Final answer:
Biotic selective pressures such as competition for food and mates have a crucial role in natural selection and speciation, relative to the traits that improve survival and reproductive success in specific environments.
Step-by-step explanation:
Examples of biotic selective pressures include competition for food and mates. In an ecosystem, this competition for limited resources like food, sunlight, and mineral nutrients dictates which organisms thrive and survive, influencing the process of natural selection.
Furthermore, organisms may display sexual dimorphism, which refers to the phenotypic differences between males and females within a population, adding another layer of biotic pressure where certain traits may be favored in one gender over the other, leading to stabilizing selection, a form of selection that favors average phenotypes.
Other selective pressures such as predation, mating preferences, and various forms of competition within and among species, determine which individuals are more likely to survive and reproduce. The principle known as the competitive exclusion principle suggests that species less adapted to compete for resources may either adapt, relocate, or face extinction. Over time, the traits of the most adaptive individuals become more common within the population, driving evolution.
In situations where environmental conditions rapidly change, such as a sharp decline in oxygen availability or alterations in habitat due to geographical changes, speciation can occur. This speciation follows the accumulation of many small genetic changes that enable organisms to survive and reproduce in the new conditions.