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Bellringer
– Explain how natural selection results in changes in a
population.
– Why is it said that natural selection acts on phenotypes
rather than the genetic material of an organism?
Evidence for Evolution
– The following pieces of evidence were all used
by Darwin to support his theory:
– Fossils
– Geography
– Embryology
– Anatomy
Fossils
– Provide strong evidence for evolution
– Fossils in bottom, older layers were more
primitive than those in upper, newer layers
The Fossil Record
Fossils
– During Darwin’s time, there were many gaps in the
fossil record
– Today, many of the gaps have been filled in with
transitional links
Indohyus – land ancestor of
whales
Geography
– Island species most closely resemble their nearest
mainland, but are NOT identical
– Variation from island to island
Ex. Variation in Galapagos
Finches
Embryology
– Similar embryonic stages or larval stages, but very
different adult forms
– Suggests a distant common ancestor
– Ex. Gill slits in vertebrates
Anatomy
– Comparison of body parts in different species lends
strong support for a common ancestor
– Homologous structures
– Vestigial structures
Homologous Structures
– Features that are similar in structure but
different in function
– Ex. Forelimbs of tetrapod vertebrates
Homologous Structures
Vestigial Structures
– Remnants of organs that once had a function in an earlier
ancestor – no function today
– Ex. Snake pelvic bones
Ex. Of Vestigial Structures
– Ostrich wings
– Human examples: appendix, tail bone, arrector pili muscle
(goosebumps)
Analogous Structures
– Structures that are similar in function but not similar in
origin
– NOT evidence of a recent common ancestor
– Result from similar environmental challenges
– Ex. Insect wing and bird wing
Molecular Biology - DNA sequence
analysis
– The more closely related two species are, the
more similar their DNA will be