The Life Sciences Recent Progress and Application to Human Affairs The World of Biological Research Requirements for the Future (1970) / Chapter Skim
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The Diversity of Life
The Diversity of Life
Pages 133-141
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From page 133... ...
It also enables prediction of some of the ecological consequences of the introduction of insecticides, pesticides, or other new agricultural practices. Clearly the most striking practical achievements based on genetic understanding have been in agriculture, particularly the creation of fertile hybrids between divergent plants, e.g., the radish-cabbage hybrid or the wheat-rye hybrid mentioned above, resistant strains of almost all primary food crops and, of course, the development of hybrid corn.
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From page 134... ...
Currently, a species of animal or plant is characterized by two major properties: a gene pool adapted to occupy a particular niche in nature and protection mechanisms that prevent mixing with other gene pools. The gene pool cannot yet be described by direct examination of the genes themselves; it is described rather by phenotypic expression in the structure, physiological function, biochemical composition, breeding and mating patterns, choice of food, annual life cycle, etc.
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From page 135... ...
This involves the spatial separation of a subpopulation from the gene pool of a parental species and the gradual building up of isolating mechanisms in the isolated population. When these have been reasonably perfected through repeated mutational changes, the external barrier can break down and the daughter species can now coexist protected by the isolating mechanisms.
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From page 136... ...
Thus, the cactus growth form has appeared in several distinct families of plants quite distantly remote from the true cacti. In Australia, where the ordinary frog is absent, a tree frog has evolved with habits, body size, shape, and appearance of the common leopard frog of North America, even though the two species are only very remotely related genetically.
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From page 137... ...
What is not clear is why certain groups have remained virtually unchanged for hundreds of millions of years-indeed appear to be immortal while others simultaneously have undergone radical changes in what would appear to have been the same environment. Indeed, the entire fossil record is punctuated by instances in which one or another group entered upon almost explosive diversification leading to a simultaneous invasion of all sorts of new adaptive zones, referred to as adaptive radiation.
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From page 138... ...
Although there has been progress in explaining the extinction of certain species owing to changes in the physical or biotic environment, explanations offered for the decline and final extinction of entire major groups, as has occurred many times in the geological past, are totally unsatisfactory. Of 60 trilobite families, the dominant group of animals at the close of the Cambrian period, 40 disappeared from the subsequent fossil record and, after flowering in the Ordovician, the entire phylum disappeared before the end of the Paleozoic.
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From page 139... ...
With so many species in existence, one would have expected at least some of them to shift into new adaptive zones and thus escape the fate of their relatives. -rig ~ ~ It may well be that the reasons were subtle, as in the rise of the angiosperm plants in the Cretaceous, which undoubtedly had an adverse effect on the ruling herbivorous reptiles, this, in turn, bringing about the decline of the carnivorous types.
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From page 140... ...
Although man arose through an evolutionary process that he did not understand and over which he had no control, he must now realize that he is unique in the living world and that the responsibility for continuance of the evolutionary process is his. The future evolution of the orangutan and the whooping crane and of most other species will be determined by human decisions and hardly at all by anything done by those species themselves.
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From page 141... ...
The capacity of biologists to develop ways by which man can determine his future evolution is undoubted. The more difficult questions are whether man will choose to take full advantage of that capacity and with what wisdom.
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