COMPONENTS OF AN ECOSYSTEM
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Biotic or living component. This consists of plants and animals. It includes not
only the large or macroscopic organisms but also the microscopic ones.
 Abiotic or non-living component. These are the physical and chemical factors.
The most important ones are climate and soil.
ABIOTIC FACTORS
Climatic factors
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Light Intensity: Light is required for photosynthesis by green plants. Animal
behaviour is also affected by intensity of light.
Temperature: Most organisms are found in areas where temperature is moderate.
However, certain plants and animals have adaptations that enable them to live in
areas where temperatures are in the extremes e.g. Hot deserts and the cold polar
regions. Temperature not only influences distribution of organisms but also
determines the activities of animals. A high temperature usually accelerates the
rates of photosynthesis, transpiration, evaporation and the decomposition and
recycling of organic matter in the ecosystem.
Water: Water exerts a profound influence on the lives of both plants and animals.
Wind: Moving air currents influence the dispersion of certain plants by affecting
the dispersal of spores, seeds and fruits. Air currents also modify temperature and
humidity of the air surrounding organisms, thus increasing the rate of
transpiration in plants and evaporation from the soil. Strong winds cause soil
erosion, bend or break branches of trees and even uproot some plants, thus
destroying the shelters of certain animals.
Soil Factors
These are also called edaphic factors. The soil is the substratum on which organisms are
found.
Components of soil
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Rock particles. These are inorganic particles such as sand,, clay or silt.
Mineral salts. These are derived from the rock particles. Their effect on
organisms is described under” Nutrition” in chapters five and six.
Water: Soil water forms a film in the spaces between the soil particles.
Air: Air is found in the spaces between the soil particles.
Humus: Humus is dead organic matter. It is present in varying quantities in
different soils. It affects the properties of soil and determines the effectiveness of
a soil in supporting life
Soil Texture
This is determined by the size of soil particles and the humus content. Humus gives the
soil a good crumb structure that allows for aeration and good drainage.
Soil pH
The acidity, alkalinity or neutrality of soil is very important to organisms living in and
growing on the soil.
Salinity
This is the salt content of a soil. Animals and plants living in saline soil have special
adaptations.
Topography
It is important to survey the area chosen for an ecological study before beginning the
actual study in order to be properly aquainted with the topography or surface features.
The factors considered are mainly gradient, altitude, depression and moulds. All these
characteristics affect the distribution of organisms in an area.
THE BIOTIC COMPONENT
This refers to the living organisms in an ecosystem.
 Trophic levels: Organisms in a particular habitat have different feeding levels.
These are referred to as trophic levels. There are two main trophic levels.
1. Producers: Organisms that occupy the first trophic level are known as producers.
These are the organisms that manufacture their own food (autotrophs).
2. Consumers: These are the organisms that feed on organic matter manufactured by
green plants. They occupy different trophic levels as follows:
(a) Herbivores (Primary consumers): These are the animals that feed on green
plants.
(b) Carnivores (Secondary consumers): These are animals that feed on flesh. First
order carnivores feed on herbivores while second order feed on other carnivores and so
on.
(c) Omnivores: These are animals that feed on both plant and animal material.
(d) Detritivores: Detritivores feed on organic wastes and dead matter derived from
the grazing food chain. Many different type of organisms feed on detritus. They include
fungi, protozoa, insects, mites, annelids and nematodes.
(e) Decomposers: These organisms feed on dead organic matter thereby causing
decomposition and decay and releasing nutrients for plants. They form a link between the
biotic and the abiotic components.
Food Chains
A food chain is a linear relationship between producers and consumers. It represents the
transfer of food energy from green plants through repeated stages of eating and being
eaten.
Types of Food Chains
 Grazing food
chain
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starts with green plants.
Detitius food chain
detritus)
starts with dead organic matter( debris or