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
