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History of Life and Classification Unit 11: Chapter 14 Standards • Compare principle of biogenesis with theory of spontaneous generation • Summarize Redi’s and Spallanzani’s experiments • Explain the importance of RNA to the origin of life • Relate photosynthesis to the development of aerobic respiration • Relate the concepts of adaptation and fitness to the theory of natural selection • Explain how anatomy and development provide evidence of shared ancestry • Compare artificial and natural selection Biogenesis • All living things come from other living things Spontaneous Generation • Living things arise from nonliving materials Redi’s Experiment Disproved Spontaneous Generation Spallanzani’s Experiment Disproved Spontaneous Generation of Microbes Pasteur’s Experiment Established Biogenesis as Cornerstone of Biology Earth’s History • Earth ≈ 5 billion years old. • calculated by radiometric dating -measure rate of radioactive decay of isotopes -half life: amount of time ½ of an isotope decays. -carbon-14 is used to measure age of fossils. Carbon-14 C-12: 6p and 6n. Stable state C-14: 6p and 8n. Isotope, which must decay to reach a stable state. First Organic Compounds • May have formed under high heat in early atmosphere- Oparin • Lightning, UV radiation may have energized simple organic compounds to become macromolecules- Miller, Urey • Meteorites may have carried organic compounds to Earth. First Nucleic Acid • First molecule of heredity may have been RNA, not DNA. -can assume more shapes than DNA. -can catalyze reactions like a protein. First Cells • First cells may have been anaerobic, heterotrophic prokaryotes -no O₂ in early atmosphere. -consumed spontaneously formed or organic molecules. • First autotrophic cells were chemosynthetic. -energy from inorganic molecules, not light. First Autotrophs • were chemosynthetic. -energy from inorganic molecules, not light. • related to Archaea bacteria -existed in harsh environments. Photosynthesis and Aerobic Respiration • photosynthetic prokaryotes released O₂ into atmosphere. -cells resembled modern cyanobacteria. -O₂ atoms were split in atmosphere to form ozone. First Eukaryotes • larger than prokaryotes, have membranebound organelles. • theory of endosymbiosis: prokaryotes were engulfed by larger prokaryotes. -mitochondria, chloroplasts -evidence: independent replication; unique DNA Theory of Evolution Unit 11: Chapter 15 Theory of Evolution • Theory of Evolution: change in inherited characteristics over time. -new species develop from pre-existing ones. • Charles Darwin: -studied beak shape in Galapagos finches. -published On the Origin of Species by Means of Natural Selection. Theory of Evolution • change in inherited characteristics over time due to environmental pressures. -new species develop from pre-existing ones. Contributing Scientists • Cuvier- catastrophism: sudden geologic catastrophes caused mass extinctions. • Lyell- uniformitarianism: past processes that changed Earth’s surface continue to be at work. • Lamarck- inheritance of acquired traits: individuals could acquire traits by behavior; traits could be passed on. Charles Darwin • Charles Darwin: -naturalist. -studied beak shape in Galapagos finches. -published On the Origin of Species by Means of Natural Selection. -proposed that natural selection is the mechanism for evolution. Steps of Natural Selection 1. Overproduction: more offspring are produced than survive. 2. Genetic variability exists in populations. -mutations (random changes to DNA) are source of variation; mutations within gametes are inheritable. 3. Struggle to survive: environment favors survival of individuals with adaptive trait. 4. Differential reproduction: adaptive trait leads to more successful reproduction. Survival of the Fittest • Measure of genetic contribution to next generation. ex. Thick fur, speed, superb vision Natural Selection and the Six Kingdoms/Tree of Life The Geologic Time Scale Natural Selection & Genetic Resistance • Ability of members of a population to resist a chemical designed to kill it. Evidence of Natural Selection • Fossil record: entire collection of preserved species. -represents ≈ 1% of all species on Earth. • Homologous structures: -similar structures in dissimilar species. • DNA analysis Limitations to Natural Selection • Genetic change must precede change in the environmental conditions. • Reproductive capacity: -species that reproduce rapidly and in large numbers are better able to adapt. Common Myths about Evolution through Natural Selection • “Survival of the fittest” is not “survival of the strongest” . (Fittest is in terms of leaving behind the most offspring ) • Organisms do not develop traits out of need or want. • No grand plan of nature for perfect adaptation (evolution is not “goal oriented). Movement of the Earth’s Continents over Millions of Years Pangea’s breakup explained: Scrat’s Missing Adventure Video Clip , Video Clip 2 Climate Change and Natural Selection • Cyclical climate changes restrict location/ survival of populations. -adapt, migrate or become extinct 4-4 Biodiversity, Speciation and Extinction • Biodiversity results from the interaction between speciation and extinction. Mass Extinctions Cenozoic Era Period Quaternary Millions of years ago Today Bar width represents relative number of living species Extinction Tertiary 65 Extinction Mesozoic Current extinction crisis caused by human activities. Many species are expected to become extinct within the next 50–100 years. Cretaceous: up to 80% of ruling reptiles (dinosaurs); many marine species including many foraminiferans and mollusks. Cretaceous Jurassic Species and families experiencing mass extinction Extinction Triassic: 35% of animal families, including many reptiles and marine mollusks. 250 Extinction Permian: 90% of animal families, including over 95% of marine species; many trees, amphibians, most bryozoans and brachiopods, all trilobites. 345 Extinction 180 Triassic Permian Paleozoic Carboniferous Devonian: 30% of animal families, including agnathan and placoderm fishes and many trilobites. Devonian Silurian Ordovician Cambrian 500 Extinction Ordovician: 50% of animal families, including many trilobites. Fig. 4-12, p. 93 Speciation Evolutionary process by which new biological species arise: • Geographic isolation: physical isolation of populations for a long period lead to… • Reproductive isolation: mutations in geographically isolated populations prevent the production of viable offspring. Endangered Species • Because of scarcity of inspectors, probably no more than 1/10th of the illegal wildlife trade in the U.S. is discovered. Figure 11-19