BIOL359 Chapter Notes - Chapter 16: Species Problem, Species Complex, Reproductive Isolation

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1. 5 million species described today, total may be about 3-5 million. Mutation, natural selection, migration & genetic drift causes populations to diverge & form new, Species concepts: species forms a boundary for the spread of alleles & different species follows different evolutionary trajectories, species consists of interbreeding populations that evolve independently of other populations, the 3 species concept. Criterion for identifying evolutionary independence is morphological similarities & differences. Pro: widely applicable, can be identified in extinct or living species, sexual or asexual reproducing species. Con: if not applied carefully, species definitions can become arbitrary & idiosyncratic, there could be incompatibilities between species designations made by different investigators & concepts will be hard to apply in groups with few measurable morphological characters. Cryptic species: groups that were or are actually independent of one another appear to be members of the same species based on morphological similarity. Criterion for identifying evolutionary independence is reproductive isolation.

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