IB BIOLOGY UNIT 5 Evidence for Evolution SUMMARY NOTES

IB BIOLOGY UNIT 5 Evidence for Evolution SUMMARY NOTES 5.1 Evidence for Evolution Saturday, 3 October 2015 4:00 PM U1. Evolution occurs when heritable characteristics of a species change. There is strong evidence for characteristics of species changing over time, biologists call this evolution. - Acquired characteristics that develop during the lifetime of individual - Heritable characteristics passed from parent to off-spring. - Evolution involves heritable characteristics through natural selection. U2. The fossil record provides evidence for evolution. Palaeontology is the research of fossils and has provided strong evidence of evolution. - U3. Selective breeding domesticated animals shows that artificial selection can cause evolution. Humans have bred specific animal species for thousands of years. Differences between original wild species and modern breeds of livestock are huge. - Domesticated breeds have not always existed in current form. - Credible explanation is that breeds have been selectively bred to suit human uses, called artificial selection. - Artificial selection has shown large changes in domesticated animals over a short period of time when compared to geological time. - Natural selection can cause evolution, however does not prove that evolution of species has occurred naturally or that mechanism of evolution is natural selection. This study source was downloaded by from CourseH on :25:25 GMT -05:00 VERIFIED U4. Evolution of homologous structures by adaptive radiation explains similarities in structure when there are differences in function. Darwin pointed out in The Origin of Species that similarities in structure between organisms is superficial. - ANALOGOUS: where different species has same functions for structures yet bone structure is different. For example, the wings of a fly and a moth. - HOMOLOGOUS: where different species has different functions for structures yet bone structure is more closely related to a species that uses the structure for a different purpose. U5. Populations of a species can gradually diverge into separate species by evolution. If two populations of a species become separated so that they do not interbreed and natural selection acts differently on the two populations, they will evolve differently. - After time they become recognisably different, if they merge and interbreed they will not actually interbreed they are actually different species. - This process is called speciation. - Speciation creates an endemic species which is a species found only in specific geographical areas. U6. Continuous variations across the geographical range of related populations matches the concept of gradual divergence. If populations gradually diverge over time to become separate species, then at any moment we would expect to find examples of all stages of divergence. - Darwin provided examples of populations that are recognizably different but not to the extent where they were completely different species. - This becomes a common problem for biologists who name and classify living organisms. - This is because species gradually diverge over long periods of time and no switch between two populations making the decision to lump populations together or to split them separately becomes subjective. This study source was downloaded by fro