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THE CHANGING EARTH

THE CHANGING EARTH. Unit C – Section Two – Evolution & Natural Selection. WHAT IS EVOLUTION?. http://www.youtube.com/watch?v=CKDSiNf_rLo http://www.youtube.com/watch?v=faRlFsYmkeY. THE IMPORTANCE OF FOSSILS. ...What’s My Job??. Paleontology. The study of “fossils”

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THE CHANGING EARTH

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  1. THE CHANGING EARTH Unit C – Section Two – Evolution & Natural Selection

  2. WHAT IS EVOLUTION? • http://www.youtube.com/watch?v=CKDSiNf_rLo • http://www.youtube.com/watch?v=faRlFsYmkeY

  3. THE IMPORTANCE OF FOSSILS ...What’s My Job??

  4. Paleontology • The study of “fossils” • Scientists have discovered approximately 250,000 fossil species. • Represents only a small number of species that can be found on earth.

  5. Paleontology • Many organisms leave no evidence of their existence in the fossil record, thus they go unnoticed.

  6. Fossils: What Can They Tell Us? • 1. Different species lived on Earth at various times in the past. Few species living today were alive 1 million years ago. • 2. The complexity of living organisms increases from the past to the present. • Why?? • 3. Living species and their most closely matching fossils are usually found in the same geographic location.

  7. Dating a Fossil • Scientists use “Radiometric Dating” to determine the age of a fossil. • Radioactive decay of isotopes help determine a fossil’s age.

  8. Fossil Flaws • The geological record is not perfect! • Some layers of rock do not contain any fossils. • A “missing link” occurs when we have no transitional organisms from one geological era to the next.

  9. “Missing Links” in Humans • Until the 20th century, there was no link between animals and modern day humans. • Discoveries of fossils were key “transition” fossils that helped connect modern humans to other animals.

  10. Biogeography • The study of the geographic distribution of life on Earth. • Attempts to answer these questions: • Where do certain species live? • Why do they live there? • How did they end up there? • Example: Why does the Arctic have polar bears and the Antarctic have penguins?

  11. IMPORTANCE OF ISLANDS • Because they are separated from larger landmasses, island are of particular importance to evolutionary biology. • Islands contain a small number of species because immigration from the mainland is difficult. • Terrestrial mammals aren’t found on oceanic islands more than 300 miles from the mainland.

  12. IMPORTANCE OF ISLANDS • But, bats are plentiful as they have a long distance flying ability.

  13. ENDEMIC SPECIES • Species that are found in one location only, typically on a remote island. • Example: Hawaii, Galapogas Islands • Suggests that they evolved in isolation with little competition. • As these species are found in so few places, their numbers tend to be smaller so are considered endangered.

  14. BLUE-FOOTED BOOBY (Endemic) • Found on the Galapogas Islands • Booby is adapted from bobo, Spanish for “stupid fellow”. • Long pointed wings and a narrow pointed bill. • Show off their feet when they are courting females with an exaggerated step-walk. • http://www.youtube.com/watch?v=1NAKg46s1DA&feature=fvw

  15. GALAPAGOS TORTOISE (Endemic) • Largest tortoises on Earth, slow moving reptiles. • Cold blooded creatures that sunbathe for several hours in the morning to absorb energy through their shells.

  16. EVIDENCE OF EVOLUTION COMPARATIVE ANATOMY • Comparing organisms in development can give us an idea about the relationship between species. • Species that looked quite different as adults often had close similarities as developing embryos. • PAGE 144, FIGURE 2 • http://www.pbs.org/teachers/connect/resources/710/preview/

  17. Homologous Structures • Features with similar structures but different functions. • Suggests that organisms share common ancestors but went through modification that led to different functions. • Can you think of any?

  18. Homologous Structure Example

  19. ANALOGOUS STUCTURES • Features that are similar in appearance and in function, but appear to have different evolutionary origins. • EXAMPLES: • Wings of Birds, Wings of Insects, Wings of Bats • All organisms use wings for same function (to fly), but developed differently

  20. Analogous Structure Example

  21. VESTIGIAL FEATURES • Structures that no longer serve a useful function, they likely served a function in an ancestor organism. • They are present in all species and serve as evidence for evolution, as they provide us with information about how organisms have changed.

  22. VESTIGIAL FEATURES • Structures that no longer serve a useful function, they likely served a function in an ancestor organism. • They are present in all species and serve as evidence for evolution, as they provide us with information about how organisms have changed. • The appendix, tail bone, and wisdom teeth all are examples of vestigial features in human beings.

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