Ecosystem

Notes

Chapter Overview

An ecosystem is a functional unit of nature where living organisms interact with each other and with the non-living environment. It is the basic structural and functional unit of ecology.

1. Definition of Ecosystem

Ecosystem: A community of living organisms (biotic components) interacting with their physical environment (abiotic components) through the exchange of energy and nutrients.

Examples

Pond

Forest

Grassland

Desert

Aquarium

Crop field

2. Components of an Ecosystem

An ecosystem consists of two major components:

A. Abiotic Components (Non-living)

These include:

Sunlight

Air

Water

Soil

Temperature

Minerals

pH

Humidity

Importance:

Provide resources for living organisms.

Affect growth, reproduction, and survival.

B. Biotic Components (Living)

Biotic components are divided into:

(i) Producers (Autotrophs)

Prepare food by photosynthesis.

First trophic level.

Examples

Green plants

Algae

Phytoplankton

(ii) Consumers (Heterotrophs)

Depend on producers or other animals.

Types

Primary Consumers

Herbivores

Examples: Deer, Rabbit, Grasshopper

Secondary Consumers

Carnivores feeding on herbivores

Examples: Frog, Small fish

Tertiary Consumers

Feed on secondary consumers

Examples: Snake

Top Consumers

Apex predators

Examples: Tiger, Eagle, Lion

(iii) Decomposers

Break down dead organic matter into simple nutrients.

Examples:

Bacteria

Fungi

Importance

Nutrient recycling

Soil fertility

Prevent accumulation of dead matter

3. Functions of an Ecosystem

Main functions include:

Productivity

Decomposition

Energy Flow

Nutrient Cycling

4. Productivity

Productivity is the rate of biomass production.

(A) Primary Productivity

Food produced by producers through photosynthesis.

Gross Primary Productivity (GPP)

Total food produced.

Net Primary Productivity (NPP)

Food available after respiration.

Formula

NPP = GPP − Respiration (R)

(B) Secondary Productivity

Production of biomass by consumers.

5. Decomposition

Decomposition is the breakdown of dead organic matter into simpler substances by decomposers.

Steps of Decomposition

(1) Fragmentation

Dead matter broken into small pieces by detritivores.

Example:

Earthworm

(2) Leaching

Water dissolves nutrients and carries them into the soil.

(3) Catabolism

Microorganisms secrete enzymes to break down organic matter.

(4) Humification

Formation of dark-colored humus.

Humus:

Rich in nutrients

Resistant to decomposition

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