Evolution Message Board - Msg: 11232011

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Politics : Evolution

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To: Null Dog Ago who wrote (47)	9/13/1999 11:15:00 AM
From: TigerPaw	Read Replies (2) of 69300

, no new species can evolve from another There are several documented cases of new species, mostly flowers. There are a couple of mechanisms in which new species evolve. I will illustrate one of them. This mechanism occurs for life which reproduces sexually, such as humans. The reproduction occurs when chains of genes known as chromosomes pair up with the nearly matching chromosomes of the opposite sex. The sets are not exactly the same and during the matchup the genes from one side or another gets included into the final zygote. The gene pairing has a pretty robust mechanism for these blends (for example virtually any human population can successfully breed with a human of the opposite sex from a different population). Sometimes chromosomes can break into two pieces. The individual with this condition can still successfully breed because the two parts of the chromosome match up with the single strand of the partner. This condition can be inherited (meaning that the zygote can contain the "weak gene" that leads to the chromosome breaking). In a population with a fair amount of inbreeding, the number of individuals with the weak gene can grow to be a fair percentage of the total population. When sex partners which both contain the weak gene mate there is a chance that the two parts of the former chromosome will link up in the opposite order than that of the original population. The resulting offspring can no longer successfully mate with the original population but is fertile with a sex partner that either has the weak gene or was born of a similar union. The result is two populations which can no longer mate with each other. Their evolutionary tracks now take different courses. The conditions which promote this type of speciation is an isolated population, otherwise frequent gene mixing from the dominant population would make the odds very low for members of the new species to find fertile sex partners. TP

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