Oct. 24; Reproductive Control

In this class we take a look at the reproductive control males and females try to have over the fertilization of eggs. These topics are varied and vast.

Sperm Competition

Sperm competition is more actively controlled by the animal that is involved. There is a variety of ways that males and females try to have the upperhand in fertilization. This occurs in insects, birds, and a variety of other species.
Males and Females can remove sperm from individuals. Some females will store sprem and control which sperm is fertilizing their eggs.

Mate Guarding Males

Males will gaurd the female, so that they will control female permiscuity. If a male can gaurd another male’s access to the female, then they can be sure their genes will make it into the next generation.

In spiders there is a step up from this mate guarding. Male spiders will produce sperm in their abdomin and use a petipalt to transfer the sperm to the female. The female will store the sperm. The male will break the palp off and it will act as a plug to the females sperm storage area.

Nuptial Gifts

This brings up the idea if females are choosing mates on quality.

Key ways the Males and Females try to Control Reproductive Decisions

Female Control: Egg investment, Mate Choice, Egg Fertilization, Offspring Investment

Male Control: Resource Transferred to Female, Elaborate Courtship, Sexual Coercion, Infanticide.

Sexual Cannibalism

Some species, one sex consumes the other sex. In sexual cannibalism, there is a subgroup of sexual suicide. The female gets a nurtitional resource. The short length of their life and the small chance of finding a mate leads to a reason why this sexual suicide makes sence.

Good Parent Theory

Females prefer to mate with males that provide more paternal care. Male courtships is linked to his parental abilities. (15- spine stickleback)


When we look at species with ornamental features the question that is brought up is do these ornamental features mean good genes? Is the male healthier? In some species, we see there is a correlation between the beauty of the ornamental feature and offspring health, but this is not always the truth. This is runaway selection. Runaway Selection is an evolution sensory bias of the female the excentuates the feature.

The female mare choice genes and the genes for the prefferred male attribute are inherited together. The daughters inherit the genes for the mate preferencec, and the sons inherit the preferred attribute. The males attract more females with the preference, and the mate preferrence takes on a life of its own. Even when the male do not have the best genes.

Chase-Away Selection Theory

This theory is explained by sensory exploitation. The initial sensory exploitation is started by the viability selection on female sensory systems. The female attration for a male trait from a preexisting bias. This mutation produces a rudimentary male display trait to exploit the females preexisting bias.

The females fitness declines due to this change, so the female mating threshold increases. The male attraction decreases, so the male attractive trait increases and this becauses a circle.

Sexual Conflict

There are a variety of ways that sexual conflict that can occur between males and females.

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