Exam 3 study guide

Exam 3 study guide - Exam 3 Study Guide The Origin of...

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Exam 3 Study Guide The Origin of Species Microevolution and macroevolution o Microevolution – adaptations that evolve within a population, confined to one gene pool o Macroevolution – evolutionary change above the species level What is a species o The biological species concept A species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring; they do not breed successfully with other populations Reproductive isolation – the existence of biological factors (barriers) that impede two species from producing viable, fertile offspring Hybrids – the offspring of crosses between different species Pre-zygotic barriers – barriers that act prior to formation of a zygote Habitat isolation – two species encounter each other rarely, or not at all, because they occupy different habitats, even though not isolated by physical barriers Temporal isolation – species that breed at different times of the day, different seasons, or different years cannot mix their gametes Behavioral isolation – courtship rituals and other behaviors unique to a species are effective barriers o Albatross courtship ritual, Giraffe courtship ritual, Blue-Footed Boobies courtship ritual Mechanical isolation – morphological differences can prevent successful mating Gametic isolation – sperm of one species may not be able to fertilize eggs of another species Post-zygotic barriers – barriers that prevent the hybrid zygote from developing into a viable, fertile adult
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Reduced hybrid viability – genes of the different parent species may interact and impair the hybrid’s development Reduced hybrid fertility – even if hybrids are vigorous, they may be sterile Hybrid breakdown – some first-generation hybrids are fertile, but when they mate with another species or with either parent species, offspring of the next are feeble or sterile Limitations of the biological species concept Can’t test interbreeding in fossil species Information about interbreeding unavailable for most species Doesn’t apply to all non-sexually producing organism, e.g., all prokaryotes o Morphological species concept – defines a species by structural features It applies to sexual and asexual species but relies on subjective criteria o Ecological species concept – views a species in terms of its ecological niche It applies to sexual and asexual species and emphasizes the role of disruptive selection o Phylogenetic species concept – defines a species as the smallest group of individuals on a phylogenic tree It applies to sexual and asexual species, but it can be difficult to determine the degree of difference required for separate species Overview of Speciation o Requires that gene flow between populations of a species be interrupted o Enough time has to pass to allow accumulation of sufficient characteristics (conferred by genetic information) to prevent interbreeding between two populations
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Exam 3 study guide - Exam 3 Study Guide The Origin of...

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