What needs to be present in a population before natural selection can occur?
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Before natural selection can occur in a population, there must be genetic variation among individuals. This variation can arise from various sources such as mutation, genetic recombination during sexual reproduction, and genetic drift.
Natural selection also requires differential reproductive success among individuals with different traits. This means that some individuals with certain traits have a higher chance of survival and reproduction than others in a specific environment. The traits that confer an advantage in a particular environment are likely to be passed on to the next generation and become more common within the population over time. This process is known as adaptation, and it drives evolutionary change through natural selection.
Thus, in summary, genetic variation and differential reproductive success are the two necessary conditions that must be present in a population for natural selection to occur.