Evidence of Evolution • Evolution is thought to have happened over millions of years. How can scientists be confident of events that no one was around to see?
Dinosaur Ridge Morrison, Colorado
Sedimentary layers (uplifted) Evidence of Evolution What patterns do you see? What are fossils, and why would we find fossilized sea creatures on the tops of mountains? A bit of geological background…
Evidence of Evolution Note the parallel layers of sedimentary rock. It may not feel like it, but the earth’s crust is slowly and constantly moving, shifting, lifting, and eroding. Erosion Canadian Rockies Grand Canyon
Evidence of Evolution Erosion Mud Shale Eroded material eventually settles and becomes layers of sedimentation.
4 Big Evidences of Evolution 1. Fossils - the remains of ancient life. Some ways fossils are formed: A. Hard parts (bones/shells) become mineralized (fossilized).
Evidence of Evolution B. Imprints – footprints, leaf outlines, etc. pressed into shale.
Evidence of Evolution C. Trapped in amber –soft tissue can be preserved in tree sap.
Evidence of Evolution Recent D. Buried remains. The deeper you dig in a given area, the older the fossil. You can observe changes in structures of species over time. Older Oldest
Evidence of Evolution A. Homologous structures: body parts that are similar in structure and embryonic development (origin), but have a different use. This is evidence for common ancestry and divergent evolution. 2. Comparative anatomy – similarities and difference in body structures. Similarities support common ancestry.
Evidence of Evolution What are we looking at in this picture? Dog Human
Remember the Giraffe and Okapi we discussed earlier? The giraffe’s neck did NOT get longer by adding extra vertebrae. Both the giraffe and okapi still have 7 cervical vertebrae (neck). Giraffe Okapi
How many vertebrae are in your neck? Evidence of Evolution Humans have 7 cervical vertebrae, too.
How about in a dolphin’s neck? Evidence of Evolution Dolphins have 7 vertebrae, too! And notice the bones of that forelimb…
Evidence of Evolution B. Vestigial organs - an organ that has no use in the organism, but may not have disappeared (because there is no disadvantage to having it, either). They can be used to show common ancestry to another species in which the organ is still used. Ex: Human “tail bone”; Whale pelvis and femur bones.
Striped Dolphin skeleton Evidence of Evolution Vestigial pelvic bones Cetaceans have no use for a pelvis (no legs!), but the “vestiges” of a pelvis still remain.
Evidence of Evolution C. Analogous structures – body parts of two different species that have different structures, but have the same function because the species have adapted to a similar environment. This does NOT suggest recent common ancestry
Evidence of Evolution A. The longer that the developing embryos of two species resemble each other, the more closely related the species are likely to be. 3. Embryonic similarities – comparison of the embryonic development of a species shows similarities that suggest common ancestry. Elephant Dog Dolphin Human
Can you tell these embryos apart? Now? Now?
Evidence of Evolution A. Amino Acids – scientists compare amino acid sequences of a similar protein in organisms to determine relatedness. The closer relationship between species, the greater their biochemical similarity. 4. Biochemical similarities – all living things contain similar biochemical compounds.
B. Karyotyping–chromosome banding patterns of species can be compared C. DNA fingerprinting – DNA sequences and genes can be compared. D. Cladistics – classifying organisms into categories showing relatedness of common ancestor with its descendants.