EVIDENCE OF EVOLUTION Biology 102Y SB5c. Explain how fossil and biochemical evidence support the theory.
What is Evolution? • CHANGE in the genetic composition of a POPULATION over time.
http://www.pbs.org/wgbh/evolution/educators/teachstuds/unit3.htmlhttp://www.pbs.org/wgbh/evolution/educators/teachstuds/unit3.html What evidence do we have that evolution has occurred? 1. Fossils • Found in sedimentary rock layers (strata) • Fossils found deeper very different from fossils found closer to surface • Relative dating- idea that fossils found deeper are older • Radiometric dating- A fossil’s carbon14 can be measured to determine actual age • Fossils have revealed changes in organisms over time and provide clues to changes in climate.
Which fossils are probably the same age? • 2 and 1 • 1 and 3 • 1 and 4 • 3 and 5 • Which is true about the fossil layers? • Fossil 5 is the youngest • Fossil 1 is older than fossil 4 • Fossil 1 is older than fossil 3 • Fossil 2 is younger than fossil 3 • What type of environment was probably around during the time these fossils were formed? • Forest • Marine environment (ocean) • Desert
What evidence do we have that evolution has occurred? • Biogeography • We can look at island species and see similarities to their mainland ancestors. • If an island is closer to a mainland then it will have more diversity and larger populations than islands farther away. • EX: Darwin discovered the species of finches in Galapagos Isl. were very similar to those he saw in South America. Galapagos South America
What evidence do we have that evolution has occurred? 3. Homology- Similarity in characteristics of different species resulting from common ancestor • Homologous structures- structures that may have different functions but have similar structure EX: human, cat, whale, bat arms are similar in bone structure but used for different things.
What evidence do we have that evolution has occurred? b. Vestigial structures- structures that are reduced & have no function but may have had a use in a common ancestor. EX: pelvic & femur bones in whales & snakes may suggest their ancestors had legs.
What evidence do we have that evolution has occurred? c. Embryological evidence- if embryo development similar, may indicate close relationship and a common ancestor.
What evidence do we have that evolution has occurred? • Biochemical Evidence- if two species have similar DNA sequences then they may have common ancestor • Most recent and most reliable source of evidence • EX: If humans have more amino acids in common with apes than mice then we are more closely related to apes.
A comparison of Human DNA (Cytochrome C protein) to other species • Which species has moredifferences in DNA compared to humans? • Does this mean it is more like humans or less like humans? • Which species has the fewest differences in DNA compared to humans? • Does this mean it is more like humans or less like humans? Yeast Less like humans b/c has 63 differences • Which is more closely related? • a. Tuna and Rattlesnake • b. Rattlesnake & chicken Chimpanzee More like humans b/c only has 1 difference
Phylogentic Trees • Also called cladograms • Show evolutionary relationships among organisms. • Show how they evolved from a common ancestor • Follow the branches up from the ancestor to analyze relationships. • Analyze which is more closely related? • 1 and 2 • 3 and 5 • 6 and 4 • 5 and 6