Speciation Biology 1-2

Speciation  Isolation is required for a new species to emerge. Speciation-evolution of a new species. Speciation-evolution of a new species. Allows population to develop their own traits. Allows population to develop their own traits. Accumulate enough differences to form a new species. Accumulate enough differences to form a new species.

Speciation  Reproductive barriers prevent different species from mating. Reproductive barrier-a biological feature of a species that prevents it from interbreeding with another species. Reproductive barrier-a biological feature of a species that prevents it from interbreeding with another species.

Prezygotic Barriers  Prezygotic barrier-prevents mating or fertilization. Different mating seasons. Different mating seasons. Living in different areas. Living in different areas. Males and females are not attracted to each other. Males and females are not attracted to each other.

Postzygotic barriers Postzygotic barrier-prevent development of fertile adults.Postzygotic barrier-prevent development of fertile adults. Organisms mate, but offspring fails to develop. Organisms mate, but offspring fails to develop. Hybrid sterility-hybrid offspring is sterile and cannot reproduce. Hybrid sterility-hybrid offspring is sterile and cannot reproduce.

Adaptive Radiation  In most cases, geographic isolation comes before reproductive barriers. Some physical barrier prevents populations from exchanging genes. Some physical barrier prevents populations from exchanging genes. Each population goes through natural selection and develops its own traits. Each population goes through natural selection and develops its own traits.

Adaptive Radiation cont’d  Geographic isolation can lead to adaptive radiation. Adaptive radiation Many species evolve from a single species introduced to a new and diverse environment. Adaptive radiation Many species evolve from a single species introduced to a new and diverse environment.

Adaptive Radiation cont’d  Different groups in the population adapt and take advantage of different resources. Diversifying selection. Diversifying selection.

Pace of Speciation  Gradualism- populations are isolated and slowly accumulated a series of small changes as they adapt. Small changes build up to big changes. Small changes build up to big changes.

Pace of Evolution cont’d  Punctuated equilibrium-the evolution of a new species occurs relatively quickly; the emergent species then changes little over time. Makes big leaps quickly. Makes big leaps quickly.