1. Fossils • Relics or impressions of organisms from the past. • Show changes over time from simple to complex. • Many fossils don't have descendants.
Fossil Record Most fossils found in sedimentary rock • Due to aquatic preservation, fossils remain largely intact and fossilize in layers Rock forms in layers, or strata • Often sand or silt is deposited on top • existing layer, compacting it into rock
Fossil Record • Limited: • Type of material preserved (bone, shell, impressions, amber) • Incomplete record • Easily disrupted
Life has changed over time. Many species failed to survive and became extinct. Evolution Relevance
Law of Superposition - Fossil Record is formed due to the layering • Older rock is “lower” than younger rocks • Fossils help show what organisms have similarities or dissimilarities
Comments 1. Fossilization is a rare event. 2. Only hard parts fossilize well. 3. Problem in finding fossils. 4. Interpretation. 5. Missing Links.
Evidence for evolution: used with fossils and current species Homologous Structures - Same structure, different function Mammal forelimbs 2. Homology
3. Vestigial structures • structures that have a major function in one organism, but less in another ex: whale limbs. ostrich wings • Evidence for descent from common ancestor
5. Development (Embryology) • Developing embryos of different organisms appear similar during maturation. • Distinctive differences occur later in the process
Comparative embryology: Similar embryo development in closely related species
6. Biogeography The geographical distribution of species. Some animals in South American tropics share similarities with African desert animals rather than African tropical animals Australia is home to more marsupial animals than anywhere else in the world, and had relatively few placental animals.
7. Plate Tectonics • How the continents moved • Supports evolution by looking at which species used to be close to each other geographically
8. Molecular Biology • In the era of DNA – - The closer the DNA sequences, the closer related • The less the sequences match, the further the relationship • Humans and Chimps 98% similar genes • Humans and Mice 70-80% similar genes