Sexual Selection

Sexual selection is a component of natural selection wherein survival is traded for mating success.

There are two types of sexual selection. Firstly, intersexual selection where the female organism (usually) chooses their mate, and secondly, intrasexual selection where male organisms compete with one another to mate with females. Both processes present the female a large choice of mates, often leading to the most genetically superior male mating with the female, creating a higher likelihood for desirable offspring to be produced.

As female gametes are “expensive” to produce and lead to a high cost to the female if fertilised, female organisms are usually very ‘choosy’ when picking a mate. Conversely, male gametes are relatively inexpensive to produce and therefore males are usually less choosy and more competitive.

Females prefer to mate with males who have demonstrated their superior genetic quality to survive, either in form and appearance or through direct competition (i.e. physical violence). This often leads to morphological differences between the sexes known as sexual dimorphism, with males usually being larger or more ornamental than females. This can be seen in peacocks, with male peacocks having elaborate and colourful feathers, while the peafowl (female) have much more subdued colours.

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Image: https://www.darwinproject.ac.uk/commentary/evolution/sexual-selection

Key Terms:

Natural Selection – The process by which individuals better adapted to their environment are more likely to survive to produce offspring.

Intersexual Selection – Individuals of the competitive sex compete through display and the opposite sex chooses based on the presence of desirable qualities

Intrasexual Selection – Individuals of the competitive sex compete among themselves with physical violence, with the key event determining reproductive success

Gametes – Cells used in sexual reproduction to carry the genetic information (i.e. sperm and egg cells)

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