|MadSci Network: Evolution|
No, Lamark's ideas do not provide a very good explanation for moths. His ideas for acquired characteristics would most likely mean that all the moths would eventually become light or dark colored. In contrast, according to Darwin's theory of Natural Selection and basic population genetics, there will tend to be (recessive) alleles that are expressed in the minority. It is the access to this minority population (of recessive alleles) that allows the species to alternate between light and dark color patterns when the environment changes. This is because studies show that these color patterns can appear as dominant or recessive alleles. Meaning that although a moth may be of one color type, it has the ability to carry and pass on the recessive color (diploid organism: they have two copies of each gene), which can express itself when mating with another heterozygote or homozygous recessive moth. So, you would have the possibility of having offspring that can express or also carry the recessive (or mal-adaptive) trait. So, mal-adapted organisms are maintained in small numbers for a long time before that allele becomes wiped from the population. The appearence of mal-adaptive moths would not occur under Lamarkian thinking. This is because Lamarkian thinking states that all individuals under the same environmental pressure would pass on the same acquired, beneficial traits to their offspring. Obviously, we do not see this occur in nature. Mike
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