Sexual Selection and Artificial Selection
Sexual selection is the method of natural selection that favors traits that increase an individual's chance of attracting mates, winning mates from others, and producing offspring. Sexual selection is a little different from the other modes of natural selection. While the favored traits of other methods of selection generally always improve overall chances of survival for the individual, sexual section favored traits can sometimes prove a hindrance.
Intrasexual selection favors the traits that help individuals from one sex compete against each other directly for mates. Intrasexual selection favors traits such as larger antlers in deer, stingers in insects, and the increased body size in many animals. All of these features allow the individual who has the better developed trait to physically defeat other individuals that want the same mates. Most of the time, traits favored by intrasexual selection are also highly favored by other types of selection.
Suppose two whitetail bucks are competing for a group of four does. A 150 pound 12 point buck has more strength and a more dangerous weapon on his head than the 100 pound 8 point buck. Typically, the heavier, better “armed” buck will defeat the smaller buck with the smaller antlers with fewer sharp points. In this way, sexual selection favors body and antler size by rewarding the larger buck with four mates, while the smaller buck doesn't mate at all that year.
The same set of antlers that allows the larger buck to secure his does from other bucks is used to fend off natural predators as well. As such, these traits typically increase the overall survivability of both the individual and the species.
Intersexual selection favors traits that make individuals more appealing to members of the opposite sex. This is where sexual selection gets tricky. In intersex populations, the females tend to be more selective in their mating choices. They seem to assess behavioral and morphological differences in their potential mates to choose which is best suited for them. The males, on the other hand, are driven by competition just as in the intrasexual example above and focus on gaining the female's attention, with little consideration to anything else.
Consider the peacock. Males have brightly colored feathers that fan out in a display meant to attract females. While males can and do sometimes fight over females, it is still up to the female to choose which male she will mate with.
While intersexual selection might well favor some traits that are beneficial to overall survival, such as size or aggressive behavior, it often also favors traits that seem to have little or no effect apart from attracting a mate, such as complicated mating rituals. The really unique thing about intersexual selection is that it can even favor traits that actually make it harder for the individual to survive long enough to mate! Consider the peacock example. The bright colors and fanned out feathers actually make the male peacock more visible to predators like lions and cheetahs.
Artificial selection, sometimes referred to as selective reproduction, occurs when humans choose mates for other organisms, thereby directly controlling which genes get passed on in a population. People choose to selectively reproduce plants and animals in order to guarantee that the traits they want to see are passed on. This can be for the sake of the survival of the species in the wild, for the sake of survival of the species in captivity or domestication, or even to favor traits aesthetically pleasing to humans or to simply satisfy academic curiosity. As is often the case with food crops and food animals, artificial selection can be used to evolve higher yields of food or other commercially viable products.
Advantages of Artificial Selection
Of the many advantages derived from the artificial selection process, the ones that stand out most include:
- It’s a largely unregulated form of scientific inquiry and experimentation which means that anyone with the proper training necessary to carry it out can do so.
- It is an effective way of producing new genes for any given species.
- It’s an effective way to improving desired traits such as strength and speed as well as any number of other attributes deemed to be desirable to replicate.
Drawbacks of Artificial Selection
Among the many drawbacks of artificial selection, there are:
- It decreases the variety among a single animal type, making it difficult for living beings to adapt to their surroundings, making them more susceptible to death.
- Because this is a newer horizon in science, the experimentation involved in experimenting with unnatural choice as a way of attaining certain attributes has a strong potential of turning out poorly at any phase in the process.
- This type of selection is complex and costly, making it difficult for just anyone to employ.