Evolution 01 23 2014 Is past evolution testable Three principles of evolution Yes by the fossil record and comparative genetics Generalized creatures are evolvable and specialized animals go extinct Generalized features can be redeployed to new functions o Thumbs grasping trees texting Extinction is the rule evolutionary recovery is slow o 5 mass extinctions in the past Geological Time Earth is 4 5 billion years old Pre Cambrian o Most of the earths history 4 55 bya 543 mya Eras o Paleozoic 543 mya 225 mya o Mesozoic 225 mya 65 mya o Cenozoic 65 mya present The Origin of Life Start o 4 0 3 5 bya o Requirements for life Self replication Cell not right off the bat but eventually o Start Viruses or RNA world Prokaryotes Eukaryotes o Fossil evidence 3 5 bya chemical signatures 4 bya o 1 3 bya chemical signatures 2 7 bya o division of cell labor into organelles Later Pre Cambrian fossils o Stromatolites algal communities o Found in Dolomite limestone o Multicellular creatures similar to jellyfish o Cellular life on land 2 7 bya Paleozoic 543 mya o Cambrian Explosion or Trickle Algae arthropods brachiopods sponges worms mussels echinoderms Increase of hard shelled creatures exploring new niches adaptive radiation fossilize better because of shell Key Developments Segmentation Trilaminar structure Endoderm o Gastrointestinal tract gut Mesoderm o Muscle and bone Ectoderm o Skin and CNS Summary Threshold reached that led to new adaptive possibilities among animals and better fossilization o First vertebrates 460 mya Ostracoderms 435 mya Agnatha jawless fish Chordata notochord Vertebrata Craniata Ectoderm Leads to partial formation of cranium bone 425 mya mass extinction first of the big five Placoderms 410 mya Jaw formed from 1st gill arch Haekel s Law Ernst Haekel 1886 Ontogeny recapitulates phylogeny o Development repeats your evolutionary history Chondrichthyes Cartilaginous fish Shark 408 mya Osteichthyes bony fish Coelacanth 400 mya Lobed fin fish Lung fishes 400 mya Tiktaalik 375 mya Fish with limbs missing link Amphibians 320 mya Animals on land but require water to lay eggs Sources of Genetic Variation 01 23 2014 o Select against left and for right the extremes o The average of the population would change in a specific The Four Forces of Evolution Natural Selection Directional Selection direction Stabilizing Selection o Select against the extremes o Select for the average o Ex 4 chambered heart Disruptive Selection o Select for extremes o Select against the average Mutation The ultimate source of genetic variation Mutation rate number of mutations per gene location per generation Average known mutation rate 10 6 1 in a million Best estimate 10 5 1 in 100 000 Most mutations have no effect Genetic Drift Sewall Wright Sampling error in small populations Chance driven directional effect leading to loss of fixation of alleles Two kinds o Founders Effect Bottlenecking in population Variations get bottlenecked then change over time from the original population o Fixation Cross generational sampling error Allele frequencies change One allele takes over and become the only one fixation Other allele is lost Gene Flow Hybridization Interbreeding Increases the amount of variation Peopling the New World Facial Features o Mongoloid wash Asian proportions and features Decreases north south Blood type o Native Americans 15 A 85 O Initial population lost B antigen to genetic drift from Bering strait lost A through second bottleneck Population could be Type O and gene flow for type A The modern theory of evolution Micro evolutionary processes translate into speciation or o South Americans 100 O o Why macroevolution o Microevolution Anagenesis over time o Macroevolution Parent population changes to daughter population Cladogenesis Origin of new species Parent species divides into two daughter species different from each other Problem Can t be tested in Paleontology Biological Species A species is a reproductive community of populations that occupies a specific niche in nature Fixed Evolutionary species o A lineage an ancestral descendent sequence of populations evolving separately from others and with its own unitary evolutionary role and What is speciation tendencies Transformational Speciation A B over time Anagenesis leads to chronospecies Allopatric speciation Changes through genetic drift and natural Sympatric speciation live in same place selection Living in different places Reinforcement choice Lemurs with bamboo Putting it all together Phyletic Gradualism o Evolution and speciation occur slowly and gradually o Includes extinction Punctuated equilibrium o Spots of no change equilibrium then speciation changes quickly Extinction Transitional extinction A africanus o Evolved into something else Terminal extinction robust australopitheses o Gone forever Questions o Neanderthals Transitional or terminal