General Science Notes Chapter 4 Class 7 Maharashtra Board

Notes For All Chapters – General Science Class 7
1. What is Nutrition?

• Nutrition is the process by which living organisms obtain food and use it for growth, energy, and repair.
• There are two types of nutrition:
  1. Autotrophic Nutrition (Plants)
  2. Heterotrophic Nutrition (Animals & Some Plants)

2. Nutrition in Plants

Plants prepare their own food through a process called Photosynthesis.

(A) Autotrophic Nutrition (Self-Feeding)

Green plants prepare their own food using sunlight, water, and carbon dioxide (CO₂).

The process is called Photosynthesis.

Equation for Photosynthesis:

Requirements for Photosynthesis:

• Sunlight (Energy source)
• Chlorophyll (Green pigment in leaves)
• Water (Absorbed by roots)
• Carbon dioxide (CO₂) (Taken from air through stomata)

(B) Heterotrophic Nutrition (Dependent on Others)

Some plants cannot make their own food. They depend on other sources for nutrition.

Types of Heterotrophic Plants:

1. Insectivorous Plants

• These plants trap and digest insects to get extra nutrients.
• Example: Pitcher plant, Venus flytrap, Sundew.
• Why? → They grow in soil that lacks nitrogen.

2. Parasitic Plants

• These plants depend on other plants for food.
• Example: Cuscuta (Dodder plant), Loranthus.
• Types:
  • Partially parasitic (Loranthus) → Performs photosynthesis but depends on the host for water and minerals.
  • Completely parasitic (Cuscuta) → Fully depends on the host for food.

3. Saprophytic Plants

• These plants feed on dead and decaying matter.
• Example: Mushroom, Fungi, Bacteria.

4. Symbiotic Plants

• Two organisms help each other to survive.
• Example: Lichen (A combination of Algae and Fungus).
  • Algae makes food.
  • Fungus provides water and minerals.

3. Nutrition in Animals

Animals depend on plants for their food. Their nutrition is heterotrophic.

Types of Nutrition in Animals:

1. Herbivores → Eat only plants (Example: Cow, Deer).
2. Carnivores → Eat only animals (Example: Lion, Tiger).
3. Omnivores → Eat both plants and animals (Example: Humans, Bears).
4. Parasites → Live on or inside other animals (Example: Lice, Tapeworm).

4. Importance of Soil in Nutrition

Plants get nutrients from the soil.

Soil testing helps farmers understand the soil’s pH, nutrients, and water-holding capacity.

Types of soil based on pH:

• Acidic soil → pH less than 7
• Neutral soil → pH 7
• Alkaline soil → pH more than 7

5. Importance of Air in Nutrition

• Air contains oxygen (O₂), carbon dioxide (CO₂), and water vapor (humidity), which are essential for life.
• Plants use CO₂ for photosynthesis and release O₂ into the air.

6. Key Differences Between Autotrophic and Heterotrophic Nutrition