Реферат: Evolution Essay Research Paper We actlike animals

habitat.

Natural selection consists of three types of selections. One, directional

selection. Two, stabilizing selection. Finally, sexual selection. Direction

selection creates new features that aid a species to adapt to its environment.

Directional selection produces a never ending change in the species toward the

more complex characteristic. Under the circumstance that a species is already

greatly adapted to its environment, stabilizing selection initiates. With

stabilizing selection, individuals with average characteristics produce the

most offspring. On the contrary, individuals that differ the most from the

average tend to produce the least offspring. For example, stabilizing selection

of human beings is the survival rate of human babies according to their birth

weight. On average, when an infants weight is average, the baby tens to survive

better that those who are either heavier or lighter than the average weight. On

the opposite side of directional selection, stabilizing selection gets rid of

complex characteristics, which in turn, decreases the amount of variation in a

population. The most common form of natural selection can most likely be

stabilizing selection. Species who favor mates who display certain types of

behavior or have certain physical features tend to fall under the category of

sexual selection. Complicated sex rituals can be created through sexual

selection. For example, bright coloring can attract a mate. Another example, is

that many males of different species of birds have more variety of colors in

their feathers than females. Genetic drift represents the random change of

genes in populations. Genetic drift is enabled by the random way that egg and

sperm cells receive some chromosomes from each parent. The circumstance that

reproductive cells consist of only half a set of chromosomes as the parent

cell, leads to the conclusion that only half of a parent’s genes are present in

an egg or sperm. As a result, some of the parent genes will not be replicated

and passed on to its offspring. In addition, genetic drift does not allow

species to evolve to accommodate to their environment. The cause of this