Ecosystem

Introduction

An ecosystem is a functional unit of nature where living organisms interact with each other and their physical environment. It consists of biotic (living) and abiotic (non-living) components. The study of ecosystems helps us understand ecological balance, energy flow, and nutrient cycling.

Types of Ecosystems

Ecosystems are broadly categorized into natural and artificial ecosystems.

1. Natural Ecosystems

• Terrestrial Ecosystem: Forests, grasslands, deserts, etc.

• Aquatic Ecosystem: Freshwater (rivers, ponds, lakes) and Marine (oceans, seas).

2. Artificial Ecosystems

• Man-made ecosystems such as crop fields, aquariums, and gardens.

Structure of an Ecosystem

The structure of an ecosystem includes biotic and abiotic components.

1. Abiotic Components

• Non-living factors such as temperature, water, sunlight, soil, and minerals.

2. Biotic Components

Living organisms in an ecosystem, categorized as:

• Producers (Autotrophs): Green plants, algae, and photosynthetic bacteria.

• Consumers (Heterotrophs): Depend on producers for food. Includes:

  • Primary consumers: Herbivores (e.g., deer, rabbits).

  • Secondary consumers: Carnivores (e.g., frogs, snakes).

  • Tertiary consumers: Top predators (e.g., lions, eagles).

• Decomposers: Fungi, bacteria, and detritivores (e.g., earthworms) that decompose organic matter.

Ecosystem Functions

Ecosystems perform four essential functions:

1. Productivity – Production of energy by autotrophs.

2. Decomposition – Breakdown of complex organic matter by decomposers.

3. Energy Flow – Movement of energy from one trophic level to another.

4. Nutrient Cycling – Recycling of nutrients like carbon, nitrogen, and phosphorus.

Energy Flow in an Ecosystem

Energy flow in an ecosystem follows the laws of thermodynamics:

• First Law: Energy cannot be created or destroyed, only transferred.

• Second Law: Some energy is lost as heat in each transfer.

Energy transfer occurs through a food chain or food web.

Food Chain

A linear sequence of organisms where energy flows from one level to the next. Example:
Grass → Grasshopper → Frog → Snake → Hawk

Food Web

An interlinked network of food chains, showing multiple feeding relationships.

Trophic Levels

Each step in a food chain is a trophic level:

• Trophic Level 1: Producers

• Trophic Level 2: Primary consumers

• Trophic Level 3: Secondary consumers

• Trophic Level 4: Tertiary consumers

10% Law (Lindeman’s Law): Only 10% of energy is transferred from one trophic level to the next, while 90% is lost as heat.

Ecological Pyramids

A graphical representation of energy, biomass, or number of organisms at each trophic level.

1. Pyramid of Number

• Shows the number of organisms at each trophic level.

• Can be upright (e.g., grassland ecosystem) or inverted (e.g., parasitic food chain).

2. Pyramid of Biomass

• Shows the total mass of living matter at each trophic level.

• Upright in terrestrial ecosystems but inverted in aquatic ecosystems.

3. Pyramid of Energy

• Always upright as energy decreases at higher levels.

Ecological Succession

A natural process of gradual replacement of species in an ecosystem over time.

1. Primary Succession

• Occurs on barren land (e.g., lava fields, newly formed ponds).

• Pioneer species (lichens, mosses) initiate succession.

2. Secondary Succession

• Occurs in areas where life existed before but was disturbed (e.g., forest fires, floods).

• Faster than primary succession.

Nutrient Cycling (Biogeochemical Cycles)

Movement of nutrients between biotic and abiotic components.

1. Carbon Cycle

• Carbon is exchanged between atmosphere, biosphere, and geosphere.

• Major processes: Photosynthesis, respiration, combustion, decomposition.

2. Phosphorus Cycle

• No atmospheric phase.

• Major processes: Weathering of rocks, absorption by plants, consumption by animals, decomposition.

Ecosystem Services

Ecosystems provide several benefits to humans:

1. Provisioning Services – Food, water, fuel, medicine.

2. Regulating Services – Climate regulation, air purification, water filtration.

3. Cultural Services – Recreation, spiritual values.

4. Supporting Services – Nutrient cycling, soil formation.

Human Impact on Ecosystems

1. Deforestation – Reduces biodiversity, affects carbon cycle.

2. Pollution – Air, water, and soil pollution affect ecosystem health.

3. Climate Change – Global warming, extreme weather events.

4. Overexploitation – Unsustainable use of natural resources.

Conservation Strategies

• Afforestation & Reforestation

• Reducing pollution & waste

• Sustainable resource management

• Protecting biodiversity through national parks & reserves

Conclusion

Ecosystems are dynamic, self-sustaining systems that support life on Earth. Understanding their structure, function, and threats is crucial for environmental conservation and sustainable living.