[ 3.7.4 ] succession

Ecosystem

The area in which abiotic and biotic factors exist together. These can range in size.

Population

A group of individuals of the same species living and breeding in the same area at the same time.

Community

An area where all the populations of different species interact.

Habitat

The place where an organism lives.

Niche

Refers to the specific role an organism plays within its ecosystem, encompassing both its biotic and abiotic interactions

Abiotic Factors

Refers to the non-living components of an ecosystem. This can include:

• space

• light intensity

• water availability

  soil pH and composition

• wind

Biotic Factors

Refers to the living components of an ecosystem. This can include:

• predation

• competition

• disease

• food availability

Carrying Capacity

The maximum stable population size of a species that an ecosystem can sustainability support. This limit is essentially the point where the birth and death rates of a population balance out, and the population size stops growing.

Interspecific Competition

Refers to the competition between individuals of different species for the same limited resources in an ecosystem.

Intraspecific Competition

Refers to the competition between individuals of the same species for the same limited resources in an ecosystem.

Succession

The gradual process of change in the structure and composition of an ecological community over tie.

Primary Succession

Succession that occurs on newly formed or exposed land with no existing soil, like bare rock after a volcanic eruption.

Secondary Succession

Succession that occurs in areas where a previous community has been disturbed, but the soil remains, like after a forest fire.

1st Stage in Succession

Colonisation by pioneer species; species that are adapted to survive harsh abiotic conditions (eg. lichens, mosses) colonise the bare environment.

2nd Stage in Succession

Pioneer species changes the environment, making it less hostile.

3rd Stage in Succession

New species colonise the environment. As more species colonise, the biodiversity and biomass increase. More complex food webs form as well.

4th Stage in Succession

A climax community is established

Pioneer Species

The first species to colonise an area. They are able to tolerate the harsh conditions of land that hasn’t undergone succession.

Climax Community

A community where the species composition remains relatively constant - no further succession occurs.

Conservation

The management of ecosystems to protect biodiversity, maintain genetic diversity, and sustain resources.

Methods of Conservation:

• protected areas (eg. national parks) → protects habitats from human activity

• seedbanks → stores seeds to avoid extinction

• protected species → avoid extinction

• hunting quotas (eg. fish) → prevents overhunting

Management Techniques:

Succession can be managed by:

• grazing → animals can graze the land to prevent the growth of vegetation

• burning → burning kills vegetation and allows secondary succession to occur

Methods of Estimating Population Size:

• randomly placed quadrats, or quadrats along a belt transect, for slow-moving or non-motile organisms

• the mark-release-recapture (MRR) method for motile organisms

Assumptions Made in MRR Method:

• no migration

• marked individuals mix randomly

• marking does not affect survival

• population size does not change between samples