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HSC Biology

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Lesson 6, Topic 1
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Effects of Selection Pressures

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Specie diversityThe number of different species and the abundance of each species in an ecosystem.
EcosystemAny area that contains a community of other living things that interact with each other and their environments. Ecosystems can be described in terms of the specie they contain.
Selection pressuresA combination of biotic and abiotic factors as well as human activity.
AbundanceThe number of individuals per specie In a specific area at a specific time.

Selection Pressures in an Ecosystem

Biotic Factors

The living components or biological features of an environment, including animals, plants and microorganisms.

  • Seasonal availability and abundance of food
  • The number of competitors
  • The number of available mates
  • The number of predators
  • The number and variety of disease-causing organisms

Abiotic Factors

The nonliving components of an environment; its physical and chemical features.

  • Temperature – Enzymes in cell
  • Light availability
  • Water
  • Availability of gases (oxygen and carbon dioxide)
  • Soil type
  • Exposure to natural forces (wind, tide, waves)