A) A textbook definition would be that genetic drift is: a random change in allele frequency caused by a series of chance occurences that cause an allele to become more or less common in a population. In layman's terms, this means that genetic drift happens when luck makes the genetic pool of the population to deviate from what is expected.
B) The cause for this genetic drift is the aformentioned couple. Because amish communities are small and they select partners from their community, having even a couple of carriers of alleles in a community can make the allele freuency much larger than expected; for example, if the community was 100 persons, the percentage would be in the order of 1%, still much larger than the general population. Thus, the cause here is that a small population had a couple of carriers.
C) Sexual reproduction leads to a mixing of alleles from both mother and father and helps diversity. When a population is isolated, the gene pool is fixed and no new genes can come in, reducing diversity. Also some people that have an allele might die, hitting diversity even more. Finally, having a small population creates a strong pressure in some circumstances that leads to elimination of some traits and diversity.
Answer:
A. Natural selection results in those individuals within a population who are best-adapted surviving and producing more offspring. The traits that promote survival are heritable.
Explanation:
Natural selection works on the genetic variations that are already present in the natural populations. Some organisms of a population are more likely to produce more offspring than the others. This is due to the presence of beneficial genetic traits in these individuals that impart survival and reproductive fitness to them. Natural selection favors those individuals. Over the generations, the frequency of the beneficial genetic trait in the population increases.
Normal cells in the body follow an orderly path of growth, division, and death. Programmed cell death is called apoptosis, and when this process breaks down, cancer begins to form.
I believe it is natural selection. Natural selection is when over a period of time, traits that are formed to help the organism survive, are passed to the next generation. For example, if there were two types of rabbits. One had black fur and the other was white. They both lived in the artic. The black furred rabbits are mostly eaten by predators because their black fur is easily seen against the ice and snow. Over a period of time, the black furred rabbit would die out. The next generation would mostly have white fur to help them survive.
