Chapter 15 3 Evidence of Evolution AP Biology

Chapter 15. 3 Evidence of Evolution AP Biology 2006 -2007 Dodo bird

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 AP Biology Leaf

§ 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 around Fish Scallop (mollusc) AP Biology

Comparative Anatomy A. 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 u evidence of change over time u § 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 AP Biology sea creatures?

Comparative embryology § Similar embryological development in closely related species u 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 u universal genetic code! § DNA & RNA u cytochrome C (respiration) § protein structure u hemoglobin (gas exchange) § protein structure Evolutionary relationships among species are documented in their DNA & proteins. Closely related species have sequences that are more AP Biology similar than distantly related species.

Comparative hemoglobin structure Human Macaque 8 Dog Bird Frog Lamprey 32 45 67 125 0 10 20 30 40 50 60 70 80 90 100 110 120 Number of amino acid differences between AP Biology hemoglobin (146 aa) of vertebrate species and that of humans

Building “family” trees Closely 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/libr ary/07/3/real/l_073_47. html AP Biology

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”

Patterns of Evolution: 2. Divergent Evolution-Adaptive Radiation • Divergent Evolution: when related species become more different as they adapt to different environments • Divergent evolution leads to 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