An organism has choice in potential mating partners - individuals whom are "picked" more often will have more offspring, spreading their genome more than those who reproduce less frequently. This type of selection, known as sexual selection, is a specific type of natural selection. Darwin found that a number of features in many species cannot be explained by their utility within an environment and some of them are actually dangerous to the organism itself. He concluded that these features must be for attracting or fighting for the potential mate/s. For examples, male peacocks have a very flamboyant tail, which will hinder its escape from predators. Yet these peacocks have better chances of getting mates than the ones without such tails. In effect, only males with effectively attractive traits will reproduce, causing the population of peacocks to tend toward flamboyant plumage. Similarly, some animals fight amongst themselves for females and only the strongest and biggest survive and mate, while others die out without reproducing. Hence sexual selection changes the genetic makeup of populations, and is a large component of evolution.
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