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Evidence For Evolution
• Direct Evidence
• Indirect
Evidence
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• Fossil Record - What you see is what you get!
• Geographic Distribution of Living Species

Comparison of
Archaeopteryx to dinosaur and chicken.
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• By comparing fossils from older rock layers with fossils from younger rock layers, scientists can see how life on Earth has changed over time.

• Hundreds of transitional fossils have been found which show intermediate stages of evolution of modern species from species now extinct this is an “incomplete record” with many gaps.
Why are there so many
“gaps” in the fossil record?

If this were where the horses were discovered what layer would you expect to see the most primitive horse?
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• Species living in different places with similar environments have similar anatomies and behaviors, even though they are unrelated.
• L: Costa Rican Rainforest
• R: African Rain Forest

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• Comparative Anatomy
• Vestigial Structures
• Embryology
• DNA/Biochemical Evidence
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• Homologous: develops from the same part of the embryo but have a different forms and functions (modified between groups)
• Analogous: parts with similar functions which develop from different parts of the embryo (similar function, different structure)
• (embryo is the early stage of development)

http://evolution.berkeley.edu/evolibrary/home.php

• Helps biologists group animals according to how recently they shared a common ancestor
• Dolphins look more like fish but their homologies show they are mammals. They have lungs rather than gills and obtain oxygen from air, not water. (evolved from land mammals, not fish)
• Phylogenetic trees show evolutionary relationships

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• Two major groups of mammals, marsupials and placentals, have evolved in a very similar way, even though the two lineages have been living independently on separate continents.
• Australia separated from the other continents more than
50 million years ago, after marsupials had evolved but before the appearance of placental mammals.

• As a result, the only mammals in Australia (other than bats and a few colonizing rodents) have been marsupials, members of a group in which the young are born in a very immature condition and held in a pouch until they are ready to emerge into the outside world.
Thus, even though placental mammals are the dominant mammalian group throughout most of the world, marsupials retained supremacy in Australia.
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• Living in the open ocean as a fish eater requires a streamlined body and the ability to move very quickly when needed. These pressures caused first sharks, then ichthyosaurs and finally dolphins, to all adopt a very similar body shape and method of movement.
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Understanding a phylogeny is a lot like reading a family tree. The root of the tree represents the ancestral lineage, and the tips of the branches represent the descendents of that ancestor. As you move from the root to the tips, you are moving forward in time.
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• Organs so reduced in size that they no longer serve the function of homologous organs in related species
• The presence of the organ does not affect its ability to survive and reproduce, so natural selection does not eliminate it

• Examples: wings on flightless birds, human coccyx and appendix
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The appendix, for instance, is believed to be a remnant of a larger, plant-digesting structure found in our ancestors.

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• Left: A is normal fish versus B the Mexican Cave
Dwelling fish with vestigial eye
• Right: Blind cave salamander with vestigial eye

• All embryos develop similarly
• Similar genes that define their basic body plan
• ‘Tails’ as embryos
• Embryos of all vertebrates especially similar; same groups of cells develop in same order and in similar patterns (homologous structures)
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Top Left=human 37 days below= cat top= right dolphin
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• All organisms use DNA and RNA to transmit genetic information
• ATP is an energy carrier in all organisms.
• You can compare the similar amino acid sequences (i.e. proteins)
• Humans and Chimpanzees share 96% of the same DNA