NCERT Solutions Class 7 Science Chapter 1 – Nutrition in Plants
NCERT Solutions for Class 7 Science Chapter 1: Nutrition in Plants
This chapter explains how plants make their own food through photosynthesis and explores different modes of nutrition in plants including autotrophic, parasitic, and insectivorous plants.
Exercise Questions and Answers
Q1. Why do organisms need to take food?
Answer: Organisms need to take food because:
- Food provides energy for various life processes like growth, movement, and repair
- Food provides nutrients needed for building and repairing body tissues
- Food helps in growth and development of the organism
- Food provides materials for protection against diseases
Q2. Distinguish between a parasite and a saprotroph.
| Parasite | Saprotroph |
|---|---|
| Lives on or inside a living organism (host) | Lives on dead and decaying matter |
| Takes nutrients from the living host | Takes nutrients from dead organic matter |
| Harms the host organism | Helps in decomposition, doesn’t harm |
| Examples: Cuscuta, lice, tapeworm | Examples: Mushrooms, bread mould |
Q3. How would you test the presence of starch in leaves?
Answer: Steps to test for starch in leaves:
- Pluck a green leaf from a plant kept in sunlight
- Boil the leaf in water to soften it
- Place the leaf in a test tube with alcohol and heat in a water bath to remove chlorophyll
- Wash the decolorized leaf with water
- Add a few drops of iodine solution to the leaf
- If the leaf turns blue-black, it confirms the presence of starch
Q4. Give a brief description of the process of synthesis of food in green plants.
Answer: The process of food synthesis in green plants is called photosynthesis:
Carbon dioxide + Water → (sunlight/chlorophyll) → Glucose + Oxygen
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
- Plants absorb carbon dioxide through stomata in leaves
- Water is absorbed by roots and transported to leaves through xylem
- Chlorophyll (green pigment) in leaves captures sunlight energy
- This energy is used to convert CO₂ and H₂O into glucose (food)
- Oxygen is released as a byproduct through stomata
Q5. Show with the help of a sketch that plants are the ultimate source of food.
Answer: Food chain showing plants as ultimate food source:
Sun → Plants (Producers) → Herbivores (Deer, Rabbit) → Carnivores (Lion, Tiger) → Decomposers
Plants capture solar energy and make food. All other organisms directly or indirectly depend on plants for food. Even carnivores depend on herbivores that eat plants.
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 _______.
Answer:
- (a) autotrophs
- (b) starch
- (c) chlorophyll
- (d) carbon dioxide and release oxygen
Key Takeaways
- Photosynthesis is the process by which plants make food using sunlight, CO₂, and water
- Chlorophyll is essential for capturing light energy
- Stomata are tiny pores on leaves for gas exchange
- Plants can be autotrophs, parasites, insectivorous, or saprotrophs
- Nitrogen-fixing bacteria help replenish soil nutrients
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