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Transcript
Evolution Species A group of organisms that can mate with one another to produce FERTILE offspring. Do Species Change Over Time? The Earth is approximately 4.6 billion years old. Over this time Earth has changed in many ways. Have species changed as well??? Evolution The process by which populations accumulate inherited changes over time. CHANGE OVER TIME Evidence of Evolution The Fossil Record Provides evidence about the order in which evolutionary changes occurred Fossils found in the upper (newer) layer of Earth’s crust tend to be more recent and reflect present day while fossils deeper in Earth’s crust are less like present-day organisms. What is a Fossil??? Solidified remains or imprints of once-living organisms. Form when a dead organism is covered by a layer of sediment. Why Are There Gaps in the Fossil Record Very specific conditions are needed to form fossils and these conditions are not always met. – Oxygen cannot be present – Organism must be buried in fine sediment. Further Evidence of Evolution Vestigial Structures – These are the remnants of once-useful structures. More Evidence Comparing Skeletal Structures Comparing DNA Comparing Embryonic Structures Formation of a New Species Can happen by following three steps: – Separation: Portion of the population becomes isolated by a new canyon, mountain range, etc. – Adaptation: As the environment changes, the population must do so as well. – Division: Over many hundreds of years, thousands of years, or even longer the two populations become so different that they can no longer interbreed and are thus different species. Some finches left the mainland and reached one of the islands. – Separation The finches reproduced and adapted to the environment. – Adaptation Some finches flew to a second island. – Separation The finches reproduced and adapted to the different environment – Adaptation Darwin’s Finches Some finches flew back to the first island but could no longer interbreed with the finches there (division). This process may have occurred over and over again as the finches flew to the other islands.
