EEES Unit 2
Ecosystems

1. Concept of Ecosystem

An ecosystem is a structural and functional unit of nature where living organisms interact with each other and with the physical environment.

• Biotic Components: Producers, consumers and decomposers.
• Abiotic Components: Air, water, soil, temperature and minerals.

Examples: Forest ecosystem, pond ecosystem and desert ecosystem.

2. Structure and Functions of Ecosystem

The structure of ecosystem includes biotic and abiotic components.

• Producers: Green plants that prepare food by photosynthesis.
• Consumers: Organisms that depend on producers for food.
• Decomposers: Microorganisms that decompose dead matter.

Main Functions:

• Energy flow
• Nutrient cycling
• Ecological balance
• Decomposition

3. Producers, Consumers and Decomposers

• Producers: Trees, algae and green plants.
• Primary Consumers: Herbivores like deer, goat and rabbit.
• Secondary Consumers: Carnivores that eat herbivores.
• Tertiary Consumers: Top carnivores like tiger and lion.
• Decomposers: Bacteria and fungi.

4. Energy Flow in Ecosystem

Energy enters the ecosystem through sunlight. Green plants capture solar energy and convert it into food by photosynthesis.

Energy Flow: Sun → Producers → Consumers → Decomposers

• Energy flow is one-way.
• Energy decreases at each trophic level.
• It follows the 10% law.
• Only about 10% energy is transferred to the next trophic level.

5. Food Chain

A food chain is a linear sequence of organisms through which energy flows from one organism to another.

Example: Grass → Deer → Tiger

• Grass acts as producer.
• Deer acts as primary consumer.
• Tiger acts as secondary or top consumer.

6. Food Web

A food web is the interconnection of different food chains in an ecosystem. It shows complex feeding relationships.

• More stable than food chain.
• Shows multiple food relationships.
• Maintains ecological balance.

7. Ecological Pyramid

Ecological pyramid is a graphical representation of trophic levels in an ecosystem.

• Pyramid of Numbers: Shows number of organisms at each trophic level.
• Pyramid of Biomass: Shows total biomass at each trophic level.
• Pyramid of Energy: Shows energy available at each trophic level.

Importance: It explains energy loss and ecosystem productivity.

8. Ecological Succession

Ecological succession is the gradual and natural replacement of one community by another over time.

Types:

• Primary Succession: Occurs on barren land without soil.
• Secondary Succession: Occurs where life previously existed.

Stages:

1. Nudation
2. Invasion
3. Competition
4. Reaction
5. Stabilization

9. Forest Ecosystem

Forest ecosystem consists of trees, animals, microorganisms and physical environment.

• High biodiversity
• Dense vegetation
• Rich nutrient cycling
• Oxygen production
• Climate regulation
• Soil conservation

10. Grassland Ecosystem

Grassland ecosystem is dominated by grasses and supports many grazing animals.

• Moderate rainfall
• Few trees
• Presence of herbivores
• Examples: Savanna and Prairies

11. Desert Ecosystem

Desert ecosystem occurs in regions with very low rainfall and extreme temperature.

• Scarcity of water
• Xerophytic plants
• Animals show water-saving adaptations
• Examples: Camel and cactus

12. Aquatic Ecosystem

Aquatic ecosystems are water-based ecosystems.

• Pond ecosystem
• Lake ecosystem
• River ecosystem
• Ocean ecosystem
• Estuary ecosystem

Importance: Maintains aquatic life, regulates climate and provides food resources.

1. Explain the structure and functions of an ecosystem.
2. Explain energy flow in ecosystem and ecological pyramids.
3. Explain ecological succession in detail.
4. Explain forest ecosystem and grassland ecosystem.
5. Explain desert ecosystem and aquatic ecosystem.
6. What is food chain? Explain different types of food chains.
7. Explain food web and its importance.
8. Explain producers, consumers and decomposers with examples.
9. Explain pond ecosystem in detail.
10. Discuss conservation and management of ecosystems.

Most Repeated Questions

• Explain aquatic ecosystem.
• What is food chain? Explain various types of food chains.
• Explain the concept of ecological pyramid and describe its types.
• Explain energy flow in ecosystem.
• What is ecosystem evolution? How is balance maintained in ecosystem?

Most Expected Questions

Topic	Importance
Food Chain	★★★★★
Ecological Pyramid	★★★★★
Aquatic Ecosystem	★★★★★
Biodiversity	★★★★★
Energy Flow	★★★★★
Forest Ecosystem	★★★★☆
Ecological Succession	★★★★☆
Human Impact on Ecosystem	★★★★☆

Must Prepare for Exam

• Structure and functions of ecosystem
• Food chain and food web
• Ecological pyramids
• Energy flow in ecosystem
• Ecological succession
• Aquatic ecosystem
• Forest ecosystem
• Biodiversity and ecosystem conservation