=Sexual Selection= ~''(also mate-selection or non-random mating)''~ Random mating allows all genotypes to have an equal chance of reproductive success. However, individuals often don't mate randomly, they may mate more often with close neighbours or choose mates that are most like themselves. Most individuals will carefully select a mate that has desirable traits (adaptations). By selecting a mate that is well adapted to the environment (greater biological fitness) there is a greater chance the offspring will inherit these traits too, increasing their chance of survival. [image:] '''Sexual Dimorphism''' In many species there are significant anatomical differences between males and females. This is known as sexual dimorphism and is usually the result of competition between males for mating partners. Males are generally capable of producing large quantities of sperm and will try to impregnate as many females as possible. It is interesting to think that one human male can produce enough sperm in a single ejaculate to impregnate every female on the planet! Females on the other hand can usually only produce a fairly limited number of offspring and are therefore much more selective about who they mate with. Females will choose to mate with the fittest individuals (those that are best adapted to the environmental conditions). This increases the likelihood that their offspring will inherit these more favourable traits, increasing their chance of survival. This has given rise to some very interesting adaptations that serve no other purpose than to attack potential mates. For instance the bird pictured left has a very large tail, that serves no other purpose than to attract a mate. A large tail may indicate to females that this bird is so good at flying that it can evade predators even with such a large tail.