Final exam review.docx - lecture 18 speciation/species...

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lecture 18 – speciation /species- origin of species .Speciation is the process that produces new species from an ancestor species Speciation is invoked to explain the diversity of types of organisms What is a species? o Two general possibilities Species are truly distinct real entities, or The ‘species’ is an idea we have imposed on nature o (Or something in between, or either, depending upon the situation?) o Definition : “An evolutionarily independent population or group of populations Speciation- a process under most models, species are not creatd instantly but over long periods of time Two patterns: (lecture 18 slide 6 for example) o Phyletic speciation à Anagenesis o Phylogenetic speciation à Cladogenesis If microevolution occurs in two halves of a gene pool that has split then we have speciation Speciation: o Remember that we are occupying a “point in time” à species can be in flux o And remember that current “species” are not fixed genetically à Species have variability and natural selection operates all the time o So it’s difficult to draw boundaries around “species” *understanding the fork species characteristics are dynamic, changing over time, but its label is that its character is fixed We consider morphology (body form) as well as physiology (internal functions), biochemistry, DNA, geography, and behaviour Biological Species Concept involving reproductive isolation “Populations whose members have the potential to interbreed in nature to produce viable and fertile offspring” “Reproductive compatibility” within species “Reproductive isolation” between species o no gene flow between breeding groups o Can lead to speciation, provided isolation is sufficiently long-lasting o Can then maintain separate gene pools as separate species o For sexually reproducing species o Pre and Post zygotic Barriers: Serve to reproductively isolate a population from other gene pools, Create and maintain species Pre-zygotic: :before the zygote” Reproductive isolation prior, Impede mating or prevent fertilization
A) those that prevent mating – 1. habitat isolation (“ecological isolation”) ex. Desert sping lizard (open areas), clarks spiny lizard (trees) 2. Geographic isolation ex. Tucuxi Dolphins (pronounced (too-koo-shee) have separate marine and riverine gene pools 3. Temporal isolation ex. Eastern Spotted Skunk and Western Spotted Skunk overlap geographically, but one species mates in winter and the other in summer. Another example (day vs night) 4. Behavioural isolation: ex, In Blue-footed Boobies, there is a scripted courtship that involves foot waving, and it secures the reproductive attention only of other Blue-footed Boobies 5. Mechanical islolation ex, Damselflies and Dragonflies have highly complex genitalia that work like lock and key and that vary considerably between otherwise closely related species.

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