Selection Pressures

Selection pressures are external agents which affect an organism’s ability to survive in a given environment

  • Selection pressures can be negative (decreases the occurrence of a trait) or positive (increases the proportion of a trait)
  • Selection pressures may not remain constant, leading to changes in what constitutes a beneficial adaptation

Types of selection pressures include:

  • Resource availability – Presence of sufficient food, habitat (shelter / territory) and mates
  • Environmental conditions – Temperature, weather conditions or geographical access
  • Biological factors – Predators and pathogens (diseases)

Selection pressures can be density-dependent (affected by population size) or density-independent (unaffected by population)

Examples of Selection Pressures

selection pressures