ECOLOGICAL

SUCCESSIONSUCCESSION

Ecological Succession

� Ecological succession is the gradual process

by which ecosystems change and develop

over time.

� It includes a series of changes that a biotic � It includes a series of changes that a biotic

community undergoes in its maturation

towards a stable condition.

� Some species may disappear altogether,

some may become more abundant, even

new species may be formed.

Important terms to know…

� Habitat: A place where organisms live.

Eg. Pond

� Population: Group of individuals of the same

species in a particular location.

� Community: All of the populations of species

in a given area.

� Ecosystem: The community, together with

the physical and chemical environment of a

particular area.

Types – based on the habitat

� Primary Succession – Begins in areas

where no soil is initially present. The area has

not been changed physically by organisms.

Eg. Colonization of newly exposed island.Eg. Colonization of newly exposed island.

� Secondary Succession – Begins in areas

where soil is already present. The area is

previously colonized and the soil is

organically enriched. Eg. Abandoned crop

lands.

Primary Succession

Secondary Succession

Types – based on the organism

� Autotrophic succession – Characterized by

dominance of autotrophic organisms like

green plants.

� Heterotrophic succession – Characterized

by dominance of heterotrophic organisms like

bacteria and animals.

The different stages…

Primary Autotrophic Succession

� Nudation – The formation of a bare area.

� Migration – Movement of organisms into a

bare area.bare area.

� Colonization – Occupation of bare area by

first or pioneer community.

� Ecesis – Establishment of the pioneer

community. They react with the medium and

establish themselves.

The different stages…

� Aggregation – The final stage of invasion by

pioneer group. The species reproduce and

aggregate into large population in the new

area. area.

� Competition – Various species compete

among themselves for space, light and

nutrients. Communities which cannot

withstand competition are replaced by other

communities.

The different stages…

� Stabilization – This is the final stage in the

process of ecological succession. The climax community becomes stabilized for a longer

period of time and it can maintain itself in period of time and it can maintain itself in

equilibrium. If undisturbed, the climax

community can maintain itself for a long time.

Lichens/mosses on bare rock

Colonization of rock

Small plants growing…

Shrubs beginning to form

Trees – the climax community

Primary succession

Secondary Succession

Secondary

SuccessionSuccession

Terminologies

� Pioneer Community – The first species to

colonize an area.

� Climax Community – The final, stable

community in a newly developed ecosystem. community in a newly developed ecosystem.

This community is not replaced.

� Sere – The progression from a pioneer to a

climax community is called a Sere.