General Science Notes Chapter 18 Ecosystems Class 8 Maharashtra Board

Notes For All Chapters – General Science Class 8
1. Introduction to Ecosystems

• An ecosystem is a system where living (biotic) and non-living (abiotic) things interact with each other.
• It includes plants, animals, microorganisms, air, water, soil, and sunlight.
• Every ecosystem has a balance, and changes in one part affect the entire system.

2. Components of an Ecosystem

(A) Biotic (Living) Factors

• Producers (Plants) → Make their own food using sunlight (photosynthesis).
• Consumers (Animals) → Depend on plants or other animals for food.
• Decomposers (Bacteria, Fungi) → Break down dead plants and animals, recycling nutrients.

(B) Abiotic (Non-Living) Factors

• Sunlight → Helps plants grow and provides energy.
• Air → Provides oxygen for animals and carbon dioxide for plants.
• Water → Essential for all living beings.
• Soil → Provides nutrients for plants.

3. Types of Ecosystems

(A) Natural Ecosystems (Formed by nature)

Terrestrial (Land) Ecosystems

• Forest: Dense trees, animals like tigers, elephants, monkeys.
• Desert: Hot, sandy, dry; animals like camels and cacti.
• Grassland: Large open lands with grasses, animals like deer, lions.

Aquatic (Water) Ecosystems

• Pond: Small body of freshwater with fish, frogs, and plants.
• River: Flowing freshwater, home to fish, crocodiles, and aquatic plants.
• Ocean: Saltwater, large marine life like whales, sharks, and corals.

(B) Man-Made Ecosystems (Created by humans)

• Farms → Grown for food and agriculture.
• Gardens → Created for decoration and nature preservation.
• Dams → Provide water and electricity but change ecosystems.

4. Food Chain and Food Web

(A) Food Chain

• A food chain shows how energy flows in an ecosystem.
• Example: Grass → Grasshopper → Frog → Snake → Eagle

(B) Food Web

• A food web is a combination of many food chains in an ecosystem.
• It shows how different organisms depend on each other for food.

5. Biomes

A biome is a large ecosystem covering a vast area with similar climate and organisms.

Examples of Biomes:

• Tropical Rainforest → Heavy rainfall, evergreen trees.
• Savanna → Grassland with scattered trees.
• Desert → Dry, very little rain.
• Tundra → Very cold, little vegetation.

6. Human Impact on Ecosystems

(A) Deforestation

• Cutting down trees destroys ecosystems.
• Causes soil erosion, reduces oxygen, and affects rainfall.

(B) Pollution

• Air pollution: Factories and vehicles release harmful gases.
• Water pollution: Waste from industries and plastic harms aquatic life.
• Soil pollution: Chemicals and plastics make land infertile.

(C) Urbanization

• Forests and wetlands are destroyed for roads, buildings, and cities.
• Wildlife loses their natural habitat, leading to species extinction.

(D) Overpopulation

• More people = More use of natural resources.
• Leads to overfishing, excessive farming, and habitat destruction.

(E) Effect of Wars on Ecosystems

• Wars destroy forests, rivers, and animal habitats.
• Nuclear explosions damage land and air for many years.

7. Conservation of Ecosystems

(A) Reforestation

• Planting trees to replace lost forests.

(B) Wildlife Protection

• Setting up national parks and wildlife sanctuaries.
• Example: Rhinoceros were reintroduced in Dudhwa National Park.

(C) Pollution Control

• Reducing plastic use and switching to biodegradable materials.
• Recycling waste to prevent land and water pollution.

(D) Sustainable Development

• Using renewable energy sources like solar and wind power.
• Conserving water and reducing overuse of natural resources.