Exam 2 Powerpoint concepts Flashcards
what makes populations different?
natural selection
genetic drift
and mutations rates
what does gene flow do?
make populations similar
what happens when gene flow stops?
a population becomes genetically isolated
what leads to genetic divergence?
selection, drift, and mutation act independently in each population
genetic divergence + genetic isolation=
speciation
when does speciation occur?
when a single ancestral species splits into two or more descendent species,, and the populations egin to evolve independently
what is a species
an evolutionarily independent population
what is the biological species concept?
defines species as populations that do not successfully interbreed (reporductive isolation )
what does reproductive isolation do?
stops gene flow, causing gene flow
prezygotic isolation
prevents different species from even mating (fertilization doesnt occur)
post zygotic isolation
prevents different species from producing viable offspring
examples of prezygotic barriers
geographical,, separation by geographical barriers
ecological/habitat,, separated by habitat
temporal (time),, ex. flowers blooming at different times
behavioral,, different courtship behaviors
mechanical (incompatible geneitalia)
gametic,, the egg and the sperm are not compatible and the egg rejects the sperm
examples of post zygotic barriers
hybrid viability,, offspring do not develop normally and die as embryos
hybring sterility,, offspring mature but they are sterile
limitations to the BSC?
- typically limited to sexual organisms
- unknown to fossils,, only applies to living organisms
- difficult to know when closely related populations don’t overlap
-what about hybrids? Prizzly Bear
what is the morphospecies concept?
defines species as populations that appear different
(assumes that size, shape, and color differences are due to divergence)
limits of MSC
- very subject to human perception
(different researchers can come to different conclusions) - sometime species can look similar but they are genetically distinct
-sometimes two species can be identified even though it is only one
-cannot identify cryptic species
why is the MSC good?
0 it is good if you have a brand new species and have no idea where to start, gets a good start on identifying species
it is a good start
the phylogenetic species concept
identifies species based on the evolutionary history of populations
what are monophyletic groups?
contain an ancestral populatiom, all of its decendents and only those descendents
what are synapomorphies
- defines monophyletic groups
- homologous traits unique to a monophyletic group, genetic developmental or structural characteristics
why do synapomorphies occur?
genetic isolation
what are the benefits of the PSC?
- can be applied to any pop
-logcal
what are the disadvantages of the PSC
-synapomorphies are difficult to identify
- can lead to a huge number of species
mechanisms of speciation
allopatric and sympatric speciation