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Gould has been to the USA, its finest teacher of evolution.
"Biological evolution is the process of change and diversification of living things over time, and it affects all aspects of their lives-morphology, physiology, behavior and ecology. Underlying these changes are changes in the hereditary materials. Hence, in genetic terms, evolution consists of changes in the organism's hereditary makeup" (Ayala 36). Now critics of evolution often say that they accept microevolution, that is, the changes in an organism's heredity makeup, the variants within species due to genetic modification and environmental pressures. (How could they deny such clear and compelling evidence?) The widely varying breeds of dogs exemplify microevolution. However, they claim that macroevolution, the process of change or diversification over time, or descent with modification, is a philosophical dogma without scientific evidence to support it. In public debates over evolution, this claim has been expressed so often that it has taken on the character of a mantra--but it simply is not true. The genetic mutations that lead to the varieties within species are the same kinds of changes in the hereditary material that eventually lead to macroevolution, or the emergence of new species. The distinction often made between micro- and macro- may serve some pedagogical and analytical functions but it does not indicate that these are essentially different evolutionary processes. In reality, they are not.
In addition to careers in Ornithology, Taxonomy and Systematics, he was a Professor of Zoology and Evolutionary Biology at Harvard and director of its Museum of Comparative Zoology.
What I Think About the Soundness of the Theory of Evolution
The widespread neglect of the role of speciation in macroevolution continued until Niles Eldredge and Stephen Jay Gould (1972) proposed their theory of punctuated equilibria.
Given these genetic phenomena and the action of natural selection upon them, how do they account for the origin of new species? In other words, how does microevolution lead to macroevolution? First, let us define what a species is. While evolutionary biologists differ in their views about the concept of species, and in practice it is not always easy to determine whether various individuals belong to the same species, this definition is a widely accepted one:
Evolution -- Essays on Evolution - Darwiniana
Adaptive radiation: Migrations of species to new environments and their resulting reproductive isolation have led to spurts of evolutionary development at different periods of life's history. The species that migrated from the oceans to land evolved from amphibians to reptiles some 340 mya. From them radiated the great number of reptilians forms, from the ancient "-saurs" (T-Rex & Co.) to modern crocodiles, lizards, snakes, geckos, and others. When the early mammals that arose in the Triassic period (248 to 206 mya) no longer needed to compete with the giant reptiles for habitat and survival, a rapid (in geological terms) radiation of various lineages emerged over time. The species of bats, rodents, whales, elephants, horses, rabbits, moles, and great apes living today are the present ends of lineages that radiated out over the lands, and some from there to the seas, from the earliest mammals of the Cretaceous Period (over 65 mya) (Price 137-143).
Changes in gene frequency, gene flow, and genetic drift by themselves do not ensure evolutionary change, for these processes are random with respect to adaptation. Natural selection, which selects for beneficial over harmful mutations, provides the directionality for such genetic changes. Not only does it make possible the survival and improvement of the organization of living beings, it also makes possible their diversity (Ayala 40). This sustained directional selection leads to major changes in the forms of living things and their ways of life, with some changes occurring with greater rapidity than others, over long periods of geologic time, that is, time calculated in millions of years. These processes illustrate a convention often expressed by biologists: "natural selection works by converting variation within populations to differences among populations" (Gould, 2002, 748).
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Essay V: Evolution for Christians - Berea College
This book identifies the types of information that genomes transmit, shows how competition between different types is resolved in the genomes of different organisms, and identifies the evolutionary forces involved.
Essay On Evolution - Professional college paper writers
His was the last of a series of major publications, by authors from several different disciplines, that became known as the neodarwinian synthesis, the foundation for modern-day evolutionary biology.
Essay on Evolution - 924 Words - StudyMode
Natural selection: Ayala has defined natural selection as "the differential reproduction of alternative hereditary variants" or alleles that enhance the survival of the organisms that carry them and enable them to "reproduce more successfully than organisms carrying alterative variants." The term "differential reproduction" includes differences in survival, fertility, mating success, and rate of development (Ayala 36). The amount of genetic variation is astonishingly high in all organisms, especially those that reproduce sexually, and thus the opportunities for evolutionary change in response to environmental conditions are virtually unlimited. While most genetic mutations are adaptively neutral, and many prove to be harmful, the comparatively smaller number of beneficial mutations is more than enough to account for innumerable variations that have made possible the emergence of new varieties and new species. As the number of favorably variable genes increases, and the number of forms of these genes likewise increases, the frequency of change in these forms is likely to grow at the expense of other variations. The frequency in a large natural population may be very small in a generation but increases in effect over several generations. It has been demonstrated mathematically that "there is a direct correlation between the amount of genetic variation and the rate of evolutionary change by natural selection" (Ayala 36, 37).
Ernst Mayr wrote an entire book on the subject of this little essay.
1. Perhaps the days stated in the Genesis 1 account are not 6 24-hour days. Scripture tells us that God's days are not our days (2 Peter 3:8 "with the Lord, a day is like a thousand years, and a thousand years are like a day" and Psalm 90:4 "A thousand years are to You like a yesterday which has passed"). The full context of these two verses is the great sweep of time from creation until the judgment day. Perhaps the days are not strictly sequential, although the order matches up pretty well with the theory of evolution. The account of Cain's wife in Genesis 4:17 cannot be strictly sequential and literal. There is also the difficulty in reconciling Genesis 1 with the second creation account in Genesis 2, where man is created first and the animals afterwards (Genesis 2:18-20).
Evolution of Language - Term Paper
Most important, and the basis of natural selection, is changes in gene frequency. Gene frequency measures the frequency in a population of a particular gene relative to other genes in its locus, i.e., its position on the chromosome. In fact, this is a measure of the frequency of alleles or alternate forms of the same gene. Four processes affect gene frequency change: "mutation, migration, drift, and natural selection" (Ayala 37). Related to changes in gene frequency are the phenomena of gene flow and genetic drift. We briefly look at these phenomena as well as reproductive isolation and adaptive radiation. In conjunction with natural selection they constitute what is called the Modern Synthesis of evolutionary theory.
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