L8 - Speciation Flashcards
how do we generally define species
fundamental unit of life, reproductive isolation is the basis
what are the different consequences of hybrid species
reduced fitness (wildebeest), infertility (mule), hybrid vigour (cypress), ring species (californian salamander)
what are the 4 mechanisms of speciation
allopatric, sympatric, peripatric, parapatric
what is allopatric speciation
when speciation occurs after a barrier is formed between population, gene flow stops, eg continents drifting apart
what is peripatric speciation
species population moves to a different area and then a barrier forms after speciation, eg silk balloon spider example
what is parapetric speciation
geneflow is significantly reduced, some connection which makes this mechanism more realistic
what is sympatric speciation
something other than physical barrier prevents gene flow, difficult to prove, example is Lord Howe palm - populations adapted to different pH soil which lead to different flowering times and prevented gene flow
under what conditions does speciation occur on islands
only on islands of larger areas, small islands have fixed number of species
how can the fact that no speciation occurs under an island area threshold be explained
niche theory - diversity is maintained by niches available, larger islands can provide resources for multiple species withing one/similar niches
how are high altitude ecosystems similar to islands?
also have a barrier of dispersal due to different environmental conditions, also have a high number of endemic species
what did research on Mt Kinabalu show
the mountainr elatively young therefore species didnt adapt as altitude increased, instead species came from other high altitude environments
why does climate change affect species in high altitudes severely?
climate changes drastically and therefore their adaptations are no longer advantageous in these environments
what is adaptive radiation
quick burst of speciation within a certain clade
what is an example of adaptive radiation
pitcher plants - different strategies that tackhle nutrient defficiency on mountain tops (nutrient runoff)
what are the different strategies among pitcher plants
carnivorous, mutualism with bacteria, symbiosis with shrew
how can race bewteen predator and prey lead to adaptive radiation
example of bornean micro snails, “extreme” environment, extravagant shapes to prevent getting eaten by different kids of predators
