Lecture 3 - Lecture 3: Variation: Phenotypes &...

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Evidence 6: Convergent evolution -Some traits that are similar in living organisms were much more diff than in the past -Similarly can result from convergent evolution in response to similar selection pressures -shared a common ancestor-homology -evolved to resemble each other bc of similar pressures-convergent evolution Analogous structures -structures that are similar bc of convergent evolution not homology Convergence in eyes of vertebrates and octupuses -common ancestor of humans and octupusses did not have eyes -these eyes have independently evolved -vertebrates-nerves go from retina to interior then exits out the back, blind spot-point on retina with no photoreceptors -octupuses-nerves run on the exterior and no blind spot Convergence in desert plants -milkweed -cactus -spurge -reduced leaves -dense trunks -photosynthesis happens on trunk and roots -great at conserving water Convergence bt marsupial and placental animals -cat like animals in marsupial -anteaters in marsupial -mice in marsupial -flying squirrels in marsupial -wolfs in marsupial Evidence 7 -We can often find transitional stages in the evolution of organisms Transitional stages in the development of an eye -simple photoreceptor- can tell day from night -photoreceptors on surface in a pit-spatial resolution -deeper spherical pit- better resolution
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Lecture 3 - Lecture 3: Variation: Phenotypes &...

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