Presentation on theme: "Evidence for evolution in Darwin’s time came from several sources."— Presentation transcript:
1 KEY CONCEPT Evidence of common ancestry among species comes from many sources.
2 Evidence for evolution in Darwin’s time came from several sources. Fossils:Fossils provide evidence of evolution.Fossils in older layers are more primitive than those in the upper layers.Extinct Fossils resemble modern animals. This shows a common ancestry.
3 There are several types of fossils. Permineralization occurs when minerals carried by water are deposited around a hard structure.b) A natural cast forms when flowing water removes all of the original tissue, leaving an impression.c) Amber-preserved fossils are organisms that become trapped in tree resin that hardens after the tree is buried.d) Preserved remains form when an entire organism becomes encased in material such as ice, ash,etc.
5 Relative dating estimates the time during which an organism lived. It compares the placement of fossils in layers of rock.Scientists infer the order in which species existed.
6 Isotopes are unstable in their nuclei, so they decay Radiometric DatingIsotopes: atoms of the same element with differing neutronsEx: 12C and 14C12C = 6 protons + 6 neutrons14C = 6 protons + 8 neutronsIsotopes are unstable in their nuclei, so they decayIsotopes have a known half life (rates of decay are known).Half life = number of years it takes for half of the isotopes to decay14C has a half life of 5700 years, and 14N is a decay productAge determined by comparing ratio of 14C to 14NWider ratio = older samples
8 2. GeographyThe study of geography provides evidence of evolution.island species most closely resemble nearest mainland speciespopulations can show variation from one island to another
9 Embryology provides evidence of evolution. identical larvae, different adult body formssimilar embryos, diverse organismsShows common ancestryLarvaAdult barnacleAdult crab
10 flipper leg wing arm flight walking swimming grasping 4. Anatomy The study of anatomy provides evidence of evolution.Homologous structures are similar in structure but different in function.Homologous structures are evidence of a common ancestor.flipperlegwingarmflightgraspingwalkingswimming
11 Homologous structures are different than Analogous Structures Analogous structures have a similar function.Human handBat wingMole footFly wingAnalogous structures are not evidence of a common ancestor.
12 Structural patterns are clues to the history of a species. Vestigial structures are remnants of organs or structures that had a function in an early ancestor.Examples include ostrich wings, human appendix, and wisdom teeth, whale and snake pelvis/hind legs.