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COURTESY OF ATIKA SCHOOL
Abiotic factors (environmental factors)
According to biology dictionary, abiotic factors are non-living factors in the ecosystem. These factors do affect the living things in it, but they are not living themselves. In this context, we will focus mainly on light, temperature, atmospheric pressure, salinity, humidity, pH and wind.
This is the hotness or coldness of an area or habitat. It directly affects the distribution and productivity (yield) of populations and communities.
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 such as the hot deserts and the cold Polar Regions. Temperatures not only influence distribution of organisms but also determine the activities of animals. High temperatures usually accelerates the rates of photosynthesis, transpiration, evaporation and the decomposition and recycling of organic matter in the ecosystem.
Light is required by green plants for photosynthesis. Light intensity, duration and quality affect organisms in one way or another.
This is the force per unit area of atmospheric air that is exerted on organisms at different altitudes. Growth of plants and activity of animals is affected by atmospheric pressure e.g., rate of transpiration in plants and breathing in animals.
This is the salt content of soil or water. Animals and plants living in saline conditions have special adaptations.
Humidity describes the amount of moisture (water vapour) in the air. It affects the rate of transpiration in plants and evaporation in animals.
pH Is the measure of acidity or alkalinity of soil solution or water, it is very important to organisms living in water and soil. Most organisms prefer a neutral pH.
Wind is moving air currents and it influences the dispersion of certain plants by effecting the dispersal of spores, seeds and fruits.
Air currents also modify the temperature and humidity of the surroundings.
These are surface features of a place. The topographical factors considered include altitudes, gradient (slope), depressions and hills, all these characteristics affect the distribution of organisms in an area e.g. the leeward and windward sides of a hill.
These are living components of an ecosystem. These factors affect the ecosystem through enhancing
Inter-relationships between Organisms
The relationships between organisms in a given ecosystem is primarily a feeding one. Organisms in a particular habitat have different feeding levels referred to as trophic levels. There are two main trophic levels:
These organisms that occupy the first trophic level, they manufacture their own food hence are autotrophic.
These are the organisms that feed on organic substances manufactured by green plants, they occupy different trophic levels as follows:
These are herbivores and feed on green plants.
These are carnivores and feed on flesh. First order carnivores feed on herbivores while second order carnivores feed on other carnivores, i.e., tertiary consumers.
These are animals that feed on both plant and animal material. They can be primary, secondary or tertiary consumers.
Competition between themselves for survival
this describes the situation where two or more organisms in the same habitat require or depend on the same resources. Organisms in an ecosystem compete for resources like food, space, light, water and mineral nutrients. Competition takes place when the environmental resource is not adequate for all.
Predation is a relationship whereby one animal (the predator) feeds on another (the prey).
Questions on Topic
1. The flow chart below shows a food web in a terrestrial ecosystem.
2. The food web represents a feeding relationship in an ecosystem.
3. State four abiotic factors in an ecosystem.