midterm - Evolution is a change in the properties of groups...

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Evolution is a change in the properties of groups of organisms over the course of generations. Fundamental Principles of Evolution: Phenotype (observed characteristics) is different from the genotype (genes in individual’s DNA). Acquired characteristics are not inherited. Environmental effects on an individual’s phenotype do not affect the genes passed on to its offspring. Hereditary variations are based on particles (genes) that retain their identity as they pass through the generations; they do not blend with other genes. Genes mutate at a fairly low rate, to equally stable alleles. Evolutionary change is a change in populational process: it entails a change in frequencies of individual organisms with different genotypes within a population. The rate of mutation is too slow for mutation by itself to shift a population from one genotype to another. Change in genotype proportions within a population occurs by either random fluctuations in proportions (genetic drift) or nonrandom changes due to superior survival/reproduction of some genotypes compared with others (natural selection). Natural selection can account for both slight and great differences among species as well as for the earliest stages of evolution of new traits. Natural selection can alter populations beyond the original range of variation by increasing the frequency of alleles that, by recombination with other genes that affect the same trait, give rise to a new phenotype. Natural populations are genetically variable and can often evolve rapidly when environmental conditions change. Populations of species in different geographic regions differ in the characteristics that have genetic basis. Differences between different species and between different populations of the same species are based on the differences at several or many genes many of which have small phenotypic effect. Differences among geographic populations of species are often adaptive and are consequences of natural selection. Different species represent distinct gene pools. Species are groups of interbreeding or potentially interbreeding individuals that do not exchange genes with other groups. Speciation is the origin of two or more species from a single common ancestor. There are many gradations in phenotypic characteristics among species assigned to the same genus, to different genera, and to different families or other taxa. Fossil record includes many gaps among quite different kinds of organisms. Essentialism is the view that, for any specific kind of entity, there is a set of characteristics or properties all of which any entity of that kind must have. In biology, all species to be unchanging throughout time and variation is accidental imperfection. Lamarck’s
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midterm - Evolution is a change in the properties of groups...

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