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Evolution Biology RiverDell High School Ms. C. Militano I. Evidence of Evolution A. Fossils 1. definition - trace or remains of organisms that are preserved 2. types a. mold (rock imprint) b. cast (mold that is filled) c. petrified d. preserved in amber or tar pits Mold Fossil Cast Fossil Fossil in Amber Petrified Wood Dinosaur Fossils Toe of a Dinosaur Plant Fossils Flower Fossil Cone Fossil I. Evidence of Evolution A. Fossils 3. location a. sedimentary rock b. amber or tar pits 4. distribution a.Law of Superposition(Steno 1638-1686) 1) relative age 2) absolute age b. biogeography Fossils Are Found in Tar Pits Sedimentary Rock Showing Layers Law of Superposition – younger fossils are closer to the surface – older fossils are deeper I. Evidence of Evolution B. Comparative Anatomy 1. homologous structures a. similar structure, evolution, development b. wing, arm, flipper) 2. analogous structures a. similar function b. wing of a bird and an insect Homologous vs Analogous Structures I. Evidence of Evolution B. Comparative Anatomy 3. vestigial structures a. useful in past organisms but not now b. appendix, tail vertebrae, ear muscles Vestigial Structures Appendix in Humans Leg Bones in a Whale I. Evidence of Evolution C. Embryology Similarities 1. Haeckel(1834-1919) [German] a. “ontogeny recapitulate phylogeny” 1) embryo undergoes changes that repeat evolutionary development Diagram Showing Similarities in Early Stages of Embryo Development I. Evidence of Evolution D. Biochemistry 1. similarity in amino acids in specific proteins 2. similarity in RNA and DNA base sequences Comparing Amino Acid Differences of Several Organisms to Humans II. Theories of Evolution A. Lamark (1744-1829) 1. Acquired traits – traits that develop during one generation can be passed to the next generation 2. Law of Use and Disuse – if a trait is not used it will be lost Lamarck and Law of Use and Disuse According to Lamarck the giraffes pictured grew longer necks in order to reach the leaves in taller trees The longer necks were then passed to the next generation II. Theories of Evolution B. Charles Darwin(1809-1882) 1. Biography a. Darwin attended medical school b. studied to be a clergyman c. 22 years old - signed on HMS Beagle 1) collect specimens as a naturalist 2) refined data for 21 years Charles Darwin Darwin’s Home HMS Beagle in Sydney Australia Harbor Darwin’s Voyage II. Theories of Evolution B. Charles Darwin(1809-1882) 2. The Origin of Species (1859) a. Descent with modification 1) all species descend from a small number of original types 2) there is variation among organisms II. Theories of Evolution B. Charles Darwin(1809-1882) b. Modification by Selection 1) environment limits growth of populations -competition for life’s necessities -specific traits are selected 2) adaptive advantage - trait favorable for a given environment - adaptations make some organisms more likely to survive than others II. Theories of Evolution B. Charles Darwin(1809-1882) 3) fitness - ability of an organism to make a genetic contribution to the next generation 4) natural selection allows individuals with survival adaptations to pass traits to offspring II. Theories of Evolution B. Charles Darwin(1809-1882) 5) speciation - formation of new species as favorable adaptations accumulate 6) “survival of the fittest” - those organisms with favorable traits reproduce and pass their traits to future generations III. Patterns of Evolution A. Coevolution 1. changes in two or more species closely associated 2. examples a. predator and prey b. parasite and host c. plants and plant pollinators III. Patterns of Evolution B. Convergent Evolution 1. similar phenotypes are selected but ancestors are very different a. natural selection of analogous structures 2. examples a. wings in insects and birds b.fins & shape of sharks, fish, porpoise Examples of Convergent Evolution III. Patterns of Evolution C. Divergent Evolution 1. two or more related populations or species become more dissimilar a. speciation - new species may form 2. example geographic isolation a. brown bear polar bear III. Patterns of Evolution C. Divergent Evolution 3. adaptive radiation a. many species evolve from same ancestor 1) ancestor migrates to different environments (example) Galapagos finches Adaptive Radiation – Darwin’s Finches Beak shape Depends Upon Food Source Adaptive Radiation – Hawaiian Honeycreepers IV. Variation in Populations A. Distribution of variations 1. graph is a bell curve B. Natural Selection and Changes in Populations 1. Stabilizing Selection – favors average form 2. Directional Selection – average shifts to one extreme or the other 3. Disruptive Selection – extreme forms are favored- number of individuals with the average form is reduced Stabilizing Selection Directional Selection Disruptive Selection Comparing Types of Selection Comparing Three Types of Selection IV. Variation in Populations C. Genetic Sources of Variation 1. Mutations a) a specific gene mutates in 1/10,0000 gametes b) thousands of genes in each gamete c) some mutations in every zygote d) most mutations are recessive IV. Variation in Populations C. Genetic Sources of Variation 2. Genetic Recombination a) random meeting of sperm and egg b) crossing over c) independent assortment 3. Genetic Drift a) occurs in small populations b) elimination of some genes by chance c) may decrease variation IV. Variation in Populations C. Genetic Sources of Variation 4. Non-random Mating 5. Migration a) immigration- movement into an area or population b) emigration – movement out of an area or population IV. Variation in Populations D. Genetic Equilibrium 1. Hardy-Weinberg Principle a) allele frequencies are stable across generations b) sexual reproduction alone does not affect genetic equilibrium 2. Conditions Necessary a) no immigration b) no mutations c) no natural selection d)large populations e) random mating IV. Variation in Populations E. Mathematics/Hardy Weinberg 1. gene pool - all the genes in a population 2. allele frequency - % occurrence of a specific allele in a population 3. phenotype frequency - % occurrence of an individual in a population with a trait 4. genotype frequency - % occurrence of individuals in a population with a specific genotype IV. Variation in Populations E. Mathematics/Hardy Weinberg 5. applying mathematics a) p = frequency of the dominant allele q = frequency of the recessive allele b) p + q = 1 c) p2 + 2pq + q2 = 1 IV. Variation in Populations E. Mathematics/Hardy Weinberg d) q2 = recessive phenotype/genotype frequency p2 +2pq = dominant phenotype frequency p2 = pure dominant genotype frequency 2pq= heterozygous genotype frequency V. Speciation and Rate of Evolution A. Species - organisms that are morphologically similar and can interbreed to produce fertile offspring 1. Speciation - process of forming species V. Speciation and Rate of Evolution A. Species and Speciation 2. Isolating mechanisms that result in speciation a) geographic barriers separate populations 1) gene flow stops and natural selection and genetic drift result in divergence b) reproductive barriers - prevent breeding of organisms in the same geographic area V. Speciation and Rate of Evolution B. Rate of Evolution 1. evolution may be defined as a) change in genetic material in a population b) change in allele frequency in a population c) change in genotype/phenotype ratio d) speciation V. Speciation and Rate of Evolution B. Rate of Evolution 2. Gradualism (Darwin) - new species arise slowly and continuously through small, gradual changes 3. Punctuated Equilibrium (Steven Gould and Niles Eldredge) - there are long periods (up to millions of years) with little or no change - then there is a short period of rapid change VI. Evolution in Action Caribbean Anole Lizards Live on Tree Trunks Stocky body Long legs Live on Slender twigs Thin body and large toe pads Short legs and tails Caribbean Anole Lizards Live in grass Slender body Very long tails * at least six anole body types - and distinct species with same body type on different islands Caribbean Anole Lizards Hypothesis Specialized twig dwellers lived on one islands and migrated to other islands Twig-dwellers evolved independently on each island from a distinct ancestor (DNA evidence) – example of convergent evolution Caribbean Anole Lizards Divergent Evolution and Radiation Divergent evolution on each island Descendants from a single ancestor diversify into species adapted for a specific environment – if populations fill many parts of the environment it is called adaptive radiation Caribbean Anole Lizards trunk dweller twig dweller grass dweller COMMON ANCESTOR Arrives on each island