Transcript Slide 1
Evidence for evolution Patrick Lind Portland State University Professor Barbara Shaw Trilobite- http://everystockphoto.s3.amazonaws.comfossil_fossils_cambrian_327288_l.jpg Evidence for evolution What did Charles Darwin (1809-1882) and others notice? •Huge variety of living things •Many similarities •Fossils of animals now extinct •The earth could be very old http://www.darwin.ie/wordpress/wp-content/uploads/2008/02/darwin.jpg Biodiversity So many species exist. Why? Bird, flower, sea-worm-courtesy Patrick Lind Cheetah-http://www.uwyo.edu/dbmcd/molmark/lect11/Cheetah.jpg Dragonfly-http://www.cssplay.co.uk/menu/slides/dragonfly.jpg Snail-http://www.animalwebguide.com/Snail-1.jpg Homology Some animals have very similar structures. Many vertebrates look and act very differently, but seem to be put together the same way. (Homology) Forelimbs= “one, two, few, many” Homology-http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=dbio&part=A69 Homology vs. Homoplasy But some similar structures aren’t put together the same way. Is one way better? Human eye Octopus eye In human eyes, the nerve fibers go in front of the retina, and there is a blind spot. Eyes-http://en.wikipedia.org/wiki/Evolution_of_the_eye http://www.bio.davidson.edu/people/midorcas/animalphysiology/websites/2003/Muller/development%20of%20the%20cephalopod%20eye.htm Developmental Homology The earliest stages of life (embryo) for related animals look more similar than adult stages. What similarities can you see? (There are gill pouches that we can’t see here). Embryos-http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=dbio&part=A36 Embryo hourglass-http://www.mk-richardson.com/pdf/Anat%20Embryol.pdf Extinctions Fossil remains are known for animals that no Megatherium longer exist. Dinosaur Trilobite Gastornis Dinosaur fossil-http://static.howstuffworks.com/gif/dinosaur-images064-resize.jpg Darwin’s Megatheriumhttp://www.christs.cam.ac.uk/darwin200/pages/index.php?page_id= c3 Uniformitarianism Darwin was influenced by Charles Lyell, who believed that slow steady processes shape the earth. This meant that the earth had to be very old. Erosion Small gully Giant canyon How long did it take the Colorado River to form the Grand Canyon? Lyell http://www.talkorigins.org/faqs/precursors/precurstrans.html http://washingtonindependent.com/wp-content/uploads/2008/11/grand-canyon.jpg http://brg.cma.nsw.gov.au/uploads///images/touchscreen/Severe%20gully%20erosion%20on%20 dispersible%20solodic%20soils%20in%20the%20Yetman%20area%20MRC.JPG Uniformitarianism Darwin was influenced by Charles Lyell, who believed that slow steady processes shape the earth. This meant that the earth had to be very old. Erosion Small gully Giant canyon How long did it take the Colorado River to form the Grand Canyon? >>>>>17 million years. Lyell http://www.talkorigins.org/faqs/precursors/precurstrans.html http://washingtonindependent.com/wp-content/uploads/2008/11/grand-canyon.jpg http://brg.cma.nsw.gov.au/uploads///images/touchscreen/Severe%20gully%20erosion%20on%20 dispersible%20solodic%20soils%20in%20the%20Yetman%20area%20MRC.JPG Evidence for evolution Four observations needed an explanation: •Biodiversity •Homology •Fossil record (extinctions) •Deep time (uniformitarianism) What did Darwin come up with? Voyage of the Beagle (1831-1836) Darwin sailed to Patagonia where he collected fossils and living animals. “Darwin’s Finches” These birds seemed closely related, yet each was specialized for the small island it lived on. Darwin’s big idea… Evolution by Natural Selection “Descent with modification” Darwin shares credit for the idea with Alfred Russel Wallace. http://www.dailymail.co.uk/sciencetech/article-1084712/Darwins-Beagle-sail--5m-replica-survey-oceans-help-NASA-craft.html http://anthro.palomar.edu/evolve/evolve_2.htm Natural Selection 1. Individuals compete for survival. 2. Variation in a given trait is natural (mutation is source). 3. Many traits are heritable. Pocket mice 4. When a heritable trait helps an individual reproduce more, that trait becomes more common in the next generation. Peppered moth http://www.smithsonianmag.com/science-nature/Evolution-in-Black-and-White.html http://biology.fullerton.edu/life/im/kettlewell.jpg Experiment Modeling Natural Selection •You are the predator. •White and black beans are the pocket mice. •Mice live on dark and light surfaces. •Any mouse that survives feeding reproduces. We will “feed” on mice on both surfaces and watch how populations change over time in each habitat. Predators will be rewarded Instructions 1. Each student takes a cup for a “stomach” and a clothespin for a “beak.” 2. Evenly spread 50 black beans and 50 white beans over the black fabric. 3. Record the initial number of beans on your data sheet. 4. When you hear “GO” start collecting as many beans as you can. 5. When you hear “STOP” put down you cups and clothespins. 6. Reproduce. Place a new black or white bean next to every surviving bean of the same color. 7. Count the white and black beans and record in the appropriate column. 8. Repeat steps 4-7 as long as directed by the teacher. 9. When directed, repeat the whole procedure, now using the white fabric. Keep all your “mice” in your “stomach” for the reward. Stopwatch 10.Wait for instructions on graphing your data. Discussion • Did our mouse populations evolve in response to natural selection? • In the mouse’s world, what is causing selection to occur? • Did any individual mice change because of natural selection? • If the mice were always all white or all black, would evolution occur? • What types of errors could be affecting our results? Well done, predators. http://gallery.photo.net/photo/6090700-lg.jpg