Transcript Chapter 7
Chapter 7 The Evolution of Living Things Review • • • • What is a hypothesis? A possible explanation or answer to a question What is a theory? A unifying explanation for a broad range of hypotheses and observations that have been supported by explanation • What is a law? • Theories that are proven time and time again What is Evolution? • Evolution is a widely accepted theory. • It is not a law. • You don’t need to believe anything I say in this chapter. • However you need to know the information behind the theory to pass you SOL’s next year. Change over time • These three frogs all look different but live in the same habitat Differences Among Species • All three frogs have different adaptations that help them survive • Adaptation – A characteristic that helps an organism survive and reproduce in its environment • Can include structures for finding food, for protection and movement Stegosaurus Dimetrodon Brontosaurus Species • Groups of organisms that can mate with one another and produce fertile offspring • Share same characteristics and adaptations • Mule vs. horse vs. donkey Do Species Change Over Time? • Scientist estimate the Earth is 4.6 billion years old • Did the same animals and plants always live here? Evolution • Process by which populations accumulate inherited changes over time • Because of evolution, scientists think all living organisms have a common ancestor Evidence of Evolution • Fossils • The solidified remains or imprints of once living organisms are found in the layers of the earth’s crust • Mold – imprint • Cast – mold filled in with sediment Fossil Record • A historical sequence of life indicated by fossils found in the layers of the Earth’s crust Vestigial Structures • Remnants of once-useful structures • Hind limb bones in whales • Other examples – Wings on flightless birds (ostriches, rheas) – Human tail bone – Erector pilli muscles and body hair – Wisdom teeth Comparing Organisms • Bones in the human arm and a bat’s arm are similar even though they are used in different ways • Indicates a common ancestor but the bones have evolved to perform different functions Birds Walk on Their Toes Comparing DNA • All living things made from the same genetic material • The more similar the species (closely related) the more similarities in DNA codes Comparing Embryonic Structures