Selective pressure refers to any environmental factor that influences the survival and reproduction of individuals within a population. It can affect the frequency of traits (phenotypes) in a population over time through the process of natural selection. Selective pressures can be biotic (such as competition, predation, disease, and parasitism) or abiotic (such as climate, habitat availability, or physical conditions).
For example, if a particular trait (like faster running speed) provides an advantage in escaping predators, individuals with that trait may be more likely to survive and reproduce, thus passing the trait to the next generation. Over time, this can lead to an increase in the frequency of that trait in the population.
Selective pressure is a key concept in evolutionary biology, as it helps to explain how populations adapt to their environments and how species evolve over time.