How do geographical barriers ecological isolation behavior isolation and polyploidy affect an organism?

Answer 1

Geographical barriers, ecological isolation, behavioral isolation, and polyploidy do not directly affect organisms at all.

These terms are all methods of speciation, or the creation of new species from older ones via evolution. They do not affect the organisms because evolution occurs among breeding populations, not single organisms. In order to understand speciation, you need to know that a species is defined as a group of animals that can interbreed and produce fertile offspring. Members of different species can look completely different, or they can differ only in their mating song or dance. It doesn't matter what the differences are as long as they prevent the different species from having grandchildren. When two groups of the same species are prevented from mating with each other, they will not be able to mix their genes. They will evolve differently until they either cannot or will not mate with each other, at which point they are different species.

Geographical barriers are the simplest to understand. If two populations of the same species can't reach each other to have sex, they can't mix their genes. Imagine two ponds of the same kind of fish. The land between the ponds is a geographical barrier preventing them from mingling.

Ecological isolation is very similar. In this case, the populations occupy the same space but breed in different habitats. For example, there are six different species of mosquitoes which are physically identical. But they can't interbreed because they all do their breeding in different areas: one mates in stagnant water, one mates in running water, etc. Behavior isolationmeans that a genetic mutation has caused an organism, almost always an animal, to have a different mating behavior from the rest of its species. For example, there are two different species of cricket that would be indistinguishable unless you heard their mating song: they are of a noticeably different pitch. A behaviorally isolated creature will only be able to conduct successful courtship with an animal with similar mating behavior. To fully understand polyploidy, you need knowledge of sex cell production. Let's use humans as an example. Sperm and eggs are produced through a process called meiosis, which divides the 46 chromosomes making up your DNA in two. Almost always, each sperm and each egg has half of the owner's DNA within it. Sex causes a sperm and an egg to fuse, which combines the two half-genomes to make a whole genome: another human. But meiosis is not a perfect process. Sometimes a sperm or egg is made with more than half its owner's DNA. Meiotic errors such as these are the cause of Down's Syndrome. Usually, offspring produced by meiotic errors are infertile because their extra chromosomes cannot line up with a normal organism's chromosomes when the sperm and egg fuse. But sometimes two mutants with matching chromosomes will produce fertile offspring. In these cases a new species is born. Polyploidy usually occurs with plants because the mutants can reproduce asexually until there are enough mutants that they can interbreed.