Evidence for…

Four Types of Evidence

• A. Fossils• B. Transitional Forms• C. Comparison of

Organisms• D. Evolution Today

A. Fossils

Types of Fossils:• 1. Actual remains--wolly

mammoth, shells• 2. Petrification--organic

substances replaced by minerals

• 3. Molds--”hollow” left after decay

• 4. Cast--filled in mold• 5. Traces--footprints, scat,

tools (often found in lava, sediments, ice)

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B. Transitional Forms

• Intermediate stages between old & new forms

• Ex: whales, birds/reptiles (Ex: archaeopterix), amphibians/fish

Evolution- How Do We Kn#1713B99

C. Comparison of Organisms--similar structures which give

support for evolution• Homologous

Structures-- structures that are biologically similar in different species, but have changed through time

• Ex: fin, arm, wing, hand

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C. Comparison of Organisms cont…

• B. Vestigial Structures --structures that are inherited but are now unused (without function)

• Ex: tail bone & ear muscles in humans, whale pelvis, hip & leg bones in a snake

C. Comparison of Organisms cont…

• Embryo Comparisons

--Similar embryonic development

Ex: vertebrate embryos look very similar (all have gill pouches & tails)

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Embryo Comparison Pictures

C. Comparison of Organisms cont…

• DNA Comparison -all living organisms have DNA with the same 4 bases (A, T, C, G)

• All have similar amino acids (only 20 different a.a.)

• Chimps & humans have 98.6% DNA relatedness

C. Comparison of Organisms cont…

• Selective Breeding -humans have bred dogs over hundreds of years to obtain new breeds; seedless oranges

D. Evolution Occurs Today• Evolution is

happening today, as we speak!

• Ex: antibiotic resistant bacteria, new strains of viruses (flu)

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Key Concepts

• Can you define………..?

• Fossils

• Vestigial and homologous structures

• Embryo

• Selective and artificial breeding

• DNA Comparision