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Evolution of Species 7.3 Read and Discuss This is what we should know by the end of this section What factors have contributed to the diversity of species? How do new species form? How do scientists infer evolutionary relationships among species? What causes the extinction of species? Review What In is selective breeding? natural selection, what determines which organisms reproduce and pass on their traits? A person who is breeding the organisms The environment Over time, different environments and genetic variations have produced, through natural selection, the variety of organisms that exist today A Variety of Species 1. Different environments – the habitat is the environment that one needs to live and reproduce 2. Genetic Diversity• Organisms of the same species have variations and different traits • Many species have a lot of variety in their gene pool • Example: humans • Some species have very similar gene pools • Example: cheetahs How do new species form? -A new species can form when a group of individuals remains isolated from the rest of its species long enough to evolve different traits Geographic isolation Species get separated from one another Example: Grand Canyon squirrels Inferring Species Relationships Similarities in DNA Comparing the sequence of nitrogen bases in DNA (A,T, C, G) More similar = more closely related Combining Evidence Use evidence from the development of the animal, anatomy, and DNA Extinction of Species Extinction and the Environment Extinction is caused by a change in a species’ environment. The members of the species may not have adaptations that allow them to survive and reproduce in the changed environment. Climate Change • Can destroy the organisms habitat Example: woolly mammoth Adaptation and survival • Some organisms will still survive • Example: horseshoe crabs have been here before the dinosaurs Now that we have read and took notes, please write a 4-5 sentence summary using the following words • Habitat • Species • Extinction
