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Evolution Controversial? Why not Creationism as well? What is evolution? Did most scientists initially support this idea? Lamarkian Interpretation? 1750: Creationism- “God creates, Linnaeus arranges” 1798: Malthus - population dynamics 1800: Catastrophism - Cuvier ; fossils were relics or impressions of the past, the earth has had a succession of flora & fauna but no change has occurred 1809: Evolution - Lamarck; theory of acquired characteristics 1833: Lyle - geology indicates earth is much older than 2K 1859: Evolution - Darwin; Descent with modification Charles Darwin •Naturalist HMS beagle - 1831 •Observations, identification, Specimen collecting, drawings •Significant data revealing species diversity 1859 - On The Origin of Species By Means Of Natural Selection 1. Organisms produce more individuals than can survive 2. No two individuals are exactly alike 3. The best adapted survives 4. Survivors reproduce and pass traits on to future generations 5. Descent with modification movie Darwinian Interpretation? Evidence of Evolution Fossils - transitional forms Homologous organs Artificial Selection in Domesticated Species Embryological Similarities Geographical Distribution - deer family DNA comparison Existence of Vestigial Organs - evidence of what was once present Change within a species a gradual process? (Gradulalism vs Punctuated Equilibrium) How might an evolutionary biologist determine if a species is evolving? Changes in allele frequencies! A population not evolving would reveal Genetic Equilibrium. Which means? What conditions would be required to maintain genetic equilibrium? (Large population & random mating - no mutation - no change in environment No immigration and no emigration) Factors that promote changes in allelic frequencies? 1- Natural Selection What if new environmental conditions are presented? Industrial Melanism Genetic Drift - dramatic shift in frequency as a result of timing not bad genes 2 - Bottleneck Effect Population size dramatically reduced by: •Natural disaster •Disease •Excessive hunting Leaving a small surviving population with gene frequencies nothing like ancestral population 3 - Founder effect A small number of individuals leaves the ancestral population and establishes a new population in another area. The new population has allele frequencies much different from ancestral population 4 - Gene Flow Genes move into or leave a population as a result of migration. 5 - Mutation / Natural Recombination & Natural Selection Formation of new genetic code or combinations of genetic code can lead to natural selecting forces causing a significant change in allelic frequencies E ll l h hh hh h 1 4 F D 2 5 3 6 F G F k kk kk i i ii i A k b B b b b c C B c bc 7 8 9 10 National Geographic March 2006 Moving into new environments promoted combinations of genes that increased chances of survival (adaptation) Skin color, eye shape, body size, location of fat deposition, and behavior are some of the more obvious differences observed in the different races of people. While 99.9% of all human DNA is identical, small differences (“markers”) have revealed the migratory route of primitive humans. Mitochondrial DNA and the Y chromosome along with key fossil finds confirm the paths and approximate times they occurred. Human Evolution (Homo sapiens) Genetic Markers reveal lineage Mutations in mitochondrial DNA and the Y chromosome happen once in a great while (every 1000 - 10,000 years) All offspring from mutant will carry the same mutation. Up to three million men living around the world today could be descended from a fifth-century Irish king, according to a new study. Are humans likely to form additional Subspecies? New species? Homo floresiensis More on Human Genetic Markers Becoming Human - awesome website Changes in gene frequencies indicates an evolving population. Microevolution - selecting forces can have one of three effects on phenotypes in a population Macroevolution - changes in frequencies extended over a great deal of time may lead to the development of new species New selecting forces supports speciation - Adaptive Radiation An expanding population moving into environments that have a different combination of selecting forces can lead to the origin of new species Isolation enhances speciation Geographical Isolation - isolation evident in islands promotes significant speciation Marsupials in Australia, Komodo dragon, marine iguana Galapagos Can these be geographical barriers •Mountain Range •Canyon •River •Freeway Behavioral Isolation courtship rituals, nesting preferences, territoriality can all prevent two genetically compatible species from breeding allowing additional change to take place over time Temporal Isolation - timing is everything. Breeding at different times of the year can prevent species from sharing a common gene pool. Reproductive Isolation - pre & post zygotic Even though breeding may occur, producing a viable, fertile offspring may not be possible.