speciation Flashcards
biological species concept
- biological species are defined by reproductive isolation
- different biological species don’t breed in nature, breed but fail to produce offspring, produce inviable offspring, produce sterile offspring
what are the mechanisms of isolation
- prezygotic isolation
- postzygotic isolation
what is prezygotic isolation
- any mechanism that prevents successful mating
genotypically
what is postzygotic isolation
- any mechanism that prevents the offspring from producing offspring of their own
which is more adaptively favoured, pre or post zygotic isolation?
- prezygotic is much less wasted effort
- when post zygotic isolation occurs, there is natural selection for pre zygotic isolation
what are the downsides to the biological species concept?
- it doesn’t apply to asexual species
- not practical to extinct species
- hard to evaluate
the morphological species concept
- morphological species are different if they look different
- useful for working with fossils or diverse groups
disadvantages to the morphological species concept
- subjective
- groups that look similar but can’t produce offspring
- it’s unclear how this relates to the conceptual definition evolution
ecological species concept
- ecological species is a set of related organisms that occupy the same ecological niche
- commonly used for small things, like asexual
phylogenetic species concept
- a phylogenetic species is monophyletic group of populations that can’t be divisible into smaller species
what is a monophyletic group
- a group defined by a single common ancestor
advantages of the phylogenetic species concept
- well defined
- broadly applicable
disadvantages of the phylogenetic species concept
- hard to estimate phylogenies
- requires a lot of information about populations
how are species generated?
- new species are generated from old species
- one species can gradually evolve into another
- species can diverge, split into two
how do species split?
- genetic isolation and genetic divergence
which comes first: isolation or divergence
- isolation, with too much gene flow populations can’t diverge
what is allopatry?
- organisms living apart from each other
- when two populations are isolated from eachother, they might diverge
what is dispersal?
- allopatry
- when some individuals in a population move to a new area and colonize it (establish a new population)
what is vicariance?
- allpatry
- when a population is split by an geographical or ecological barrier
what is sympatry
- organisms living in the same geographic area
why is hard for populations in sympatry to diverge?
- gene flow and competition
sympatric divergence
- populations are not physically isolated yet isolated by their traits (ie. preferences in food sources)
genetic incompatiability
- can be caused by genetic incompatibility
- if they’re in the same place but they can’t produce fertile offspring
polyploidy
- reproductive mistakes that produce individuals with with extra copies of each chromosome
