Evidence for Evolution 4 areas

1. Fossil Record A fossil is any evidence of an organism that lived years ago. Paleontologists - scientists who study ancient life & fossils

How do fossils form? Most fossils – sedimentary rock The animal dies & sinks to sea floor or river bottom The body begins to decay & is buried under layers of sediment (ex. mud or sand). These layers become rock.

Rapid burial conditions include: Beach storm deposits, stream flood deposits, tar/mud pits, volcanic lava flows Environment determines fossil formation; Very few organisms  fossils

Dating Fossils Relative dating: layers at the bottom are older than those above (approximate age) Radiometric dating: involves radioactive isotopes C14 & K40 (more exact age)

How fossils show evolution Age & Behavior patterns Show changes in climate & geography Shows evolution & adaptation Problems: Incomplete fossils & Imperfectly preserved

Increased food source - vast grasslands Wider, flatter molars better for eating grass Grasslands made horses more visible to predators With hoof-like feet horse can run faster & get away from predators

Do you see any similarities among the forelimbs of these animals? If you said “yes” then you just made a type of observation that scientists use to establish evolutionary relationships among organisms.

2. Anatomy/body structures Homologous structures = modified structure in different groups of organisms Similar structure, but may have same/different function Ex. Bones in forelimbs of vertebrates Implies common ancestor

What is a similar feature of these 2 organisms?

Analogous Structures Structures w/similar function, but different structure Shows evolution Ex: wings – bats, insects, & birds NOT common ancestor Any body part that is similar in function but different in structure is an analogous structure.

Vestigial Structures Structures/organs appear to have little/no use May have been used in ancestor Indicate evolution

Examples Ostrich wings Human appendix Whales pelvic/hip bones

3. Embryology Many different animals – same organs as embryos Ex: embryos of fish, reptiles, birds & mammals all have gill slits Suggests common ancestor zebrafish chicken dog human skunk

4. Genetic Comparisons Similarities in DNA/RNA sequences Shows evolutionary relationships Ex. Organisms use ATP, Same genetic sequences in organisms w/ homologous structures

Which 2 insects are most closely related? Most distantly related?