Mutation Process
Very rare. Sudden chance alteration in the DNA-molecule resulting in inherited change in features or function. Usually cased by injury, e.g. x-ray. Practically all are fatal and if not, at least injurious, reducing fitness to survive.
This statement starts out correct. Mutations are infrequent but not very rare. Most arise after a creature is born via radiation, virus, or other means. The most harmful are eliminated by the sex act. For example in mammals a mutated sperm is less likely to be the one to find the egg. A mutated egg is more likely to result in a miscarrage than a birth. The results are that mutations which survive the sex act are the least harmful.
Next comes the pairing of genes from male/female to complete the DNA of the offspring. This act dilutes the effect of mutations, on average only half will get into the genome. Finally, many genes, especially the important ones have more than one copy. The extra copies are used to filter out changes in important body functions (this is the notion of a dominate/recessive gene). The recessive gene can make it into the next creature but does not get expressed. It is in effect, out voted by the other copies.
Reproduction via DNA is a remarkable stable copy of the prior generation, and the little changes that arise stay recessively in the background.
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