23.3 Sexual Selection

The genetic changes allow these strains to grow on contaminated soil, but they are not allowed to grow on non-contaminated soil.

Plants that do not show metal tolerance grow on contaminated sites that are close to plants that grow on uncontami nated land.

Natu ral selection doesn't always cause the elimination of weaker or less-fit alleles.

Heterozygote over either correspond area can be favored by the frequencies of the b-globin genes in the same balancing selection.

In the homozygous condition, the HS allele causes a cell type called a homozygote.

In areas where Malaria is prevalent, the Heterozygote advantage can explain the persistence of this allele.

The red blood cells form a shape.

It is possible that rare organisms are subject to a lower rate of predation because of their suck-shaped cells.

Explain how Seehausen and van Alphen relate to sexual selection.

A higher mean fitness of the population is a result of this balanced polymorphism.

This pattern is likely to result in successful reproduction.

Common and rare individuals have different fitness levels, and certain individuals have a higher fitness level than others.

In this section, we will look at how sexual selection can affect how common individuals are less likely to reproduce.

Sexual selection can affect the appearance of animals, making them less likely to be seen by a predator.

Cryptic female choice is a less obvious type of intersexual selection.

Secondary sex characteristics that favor reproductive of sperm are influenced by the prevalence of the female reproductive system.
sperm that are genetically unrelated to the female are significant.

Sexual selection can be done in two ways.

The egg may have mechanisms to prevent fertilization.

The male already inside stands in the burrow shaft and blocks unrelated plants from getting into the bur, if another male attempts to enter the bur the same flower is unsuccessful.
The biggest choice of males is that it causes inbreeding.
Cryptic female choice may promote genetic diver able to mate, and therefore more likely to pass on their genes to unrelated individuals, since they are more likely to be successful at driving off their rivals and being the population level.

Males spar with their antlers, which can turn into a push of sexual selection, which results in showy characteristics in males.

Sexual selection can explain the existence of long and brightly colored tail feathers that decrease an individual's chances of survival but increase their chances of getting married.

Female peahens select males based on their reproduction rate.

Direct male-to-male competition uses the enlarged claw of the male fiddler crab.

A male in a burrow extends his claw out of the burrow to prevent another male from entering and having sex with the female.
Female peahens choose male peacocks based on their display and the males' colorful and long tail feathers.
Male guppies are bright colored to attract females, but are less common in high-pregnant areas.
The photos show the concept of sexual dimorphism.
Birds have loud and elaborate songs.

Females prefer males with bright colors.

Males that are relatively colored are more likely to be seen and eaten by animals.
In fewer offspring, and their reproductive success may not be limited, the males tend to be brightly colored.
If females choose males that are good defenders, they will have higher fitness because they are less likely to be preyed upon.
The survival advantage of bright and dully colored males depends on their offspring.

One measure of fitness is age.

The males prefer dull coloring.

Many animals have secondary sexual characteristics, and female biologists agree that sexual selection is a factor in determining such characteristics.

Why should older males compete more than immature ones?
Researchers have proposed various hypoth cies of birds, females tend to choose males with a larger eses to explain the underlying mechanisms.
Songs are more likely to occur in older males.

In some animal species, the female is in the evolution of traits that are not directly related to sex, whereas the male plays a minor role.

The fitness of both males balancing selection can be influenced by the behavior of females.
Males increase their fitness by having multiple brightly colored tails of the male peacock.
It increases their chance of passing their genes on.

Sexual selection may be involved in the male coloration of two species of tropical freshwater fish popu lar among aquarium enthusiasts.

It is one of the largest and most diverse families of animals, with more than 3000 species that vary in body shape, color, and feeding habits.
The most diverse of these fish can be found in Lake Victoria, Lake Malawi, and Lake Tanganyika in East Africa.

The chapter opening photo shows how females play an important role in choosing males with particular characteristics.

Two men are on their sides.

The same species under orange males for mates based on their color.

The light obscures their color differences.

This experiment would have likely affected female choice.

Men would prefer.

The females choose mates based on the males' color.

Two species of cichlid were chosen.

The males have different colors.
A total of 16 males and 16 females were tested.

There is a sexual separate glass enclosure for each male.

Female enclosures contain 1 male from 2 species.

If a female approached the enclosure that contained the male, this was scored as a positive encounter.

Under normal light and orange light, this protocol was performed.

The male's display was followed by the female approaching him.

It was lost motion.

When the colors were masked by artificial light, the courting behavior was looked at.