Soil and rocks maybe. not too sure.
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:
Earliest- gametophyte dominance, sporophyte dependence
Middle- sporophyte dominance, gametophyte independence
Recent- sporophyte dominance, gametophyte dependence
Explanation:
The life cycle of plant alternates between the two phases: the haploid gametophyte which produces gametes and the diploid sporophyte which produces spores. The evolution of land plants shows how these are dependent on each other in terms of the requirement of nutrition.
In bryophytes, the gametophyte is the dominant phase on which the sporophyte depended. Later in pteridophytes, the sporophyte became dominant which is present in the later evolved groups namely the gymnosperms and the angiosperms. The gametophyte was independent on the sporophyte but in angiosperms and gymnosperms, it is dependent.
