A2 Biology- On the wild side

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What determines which species occur in a habitat?

The conditions in which species compete for survival are defined by the ecologial factors in their habitat. These are classified into abiotic and biotic:

Abiotic (NON-LIVING)

  • Solar energy input
  • Climate, including rainfall, wind exposure, temperature.
  • Topography, such as altitude, slope, aspect, drainage.
  • Oxygen availability
  • Edaphic, including soil pH and mineral salt availability. Can also include soil texture. 
  • Pollution- air, water, land.
  • Catastrophies- infrequent events such as earthquakes, floods, volcanic eruptions. 

Biotic (LIVING)

  • Competition for resources like light, food, water. Can be interspecific (inbetween species) or intraspecific (within species). 
  • Grazing, predation or parasitism
  • Mutualism 

Species survive in their habitat because they have adaptions that enable them to cope with both biotic and abiotic conditions in their niche.

niche refers to the way in which an organism fits into an ecological community or ecosystem. 

Primary succession

This refers to newly formed habitats where there has  never been a community before. 

example: the first species to colonise bare rock are lichens and algae- pioneer species. These are the only species that can…


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