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Posted by Rich on January 20, 1999 at 23:51:10:
In Reply to: Muzzy likes making things up that he thinks I think posted by Homo sapiens on January 20, 1999 at 21:36:47:
1) mutation is the only source of novel genetic material
2) Indpendent ortment can lead to extremely bizarre variations, even without mutation. However, this genome will most likely be broken up by meiosis in the F1 generation.
2) There are 5 ways for allelic frequencies in a POPULATION to evolve: mutation, genetic drift, ortative mating, natural selection and gene flow. They ALL play a role in evolution. The combination of genetic drift, mutation and natural selection is a particularly powerful combination of evolutionary forces.
3) When I pointed out similarities between fish and humans, I mentioned urea metabolism. You smugly informed me of the ammonia flushing system of fish. However, you failed to remember the old addage, "There's more than one fish in the sea." Many marine fish use urea as a way of neutralizing nitrogenous poisons, and as a way of maintaining osmotic balance. Sharks and a variety of other fish do this. Notably, lobe-fin fish, our putative ancestoral line, either utilize this system (Coelocanths), or can resort to urea metabolism in water limiting environments (lungfish).
4) Are you familiar with homeotic genes? These are genes that essentially provide a set of instructions for cell development. There are a series of these homeotic genes that are coded in sequences, such that one set of enzymes are produced that begin building a limb or a segment, meanwhile activator and repressor proteins are being produced turning on and off different homeotic genes. Changes to these genes can result in rapid and profound changes --> the loss of tails, the placement of body parts in weird places. Point--> single genes changes can have big effects.
5) I wasn't satisfied with your explanation for the biogeography of Australia and Madagascar. Could you explain yourself again?