Evolution of a Species

• Changes to a gene pool can lead to the evolution of a new species

• Speciation = members of similar populations can no longer interbreed

• Geological Isolation = physical barriers divide a population

• Over time, the

divided populations may become two species that can no longer interbreed, even if reunited

• Reproductive Isolation = occurs when formerly interbreeding organisms can no longer mate and produce fertile offspring; 2 types– 1. Genetic Isolation = genes of two populations

are so different they cannot produce fertile offspring

– 2. Behavioral isolation (ex: one population mates in the spring, another population mates in the fall)

• Change in Chromosome Numbers = mistakes in cell division lead polyploid individuals (abnormal sets of chromosomes)

• Polyploids can be sterile, unable to reproduce• Polyploids can also reproduce and generate a

new species through interbreeding

Speciation Rates

• Gradualism = species originate through gradual change of adaptations

• Punctuated Equilibrium = speciation occurs in quick, rapid bursts

Patterns of Evolution

Divergent Evolution = species that were once similar evolve to look differently– Adaptive Radiation =

ancestral species evolving to fit into a lots of different habitats

Convergent Evolution = very distantly related organisms evolving similar traits

• Hummingbird moths are night-flying insects whose behavior and appearance are similar to those of hummingbirds. Explain how these two organisms demonstrate convergent evolution and analogous structures. (1 paragraph, 5-8 sentences)