How Scientists Determined that Living Things Change Over Time 4/6/2017 Evidence of Evolution How Scientists Determined that Living Things Change Over Time Video #3 – “How Do We Know Evolution Happens?” Printed off Blackboard

Fossil Record Fossil = remains of any living things or their prints Fossils include: Bones Casts or molds Impressions Top left – impression of a worm; center – cast of a mollusk; right – humerus bone of a turtle “Becoming a Fossil” – 2:34

Comparative Anatomy- body parts Comparing the structures of organisms Similarities indicate evolutionary relationships.

Comparative Anatomy, cont’d Homologous structures – have similar insides these have a similar structures and may or may not have a similar function indicate common ancestry:

Comparative Anatomy, cont’d Analagous structures – have similar outsides these have a different structure but similar function indicate common environmental pressures:

Comparative Anatomy, cont’d Vestigial structures – seem to have little or no importance in modern organisms Indicates that the structures were useful (a long time ago) The pelvis (and femur) of a whale is a vestigial structure; it suggests that ancestors of whales had four legs Humans also have vestigial structures Tonsils & Appendix Whale Evolution – 5:09

Comparative Embryology Closely related organisms appear to go through similar stages as embryos “Common Past, Different Paths” – 1:36

Comparative Biochemistry / Molecular Biology There is a common genetic code DNA Analyzing and comparing DNA sequences and proteins can show a relationship among species. “The Common Genetic Code” – 4:20

The genetic similarities between humans and primates indicates that we share a common ancestor – NOT that humans came from apes! Humans are more similar (genetically) to chimpanzees than to gorillas or orangutans. This suggests that humans and chimpanzees split / branched off from our common ancestor more recently than gorillas and orangutans. “Human Chromosome 2” – 3:27