EVIDENCE FOR EVOLUTION

WHAT IS EVOLUTION? To evolve: to change A theory stating that all life has changed from simpler life to more complex life Occurs over LONG periods of time Evolution often supports that organisms have evolved from a common ancestor

FOSSIL EVIDENCE Fossils: remains of organisms that lived in the past Footprints/bones/teeth/preserved organisms Tell us about climate of the past Tell us about what organism ate Indicate change (see what organism looked like then compared to now; see organisms that lived in past but no longer exist today

Older fossils will be deeper in sediment Layers are deposited over time on top of the older layer Fossils show that organisms have evolved from SIMPLER organisms (bacteria, invertebrates) in the lower layers to more COMPLEX organisms (vertebrates: fish… reptiles…mammals) in the upper layers EX: a magnolia (flowering plant)would be younger than a fern A squid (invert) would be older than a lizard (reptile)

EVIDENCE FROM FOSSILS How has the horse changed over time? How would studying the fossil evidence of the horse support the theory of evolution? The fossil evidence shows that the horse has changed over time in height, teeth structure,and bone structure

What would this fern fossil tell us about climate? This fossil was found in Antarctica. How could Antarctica have the type of climate suggested by this fossil evidence? Antarctica must have been a warmer climate; ferns are tropical plants If it had been closer to Equator; Pangaea

These two crocodiles were found on different continents

STRUCTURAL EVIDENCE

HOMOLOGOUS STRUCTURES Similar in structure; not necessarily similar in function Suggests common ancestry

The structures illustrated above are called HOMOLGOUS Structures The structures illustrated above are called HOMOLGOUS Structures. Each limb has a similar STRUCTURE, but some of the limbs have different FUNCTION. The similarity of structure is evidence that the animals may have A COMMON ANCESTOR

ANALOGOUS STRUCTURES Similar in structure & function; Not similar in ancestry Organisms adapt to similar environments; Therefore, they develop similar characteristics

EXAMPLES HOMOLGOUS ANALOGOUS Leg of dog Arm of human Wing of bird Flipper of whale All have similar bone structure, but the function is different (leg: walking; arm: carrying; wing: flying; flipper: swimming) Wing of bird Wing of bat Leg of lizard Leg of cow These structures are similar in bone structure & function, but are unrelated species…different ancestors

VESTIGIAL STRUCTURES Structures present, but have no purpose Structures that are incomplete The presence of these structures indicates the structure once had a purpose (support for evolution) EX: leg bones in whales, snakes

Vestigial Structures in Humans

EMBRYONIC EVIDENCE EMBRYO: early stage of development of living things Many organisms look similar very early in their development More stages similar… the more closely related they are Suggests common ancestry (note how similar these different organisms are in early stages)

BIOCHEMICAL EVIDENCE BIOCHEMICAL SIMILARITIES OF ORGANISMS Comparison of Organisms % substitutions of amino acids in Cytochrome C Two orders of mammals 5-10 % Birds vs. mammals 8-12 % Amphibians vs. birds 14-18 % Fish vs. Land vertebrates 18-22 % Insects vs. vertebrates 27-34 5 Algae vs. animals 57 % BIOCHEMICAL evidence is referring to similarities in DNA, proteins, amino acids, enzymes, etc. The more similar these compounds are in different organisms, the more closely related they are Suggests common ancestry

We are most similar/ most closely related to chimp least similar/ closely related to chicken Hedgehog is most similar to mouse… based on the closeness of the DNA similarities…3% difference