Replace:
Lines 6 – 8, p138 …… “However, pure chance…..nothing to do with natural selection “
With:
Thus, tube shape plasticity in the larvae of chironomid midges such as Chironomus plumosus seem adaptively appropriate to their location in the mud of a pond or stream. There are at least two possible explanations for the evolution of this phenomenon. First, an evolutionarily stable strategy (Maynard Smith, 1974), with a fixed proportion of the population genetically programmed to survive only if they settle in the appropriate depth of sediment. Although this kind of lottery carries greater fitness benefits than a single strategy, such a wasteful programme where a proportion of offspring always perish because they settle in the wrong place, seems unlikely to be favoured by natural selection. Second, all larvae could have inherited the ability to build their tubes and develop in whatever depth of sediment they find themselves. It is the second possibility that excites my interest here. In this case it is the environment, perceived as sediment depth, that appears to be the selective force leading to the evolution of behavioural flexibility enabling larvae to build different tubes as required. If such an alternative proves to be the correct one, it as a pretty demonstration of the role of environment over mutation in evolution. In the words of Lee van Valen , quoted by Stephen Gould p1....."…evolution is the control of development by ecology"
Gould, S. J. 1977. Ontogeny and Phylogeny. Harvard University Press, London.
Maynard Smith, J. 1974. The theory of games and the evolution of animal conflicts. J. Theor. Biol 47, 209-221.
No comments:
Post a Comment