ENVIRONMENTAL STUDIES Unit-II: A Simple language notes for BAJMC Students (CCS University)

 ENVIRONMENTAL STUDIES NOTES...

UNIT–II: ECOSYSTEM

 

1. Concept of Ecosystem

An ecosystem is a functional unit of nature in which living organisms interact with one another and with the non-living components of their physical environment.

The term ecosystem combines:

• Eco – environment or surroundings
• System – a group of interconnected components working together

Thus, an ecosystem consists of biotic components and abiotic components that interact through energy flow and nutrient cycling.

Simple Definition

An ecosystem is a functional unit in which living organisms interact with each other and with their physical environment.

Examples

• Forest ecosystem
• Grassland ecosystem
• Desert ecosystem
• Pond ecosystem
• Lake ecosystem
• River ecosystem
• Marine ecosystem

 

2. Components of an Ecosystem

An ecosystem has two major components:

A. Abiotic Components

These are the non-living components.

Examples:

• Sunlight
• Air
• Water
• Soil
• Temperature
• Humidity
• Minerals
• Nutrients

B. Biotic Components

These are the living components.

They include:

1. Producers
2. Consumers
3. Decomposers

Basic Structure

ABIOTIC COMPONENTS
↓
Sunlight + Water + Air + Soil + Minerals
↓
PRODUCERS
↓
CONSUMERS
↓
DECOMPOSERS
↓
Nutrients returned to environment
↓
Producers

This shows the interdependence of different ecosystem components.

 

3. Abiotic Components

Abiotic components provide the physical and chemical conditions necessary for life.

3.1 Sunlight

Sunlight is the primary source of energy for most ecosystems.

Green plants use sunlight during photosynthesis to produce food.

Sunlight → Plants → Animals

3.2 Water

Water is essential for:

• Photosynthesis
• Metabolism
• Growth
• Reproduction
• Nutrient transport

3.3 Air

Atmospheric gases such as oxygen and carbon dioxide are essential for organisms.

• Plants use carbon dioxide for photosynthesis.
• Animals generally require oxygen for respiration.

3.4 Soil

Soil provides:

• Nutrients
• Water
• Physical support to plants
• Habitat for many organisms

3.5 Temperature

Temperature affects:

• Growth
• Reproduction
• Metabolism
• Distribution of organisms

3.6 Minerals and Nutrients

Minerals such as nitrogen, phosphorus, potassium and other nutrients are essential for plant growth and ecosystem functioning.

 

4. Biotic Components

Biotic components are living organisms within an ecosystem.

They are broadly classified as:

Producers

Organisms that prepare their own food.

Consumers

Organisms that obtain food from other organisms.

Decomposers

Organisms that break down dead organic matter.

 

5. Producers

Producers are organisms capable of producing food, generally through photosynthesis.

Examples

• Green plants
• Algae
• Phytoplankton

Plants use:

Sunlight + Carbon dioxide + Water → Food + Oxygen

Producers form the first trophic level of most ecosystems.

Importance

Producers:

• Capture solar energy.
• Produce organic food.
• Support food chains.
• Provide oxygen through photosynthesis.
• Form the foundation of ecosystem energy flow.

 

6. Consumers

Consumers cannot generally produce their own food and depend on other organisms.

Primary Consumers

They feed directly on producers.

Examples:

• Deer
• Cow
• Rabbit
• Grasshopper

They are generally herbivores.

Example

Grass → Deer

 

Secondary Consumers

They feed on primary consumers.

Examples:

• Frog
• Small carnivorous animals

Example

Grass → Grasshopper → Frog

 

Tertiary Consumers

They occupy higher trophic levels and may feed on secondary consumers.

Examples can include:

• Large predatory birds
• Large carnivores

 

Omnivores

Organisms that consume both plant and animal food.

Examples:

• Humans
• Bears

 

7. Decomposers

Decomposers break down dead plants, animals and organic matter.

Examples

• Bacteria
• Fungi

They convert complex organic material into simpler substances.

Importance

Decomposers:

• Break down dead organisms.
• Return nutrients to soil and environment.
• Support nutrient cycling.
• Help prevent accumulation of dead organic matter.

Example

Dead leaves → Fungi/Bacteria → Nutrients → Soil → Plants

Thus, decomposers are essential for maintaining ecosystem productivity.

 

8. Functions of Ecosystem

An ecosystem performs several important functions.

8.1 Energy Flow

Energy moves through different trophic levels.

Sun → Producers → Consumers

8.2 Nutrient Cycling

Elements such as carbon, nitrogen and phosphorus circulate between living organisms and the physical environment.

8.3 Decomposition

Dead organic matter is broken down by decomposers.

8.4 Food Production

Producers manufacture organic food that supports other organisms.

8.5 Ecological Balance

Interactions among organisms and environmental components help maintain ecosystem functioning.

 

9. Forest Ecosystem

A forest ecosystem is an ecosystem dominated by trees and associated plants and animals.

Components

Abiotic:

• Soil
• Water
• Air
• Sunlight
• Temperature
• Minerals

Biotic:

• Trees
• Shrubs
• Herbs
• Birds
• Mammals
• Insects
• Microorganisms

Food Chain Example

Plants → Deer → Tiger

Importance of Forest Ecosystem

Forests:

• Provide habitat.
• Support biodiversity.
• Protect soil.
• Influence water cycles.
• Store carbon.
• Provide resources to human communities.

Major Problems

• Deforestation
• Habitat loss
• Forest fires
• Illegal cutting
• Pollution
• Fragmentation

 

10. Grassland Ecosystem

Grasslands are ecosystems where grasses and herbaceous vegetation are dominant.

Components

Producers: Grasses and herbs

Primary consumers: Deer, cattle, grasshoppers

Secondary consumers: Snakes, frogs and other predators

Higher consumers: Larger carnivores

Example Food Chain

Grass → Deer → Carnivore

Importance

Grasslands:

• Provide grazing resources.
• Support herbivores.
• Support predators.
• Store carbon.
• Help maintain biodiversity.

Problems

• Overgrazing
• Conversion to agricultural land
• Urbanisation
• Invasive species
• Habitat degradation

 

11. Desert Ecosystem

A desert ecosystem is characterised by very low rainfall and organisms adapted to dry conditions.

Major Characteristics

• Low rainfall
• Limited vegetation
• High evaporation
• Temperature variation
• Water scarcity

Adaptations

Desert plants and animals have special adaptations for conserving water.

Examples include:

• Cacti and other drought-resistant plants
• Reptiles
• Small mammals
• Insects

Indian Example

Thar Desert

Importance

Desert ecosystems support specially adapted species and provide important ecological functions.

 

12. Aquatic Ecosystem

Aquatic ecosystems occur in water.

They can broadly be classified into:

A. Freshwater Ecosystems

Examples:

• Rivers
• Lakes
• Ponds
• Streams

B. Marine Ecosystems

Examples:

• Seas
• Oceans
• Coastal ecosystems

 

Freshwater Ecosystem

A pond is a simple example.

Producers

• Algae
• Aquatic plants
• Phytoplankton

Consumers

• Small aquatic animals
• Fish
• Insects
• Larger aquatic organisms

Decomposers

• Bacteria
• Fungi

Food Chain

Phytoplankton → Small fish → Large fish

 

Marine Ecosystem

Marine ecosystems include:

• Oceans
• Seas
• Coral reefs
• Coastal environments

They contain enormous biodiversity and play important roles in climate regulation and nutrient cycling.

 

13. Energy Flow in an Ecosystem

Energy flow refers to the movement of energy through different components of an ecosystem.

The Sun is the primary source of energy for most ecosystems.

Energy Flow

Sun

↓

Producers

↓

Primary Consumers

↓

Secondary Consumers

↓

Tertiary Consumers

At each trophic level, some energy is used for life processes and lost as heat. Therefore, the amount of available energy decreases at higher trophic levels.

Important Point

Energy flow in an ecosystem is generally unidirectional.

It moves from the source through trophic levels and ultimately dissipates as heat.

 

14. Trophic Levels

A trophic level represents a feeding position in a food chain.

First Trophic Level

Producers

Second Trophic Level

Primary consumers

Third Trophic Level

Secondary consumers

Fourth Trophic Level

Tertiary consumers

Example

Grass → Deer → Tiger15. Ecological Pyramids

Ecological pyramids represent the relationship between different trophic levels of an ecosystem.

There are three major types:

1. Pyramid of Number
2. Pyramid of Biomass
3. Pyramid of Energy

 

15.1 Pyramid of Number

It represents the number of organisms present at different trophic levels.

For example:

Grass → Grasshopper → Frog → Snake

The number of organisms may decrease at higher trophic levels.

 

15.2 Pyramid of Biomass

Biomass refers to the total mass of living organisms at a trophic level.

A pyramid of biomass represents the biomass present at different trophic levels.

 

15.3 Pyramid of Energy

It represents the amount of energy available at each trophic level.

Energy generally decreases as we move upward through trophic levels.

Producers → Primary Consumers → Secondary Consumers → Tertiary Consumers

The pyramid of energy is therefore generally upright.

 

16. Food Chain

A food chain represents a sequence through which food and energy pass from one organism to another.

Example 1

Grass → Deer → Tiger

Example 2

Grass → Grasshopper → Frog → Snake

The arrows represent the direction of transfer of food and energy.

 

17. Types of Food Chains

Grazing Food Chain

Begins with green plants.

Grass → Deer → Tiger

Detritus Food Chain

Begins with dead organic matter.

Dead leaves → Decomposers/Detritivores → Predators

Both types contribute to ecosystem functioning.

 

18. Food Web

A food web is a network of interconnected food chains.

In nature, organisms usually have more than one food source or predator. Therefore, ecosystems contain food webs rather than isolated food chains.

Example

Grass may be eaten by:

• Deer
• Rabbit
• Grasshopper

The grasshopper may be eaten by:

• Frog
• Bird

The frog may be eaten by:

• Snake

Thus, several food chains become interconnected.

Importance of Food Webs

Food webs:

• Show interdependence.
• Provide greater understanding of ecosystem relationships.
• Help explain ecosystem stability.
• Demonstrate multiple pathways of energy transfer.

 

19. Food Chain vs Food Web20. Ecological Succession

Ecological succession is the gradual and relatively predictable change in the composition and structure of an ecological community over time.

It occurs as one community is gradually replaced by another under changing environmental conditions.

Simple Example

Bare area → Pioneer organisms → Grasses → Shrubs → Trees → Mature community

 

Primary Succession

Primary succession begins in an area where there was previously little or no developed soil or established community.

Examples can include newly exposed surfaces.

Secondary Succession

Secondary succession occurs in an area where a previous community existed but was disturbed, while some soil and biological components remain.

Examples:

• Abandoned agricultural land
• Areas recovering after certain disturbances

 

21. Interdependence in Ecosystem

No organism exists completely independently.

For example:

Plants provide food → Herbivores eat plants → Carnivores eat herbivores → Decomposers break down dead matter → Nutrients return to soil → Plants use nutrients

This demonstrates the interconnected nature of ecosystems.

 

22. Human Impact on Ecosystems

Human activities can alter ecosystem structure and functioning.

Major activities include:

• Deforestation
• Urbanisation
• Industrialisation
• Pollution
• Mining
• Overexploitation
• Habitat destruction
• Climate change
• Introduction of invasive species

Effects

• Biodiversity loss
• Habitat degradation
• Disruption of food chains
• Changes in nutrient cycles
• Ecosystem imbalance

 

23. Conservation of Ecosystems

Ecosystem conservation requires responsible management of natural resources and protection of habitats.

Important Measures

1. Protection of natural habitats
2. Afforestation
3. Pollution control
4. Sustainable resource use
5. Wildlife protection
6. Water conservation
7. Reduction of waste
8. Public awareness
9. Community participation
10. Environmental education

 

24. Role of Media in Ecosystem Conservation

For BAJMC students, media can play an important role in communicating ecosystem-related issues.

Environmental Journalism

Journalists can report on:

• Forest degradation
• Water pollution
• Wildlife conservation
• Biodiversity
• Ecosystem restoration
• Climate-related ecosystem impacts

Television

Visual storytelling can show:

• Forest ecosystems
• Wildlife
• Rivers
• Wetlands
• Environmental damage

Radio

Radio can reach communities through:

• Local environmental programmes
• Community discussions
• Conservation messages
• Agricultural and water-related awareness

Digital and Social Media

Digital platforms can promote:

• Short environmental videos
• Infographics
• Awareness campaigns
• Conservation initiatives
• Citizen reporting

Thus, communication can contribute to environmental awareness and conservation.

 

25. Important Examples for Examination

Example 1 – Forest

Sun → Trees → Deer → Tiger

Example 2 – Grassland

Sun → Grass → Grasshopper → Frog → Snake

Example 3 – Aquatic

Sun → Phytoplankton → Small Fish → Large Fish

Example 4 – Decomposition

Dead leaves → Fungi/Bacteria → Nutrients → Plants