Discuss with your table partner: What is speciation? __________________________________ How could speciation occur? _________________________________________ _________________________________________ _________________________________________ _________________________________________ Divergent Evolution Divergent evolution is the accumulation of differences which can lead to_________. Homologous structures: similarities in structures due to ________ ______________ but adapted to different functions. Same origin Examples of Homologous Structures- passed down from a common ancestor (Present throughout the portion of the branching tree of ancestry) Vestigial structure: A structure that is _____________ in function or structure, but may have had function in ancestor. Examples: _________ Ostrich wings Star Nosed Mole: Reduced sense of vision. Convergent evolution: Distantly related species evolve similar adaptations, because they ___________ ________________________________. Example: Anteater and aardvark In convergent evolution, trait is not shared by more closely related species. The trait evolved independently in more distantly related species because the of similarities in natural selection pressure. The similarities in structure on more distantly related species, due to convergent evolution are called analogous structures. Example: wings of butterflies and bats Discuss with your table partner the questions on the next 3 slides. Some snakes have skeletal remnants of legs. What term describes this type of structure? ___________________________ Whales and other sea mammals have a similar shape to fish, even though they are more closely related to land mammals. What type of evolution is this an example of? ____________________ What term describes the relationship between fish and whale fins? _____________________ The teeth of beavers and the tusks of elephant stem from a common ancestor, but they are adapted for different functions. What is this an example of? ________________________ Coevolution A process in which two (or more) species reciprocally ___________________________. Changes in the gene pool of one population resulting changes in the gene pool of the other species. Coevolution can be a positive interaction, resulting in a highly __________relationship. Example: Specialist pollinators that only pollinate one type of flower. Advantage to pollinator- no competition for food source. Advantage to plant- _____________ _____________________________ Coevolution can be an adaptation to a negative effect of another species. “An evolutionary arms race” Example: Increasing levels of toxins in one species to avoid predation, with the predator developing increasing tolerance to the toxin. Fossils Relative Dating: Age is determined____________________________. Law of Superposition: For sedimentary rock layers, if undisturbed the youngest layers will be on the _____. Absolute Dating: Radioisotope Dating Half-Life: The amount of time that it takes half of a radioactive sample to decay. Half-life Comparisons Radioisotope Half-life Berillyium-11 13.81 seconds Iodine-131 8 days Strontium-85 11 years Tritium (Hydrogen-3) 12 years Uranium-235 700 million years Uranium-238 4.5 billion years Determining amount of radioactive isotope remaining Number of Fraction Formula for Half-lives Remaining Fraction Remaining 1 1/2 (1/2) 1 2 _____ ____ 3 _____ ______ 4 _____ ____ t Formula: N = No (1/2) t= number of half-lives N = amount left No = original amount Discuss with your table partner: Strontium-23 has a half-live of 11 years. If 1/16 of the original sample is left, how old is it? __________________________ Carbon-14 has a half life of 5, 370 years. If a sample is 16,110 years old, what fraction of Carbon-14 would remain? ___________________________ Evidence for Evolutionary Relationships Fossil Record: Transitional Fossils Example: Archaeopteryx is a transitional fossil between dinosaurs and birds. Evidence for Evolutionary Relationships Anatomical Comparisons: comparing body structures. Discuss with your table partner: Why might anatomical comparisons be misleading when trying to determine how closely related to species are? ____________________________________________ ____________________________________________ ____________________________________________ Evidence for Evolutionary Relationships Biochemical Evidence: • ______ sequence (also known as genetic evidence) • Protein sequence: since each gene encodes a protein, changes in the gene will be reflected in changes in the amino acid sequence of the protein. Discuss with your table partner: Go to the website (see link in evolution folder by Evolution Notes Part 3: http://ngm.nationalgeographic.com/2013/07/125- explore/shared-genes Drag the different organisms to the correct percentage of DNA the species has in common with humans (consider how closely related each is to humans and use trial and error as needed.) . Biochemical evidence is considered to be the most _____________ way to compare evolutionary relationships among species. .