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  • Created by: J.E.C.
  • Created on: 12-01-14 16:54

Pioneer Species

Common features of pioneer species

1. Produce vast quantities of wind-dispersed seeds / spores that can reach isolated situations.

2. Rapid germination of seeds - as they do not require a period of dormancy

3. Ability to photosynthesise as light is usually only available 'food' source. Not dependant on animal species.

4. Ability to fix Nitrogen from the atmosphere because only few-no nutrients in the soil

5. Tolerance to extreme conditions

Succession takes place over a series of stages. Certain species can be identified that change the environment for future species. The new species can out-compete the original species and form a new community.

E.g. Bare rock > Lichens survive here > weathered until sand / soil forms > Lichens die & decompose releasing sufficient nutrients to support a community of small plants > Mosses > Ferns.

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Succession & Climax Communities

Climax Community = The organisms that make up the final stage of ecological succession (determined by the main abiotic factor). Within a climax community there is usually a dominant plant species & a dominant animal species. During Succession: 

1. Non-living environment becomes less hostile (e.g. nutrients & shelter become available)

2. Greater number & variety of habitats that produce

   2.1. Increased biodiversity - diversity peaks mid-succession, decreases towards climax community - dominant species out-compete pioneer/other species until they are eliminated from the community. Increased biodiversity:

   2.2. More complex food webs, leading to 

   2.3. Increased biomass, especially during mid-succession

Climax communities are in stable equilibrium with the prevailing climate. Abiotic factors determine the dominat species.

Other succession > land that has already sustained life suddenly alters (e.g. land clearance). Climax community reached more quickly & possibly with different dominant species.

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Conservation = method of maintaining ecosystems and the living organisms that occupy them. Requires planning & organisation to make the best of the resources whilst preserving the natural landscape & wildlife. Reasons for conservation:

1. Ethical - Other species have occupied the Earth longer than we have and should be able to coexist amongst us. Respect for living organisms rather than discarding them.

2. Economic - living organisms contain a massive gene pool with the capacity to make millions of substances. Greater long-term productivity if ecosystems maintained in their natural balanced state.

3. Cultural & aesthetic - habiatats & organisms add to, inspire & enrich our lives. 

To conserve habitats and their species we can manage succession in a way that prevents a change to the next stage..

E.g. Burning & grazing of heather on moorland prevents it reaching its climax community because young tree saplings are destroyed.

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