1. EVIDENCE FOR EVOLUTION Chapter 15

2. Biogeography SStudy of the distribution of plants & animals over Earth’s surface LLiving organisms arose in areas where similar forms once lived

3. The Fossil Record  Fossil: a trace of a long-dead organism  Found in layers of Sedimentary Rock : formed when small particles build up in lakes, streams and oceans over time  As layers form, dead organisms become buried

4. Distribution of Fossils LLaw of Superposition: successive layers of rock or soil are deposited on top of one another SStratum: a layer of rock or soil Oldest layer is at bottom Fossils in same stratum are approx. same age

5. Types of Fossils 1) Mold: a rock imprint in the shape of the organism 2) Cast: a 3-D rocklike model of an organism 3) Amber: organisms trapped in hardened tree sap 4) Ice: organisms frozen in ice

6. Age of Fossils 11) Relative Age: approximate age DDetermined by comparing fossil to those in other strata 22) Absolute Age: age in years DDetermined by radioactive dating

7. Succession of Forms FFossil records indicate that species come & go EExtinction: the death of a species MMass Extinction: a brief period of time when large #’s of species become extinct HHave been several throughout Earth’s history UUsually result of sudden changes in environment i.e.: volcanic activity, asteroid collisions, severe climate changes

8. Homologous Structures OOrganisms change (evolve) through gradual modifications HHomologous Structures: similar features that originated in a shared ancestor ii.e. Forelimbs of different species

9. Analogous Structures AAnalogous Structures: serve similar functions in different organisms, but look differently AAre developed very differently; NOT from shared ancestor ii.e.: wings of both birds and bats

10. Vestigial Structures VVestigial Structures: were once useful to an ancestor; no longer useful in modern organism ii.e. human tailbone & appendix; limb bones in snakes