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Nutrition in Plants – Class 7 Science Chapter 1 Notes & Questions Answers (NCERT)

Overview: This post covers Class 7 Science Chapter 1 “Nutrition in Plants” with easy, student-friendly Notes and a complete Q&A practice set (28 questions) including MCQs, Very Short, Short, and Long answer questions. It is designed for exam preparation, quick revision, and strong conceptual clarity while remaining clean, readable, and optimized for search.

📘 Notes: Nutrition in Plants (Easy & Exam-Ready)

1) What is Nutrition?

Nutrition is the process by which living organisms obtain and utilize food for growth, energy, repair, and maintenance. Food provides nutrients such as carbohydrates, proteins, fats, vitamins, and minerals.

  • Carbohydrates: main energy source.
  • Proteins: body-building and repair.
  • Fats: reserve energy and insulation.
  • Vitamins & Minerals: protective, regulatory functions.

2) Modes of Nutrition

Autotrophic nutrition: Organisms make their own food from simple substances. Plants are mostly autotrophs.

Heterotrophic nutrition: Organisms depend on others for food (animals, many fungi, some plants like Cuscuta).

Nutrition in Plants – Class 7 Science Chapter Notes with NCERT Questions & Answers (MCQ, Very Short, Short, Long)

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3) Photosynthesis (The Food-Making Process)

Photosynthesis is the process by which green plants make food (glucose) using carbon dioxide and water in the presence of sunlight and chlorophyll. Oxygen is released as a by-product.

Word equation: Carbon dioxide + Water —(Sunlight, Chlorophyll)→ Glucose + Oxygen

  • Chlorophyll (green pigment) absorbs light energy.
  • Stomata are tiny pores on leaves for gas exchange (CO₂ in, O₂ out).
  • Roots absorb water and minerals from the soil.
  • Vessels (xylem/phloem) transport water, minerals, and food.
Exam Tip: Remember: Sunlight + Chlorophyll are necessary conditions; CO₂ + H₂O are raw materials; Glucose + O₂ are products.

4) How Do Leaves “Breathe” and “Eat”?

Leaves have stomata guarded by guard cells. When stomata open, CO₂ diffuses into the leaf; O₂ and water vapor diffuse out. Veins carry water to leaf cells and transport prepared food to other parts.

5) Other Nutritional Strategies in Plants

  • Parasites: Plants like Cuscuta (dodder) lack chlorophyll and steal nourishment from host plants via haustoria.
  • Saprotrophs: Fungi such as mushrooms and bread mold feed on dead/decaying matter using digestive enzymes (external digestion).
  • Insectivorous plants: Pitcher plant, Venus flytrap, and Drosera trap insects to supplement nitrogen; they are usually green and photosynthetic but grow in nitrogen-poor soils.
  • Symbiosis: Lichens (alga + fungus) share resources; Rhizobium bacteria in legume root nodules fix nitrogen for the plant and receive food in return.

6) Nutrient Replenishment of Soil

Soil nutrients get depleted by continuous cropping. Nature replenishes nitrogen through nitrogen-fixing bacteria like Rhizobium and by lightning converting atmospheric nitrogen to nitrates. Farmers also add manure and fertilizers to restore nutrients.

7) Testing for Starch (Conceptual Step-By-Step)

To check whether leaves make starch via photosynthesis:

  1. Keep a plant in the dark for ~24 hours (destarch).
  2. Expose some leaves to sunlight; cover a part of a leaf with opaque paper.
  3. Boil the leaf briefly in water, then in alcohol (to remove chlorophyll), rinse, and add iodine solution.
  4. Blue-black color indicates starch formed in areas that received light.

8) Key Terms at a Glance

Autotroph: Self-feeder; makes food via photosynthesis.

Heterotroph: Depends on others for food.

Chlorophyll: Green pigment in leaves.

Stomata: Pores on leaf surface for gas exchange.

Saprotroph: Organism feeding on dead/decaying matter.

Symbiosis: Two organisms living together for mutual benefit.

Rhizobium: Nitrogen-fixing bacteria in legume roots.

Remember Like This: “Sun-Chlo-CO-H₂O → Glu-O₂” = Sunlight + Chlorophyll + Carbon dioxide + Water → Glucose + Oxygen.

📝 Questions & Answers: Nutrition in Plants (28 Qs)

A) Multiple Choice Questions (7)

Q1. The green pigment essential for photosynthesis is:

  1. Haemoglobin
  2. Chlorophyll
  3. Carotene
  4. Anthocyanin

Answer: B) Chlorophyll

Q2. Tiny pores on the leaf surface used for gas exchange are called:

  1. Vacuoles
  2. Stomata
  3. Lenticels
  4. Trichomes

Answer: B) Stomata

Q3. Which plant is a parasite?

  1. Sunflower
  2. Cuscuta
  3. Mango
  4. Neem

Answer: B) Cuscuta

Q4. Insectivorous plants trap insects mainly to obtain:

  1. Glucose
  2. Nitrogen
  3. Carbon dioxide
  4. Chlorophyll

Answer: B) Nitrogen

Q5. The symbiotic association between fungus and alga is called:

  1. Mycorrhiza
  2. Lichen
  3. Nodule
  4. Epiphyte

Answer: B) Lichen

Q6. Which statement best represents photosynthesis?

  1. O₂ + Glucose → CO₂ + Water + Energy
  2. CO₂ + Water —(Light, Chlorophyll)→ Glucose + O₂
  3. Proteins + O₂ → Energy + CO₂
  4. Fats → Fatty acids + Glycerol

Answer: B) CO₂ + Water —(Light, Chlorophyll)→ Glucose + O₂

Q7. Nitrogen fixation in leguminous plants is carried out by:

  1. Yeast
  2. Rhizobium
  3. Algae
  4. Mosquito

Answer: B) Rhizobium

B) Very Short Answer Questions (7)

Q1. Define autotrophs.
Ans: Organisms that synthesize their own food using simple substances are autotrophs (e.g., green plants).

Q2. Name the pores in leaf through which exchange of gases occurs.
Ans: Stomata.

Q3. Write the end products of photosynthesis.
Ans: Glucose and oxygen.

Q4. Which pigment traps solar energy?
Ans: Chlorophyll.

Q5. Name one insectivorous plant.
Ans: Pitcher plant (also Venus flytrap, Drosera).

Q6. What is a saprotroph?
Ans: An organism that feeds on dead/decaying matter externally (e.g., fungi).

Q7. Name the bacterium that fixes nitrogen in legume roots.
Ans: Rhizobium.

C) Short Answer Questions (7)

Q1. Why are leaves called the food factories of plants?
Ans: Leaves contain chlorophyll, receive sunlight, absorb CO₂ through stomata, and get water via veins. All requirements of photosynthesis meet in leaves, so they prepare food for the whole plant.

Q2. Distinguish between autotrophs and heterotrophs with one example each.
Ans: Autotrophs make their own food (e.g., wheat, mango). Heterotrophs depend on others for food (e.g., humans, mushroom, Cuscuta).

Q3. State the role of stomata in photosynthesis.
Ans: Stomata allow CO₂ to enter leaves and O₂ to exit; they also regulate water vapor loss. Guard cells control the opening/closing of stomata.

Q4. What is meant by symbiotic relationship? Give one example from plants.
Ans: In symbiosis, two organisms live together and benefit each other. Example: Lichen (alga provides food; fungus offers shelter and moisture).

Q5. How do insectivorous plants supplement their nutrition?
Ans: They grow in nitrogen-poor soils; by trapping and digesting insects, they obtain nitrogen compounds to supplement their diet while still photosynthesizing.

Q6. Why are fungi commonly seen on stale bread or damp wood?
Ans: Fungi are saprotrophs. Warm and moist conditions help fungal spores germinate; they secrete enzymes, digest, and absorb nutrients from such surfaces.

Q7. How is soil nitrogen naturally replenished?
Ans: By nitrogen-fixing bacteria (e.g., Rhizobium) in legume root nodules and by lightning converting atmospheric nitrogen into nitrates washed into soil by rain.

D) Long Answer Questions (7)

Q1. Explain the process of photosynthesis with the role of each requirement.
Ans: Photosynthesis converts light energy into chemical energy. Sunlight provides energy; chlorophyll absorbs light; CO₂ enters via stomata; water is absorbed by roots and transported to leaves. Inside chloroplasts, a series of reactions synthesize glucose, which is used for energy or stored as starch. Oxygen formed is released into the atmosphere. Efficient photosynthesis requires adequate light, intact chlorophyll, proper water availability, and open stomata.

Q2. Describe parasitic, saprotrophic, and symbiotic modes of nutrition with plant examples.
Ans: Parasitic: Plants like Cuscuta lack chlorophyll; they attach to hosts and draw nutrients via special sucking roots (haustoria). Saprotrophic: Fungi (mushrooms, molds) secrete enzymes on dead organic matter; dissolved nutrients are absorbed externally. Symbiotic: In lichens, alga synthesizes food; fungus offers protection and water. In legume-Rhizobium association, bacteria fix nitrogen and receive plant food—both partners benefit.

Q3. What are insectivorous plants? Explain their structure and nutrition with an example.
Ans: Insectivorous plants are primarily autotrophs that trap insects to obtain nitrogen. In a pitcher plant, the leaf is modified into a pitcher with a lid; nectar attracts insects, downward-pointing hairs prevent escape, and digestive juices break down the insect body. The plant absorbs nitrogenous compounds produced, supplementing soil deficiency.

Q4. Outline an activity to demonstrate that chlorophyll is necessary for photosynthesis.
Ans: Use a variegated leaf (green and non-green areas). Keep the plant in sunlight for a few hours, then boil the leaf in water, then in alcohol to remove chlorophyll. Rinse and add iodine solution. Only green (chlorophyll-containing) regions turn blue-black (starch present). Non-green parts do not, proving chlorophyll is essential for starch formation.

Q5. How do plants transport water, minerals, and food?
Ans: Specialized tissues form a conducting system. Xylem transports water and minerals upward from roots to leaves through vessels and tracheids. Phloem transports prepared food (sugars) from leaves to storage and growing regions (translocation). This bidirectional flow in phloem ensures all parts receive nourishment for growth and repair.

Q6. Explain the role of Rhizobium in improving soil fertility and its benefits to farmers.
Ans: Rhizobium bacteria reside in nodules of legumes (pea, gram). They convert atmospheric nitrogen into usable nitrogen compounds for the plant. In return, the plant supplies them food. This natural fertilization reduces farmers’ dependence on chemical fertilizers, improves soil structure and fertility, and promotes sustainable agriculture.

Q7. Compare autotrophic nutrition of plants with heterotrophic nutrition in animals on key features.
Ans: Source of food: Plants synthesize food from inorganic substances; animals ingest complex organic food. Site of process: Plants use chloroplasts in leaves; animals digest food in digestive systems. By-products: Plants release oxygen; animals release carbon dioxide during respiration. Dependence: Animals ultimately depend on plants for food and oxygen, while plants are largely self-sustained given light, CO₂, water, and minerals.

Quick Revision Keys:
  • Equation: CO₂ + H₂O —(Light, Chlorophyll)→ Glucose + O₂
  • Chlorophyll & sunlight: conditions; CO₂ & water: raw materials.
  • Stomata: gas exchange; guard cells control opening.
  • Parasite: Cuscuta; Saprotroph: fungi; Symbiosis: lichen, Rhizobium-legume.
  • Insectivorous: pitcher plant traps for nitrogen; still photosynthetic.
  • Soil fertility: Rhizobium, lightning, manure, crop rotation.

Keep learning—concept clarity today becomes exam confidence tomorrow.