species and speciation Flashcards
the only real taxonomic group in nature is
species
what is speciation
the process by which one genetically-cohesive population splits into two or more reproductively-isolated population
what are the two major categories of evolutionary change?
- cladogenesis (branching of a lineage)
- anagenesis (evolutionary changes within a lineage)
what is the issue with the morphological species concept?
- many individuals that look the same may have very different genetic differences
what are some issues with the biological species concept
- bacterial species use horizontal gene transfer, and thus share lots of genetic material between members of difference species (only 6% of genes are shared by all strains)
- there is within-population variance, such as color variation. phenotypically, this variance usually occurs because different populations are geographically separated and lack gene flow. so causes different pops to look different
- hybrids. mixed offspring complicates this species concept.
- fossils. Can’t breed or observe them to determine if they are individual species
what mechanisms allow individuals to recognize their own type and differentiate those that dont match?
- reproductive isolation!
- barriers that isolate gene flow between two species
- pre-mating, post mating pre-zygotic, and pot-zygotic
What are pre-mating barriers for reproductive isolation?
- ecological isolation (live in different habitats)
- mate recognition (no sexual attraction between different species)
- temporal isolation (mating occurs at different times/seasons)
What are post-mating barriers for reproductive isolation?
- mechanical isolation (structural differences prevents copulation)
- gametic isolation (female+male gametes fail to attract one another, are inviable)
What are post-zygotic barriers for reproductive isolation?
- reduced hybrid viability (hybrid zygote fails to reach sexual maturity)
- hybrid breakdown (offspring of hybrids have reduced viability/fertility(
intrinsic factors effecting hybrids?
- genetic incompatibility, causing individuals who are sterile or whos second generation is sterile
extrinsic factors effecting hybrids?
- reduced survival due to ecological factors
how do we distinguish sibling species?
ecological, behavioural, and chromosomal differences
what is cryptic biodiversity
species that at one point may look very different, but at another point look the same
what is allopatric speciation by vicariance?
- divergence of two large populations by a physical barrier, that causes them to evolve slowing into new species (due to different gene pools)
what is peripatic speciation?
- also known as allopatric speciation by dispersal
- divergence of a small population from a widely distributed ancestral forms (divergence)
- causes founder effects
what is sympatric speciation?
- evolution of reproductive barriers within the same population and geographic area
- a single population evolves away from each other, even if its in the same place, due to preference and diversifying selection
what is parapatric speciation?
- two pops having a shared border but non-overlaping distributions
- slightly different environments
- low gene flow between them
what is speciation by allopolyploidy?
- the production of polyploid hybrids that are fertile, but reproductively isolated from their parent species
- these hybrid species often grow faster and larger than parentals
What is the most widely used definition of species?
- biological species concept: species are groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups
what is adaptive radiation? what causes it?
- the evolution of ecological and phenotypic diversity within a rapidly multiplying lineage.
- involves the differentiation of a single ancestor into an array of species that inhabit a variety of environments that differ in traits used to exploit those environments
what precipitates adaptive radiation?
- ecological opportunity (invasion of new niche lead to rapid diversification)
- key innovation (adaptation of new trait that allows organisms to exploit previously unavailable niches)
How does a single species become many?
- opportunity (genetic drift, mutation, change in gene flow)
- selection (novel environment, change in mating preference)
