Chapter 23

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Biological Sciences
Kamini Persaud

Chapter 23 Speciation Species - (1) literally means kinds - Carolus Linaeus originated the binomial system of Latin nomenclature by which species are known today; since he knew nothing of genetics and mating behaviour of the organisms, he classified them based on their appearance which is called the MORPHOLOGICAL SPECIES CONCEPT - (2) not all members of a species must look alike: information other than appearance is used to decided whether distinguished individuals are members of the same or different species - (3) species are like branches of trees: each species has a history that starts at a speciation event and ends at either extinction or another speciation event - SPECIATION the process by which one species splits into two or more daughters species, which thereafter evolve as different lineages; this process is often gradual and guarantees that in many cases, two populations at various stages in the process of becoming new species will exist REPRODUCTIVE ISOLATION an important component of the process of speciation: if individuals of a population mate with one another, but not with individuals of another populations, they constitute a distinct group within genes recombine (that is, separate branches on the tree of life) - Ernst Mayr proposed the definition of species known as the BIOLOGICAL SPECIES CONCEPT: (4) species are groups of actually and potentially interbreeding natural populations which are reproductively isolated from other such groups actually says that the individuals live in the same area and interbreed with one another potentially says that although the individuals do not live in the same area, and therefore cannot interbreed, other information suggests that they would do so if they did get together * this definition does not apply to organisms that reproduce asexually * Speciation Barriers (Mode of Speciation) - speciation requires that gene flow within a population whose members formerly exchanged genes be interrupted; gene flow can be interrupted in two major ways, each of which characterizes a mode of speciation: Allopatric Speciation (Geographic Speciation)
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