a. Zygote mortality is when hybrids (offspring of parents of two different species) do not live to reproduce. b. Hybrid sterility occurs when the hybrid offspring are sterile (e.g., c. In F2 fitness, the offspring are fertile but the F2 generation is sterile. C. Modes of Speciation 1. Allopatric speciation occurs when new species result from populations being separated by a geographical barrier that prevents their members from reproducing with each other. b. While geographically isolated, variations accumulate until the populations are reproductively isolated. c. First postzygotic isolation occurs, then prezygotic reproductive isolation occurs. 2. Sympatric speciation occur when members of a single population develop a genetic difference (e.g., chromosome number) that prevents them from reproducing with the parent type. a. The main example of sympatric speciation is in plants. b. Failure to reduce chromosome number produces polyploid plants that reproduce successfully only with polyploids. c. Backcrosses with diploids are sterile. D. Adaptive Radiation 1. Adaptive radiation is a rapid development from a single ancestral species of many new species. 2. The case of Darwin's finches illustrates the adaptive radiation of 13 species from one founder mainland finch. 3. On the Hawaiian Islands, a wide variety of honeycreepers descended from one goldfinchlike ancestor; Hawaii is also the home of the silversword plants that radiated from ancestral tarweeds. Environmental impacts: What is Pangea? Continental Drift?
a. Zygote mortality is when hybrids (offspring of parents of two different species) do not live to reproduce. b. Hybrid sterility occurs when the hybrid offspring are sterile (e.g., c. In F2 fitness, the offspring are fertile but the F2 generation is sterile. C. Modes of Speciation 1. Allopatric speciation occurs when new species result from populations being separated by a geographical barrier that prevents their members from reproducing with each other. b. While geographically isolated, variations accumulate until the populations are reproductively isolated. c. First postzygotic isolation occurs, then prezygotic reproductive isolation occurs. 2. Sympatric speciation occur when members of a single population develop a genetic difference (e.g., chromosome number) that prevents them from reproducing with the parent type. a. The main example of sympatric speciation is in plants. b. Failure to reduce chromosome number produces polyploid plants that reproduce successfully only with polyploids. c. Backcrosses with diploids are sterile. D. Adaptive Radiation 1. Adaptive radiation is a rapid development from a single ancestral species of many new species. 2. The case of Darwin's finches illustrates the adaptive radiation of 13 species from one founder mainland finch. 3. On the Hawaiian Islands, a wide variety of honeycreepers descended from one goldfinchlike ancestor; Hawaii is also the home of the silversword plants that radiated from ancestral tarweeds. Environmental impacts: What is Pangea? Continental Drift?
BI30-LI2-Evolution-and-Evidence.docx