Daily Warm-up February 25th What do you think defines a species Daily Warm-up February 25th What do you think defines a species? HW: Read 17.3 Turn in: Pre-registration form

Species Two types What is a species? Members of a population that are able reproduce fertile offspring Speciation: process whereby some members of a population change so much that they can no longer produce fertile offspring Reproductively isolated Two types

Prezygotic Isolation Prevent reproduction by making fertilization unlikely Behavior, ecological, geographical, timing ecological isolation temporal isolation geographic isolation behavioral isolation mechanical isolation gametic isolation

Postzygotic Isolation When fertilization occurs but a hybrid offspring cannot develop or reproduce

Speciation If reproductively isolated for long enough time…speciation Allopatric speciation Physical barrier separates a population into two or more populations Sympatric speciation Evolves into a species without a physical barrier

Geographic isolation Species occur in different areas physical barrier Ammospermophilus spp Species occur in different areas physical barrier allopatric speciation Harris’s antelope squirrel inhabits the canyon’s south rim (L). Just a few miles away on the north rim (R) lives the closely related white-tailed antelope squirrel

Patterns of Evolution Speciation is a long process Evidence of speciation is visible in patterns of evolution Adaptive radiation Coevolution Species evolve in close relationship with another species Convergent evolution Unrelated species evolve similar traits because of a similar climate even though in far away places.

Adaptive Radiation New habitat leads to rapid speciation

Coevolution Two species evolving in close relationship with other species. Might be so close that the evolution of one species affects the evolution of other species. Mutualism, parasitism

Rates of Speciation Punctuated Equilibrium Gradualism Punctuated Equilibrium gradual accumulation of small changes over long time rapid bursts of change mixed with long periods of little or no change