Chapter 14 Speciation Flashcards
recall ….. Microevolution leads to Macroevolution
speciation and macroevolutionary changes result from an increase of microevolutionary
different mechanisms of isolation
geographic (environmental disasters, habitat fragmentation), reproductive, spatial, and temporal — influence gene flow
Reproductive isolation
the separation of populations that are unable to interbreed because of changes that produce physical, biological, or behavioural barriers
Geographical isolation (spatial isolation)
-Two populations are separated by geographical barriers or habitat fragmentation (rivers, mountains, oceans)
-Become separate species, die out altogether
Temporal isolation/seasonal isolation
when individuals breed during different seasons of the year or times of the day
Three main forms of speciation
Allopatric, sympatric, Parapatric
Allopatric
where an extrinsic barrier exists between populations during divergence
-geographical isolation
Sympatric
where there is no extrinsic barrier
-Speciation that occurs without physical or geographic isolation
Parapatric
where there is a partial extrinsic barrier
diversification between species can follow one of four patterns (patterns of evolution)
divergent, convergent, parallel and coevolution
Divergent evolution
related species evolve new traits over time, away from the common ancestor
-may occur as a response to changes in abiotic factors (environmental conditions)
Convergent evolution
unrelated organisms evolve similar adaptions in response to similar environmental conditions
Parallel evolution
related species evolve similar adaptations independently in response to the same environmental pressures
Co-evolution
evolutionary change in one specie influences the evolution of another species
Extinction
low genetic diversity increases the risk of extinction e.g. those affected by population bottlenecks
