Processing Activities Which animals would your group together based on their similarities? horse, rabbit, zebra, squirrel, donkey, deer, chipmunk, and mouse. Describe below how you would group them. 1
Evidence of Evolution Scientists use similarities among living species to infer how species evolved. Evolution is a theory not a fact. Theories are explanations based on evidence. Evidence for Evolution 1) Fossils- fossils show organisms in the past were different from organisms today. 2) Many different organisms are similar early in their life.- see p 149 These organi all have: 1) tails 2) gill like slits in their throat 3) large heads 4) curved backs Although, there are many differences as you can see in the diagram above. Many scientists use these differences evidence to refute evolution. 3) Homologous structures- similar body structures that related species inherited from a common ancestor. 2
Processing Activities Grouping Animals Which animals would your group together based on their similarities? horse, rabbit, zebra, squirrel, donkey, deer, chipmunk, and mouse. Describe below how you would group them. Give a specific example of each part of the key concept below. 1) Fossils provide evidence that organisms have changed over time. For example,... 2) Patterns of early development provide evidence that organisms have changed over time. For example,... 3) Homologous structures provide evidence that organisms have changed over time. For example,... 3
Processing Activities Create a branching tree of your family or a fictitious family showing three generations. 4
Inferring Relationships between Different Species DNA evidence has only been around since the late 1980's Before this was possible scientists could only compare fossils, similarities in early development and homologous body structures to figure out how different species could be related. DNA evidence has allowed scientists to check their work and discover more relationships. DNA Evidence- Scientists compare the order of the nitrogen base pairs in DNA to determine how closely related two species are. They more similar the order, the more closely related they are. Branching Trees Scientists make branching trees to show how they think animals are related. How does a species turn into a species? If a group of individuals in a species are separated from the others long enough, they can form a new species. Ex: Squirrels on either side of the grand canyon. 5
Processing Activities Create a branching tree of your family or a fictitious family showing three generations. Section 2 Assessment: 1)(a) Listing List three kinds of evidence that support the theory of evolution. (b) Comparing And Contrasting What major difference have scientists discovered between today s whales and the fossils of whales ancient ancestors? (c) Drawing Conclusions How does this difference show that whales and animals with four legs are probably descended from a common ancestor? 2)(a) Identifying When scientists try to determine how closely related species are, what evidence do they examine? (b) Inferring Of the kinds of evidence you listed above, which are probably the most reliable? Explain your answer. (c) Applying Concepts Insects and birds both have wings. What kinds of evidence might show whether or not insects and birds are closely related? Explain your answer. 3)(a) Reviewing How can isolation lead to the formation of new species? (b) Predicting A species of snake lives in a forest. A new road separates one group of the snakes from another. Is it likely that these two groups of snakes will become separate species? Why or why not? 6
Processing Activites How do we know so much about dinosaurs if none of them are alive now? 7
The Fossil Record The fossil record is all the millions of fossils scientists have collected over the years. Scientists use the fossil record to figure out the history of life on earth. Fossils Very rare. Most things that die do not become fossilized Only happen when something dead is buried in particles of soil and rock. These sediments become rock over millions of years. 3 ways this happens: 1) Petrification- minerals in the sediments dissolve in water and get absorbed into the dead organisms body. As the body decays, the minerals replace it and form petrified fossils 2) Molds and Casts- hard parts of dead organisms (shells, exoskeletons) take up space in sediments. As the sediments become rock, the dead organism erodes leaving a hollow space. hollow space gets filled. 3) Preservation- animals preserved in ice. Age of Fossils: 2 Methods: 1) Relative Dating- determining what is older based on where it is found. Cannot give actual age. 2) Radioactive Dating- most rocks contain some radioactive elements. Radioactive elements break down overtime. How broken down the radioactive element is can tell you the age of a fossil. Information from fossils Extinct organisms The calender of earth's history- Geologic Time Scale 8
Processing Activities How do we know so much about dinosaurs if none of them are alive now? 1)Pretend you did not clean your room for over a year. How could you determine the order you dropped everything on the floor? How is this similar to scientists using relative dating on fossils? 2) Pretend you went back in time to the Paleozoic Carboniferous period. (use p 160 for more info) Write an eyewitness report that could be reported on television or published in a newspaper. 9
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