topic 8 Flashcards
how did darwin imagine speciation
a branchiing event
macroevolution
broad patterns of evolutionary change above the species level (evolution of wings in bird ancestors)
biological species concept
group of interbreeding individuals that are reproductively isolated and produce viable offspring
limitations of bsc
not applicable to fossils/asexuals, gene flow/hybridization can occur
morphological species concept
defined based on physical/structural traits (arbitrary)
ecological speices
defined based on ecological niche (how it interacts with environment)
phylogenetic species
smallest group of individuals that have a common ancestor (good for evolutionary process too)
what keeps species distinct under bsc
reproductive isolation (pre or postzygotic)
prezygotic barriers
habitat isolation (species dont encounter eachother), temporal isolation (breed at different times), behavioral isolation (courtship rituals), mechanical (anatomic incompatibility), gametic (gametes cant fertiliza eachother esp for broadcast spawners)
postzygotic barriers
reduced hybrid viability (hybrids cant survive past embryos), hybrid fertility (hybrids live, but are sterile), hybrid breakdown (second generation hybrids are eventually feeble or sterile)
allopatric speciation
geographic isolation causing speciation
dispersal
a small population is isolated from the main population
vicariance
range of a species is split by a change in environment
allopatric speciation
seperate subpopulations evolve independently because of intrinsic reproductive barriers
snapping shrimp
land bridge split north and south, caribbean and pacific cant produce offspring
requirements for sympatric speciation
must become reproductively solated in some way because of hromosonal errors during meiosis or hybridization, or through natural selection for reproductive isolation
polyploid speciation
changes in number of chromosome sets to create genetically distinct descendants, different number of chromies
hybrid speciation
interbreeding between related species creates genetically distant species that cannot reproduce with parent species
allopolyploids
different numberof chromies because of hybrid speciation
autopolyploids
chromosomal error during meiosis
homoploids
hybrid speciation with no change in ploidy
habitat differentiation
causes sympatric speciation, increasing reproductive isolation (hawthorn vsapple)
sexual selection
sympatric, results in secyal dimorphism (male and female visibly), natural selection for mating success (sexually selected traits might not be best for survival)
hybrid zones
incomeplete reproductive barriers –> hybrids forming in ranges of overlap
