Ecosystem

Notes

Ecosystem

1. Ecosystem

An ecosystem is a functional unit of nature where living organisms interact among themselves and also with their surrounding physical environment.

• The term Ecosystem was coined by A. G. Tansley in 1935.
• An ecologist considers the entire biosphere as a global ecosystem comprising many local ecosystems on Earth.
• An ecosystem is an open system.
• It receives solar energy and inorganic nutrients as inputs.
• These inputs result in productivity or synthesis of food.
• Food containing energy passes through different components of the ecosystem through food chains, nutrient cycling and food webs.
• Matter circulates within an ecosystem, while energy ultimately flows out.

2. Structure and Function of Ecosystem

Ecosystems may be natural or artificial.

Natural Ecosystem

Natural ecosystems are capable of maintaining and operating themselves without human interference.

• Terrestrial ecosystems: Forest, grassland, desert, etc.
• Aquatic ecosystems: Pond, lake, river, wetland, estuary, etc.

Artificial Ecosystem

Artificial ecosystems are maintained and manipulated by humans for different purposes.

Example: Aquarium.

3. Components of Ecosystem

An ecosystem has two major components:

1. Abiotic Components
2. Biotic Components

Abiotic Components

Abiotic components are the non-living components of an ecosystem.

• Temperature
• Water
• Light
• Soil

Biotic Components

Biotic components of an ecosystem are classified into:

1. Producers
2. Consumers
3. Decomposers

Producers

• All green plants are called producers.
• In terrestrial ecosystems, herbaceous and woody plants are producers.
• In aquatic ecosystems, phytoplankton, some algae, submerged plants and marginal plants act as producers.
• Producers are also called autotrophs.

Consumers

• Animals depend directly or indirectly on plants for food.
• They are known as consumers or heterotrophs.

Decomposers

• Decomposers are also called saprobes, saprophytes or mineralisers.
• Fungi and bacteria are important decomposers.
• They decompose dead organic matter.

4. Important Structural Features of an Ecosystem

Two important structural features of an ecosystem are:

1. Species Composition
2. Stratification

Species Composition

Species composition is determined by the identification and enumeration of plant and animal species of an ecosystem.

Stratification

Stratification is the vertical distribution of different species occupying different levels in an ecosystem.

Example:

• Trees occupy the top vertical strata or layer of a forest.
• Shrubs occupy the second layer.
• Herbs and grasses occupy the bottom or third layer.