evidence for descent with modification. 1. direct observation guppy coloration hiv resistance
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Evidence for Descent with Modification
1. Direct Observation• Guppy coloration• HIV resistance
2. Fossil Record
• Species were different in the past
• Extinctions• Transitional forms
3. Homology
• Variations on a structure that was present in a common ancestor– Ex: forearm bones of mammals, wings of birds and bats
Anatomical Homologies
• Vertebrate embryos– All have a tail and “throat pouches” during
development
Cat Human Dolphin
Vestigial Structures
• Remnants of features that served important functions in ancestors– Ex: whale pelvic
bones
Evolutionary Tree
• Use homologies to create a “tree” that show relatedness
Analogy
• Analogous traits are similar but not due to a common ancestor– Ex: wings of birds and
insects
Convergent evolution
• Happens because of similar environmental pressures• Organisms do not have a recent common ancestor
but resemble one another– Ex: whales and sharks
4. Biogeography
• Use our understanding of Pangaea and continental drift to search for fossils
What Darwin didn’t know….
• Now, we compare DNA and proteins to get a better idea of relatedness– More differences = more
time since a common ancestor