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Transcript
Fall 05 skip Acclimatization effects on final rectal temperature, heart rate, and sweat rate, for a group of men exposed daily to 2 hr of hard work in a hot environment. (after Leithead CS, Lind AR. Heat Stress and Heat Disorders. 1964. Philadelphia, Pa.: FA Davis Co, 304. acclimitization EMILI GARCÍA-BERTHOU Ontogenetic Diet Shifts and Interrupted Piscivory in Introduced Largemouth Bass (Micropterus salmoides) Internat. Rev. Hydrobiol. 87 2002 4 353–363 Fall 05 skip acclimitization Fall 05 skip acclimitization Fall 05 skip acclimitization Fall 05 skip acclimitization Fall 2005 Life Table Fall 05 Start Notes on Evolution, Natural Selection, and Speciation One picture of evolution What is going on before a split? How did the splits occur? What is speciation? Types of evolution migration • Macro • Micro – Gene flow (E and I) • • • • In isolated populations Migrating indivs. start breeding Immigrants can add new alleles Not necessarily random – Genetic Drift • • • • Mainland ↑NA Random mating in small populations Causes relative success of only a fraction of individuals Population bottlenecks (large population) Founder effects (small population) ↓NA – Natural Selection • Differential contribution of offspring to next generation by individuals in a population • Not Random Recall: Normal curve of phenotypic variation Height of students in class Another way to look at it… Fitness • Directional Selection Trait Positive Directional Selection Trait Negative Directional Selection Peppered Moth – Biston betularia Fitness • Stabilizing selection average trait value Egg laying wasp that eventually kills the cactus Malaria and Sickle Cell Anemia SSA caused by mutation in the past… Fitness • Disruptive Selection average trait value Black-bellied seed cracker (Pyrenestes ostrinus) • Smith, T. B. 1990. Evolution. 44(4):832 • Black-bellied seed crackers (Pyrenestes) in Cameroon skip Same birds different study Open portion of bar – Number hatched Black portion of bar – Number survived skip Two more types of selection • Correlational – working on combinations of traits at once. (body size) (Wing length) • Frequency Dependent Selection – Level of selection dependent upon most common phenotype (at the time) Genyochromis Scale eater Scalebiters – frequency dependent selection Right “mouthedness” Left “mouthedness” Frequency of left “mouthedness” Frequency of right “mouthedness” Time • Selection can lead to speciation • Speciation: – Splitting of one species into two or more species (cladistic or punctuated). – Transformation of one species into a new species over time (gradual or anagenic). Anagenetic (gradual) versus Cladistic (punctuated) Speciation B A TIME TIME B A A PHENOTYPIC VARIATION PHENOTYPIC VARIATION Species • Many, many definitions • Biological species definition: A group of actually or potentially breeding individuals which are reproductively isolated from all other groups. • Doesn’t work in all situations – Fossils – Asexual organisms Isolating mechanisms • Prezygotic – • Postzygotic - Prezygotic I.M.s • Habitat isolation – Dendroica warblers in Eastern US Modes of speciation • Allopatric – allo = different, patri = fatherland • Sympatric – sym = together • Has to do with location or habitat Allopatric Speciation Speciation occurs with reproductive isolation Grand Canyon Kaibab Squirrel Abert’s Squirrel Sympatric speciation • Rare • Polyploidy in plants • Hybrids Evolution & Speciation of Primates including Homo Divisions of Primates • Prosimians (“before ape”) – – – – Lemurs Tarsiers Lorises Galagos • Lemurs sifaka • Tarsier • Lorises and Galagos Slow-loris galago • New World Monkeys • Old World Monkeys – Baboons – Macaques Asian apes • Gibbons African Apes • • • • Chimps Gorillas Hominids etc… bonobo Hominids • Several genera • Homo 4w human embryo • Most Homonid adaptation related to bipedialism • Sahelanthropus tchadensis – “Toumai child” – 6-7 MYA – Chad • Ardepithecus ramidus – 5.8 – 4.4 MYA – Ethiopia Australopithecines • Genus Australopithecus – Slender (“gracile”) forms • A. africanus, A. afarensis – Robust forms • A. robustus, A. boisei, A. aethopicus • A. africanus – South Africa – 3 – 2 mya – “slender” type • A. afarensis – – – – Slender form “lucy” East Africa ~3mya Dr. Corbin • A. robustus – Robust form – Olduvai gorge – 1.8 mya Genus Homo • Homo habilis – 2.0 – 1.9 mya – Brain size 775 cc • Speech centers – Omnivore – Olduvai gorge • H. habilis (cont.) • H. erectus – Java – 1.9-0.3 mya – Brain 800-1000cc • • • • H. erectus (cont) Extensive tool use Fire Dispersed into Europe and Asia • H. neanderthalensis – 200k bp – Neander valley – 1450 cc • H. sapiens – Cromagnon man • 100-150k bp • ~1360 cc • Culture • Timeline of Homonid evolution Out-of-Africa Hypothesis Thousands of years before present Note on human variability • Ethnic - of or relating to large groups of people classed according to common racial, national, tribal, religious, linguistic, or cultural origin or background. Lewontin – 17 genes, 7 ethnic groups Morphological differences not adaptive Genetic variation a b a b c d …