Evolutionary Catechism (Evolution)

by George Jelliss , Crewe, Wednesday, January 13, 2010, 16:23 (5426 days ago) @ dhw

Responses to your catechism, but please bear in mind that I'm not a biologist, just someone with a interest in the subject:-1) Do I believe that all life is descended from one form (or a few forms)?
(If so, there must be a line from those early forms to all species, including ourselves.)-It may depend how you distinguish one "form" from another. For instance, the earliest replicating molecules may have formed a system of related structures that reproduce each other cyclically. Also there is not a single line but a branching tree.-2) If the answer to 1) is yes, do I believe that the line from early forms to ourselves has been gradual and continuous, or a "punctuated equilibrium"?-This may depend on how close you look, i.e. what magnification you use. Since everything is made from atoms, which are discrete objects, strictly continuous evolution in the mathemartical sense of continuity is impossible. But generally changes to an organism will be very minor. I can't see how big changes can occur by natural processes. -3) Do I believe that all complex organs have come into existence through random 
mutations followed by successive modifications?-Random variation followed by natural selection. There may be many different ways in which variations occur, not necessarily mutation caused by radiation. -4) Do I believe that organisms can be changed by their environment?-Populations of organisms with variation may be subject to environmental changes that are advantageous to part of the population but deleterious to others, thus resulting in the next generation having a different distribution of variations, and over many generations this can result in a change of significant magnitude.-5) Do I believe that natural selection results in the preservation and improvement of advantageous characteristics?-The characteristics need not be advantageous in any absolute sense, only in relation to the circumstances. For example loss of sight in cave dwellers. Or loss of brain in inactive creatures.-6) Do I believe that natural selection gives rise to new species? -Over a considerable time period, subject to environmental changes.-7) Do I believe that the gaps in the fossil record are caused by "the extreme imperfection of the geological record" (Darwin) or by imperfections in Darwin's theory?-We are lucky to have any fossils at all, in view of the special conditions necessary for dead bodies to be preserved in this way.

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GPJ