My name is Mollie. I'm a junior at Olathe North. I have the coolest boots you will ever see. I love my chinchillas, my dogs (a corgi and lab), my quarter horse, rubber ducks, heavy metal, movies, reading, and everything Jhonen Vasquez and Tim Burton. My favorite naturalist buddies are Tank, the leopard gecko, the savanna monitor, and I guess the hedgehog too, because I know I'm probably his favorite person to pee on. I love going to my uncle's farm and riding horses and just spending time with the horses and goats, which is a very rare opportunity for me. But, I enjoy every moment when I do.
All You Will Ever Probably Want, Or Need, To Know About Genetic Drift! ~
Genetic drift, also known as allelic drift, is when a species splits into two groups. Genetic drift usually happens as a result of a geographical factor that makes it difficult for these two groups to come in contact. With this separation and different environments, natural selection will favor different genes in each of the groups. These genes will vary for the groups because the natural selection will be favoring those needed in the new environment. After a period of time, the difference in the gene pools of the groups can become quite dramatic.
Such examples of genetic drift in human history can be explained in the Toba
Catastrophe Theory. According to this theory, a volcano severely reduced the human population around 70,000 to 75,000 years ago. Supposedly, the Toba Caldera in Indonesia underwent a category 8 eruption. This was a "mega-colossal" and reduced the global temperature by 5 degrees Celsius for several of years which may have caused an ice age. This ended up killing off all the human species, also known as a bottleneck, except for what branches that became Neanderthals and modern humans. With computer models and some geological evidence support the plausibility of this happening. This suggests that all humans today came from a small group, around 1,000 and 10,000 breeding pairs.
Another example of genetic drift and a bottleneck is the cheetah. There is very little genetic variation in the cheetah population because of a population bottleneck that probably happend around 10,000 years ago or less. Even today, the cheetah population, as large as it is, hasn't been able to recover it's genetic diversity. A strange example of genetic drift being resisted was in a
remote sheep population on Haute Island in the Indian Ocean. The mouflon had been put there to establish a group for sport hunting. After being bred over a dozen generation from a single male and female pair, scientists were surprised to find the sheep had maintained the genetic diversity of the founding parents. As genetic drift goes, with an inbred population, genes should have been lost, not maintained. Evolutionary geneticist Dr. David Coltman believes the harsh environment of Haute Island, with its cold winters, scarce resources and grass-borne parasites, has "kept the mouflon on their genetic toes, so to speak." He believes that the extreme conditions of the island have prevented genetic drift due to the premium advantage the more genetically diverse mouflon on the island hold over their less genetically diverse cousins. Mouflon are a hardy and fecund species of sheep, with the ewes able to produce an average of more than five offspring in a four-year lifespan. The Haute Island mouflon population peaked around 700 in the 1970s and since then has bounced between 200 and 600. The geneticists were able to trace the DNA from the original pair on the island using teeth, fur, and bone from the zoo in France they originally came from in the 1950s. Samples from the generations after were taken from "trophies" that hunters had, and in the 70s scientists began taking their own samples.All You Will Ever Probably Want, Or Need, To Know About Speciation! ~
Speciation, on the other hand, is when genetic drift in a species becomes so great that a brand new species occurs. It is considered a new species because the organisms who are capable of reproducing but can't with a member of the same species, are considered a different species. It is one of the key evolutionary processes and is responsible for the diversity of life that exists on Earth.
One example would be how the domestic dog came about. The earliest dogs came about when humans began keeping wolves, separating the wild wolves from the ones humans were keeping. This was the barrier which created the genetic drift between the domestic wolves and dogs, and with time and inbreeding, the domestic dog was born. As breeding continued, people began breeding dogs for certain qualities, which resulted with the mass number of different dogs we have today.
Another more dramatic example of speciation would be the continent of Australia. Millions of years ago the earth existed as one giant continent, Pangaea. When the continent began to split, the genetic ancestor of all of Australia’s marsupial mammals was caught on what would become Australia. With time, that common ancestor became what we know today as the kangaroo, wallaby, and kola. Kangaroos adapted to living on the ground, with their long, powerful hind feet for moving quickly over large areas. More closely related to the kangaroo, wallabies are smaller version of the kangaroo. The wallaby’s smaller size comes from living in rocky areas where their smaller size makes them more agile. Kolas on the other hand, adapted to living in the trees and feeding on a diet of eucalyptus leaves. Due to the isolation from all the other mammals in their ancestral line, they've become so different from members of their line on other continents. The main difference between them and other mammals of their line is that they bear their young inside a pouch, while all the other mammals are placental.
However, it is occasionally possible to produce a hybrid between two different
species. The down side is, is that the offspring is infertile, due to genetic disorders that arise when mating takes place between distinct species, and even this imperfect product is possible only by mating two species that are very closely related. Animals in which this is common are horses and mules, lions and tigers, and wolves and dogs. For example, these happy face spiders look different, but since they can interbreed, they are considered the same species: Theridion grallator. 
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2 comments:
very good. easy to under stand and nice set up. i really like the pictures. i didnt really see any thing wrong with it.
The only real thing that I found wrong in your paper was in the third paragraph it says "the population dropped from 70,000 to 75,000. Overall, it was easy to read, very informative, and had good examples. I think what really made this essay worth reading were the examples you gave, which you gave in great detail.
-Tyler Paschall
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