Biology - Colonisation and Succession

CHAPTER 8:

DYNAMIC ECOSYSTEM

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8.2 COLONISATION AND SUCCESSION IN AN ECOSYSTEM

Ecosystem

Dynamic Ecosystem

Habitat

A community of organisms which interact with their non-living environment and function as a unit

Biotic components are well balanced with one another and with the abiotic components

- Natural environment where organisms live-Provides basic resources og life such as food, shelter, living space, nesting sites and mates

Species

Ecosystem

community Population

Species

A group of organisms that: look alike and have similar characteristics share the same roles in an ecosystem capable of interbreeding to produce fertile offspring

population

A group of organisms of the same species living in the same habitat at the same time

- A several populations of different species living in the same habitat of an ecosystem-Interpendent and interact with one another in order to survive

Community

NICHE-A niche of an organism is its role in the ecosystem-Niche of a population:

ranges of temperatures at which it lives the type of food it eats the space it occupies

-animals that undergo metamorphosis in their cycle occupy different niches.

A tadpole lives entirely in water

A frog lives mainly on the land

Climax community

(trees )

COLONISATION

Dominant species

(shrubs )

Successor species

(herbaceous plant )

Pioneer species ( grasses )

Bare ground

BARE GROUND

• An environment of bare rocks and sand left behind by a forest fire is not suitable for most organisms.

• After the ground cools down, water re-enters the environment. When water, air, nutrients and sunlight are available, spores and seeds of certain plants start to germinate and grow.

PIONEER SPECIES

• The first colonizers• Special adaptations is enable to survive on dry

and nutrient-poor soil• Hardy plants which usually have dense root

system to bind the sand particles and hold water and humus

• Short life cycle• When die, they remains add to the humus

content of soil

Successor species

• Modify the environment, eventually creating conditions which are less favorable to themselves

• Grow bigger than pioneer species, thus reducing the amount of sunlight that reaches them and gradually replacing them

• Have small wind-dispensable seeds which are able to spread and grow rapidly

• Change the structure and quality of the soil, making it more conductive for larger plants to grow

Dominant species

• Can grow faster and so they out-compete the pioneers which grow at a slower rate

• Turn modify the environment which allows larger trees to grow

• The larger trees out-compete the shrubs, which are replaced by forest-floor species which require low light intensit

(succession)

Climax community

• Ecological success leads to a relatively stable community which is in equilibrium with its environment

• Example: tropical rainforest in Malaysia• A stable community that undergoes little or no

change in its species composition

Colonisation

• A process whereby a species invades and occupies a newly formed area where no life has existed previously

Succession

• The gradual process through which one community changes its environment so that it is replaced by another community