Ecological succession is a chain of events in which one community is gradually replaced by
another in an orderly series, until a suitable community climax which is best adapted to the
environment is established. The terminal climax community is a state of stability with the
ecological conditions existing within the locality.
General characteristics and outcome of succession.
- Succession brings about greater species diversity, greater species population
density and large life form.
- Succession is predictable and occurs along one direction in the ecosystem
iii. As communities are constantly undergoing changes. It shows that the biosphere
and ecosystem are dynamic
- Succession is caused by the modification of physical environment by the
- Ecological successions show that some organisms are more easily dispersed and
are more vigorous and grow more rapidly than others.
- Succession occurring in different places and at different times involved are often
vii. Climax communities are formed after a long period of time and once formed
they maintain their structures.
viii. Succession makes the food web become more complex and the relations
between the species become better defined or more specialized.
- The amount of inorganic nutrients held by the organisms and soil of the
Types of Succession
- Primary Succession is a type of succession that occurs on a bare surface where no
Community of plant existed before it involves the formation of new soil. It begins from
(a) Dry rock slope which eventually changes to a forest
(b) Shallow lake gradually filled up with vegetation to become a marsh and eventually a
(c) Mouth of a river where silt or mud is deposited thereby forming a bank on which a
mangrove swamp develop and eventually a tropical forest.
- Secondary Succession is a succession or changes on a surface that already or previously
has a community of plant to be replaced by another. For instance changes occurring on (i)
overgrazed grassland (ii) abandoned farm land.
A climax community is the end product of the succession of several seral communities over
a long period at one place. Once climax community is established it may remain indefinitely.
The climax community is regarded as steady state which has restored the community
structure towards steady state.
Characteristics of a stable ecosystem or climax communist
- It is generally believed that once the climax is attained, the community does not
change at all. Climax community changes due to aging and it is heterogeneous
- The climax community depends on the broad climax of the region
iii. Climax ecosystem has numerous micro-habitat which are inhabited by different
types of organisms.
- Climax community does contain many sub-communities.
Over-grounding is defined as a situation which occurs when a population in a given habitat
Increases beyond a point where the resources in the habitat such as space and food are not
Enough to support the individual in population.
Factors responsible for over-grounding
- Limited space
- Increase in birth rate
iii. Limited food supply
- Flux of immigrants
- Less emigration
- Decrease in mortality rate
vii. Increase in survival rate
Effect of over-grounding
- Shortage of space
- Shortage of food
- Anti – social behaviour
- Spread of diseases
- Preying on each other
vii. Death of the organism
Adaptation to avoid over-grounding
- Territorial Behaviour – is an act in which an organism defend an area or a territory against
an intruders especially in animals lizards, birds.
- Dispersal of seeds and fruit – the disposal of seeds and fruit either by water, winds,
Animals, insect and explosive mechanism reduces the chance of over-grounding.
- Emigration is the movement of organisms away from habitat or a particular locality.
- Swarming – it contain insects such as termite and bees to form new colony is a way of
decongesting the population.
- Production of chemicals by plant as this prevent the growth of plants sometimes prevent
the growth of other plants.
- Production of canopies by tall trees which prevent the trees underneath from growing.
QUESTIONS (POST YOUR ANSWERS USING THE COMMENT BOX FOR EVALUATION AND DISCUSSION)
1a.What is climax community
- Discuss briefly the various stages starting with a bare rock to a climax community
- Describe a succession in a pond or abandoned farmland
c.State some effect of over-crowding.