Evidence of Evolution

5 Pieces of Evidence for Evolution

• Fossils
• Anatomy
• Biogeography
• Embryology
• Biochemistry (DNA, RNA, Proteins)

Fossil Evidence

• Fossils are evidence of evolution because they show different organisms have lived on earth at different times.
• Superposition: The deeper the fossil, the older the fossil.
• What is the difference between Relative Age vs. Absolute Age of a fossil?

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Inferences from the Fossil Record

• Different organisms lived at different times
• Today’s organisms are different from past organisms
• Fossils in adjacent levels are more similar than fossils found in deeper or higher levels.
• By comparing fossils and rocks around the planet, we can infer where and when organisms existed

Transitional Fossils

Comparative Anatomy

• “Descent with Modification” predicts that more closely related organisms will have similar anatomy
• Example: All four of these animals had an early ancestor, shared by all vertebrates, that had a similar forelimb structure. As generations passed, different populations of descendants adapted to different environments. Bones inherited from ancestors became modified for different tasks.

Comparative Anatomy: Vocabulary

• Homologous Structures: Structures that occur in different species but are inherited from a shared most recent common ancestor. May be used for different functions but have similar structures.
• Analogous Structures: Structures that have similar functions in different species, but do not share a common ancestor with that structure.

Comparative Anatomy: Vocabulary

• Vestigial Structures: Structures that now seem to serve no function, but resemble useful structures used in related species.

Biogeography

•The study of the locations of organisms in the world.

•Observed by both Darwin and Alfred Wallace.

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Plate Tectonics & Evolution

•Scientists noticed that the South America and Africa fit together like puzzle pieces. This would explain the distribution of fossils across continents. Alfred Wegner would publish his theory of plate tectonics in 1915

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Biogeographical Record

•Darwin noted on his voyage that

•Islands are often missing plants and animals common on continents

•Species present on islands often diverged from continental relatives

•Island species usually are more closely related to species on nearby continents

•Adaptive Radiation: As the finches spread out to the islands, they changed to their environment.

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Biogeographical Record

•Darwin concluded:

•Species arrive on islands by dispersing across the water

•Dispersal from nearby areas is more likely than distant sources

•Species that can fly, float or swim can inhabit islands

•Colonizers often evolve into many species

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Biological Molecules

• In all species, DNA and RNA are the molecules that control inheritance of traits.
• Every living thing’s DNA codes for protein the same way.
• Biologists compare DNA or RNA or proteins between different organisms. The more similarities, the more closely related they are. The more differences, the longer ago they shared an ancestor.

Embryology

• Development of animal embryos is also evidence of descent with modification.
• Some stages of vertebrate development are very alike, although similarities fade as the embryo develops
• An explanation is that these vertebrates share a common ancestor and have inherited similar stages of development