lecture 20- origin of species Flashcards
what is macroevolution
evolutionary change above the species level
origin of a new species or cumulative evolutionary change of a long period of time
what is speciation
when species split into 2 or more species (new species)
what does the biological species concept refer to
reproductive isolation
species are organisms who can breed together in nature and produce viable and fertile offsprings for multiple generations
cannot produce viable and fertile offsprings with members of other species
what does reproductive isolation entail
existence of biological factors that impede members a two species from producing viable and fertile offsprings
preserving genetic integrity (no gene flow)
types of isolating mechanisms
prezygotic barriers (5 types): prevent mating or fertilization, zygote is never produced
postzygotic barriers (3 types): prevent hybrid zygote from developing into viable and fertile adult
types of prezygotic barriers
habitat isolation
temporal isolation
behavioural isolation
mechanical isolation
gametic isolation
what is habitat isolation
different habitats for mating
what is temporal isolation
mate at different times of the year
what is behavioural isolation
courtship rituals are specific to species so females wont mate with different species
what is mechanical isolation
genitals dont align
what is gametic isolation
sperm cannot fertilize other species egg (cant penetrate, cant survive)
what are the postzygotic barriers
reduced hybrid viability
reduced hybrid fertility
hybrid breakdown
what is reduced hybrid viability
hybrid is frail/doesnt make it to birth
dies easily
what is reduced hybrid fertility
hybrid is sterile but strong
what is hybrid breakdown
first gen. can survive and reproduce but second is weak or sterile
what cant the biological species concept be applied to
asexual organisms
organisms that we dont know the reproduction system of
what is the morphological species concept
characterization of a species based on visible characteristics
what is the ecological species concept
views a species in terms of its ecological niche
what is the phylogenetic species concept
traces the phylogenetic history of organisms
how does speciation happen
allopatric speciation: geographic separation
sympatric speciation: same area
what is allopatric speciation
geographically separated
gene pools diverge
mutations and genetic drift
change enough and cant breed with other pop. and make fertile offsprings
-> new species
what is sympatric speciation
occurs through
changes in ploidy (plants)
changes in ecology (animals)
autoploidy
extra chromosomes: 2n in gametes instead of n
cant mate with parent plant but can self pollinate with other tetraploids of the same species
allopolyploid
parents (different n) result in offspring having an odd number of chromosomes making it sterile with other parent species but fertile with other polyploid hybrids
if the hybrid doubles its chromosomes it can perform meiosis and make gametes
