Transcript Document
Evidence for Evolution Evidence for Evolution •Homology •Convergent evolution •Vestigial structures •Selective Breeding •Fossils •Embryology •DNA •All of these evobots used the same red pieces that were present in their ancestor but not in earlier generations. •We can see the steps between the reptile jaw and the human ear– they use what appear to be the same bones. •When we see very similar parts in many living things, we gain evidence of their common ancestor and its characteristics. •This is especially true when similar parts have different functions Convergent Evolution •Most evolution appears to be divergent– those closest to the ancestral state are the most similar and organisms become more different as they evolve. •This is not always the case. Sometimes, organisms come up with similar solutions to the same environmental problems. Convergent Evolution Convergent Evolution •Most evolution is Divergent (species with similar traits have a common ancestor) •According to Natural Selection, species evolve traits that help them survive in an environment. •Sometimes, the requirements to survive in an environment are so strong that several VERY DIFFERENT SPECIES evolve traits that function in similar ways. This is convergent evolution. •Structures that are no longer useful, such as our appendix,, or the fingers on a whale are vestigial structures. They are evidence that these creatures evolved from other creatures that used these structures. Kakapo (New Zealand) Kiwi (New Zealand) Cassowary (New Giunea) Spine Structure and tailbone Body Hair and Goosebumps •We humans have been selecting characteristics of pets and domesticated plants and animals for thousands of years. In many cases, we have dramatically changed how species look and behave. •In some ways, animals do this too both through sexual selection and natural selection itself. Cows are bred for beef or milk production (Video). Corn has been selectively bred for 600 to 10000 years by people in North America. Peacock Colors Bowerbird Nests In many animal species, females choose males that win competitions with other males. Alleles that help them win these competitions are then selected for. Pollinators “select” flowers that are more appealing. Bees tend to select blue and purple flowers whereas humming birds prefer red. Fishes “select” the angler fish with the most attractive lure-- by getting eaten by them! Any prey species, inadvertently selects characteristics in a predator that allows the predator to catch and eat them. •There are fossils of many creatures that no longer exist today. They often show intermediate forms between species that exist today and their ancestors. •We also see that fossils deeper in the earth only show simpler creatures with more advanced life forms closer to the surface. •Embryos of some animals show traits that are not present in adults such as gills and tails in humans. These are evidence that these traits were found in our ancestors. If you look at the DNA of living creatures you can see the similarities. Many sections of DNA are don’t code foe anything at all. These sections are similar to working or useful sections in other creatures. Even in human DNA, you can see the broken parts of code that were important in an organism long ago Pseudogenes are sections of chromosomes that resemble functioning genes in related creatures, but lack start codons (or promoters) and are never translate into proteins. For example, genes for gills may be present in mammals, but in a non-functional, mutated, broken form. Humans and other chimps split from dogs long before they spit from each other. We would expect to see more genetic similarities between chimps and humans than either would have with dogs. We would ALSO expect humans and chimps to show similar difference from chimps, and they do. Evidence for Evolution •Homology •Convergent evolution •Vestigial structures •Selective Breeding •Old Earth •Embryology •Fossils •DNA