atmosphere. During photosynthesis, green plants absorb carbon dioxide from the air and use it to produce food, releasing oxygen as a byproduct. This oxygen is then used by living organisms for respiration, which in turn releases carbon dioxide back into the atmosphere. This continuous cycle ensures a stable level of these gases, preventing excess carbon dioxide buildup and maintaining the oxygen supply necessary for life.

Think and Answer [Page 3]

Name the substances that are transported by different vessels in plants. Answer: Plants have two types of transport vessels: Xylem – It transports water and minerals from the roots to different parts of the plant. Phloem – It transports food (mainly in the form of sugars) from the leaves to other parts of the plant.

Lab Activity

A. Take a money plant and keep it in sunlight for a few days. Pluck one leaf and perform iodine test on it. 1. Which portion of the leaf developed blue-black colour? Answer: The portion of the leaf that developed blue-black colour is the green part of the leaf. 2. Name the pigment present in this part of the leaf. Answer: The pigment present in this part of the leaf is chlorophyll. B. Take a potted plant and keep it in the dark for a few days. Take a conical flask and add some KOH (potassium hydroxide) into it. Insert a leaf of the plant (without plucking) into this conical flask and put a cork. Place this plant in sunlight for a few hours. Remove the conical flask and pluck that leaf This is leaf P. Pluck another leaf Q of the same plant and perform iodine test on both of them. 1. Which leaf developed blue-black colour? Answer: Leaf Q (which was not placed inside the conical flask) developed a blue-black colour after the iodine test, indicating the presence of starch. 2. From the lab activity, name the gas that is required for photosynthesis. Answer: The gas required for photosynthesis is carbon dioxide (CO₂). 3. Find out and write the use of KOH in this activity. Answer: KOH (potassium hydroxide) absorbs carbon dioxide from the air inside the conical flask. This prevents photosynthesis in leaf P, showing that CO₂ is necessary for starch production.

Think and Answer [Page 6]

Why are proteins important for our body? Answer: Proteins are essential for our body because:They help in growth and development by building and repairing tissues.They are important for the formation of enzymes and hormones, which regulate various body functions.They strengthen the immune system, helping to fight infections.They provide structural support to muscles, skin, and organs.They serve as an energy source when carbohydrates and fats are insufficient.

Quick Check [Page 6]

Name the following: 1. A type of nutrition in which the organism depends on other organisms for food Answer: Heterotrophic nutrition 2. The pigment present in the chloroplasts of plant cells Answer: Chlorophyll 3. A plant containing variegated leaves Answer: Money plant / Croton 4. The process of conversion of nitrogen in the atmosphere into usable form Answer: Nitrogen fixation

Quick Check [Page 8]

Fill in the blanks to complete the given sentences. 1. The organism from which a parasitic plant derives its food is called host. 2. The saprophytic plants absorb nutrients from the dead and decaying matter. 3. Plants that trap insects and digest them are called insectivorous plants. 4 Symbiotic plants share nutrients and shelter with other plants.

Picture Study

A. Cuscuta B. Venus flytrap C. Mushroom D. Lichen 1. The plant in picture A (Cuscuta) is a parasitic plant that obtains its food from the host plant. 2. The plant in picture B (Venus flytrap) eats insects to fulfil the deficiency of nitrogen. 3. The plant in picture C (Mushroom) is an edible fungus. 4. The plant in picture D (Lichen) lives in symbiotic association with other plants.

Apply Your Learning

A. Identify and Rectify

B. Observe and Answer

Observe the pictures of two plants given below. Identify their differences and answer the questions that follow.

Plant A: Venus flytrap

Plant B: Bread Mould (Fungus)

1. Write the names of plant A and plant B.

Answer: Plant A: Venus flytrap Plant B: Bread Mould (Fungus)

2. What does plant A eat?

Answer: Plant A (Venus flytrap) eats insects to obtain nitrogen and other nutrients.

3. Which of the following plants can make its food as well as feed on other organisms?

1. Plant A ✔
2. Plant B

4. Which of the following plants feeds on dead and decaying matter?

1. Plant A
2. Plant B ✔

C. Life Skills

Photosynthesis is important for the continuity of life on earth. Plants prepare food in this process and also release oxygen in the air. Oxygen is required for all living organisms to breathe. It is very important to plant more trees as they help to purify air by taking in carbon dioxide and releasing oxygen.

How can you justify that photosynthesis is important for the continuity of life on earth?

Answer: Photosynthesis is crucial for the continuity of life on Earth because:

• Food Production: Green plants prepare food through photosynthesis, which serves as the primary source of energy for all living organisms, directly or indirectly.
• Oxygen Release: Oxygen, essential for respiration in humans and animals, is released as a byproduct of photosynthesis.
• Carbon Dioxide Balance: Plants absorb carbon dioxide from the atmosphere, helping to maintain the balance of gases and reduce pollution.
• Energy Flow in Ecosystem: It forms the base of the food chain, supporting herbivores, carnivores, and decomposers.
• Maintaining Climate: Large-scale photosynthesis helps regulate global temperatures and maintains ecological balance.

D. Reason Out (HOTS)

Think carefully and answer the following questions.

1. Your leather shoes appear white if left in humid weather for a long time. Why?

Answer: In humid weather, fungal spores present in the air settle on the shoes and grow due to the moisture. These fungi form a whitish layer, which is actually a fungal colony, commonly referred to as mould.

2. Why is Venus flytrap considered as an insectivorous plant as well as an autotroph?

Answer: Venus flytrap is an autotroph because it has chlorophyll and can perform photosynthesis to prepare its own food. However, it grows in nitrogen-deficient soil, so it also traps and digests insects to obtain additional nutrients like nitrogen, making it an insectivorous plant as well.

3. Animals do not have the ability to prepare their food using sunlight and carbon dioxide. Why?

Answer: Animals lack chlorophyll, the green pigment required to capture sunlight and carry out photosynthesis. Additionally, they do not have chloroplasts, the organelles responsible for converting sunlight, water, and carbon dioxide into food. As a result, animals depend on plants or other organisms for their nutrition, making them heterotrophs.

F. Mind Map

Prepare your own mind map on the topic Types of Nutrition in Plants Briefly describe each type of nutrition. Also, make further divisions, if any. Make it in a systematic manner that is easy to understand and comprehend.

Answer: Mind Map for Types of Nutrition in Plants:

1. Autotrophic Nutrition (Self-feeding)

• Definition: Plants prepare their own food using sunlight, carbon dioxide, and water through photosynthesis.
  Example: Green plants, algae.
• Further Division:
  • Photoautotrophs (Use sunlight) → Example: All green plants.
  • Chemoautotrophs (Use chemicals) → Example: Certain bacteria.

2. Heterotrophic Nutrition (Dependent on Others)

• Definition: Plants obtain nutrients from other organisms as they cannot prepare their own food.
• Types of Heterotrophic Nutrition:
  A. Parasitic Nutrition
  • Definition: The plant absorbs food from a host plant.
  • Example: Cuscuta (Dodder plant), Mistletoe.
• B. Saprophytic Nutrition
  • Definition: The plant feeds on dead and decaying matter.
  • Example: Mushroom (Fungi), Bread mould.
• C. Insectivorous Plants
  • Definition: Plants trap and digest insects to obtain nutrients, especially nitrogen.
  • Example: Venus flytrap, Pitcher plant, Sundew.
• D. Symbiotic Nutrition
  • Definition: Two organisms live together and benefit from each other.
  • Example: Lichen (Algae + Fungi), Rhizobium bacteria in leguminous plants.

H. Case Study

Nitrogen Cycle

Plants synthesise food other than carbohydrates. There are plants that synthesise protein-rich foods by utilising nitrogen from the soil. The nitrogen in the atmosphere is converted into a form that can be used by plants. The nitrogen present in the soil also goes back into the atmosphere as nitrogen gas. This process has been shown in the diagram given below.

1. What is the nitrogen cycle?

Answer: The nitrogen cycle is the continuous movement of nitrogen in different forms between the atmosphere, soil, and living organisms. It includes processes like nitrogen fixation, nitrification, assimilation, ammonification (mineralisation), and denitrification, ensuring that nitrogen is available for plant and animal use while maintaining the balance in nature.

2. Write the name of one microorganism that helps in nitrogen fixation.

Answer: Rhizobium bacteria help in nitrogen fixation by converting atmospheric nitrogen into ammonia, which plants can absorb and use.

3. What do you mean by mineralisation?

Answer: Mineralisation is the process in which organic nitrogen (from dead plants and animals) is converted into inorganic nitrogen compounds like ammonia by decomposers (bacteria and fungi) in the soil.

4. Which compounds of nitrogen are formed during nitrification?

Answer: During nitrification, ammonia (NH₃) is first converted into nitrite (NO₂⁻) and then into nitrate (NO₃⁻) by nitrifying bacteria like Nitrosomonas and Nitrobacter.

5. Which process is known as reverse of mineralisation?

Answer: Denitrification is the reverse of mineralisation, where nitrates (NO₃⁻) are converted back into nitrogen gas (N₂) and released into the atmosphere by denitrifying bacteria like Pseudomonas.

6. Find out the reason stating the importance of nitrogen cycle.

Answer: The nitrogen cycle is essential because:

• It ensures a continuous supply of nitrogen for protein and DNA synthesis in plants and animals.
• It maintains the balance of nitrogen in the atmosphere and soil.
• It helps in soil fertility by replenishing usable nitrogen for plant growth.
• It supports the food chain, as all living organisms require nitrogen to survive.

Exercises

A. Choose the correct answer.

1. Which of the following is/are required by plants to synthesise food?

(a) Chlorophyll

(b) Sunlight

(c) Carbon dioxide

(d) All of these ✔

2. Which of the following gases is formed during photosynthesis?

(a) Hydrogen

(b) Oxygen ✔

(c) Carbon dioxide

(d) Nitrogen

3. Which of the following is a parasitic plant?

(a) Cuscuta ✔

(b) Venus flytrap

(c) Mushroom

(d) Fungi

4. Which type of plant is a sundew?

(a) Saprophytic plant

(b) Insectivorous plant ✔

(c) Symbiotic plant

(d) Parasitic plant

5. In which of the following plants, photosynthesis does not take place in all the areas of its leaves?

(a) Money plant ✔

(b) Pea plant

(c) Rose plant

(d) Coriander plant

B. Write True or False. Also, rectify the incorrect statements.

1. The roots of a plant are the site of photosynthesis.
False – Photosynthesis takes place in the leaves of a plant, not in the roots.
2. The energy from the sun is trapped by chlorophyll.
True
3. Photosynthesis does not take place in the croton plant.
False – Photosynthesis takes place in the croton plant because it has chlorophyll, even though its leaves appear red or purple due to other pigments.
4. Rhizobium bacteria live on the roots of legumes.
True
5. Carbon dioxide gas is released into the atmosphere after photosynthesis.
False – Oxygen gas is released into the atmosphere after photosynthesis, not carbon dioxide.

C. Match the columns.

Column A	Column B
1. Pitcher plant 2. Rhizobium 3. Nitrogen fixing 4. Coleus 5. Hyphae	(a) Variegated leaves (b) Carnivorous plant (c) Cotton-like threads on bread (d) Conversion of nitrogen into usable form (e) Crop rotation

Answer: 

1. Pitcher plant → (b) Carnivorous plant

2. Rhizobium → (e) Crop rotation

3. Nitrogen fixing→ (d) Conversion of nitrogen into usable form

4. Coleus → (a) Variegated leaves

5. Hyphae → (c) Cotton-like threads on bread

D. Name the type of plant.

1. Amarbel – Parasitic plant

2. Lichen – Symbiotic plant

3. Yeast – Saprophytic organism (Fungus)

4. Pea plant – Leguminous plant (Symbiotic with Rhizobium bacteria)

5. Bladderwort – Insectivorous plant

E. Name the plant that has the following description.

1. A non-green plant that feeds on dead and decaying organic matter – Mushroom

2. An edible fungi – Yeast / Mushroom

3. A plant that derives its food from a host – Cuscuta (Amarbel)

4. A plant that lives in symbiotic association – Lichen

5. A legume – Pea plant

F. Give two examples of each of the following categories.

1. Variegated plants – Coleus, Croton

2. Parasitic plants – Cuscuta (Amarbel), Mistletoe

3. Insectivorous plants – Venus flytrap, Pitcher plant

4. Nutrients obtained from plants – Carbohydrates, Proteins

5. Saprophytic plants – Mushroom, Yeast

A. Define the following terms.

1. Nutrition – The process by which living organisms obtain and utilise food for their growth, development, and energy.

2. Photosynthesis – The process by which green plants use sunlight, carbon dioxide, and water to prepare food in the form of glucose, releasing oxygen as a by-product.

3. Nitrogen fixation – The process of converting atmospheric nitrogen into a usable form such as ammonia, nitrates, or nitrites, which can be absorbed by plants. This process is carried out by nitrogen-fixing bacteria like Rhizobium.

4. Saprophytic plants – Plants that obtain their nutrition by decomposing dead and decaying organic matter. Examples include mushrooms and yeast.

5. Symbiosis – A mutually beneficial relationship between two different organisms where both depend on each other for survival. An example is lichen, which consists of algae and fungi living together.

B. Answer the following questions briefly. (Short Answer Questions)

1. What are nutrients? What are the different nutrients that we get from plants?

Answer: Nutrients are substances required by living organisms for growth, energy, and maintenance. The different nutrients we get from plants include carbohydrates (rice, wheat), proteins (pulses, soybeans), fats (nuts, seeds), vitamins (fruits, vegetables), and minerals (leafy greens, nuts).

2. What are the different components required for photosynthesis?

Answer: The components required for photosynthesis are:

• Sunlight – Provides energy for the process.
• Chlorophyll – A green pigment in leaves that captures sunlight.
• Carbon dioxide (CO₂) – Taken from the air through stomata.
• Water (H₂O) – Absorbed from the soil by roots.

3. Why do insectivorous plants trap insects for food?

Answer: Insectivorous plants grow in nitrogen-deficient soil and trap insects to obtain nitrogen, which is essential for their growth. Examples include Venus flytrap and pitcher plant.

4. What type of plant is amarbel? How does it obtain its food?

Answer: Amarbel (Cuscuta) is a parasitic plant that lacks chlorophyll. It obtains food by wrapping around a host plant and absorbing nutrients from it using special structures called haustoria.

5. Why do farmers add fertilisers to the soil?

Answer: Farmers add fertilisers to increase soil fertility and replenish essential nutrients like nitrogen, phosphorus, and potassium, which help plants grow better and yield more crops.

Think and Explain (Long Answer Questions)

Answer the following questions in detail.

1. Describe autotrophic and heterotrophic nutrition in plants.

Answer: Autotrophic Nutrition:

• Plants that prepare their own food using sunlight, carbon dioxide, and water through the process of photosynthesis are called autotrophs.
• They contain chlorophyll, which helps capture solar energy.
• Examples: Green plants like mango tree, sunflower, grass.

Heterotrophic Nutrition:

• Plants that cannot make their own food and depend on other organisms for nourishment are called heterotrophs.
• They either absorb nutrients from dead matter, live on other plants, or trap insects for food.
• Examples: Cuscuta (parasitic), Mushroom (saprophytic), Venus flytrap (insectivorous).

2. Explain the process of photosynthesis in plants. Also, write the equation.

Answer: Photosynthesis is the process by which green plants prepare their own food using sunlight, water, and carbon dioxide. This takes place in the chloroplasts of plant cells.

Steps of Photosynthesis:

• Absorption of sunlight: Chlorophyll in leaves captures solar energy.
• Intake of carbon dioxide: Stomata (tiny pores on leaves) absorb CO₂ from the air.
• Uptake of water: Roots absorb water from the soil and transport it to the leaves through xylem vessels.
• Production of glucose and oxygen: Sunlight helps convert CO₂ and water into glucose and oxygen.

Equation for Photosynthesis:

3. Describe different types of heterotrophic plants.

Answer: Heterotrophic plants are classified into the following types:

1. Parasitic Plants: These plants depend on a host plant for food and nutrients.
   Example: Cuscuta (Amarbel), which wraps around the host and absorbs nutrients.
2. Saprophytic Plants: These plants feed on dead and decaying organic matter.
   Example: Mushroom, Yeast.
3. Insectivorous Plants: These plants grow in nitrogen-deficient soils and trap insects to obtain nitrogen.
   Example: Venus flytrap, Pitcher plant.
4. Symbiotic Plants: These plants form mutual relationships with other organisms for survival.
   Example: Lichen (association of algae and fungi).

4. Explain how a pitcher plant traps its food.

Answer: A pitcher plant is an insectivorous plant that traps insects to fulfil its nitrogen requirements.

Mechanism of Trapping Food:

1. Modification of Leaf: The leaf is modified into a pitcher-like structure with a lid at the top.
2. Attraction of Insects: The inside of the pitcher contains nectar that attracts insects.
3. Slippery Surface: The walls of the pitcher are slippery, causing insects to fall inside.
4. Digestion: The plant secretes digestive enzymes that break down the insect’s body and absorb nutrients.

5. What is symbiotic association? Describe symbiotic association in lichens.

Answer: Symbiotic association is a type of relationship where two different organisms live together and benefit from each other.

Symbiotic Association in Lichens:

• Lichens are a combination of algae and fungi living in a symbiotic relationship.
• Algae prepare food through photosynthesis and provide nutrition.
• Fungi absorb water and minerals from the environment and provide support.
• This relationship helps both organisms survive in harsh conditions like rocks, tree bark, and even deserts.

PTP 50 Multiple-Choice Questions (MCQs) 

1. Which part of the plant absorbs water and minerals from the soil?

a) Stem

b) Root ✔

c) Leaf

d) Flower

2. What is the main function of the stem?

a) Absorbs water

b) Prepares food

c) Supports the plant  ✔

d) Produces seeds

3. Which part of the plant is responsible for photosynthesis?

a) Root

b) Stem

c) Leaf  ✔

d) Flower

4. The reproductive part of a plant is the:

a) Stem

b) Root

c) Leaf

d) Flower  ✔

5. The process by which leaves prepare food is called:

a) Germination

b) Photosynthesis  ✔

c) Transpiration

d) Respiration

6. The process of taking in food and using it for energy is called:

a) Respiration

b) Photosynthesis

c) Nutrition  ✔

d) Digestion

7. Organisms that can prepare their own food are called:

a) Heterotrophs

b) Autotrophs  ✔

c) Parasites

d) Decomposers

8. What do green plants use to prepare food?

a) Carbon dioxide

b) Water

c) Sunlight

d) All of the above  ✔

9. The organisms that depend on others for food are called:

a) Autotrophs

b) Heterotrophs  ✔

c) Producers

d) Decomposers

10. Which of the following is an example of an autotroph?

a) Cow

b) Mushroom

c) Mango tree  ✔

d) Human

11. What is the main site of photosynthesis in a plant?

a) Stem

b) Roots

c) Leaves  ✔

d) Flowers

12. Which pigment is responsible for the green colour of plants?

a) Haemoglobin

b) Chlorophyll  ✔

c) Keratin

d) Xanthophyll

13. What is released during photosynthesis?

a) Oxygen  ✔

b) Carbon dioxide

c) Nitrogen

d) Sulphur dioxide

14. Which gas is required for photosynthesis?

a) Oxygen

b) Carbon dioxide  ✔

c) Nitrogen

d) Hydrogen

15. Which equation correctly represents photosynthesis?

a) CO₂ + O₂ → Carbohydrates + H₂O

b) CO₂ + H₂O → Carbohydrates + O₂  ✔

c) H₂O + O₂ → CO₂ + Energy

d) CO₂ + H₂O → Proteins + O₂

16. Which component is NOT required for photosynthesis?

a) Sunlight

b) Water

c) Oxygen  ✔

d) Carbon dioxide

17. Water is transported from roots to leaves through:

a) Phloem

b) Xylem  ✔

c) Stomata

d) Chloroplast

18. The small openings on leaves that allow gas exchange are called:

a) Guard cells

b) Stomata  ✔

c) Xylem

d) Phloem

19. The gas released during photosynthesis is:

a) Carbon dioxide

b) Nitrogen

c) Oxygen  ✔

d) Hydrogen

20. In which part of the plant does photosynthesis mainly take place?

a) Flowers

b) Roots

c) Leaves  ✔

d) Stems

21. Which type of plants depend on others for food?

a) Autotrophic

b) Heterotrophic  ✔

c) Photosynthetic

d) Self-sufficient

22. Which of the following is a parasitic plant?

a) Mango tree

b) Mushroom

c) Cuscuta (Amarbel)  ✔

d) Banyan tree

23. What type of nutrition does a mushroom have?

a) Autotrophic

b) Parasitic

c) Saprophytic  ✔

d) Symbiotic

24. Insectivorous plants trap insects to obtain:

a) Water

b) Nitrogen  ✔

c) Oxygen

d) Carbon dioxide

25. Which of these is an insectivorous plant?

a) Pea plant

b) Venus flytrap  ✔

c) Lichen

d) Mushroom

26. Cuscuta (Amarbel) is an example of a:

a) Parasite  ✔

b) Saprophyte

c) Symbiotic plant

d) Insectivorous plant

27. Which of the following is a saprophytic plant?

a) Pea plant

b) Mushroom  ✔

c) Venus flytrap

d) Cuscuta

28. Lichens show which type of relationship?

a) Parasitic

b) Saprophytic

c) Symbiotic  ✔

d) Insectivorous

29. A pitcher plant traps insects using:

a) Poison

b) Sticky leaves

c) A modified leaf structure  ✔

d) Sharp thorns

30. What does Rhizobium bacteria help in?

a) Oxygen production

b) Nitrogen fixation  ✔

c) Water absorption

d) Photosynthesis

31. What is the process of converting atmospheric nitrogen into a usable form?

a) Photosynthesis

b) Respiration

c) Nitrogen fixation  ✔

d) Transpiration

32. Which bacteria help in nitrogen fixation?

a) Lactobacillus

b) Rhizobium  ✔

c) E. coli

d) Streptococcus

33. What do farmers add to soil to improve its fertility?

a) Salt

b) Fertilisers  ✔

c) Sand

d) Rocks

34. What is the main function of potassium in plants?

a) Nitrogen fixation

b) Water absorption

c) Growth and development  ✔

d) Seed dispersal

35. Manure and fertilisers help in:

a) Soil erosion

b) Increasing soil fertility  ✔

c) Decreasing soil fertility

d) Stopping plant growth

36. Which plant shows a symbiotic association?

a) Mango tree

b) Lichen  ✔

c) Cuscuta

d) Venus flytrap

37. Which pigment is responsible for photosynthesis?

a) Carotene

b) Xanthophyll

c) Chlorophyll  ✔

d) Haemoglobin

38. What do plants store extra carbohydrates as?

a) Starch  ✔

b) Proteins

c) Fats

d) Vitamins

39. Which part of a leaf carries out photosynthesis?

a) Veins

b) Guard cells

c) Chloroplast  ✔

d) Phloem

40. Which vessel transports food in plants?

a) Xylem

b) Phloem  ✔

c) Stomata

d) Guard cells

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