Key Terms
Result
Individuals with traits that help them compete for limited resources survive and reproduce more. Those traits increase i
Adaptation
Heritable trait that aids survival and reproduction in current environment Allopatric speciation: speciation via geograp
Divergent evolution
Two species evolve away from each other starting from a common ancestor.
Convergent evolution
Unrelated species independently evolve similar traits due to similar environmental pressures.
Homologous structures
Same basic form in different species because they share a common ancestor. The bones in a human arm, a dog leg, a bird w
Vestigial structures
Structures with no apparent current function; remnants of structures that were functional in ancestors.
Biological species definition
A group of organisms that interbreed and produce fertile, viable offspring.
Gene pool
The collection of all gene variants in a species. Changes in a gene pool are what evolution actually tracks.
Speciation
The formation of two species from one original species. Requires two populations to diverge to the point where they can
Polyploidy
A cell or organism has extra sets of chromosomes due to errors in meiosis.
Autopolyploidy
Extra chromosomes come from the same species. A plant with 2n=6 produces diploid gametes instead of haploid.
Allopolyploidy
Extra chromosomes come from two different species combining. Two species mate, produce a hybrid; chromosomes from both s
Gradual speciation model
Species change slowly and continuously in small increments over long periods of time.
Punctuated equilibrium model
Species remain largely unchanged for long periods, then undergo rapid change in a short burst, then stabilize again. Rap
Dispersal
A few individuals move to a new location; one route to allopatric speciation Divergent evolution: related species evolve