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AP Biology 2006-2007
Chapter 15.3
Evidence of Evolution
Dodo bird
AP Biology
Fossil Record The fossil record is incomplete but provides
some evidence about the history of the earth. Fossils can show the progression of ancient,
primitive organisms to modern day forms.Trilobite Leaf
AP Biology
Fossil Record: The history of life on Earth can be partially constructed by dating (age) and comparing fossils
- Relative Dating: approximate age based on position on the rock layers
- Absolute Dating: Exact age determined by radioactive dating
AP Biology
Extinct: Trilobite (crustacean) Ammonite (mollusc)
Similar to present-day species: still aroundFish Scallop (mollusc)
AP Biology
Comparative AnatomyA. Homologous structures: Homologous
structures develop from the same tissues, but have different forms with different functions.
Same origin -- different form/function
The similarity is due to having derived from the same common ancestor.
Example: Bone structure of arms and legs in all vertebrates.
AP Biology
B. Analogous Structures: Different origin but have similar function
AP Biology
Vestigial structures Modern animals may have structures
that serve little or no function remnants of structures that were
functional in ancestral species evidence of change over time
some snakes & whales show remains of the pelvis & leg bones of walking ancestors
eyes on blind cave fish
human tail bone
AP Biology
Hind leg bones on whale fossils
Why would whales have pelvis & leg bones if they were always sea creatures?
AP Biology
Comparative embryology Similar embryological development in
closely related species all vertebrate embryos have a gill pouch
at one stage of development fish, frog, snake, birds, human, etc.
AP Biology
Molecular record Comparing DNA & protein structure
universal genetic code! DNA & RNA
cytochrome C (respiration) protein structure
hemoglobin (gas exchange) protein structure
Evolutionary relationships among species are documented in their DNA & proteins.Closely related species have sequences that are more similar than distantly related species.
AP Biology
Comparative hemoglobin structure
Number of amino acid differences betweenhemoglobin (146 aa) of vertebrate species and that of humans
Number of amino acid differences betweenhemoglobin (146 aa) of vertebrate species and that of humans
100 20 30 40 50 60 70 80 90 100 110 120
LampreyFrogBirdDogMacaqueHuman
328 45 67 125
AP Biology
Building “family” treesClosely related species (twigs of tree) share same line of descent until their recent divergence from a common ancestor
AP Biology
VIEW: http://www.pbs.org/wgbh/evolution/library/07/3/real/l_073_47.html
What data from whole genome sequencing can tell us about evolution of humans
What data from whole genome sequencing can tell us about evolution of humans
• Macroevolution – evolution on a large scale (above population level)
How fast is evolution?How fast do organisms change?
Gradualism Punctuated Equilibrium
Gradualism• Organisms go through gradual and continuous
change
Punctuated Equilibrium• Organisms go through fast periods of change,
followed by long periods of no change (according to fossil record)
Gradualism Punctuated Equilibrium
Patterns of Evolution: 1. Convergent Evolution
• Convergent Evolution: When 2 or more unrelated species become more similar due to similar adaptations to their environment.
Convergent evolution• Flight evolved 3 separate times
– evolving similar solutions to similar “problems”
• Divergent Evolution: when related species become more different as they adapt to different environments
• Divergent evolution leads to Adaptive Radiation
Patterns of Evolution: 2. Divergent Evolution-Adaptive Radiation
Adaptive Radiation• Process by which a
single species or small group of species evolved into several different forms that live in different ways
Coevolution• Predator-prey relationships• Parasite-host relationships• Flowers & pollinators
Process by which two species evolve in response to each other over time