NCERT Solutions Science Chapter 1 Nutrition in Plants for Class 7th
Class 7 Science, Chapter 1 focuses on “Nutrition in Plants.” Here’s a brief overview of the key concepts covered in the chapter:
1. Definition of Nutrition
Nutrition is the process by which organisms obtain and utilize food for growth, energy, and maintenance.
2. Types of Nutrition
Plants primarily exhibit two types of nutrition:
Autotrophic Nutrition: This is when plants make their own food using sunlight, carbon dioxide, and water through a process called photosynthesis. Green plants (like trees and shrubs) are autotrophs because they contain chlorophyll, which captures sunlight.
Heterotrophic Nutrition: Some plants cannot make their own food and rely on other organisms for nutrition. Examples include carnivorous plants (like the Venus flytrap) and parasitic plants (like dodder).
3. Photosynthesis
Photosynthesis is the process by which green plants convert light energy into chemical energy in the form of glucose.
This means that carbon dioxide and water, in the presence of sunlight, produce glucose and oxygen.
4. Factors Affecting Photosynthesis
Several factors can influence the rate of photosynthesis:
- Light Intensity: More light generally increases the rate, up to a certain point.
- Carbon Dioxide Concentration: Higher levels of CO₂ can enhance photosynthesis.
- Temperature: Photosynthesis occurs best within a certain temperature range.
5. Mineral Nutrition
Plants also require minerals for growth. Essential nutrients include nitrogen, phosphorus, potassium, and others, which are absorbed from the soil. These nutrients are vital for various physiological functions.
6. Nitrogen Fixation
Some plants, especially legumes, have a symbiotic relationship with certain bacteria (like Rhizobium) that convert atmospheric nitrogen into a form that plants can use. This process is essential for plant nutrition since nitrogen is a critical component of proteins and nucleic acids.
7. Heterotrophic Plants
- Carnivorous Plants: These plants capture and digest insects to obtain nutrients (e.g., the Venus flytrap).
- Parasitic Plants: These plants derive nutrients from other living plants (e.g., dodder).
NCERT Solutions Science Chapter 1 Nutrition in Plants
Q1. Why do organisms take food
Answer: All organisms require energy for their life processes. Plants prepare their food and acquire nutrients from abiotic components like soil, air, water and sunlight. On the other hand, animals need to get food from either plants or other animals to obtain nutrients; hence animals need to take food to acquire nutrients and energy.
Q2. Distinguish between a parasite and a saprophyte.
Answer:
| Saprophytes | Parasites |
| Acquire nutrients from dead and decaying matter | Parasites live on or in a host and get its food at the expense of its host |
| Example: Fungi | Example: roundworm |
Q3. How would you test the presence of starch in leaves?
Answer:
Take two potted plants of the same kind. Keep one in the dark for 72 hours and the other in sunlight. Perform the iodine test with the leaves of both the plants as given below. Now leave the pot which was earlier kept in the dark, undisturbed for 3 – 4 days and perform the iodine test again on its leaves.
Iodine test:
Put iodine solution on the leaf
Observation:
Blue-black colour will be observed on the leaves of the plant kept in sunlight, which indicates the presence of starch.
Blue-black colour will not be observed on the leaves of plant kept in the darkroom. This indicates the absence of starch.
Q4. Give a brief description of the process of synthesis of food in green plants
Answer:
Green plants use a process called as photosynthesis to prepare their food. The process is as follows
- Water is taken from the roots of the plant, and it is transported to leaves of the plant.
- Carbon dioxide from air enter the leaves through pores called stomata. This diffuses the cell containing chlorophyll.
- Water molecule is broken down into Hydrogen and Oxygen with the help of sunlight.
- Hydrogen combines with Oxygen and Hydrogen to form carbohydrates.
- Photosynthesis is represented by the following equation.
Q5. Show with the help of a sketch that plants are the ultimate source of food.
Answer:
Q6. Fill in the blanks:
(a) Green plants are called _________________ since they synthesise their own food.
(b) The food synthesised by plants is stored as _________________.
(c) In photosynthesis solar energy is absorbed by the pigment called ___________.
(d) During photosynthesis plants take in ______________________ and release __________________ gas.
Answer:
(a) Green plants are called autotrophs since they synthesise their food.
(b) The food synthesised by plants is stored as starch.
(c) In photosynthesis, solar energy is absorbed by the pigment called chlorophyll.
(d) During photosynthesis, plants take in Carbon dioxide and release Oxygen gas.
Q7. Name the following:
i) A parasitic plant with yellow, slender and branched stem.
ii) A plant that is partially autotrophic.
iii) The pores through which leaves exchange gases.
Answer:
i) Cuscuta
ii) Pitcher plant
iii) Stomata
Q8. Tick the correct answer:
(a) Cuscuta is an example of:
(i) autotroph
(ii) parasite
(iii) saprotroph
(iv) host
(b) The plant which traps and feeds on insects is:
(i) Cuscuta
(ii) china rose
(iii) pitcher plant
(iv) rose
Answer:
- (ii) Parasite
- (iii) pitcher plant
Q9. Match the items given in Column I with those in Column II:
| Column- I | Column-II |
| Chlorophyll | Rhizobium |
| Nitrogen | Heterotrophs |
| Cuscuta | Pitcher plant |
| Animals | Leaf |
| Insects | Parasite |
Answer:
| Column- I | Column-II |
| Chlorophyll | Leaf |
| Nitrogen | Rhizobium |
| Cuscuta | Parasite |
| Animals | Heterotrophs |
| Insects | Pitcher plant |
Q10. Mark ‘T’ if the statement is true and ‘F’ if it is false:
(i) Carbon dioxide is released during photosynthesis. (T/F)
(ii) Plants which synthesise their food are called saprotrophs. (T/F)
(iii) The product of photosynthesis is not a protein. (T/F)
(iv) Solar energy is converted into chemical energy during photosynthesis. (T/F)
Answer:
- False
- False
- True
- True
Q11. Choose the correct option from the following:
Which part of the plant takes in carbon dioxide from the air for photosynthesis?
(i) Root hair (ii) Stomata (iii) Leaf veins (iv) Petals
Answer:
The answer is (ii) Stomata
Q12. Choose the correct option from the following:
Plants take carbon dioxide from the atmosphere mainly through their:
(i) roots (ii) stem (iii) flowers (iv) leaves
Answer:
Answer is(iv) leaves
Q13. Why do farmers grow many fruits and vegetable crops inside large greenhouses? What are the advantages to the farmers?
Answer:
Fruits and vegetable crops are grown in large greenhouses because it protects crops from external climatic condition and to provide suitable temperature for the growth of crops.
Advantages to farmers while growing fruits and vegetable crops inside greenhouses are
- It protects crops from diseases and adverse climatic conditions.
- It protects crops from wind and rodents