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Evolution Charles Darwin At age 22 traveled around the world on the ship called H.M.S Beagle. 1831-1836 Galapagos Islands • Off the coast of South America • Found many species never seen before • Darwin wanted to know why these species were only found on these islands Finches • Finches had different beak shapes on the different islands. • Beak shape was a result of the different seeds on the islands Tortoises Ideas that shaped Darwin’s thinking 1. Lyell and Hutton: • Geologists • Proved that the features of Earth took millions of years to form Shows that Earth is extremely old Ideas that shaped Darwin’s thinking 2. Lamarck: • Biologist • Inheritance of acquired traits Wrong • 1st to come with an idea about how animals change Ideas that shaped Darwin’s thinking 3. Malthus: • Economist • Predicted that population size will outnumber available resources • Individuals will have to compete b/c there is not enough for everyone Putting the ideas together Charles Darwin and Alfred Wallace formed a theory to explain how evolution may take place. Darwin publishes: On the Origin of Species by Means of Natural Selection Darwin’s description of evolution: Descent with modification: -All organisms (species) had descended from one form of life -little changes occur over time Example Finches from the Galapagos: Descent with modification is accomplished through the process of natural selection Process of natural selection as presented by Darwin 1. Overproduction: Each species produces more individuals than can survive to maturity Process of natural selection as presented by Darwin 2. Struggle for survival: Individuals compete for resources and with predators Process of natural selection as presented by Darwin 3. Genetic variation: Individuals in a population are all different Process of natural selection as presented by Darwin 4. Differential reproduction: Some individuals have better genes and can compete better and produce more offspring • Adaptations animal survive Live longer -traits that help an more offs Example of natural selection Just because you want it doesn’t mean your gonna get it Homework Pick one of the following animals and describe (in words or a drawing) how that animal could have evolved through natural selection. Elephant Leaf bug Bellwork How would Lamarck and Darwin explain how an elephant got its long trunk? Evidence for Evolution 1. Fossils The ancient remains of animals and plants 1. Fossils • Fossils show that different types of organisms appeared at different times and places • Show extinct species • Shows earlier forms of modern organisms Dating fossils Rock strata 2. Transitional species Organisms that have features of modern organisms and extinct species 3. Biogeography Organisms with similar traits that evolved in different regions 4. Anatomy a. Homologous structures 4. Anatomy b. Analogous structures • Similar function but not structure • Independent evolution Homologous Analogous 4. Anatomy c. Vestigial organs 5. Embryology 6. Biological molecules All organisms have the same genetic code DNA RNA Protein Same amino acids Population Genetics Population genetics Study of evolution from a genetic point of view. Microevolution- changes in genetics of a population. Population- organisms of the same species that live in the same area Species- organisms that are able to breed and produce fertile offspring. Individuals in a population vary in observable traits Causes of Variation 1. mutations a random change in DNA that can be passed from parents to offspring. 2. Recombination reshuffling of genes during meiosis 3. Random pairing of gametes each organism produces large number of gametes. Which gametes combine is pure chance 4. Polygenic traits variation in one trait Gene Pool • Describes the total genetic information available in a population. • Knowing the available alleles you can predict the genotypes and phenotypes. Genetic Equilibrium Hardy-Weinberg- showed that allele frequencies in a population tend to remain the same from generation to generation unless acted on by outside influences. Hardy-Weinberg Equilibrium P2 + 2PQ + Q2= 1 No Evolution When: 1.No mutations 2.No immigration or emigration 3.The population is large 4.Individuals mate randomly 5.Natural selection does not occur Disruption of genetic equilibrium When genetic equilibrium is disrupted and allele frequencies change then evolution will occur 1. Mutations Can create totally new alleles 3 Types: a. harmful b. neutral c. beneficial 2. Gene Flow The process of genes moving from one population to another. Immigration- movement into a population Emigration- movement out of a population 2. Gene Flow Movement of seeds by air, water, insects Male animals leave one group at adulthood to another group 3. Genetic Drift Change in allele frequency due to random change. Most obvious in small populations 2 types 3. Genetic Drift Founder Affect- small group leaves a larger population Amish Founder Affect 3. Genetic Drift Bottleneck effect- a large number of individuals are removed or killed from the population Over Hunting: Northern Elephant Seal Discussion Question How can the founder affect and bottleneck affect harm a population? 4. Nonrandom Mating • Mating based on location -inbreeding • Mating with individuals with similar traits -assortative mating • Sexual selection 5. Natural Selection Population Can Evolve Through Mutation Gene Nonrandom Genetic Natural Flow Mating Drift Selection Timber wolf Canis lupus Husky Canis lupus familiaris Arctic fox Vulpes lagopus Bull dog How many species are shown below? Brassica oleracea. broccoli Brussels sprouts cauliflower cabbage “mutant” flowers: “mutant” buds: “mutant” leaves: How many species are shown below? Panthera onca Jaguar Neofelis nebulosa Clouded leopard Panthera pardus Leopard Cheetah Acinonyx jubat SPECIATION Speciation Existing species are changed versions of older species. Speciation- the process of species formation Species • Morphologically similar • Can interbreed to produce fertile offspring Speciation begins with the isolation of a formally interbreeding population 2 important ways of isolation: Physically Biologically Geographic Isolation Allopatric -physical separation -gene flow stops -natural selection and genetic drift change the populations Examples of geographic isolation Reproductive Isolation Sympatric -Organisms are unable to breed and produce fertile offspring Populations breed at different time periods. Different mating rituals.