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Transcript
Evolution Chapters 15/16 Intro Video • https://youtu.be/FpfAZaVhx3k?list =PLISBHwlJXpn2bmLjfiShKcIHpBP cov24O Evolution • A change over time • A process by which modern organisms have descended from ancient organisms • Theory- a broad, well tested explanation that unifies a broad range of observations Earth’s History • More than 4 Billion years old • Fossils- preserved remains of ancient organisms • Many modern life forms appear to be modifications of fossil forms Theories of Evolution • Three Scientists • Lamarck • Malthus • Darwin Lamarck • French Scientist • Proposed that acquired traits were passed on to offspring • Acquired Trait- one that is not determined by genes, instead arises over time by experience or behavior – Example- developing large muscles • Disproved by current knowledge of genetics Malthus • Stated that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone Charles Darwin • British Scientist • Sailed on ship HMS Beagle on trip to explore S. America • Was the Naturalist on board, collecting plant and animal samples Darwin’s Work • While on the Beagle, Darwin collected and recorded information about all types of living species • Back in Britain he analyzed his observation and published The Origin of Species Darwin’s Theories • Descent with Modification- newer forms of life are modified descendents of older species • Modification by Natural Selectionstates how evolution is occurring Theory Part 2 Concepts • Natural Selection- organisms best suited to their environment will reproduce more successfully • Adapt- a change in a population in response to the environment • Fitness- an individual’s genetic contribution to the next generation – High fitness= more offspring • Survival of the fittest- competition for food and living space will only allow for those best suited to environment to reproduce Evidence of Evolution • Homologous Features • Analogous Features • Vestigial Structures • Conserved Genes • Similarities in Embryos • Macromolecules Homologous Features • Similar features that have slightly different mature forms but originated from a common ancestor – Example- forearm of mammals Analogous Feature • Have same function, but have different development – Example: Wings on bird and insect Vestigial Structures • Organ that serves no current purpose in organism, but is believed to have one in ancestor – Examples: • Tailbone in humans • Appendix in humans • Pelvic bones in Conserved Genes • A gene that remains unchanged within DNA, but is turned off and not used – Example: hind legs in whales Similar Embryos • During early fetal development, vertebrates all appear the same Macromolecules • All have DNA as basis • Similar amino acid sequence that make up proteins – More similarities the closer related the two organisms are Patterns of Evolution • Co-evolution • Convergent • Divergent Coevolution • Changes in two or more species in close association with each other – Example- plant and animal pollinators Convergent • Occurs when the environment selects for similar phenotype, even though ancestry is very different – Example- body shape of dolphins and sharks Divergent • Two related species becoming different from one another • Two Types – Adaptive – Artificial • Divergent Adaptive- change is in response to habitat – Example: Galapagos finches • Divergent Artificial- other interference speeds up differences (breeding) – Example: Dog breeding Genetic Equilibrium • Population Genetics- looking at evolution from a genetic point of view • Population- members of a species that live in the same area and make up a breeding group • In normal circumstances the percentages of a particular trait remain constant – Equilibrium Disruption of Equilibrium • Mutation • Genetic Drift • Migration • Non-random Mating • Natural Selection • Mutation- any change to DNA – Can affect the protein made which can affect the individual and their offspring • Genetic Driftallele frequencies (%) change due to chance or random events – Example- Natural disasters • Migration- net movement in or out of a population – Immigration- moving into a population – Emigrationmovement out of a population • Migration creates gene flow • Gene Flowmovement of genes from one population to another • Non-random Mating- mating in small populations – Leads to higher occurrences of disorders – Example- Amish Natural Selection • Traits being selected for or against • Three Types – Stabilization – Directional – Disruptive Stabilization Selection • Type of natural selection in which the average form is being selected for Directional Selection • Type of natural selection in which one extreme is being selected for, creating movement in one direction Disruptive Selection • Type of natural selection in which the average is being selected against and both extremes are being selected for Formation of Species • Speciation- process of forming new species • Morphology- internal and external structure and appearance – Scientists use this as basis for classifying species • Biological Species Concept- A species is a population that can interbreed, but not breed with other groups Isolating Mechanisms • Mechanisms that can cause new species to form • Two Types – Geographic – Reproductive • Geographic Isolation- having a physical barrier between groups – Example: river, canyon, mountain • Reproductive Isolation- barrier to successful breeding • Examples: different mating calls, different mating seasons Rates of Speciation • Gradual- slow change over time – Lots of intermediates in fossil record • Punctuated- sudden shift in fossil record – Could be caused by natural disaster or other sudden change to environment