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chapter7 and 11 fall 2017 posted

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Published on October 21, 2017

Author: acocil

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Gene Expression-chapter 7: Gene Expression- chapter 7 Evidence of Evolution- chapter 11 and Slide2: Normal Iris Slide3: Iris less Slide4: Normal Fruit Fly Slide5: Eyeless Fruit Fly Slide6: Eye On A Wing DNA molecules contain sequences called Genes: DNA molecules contain sequences called Genes Slide8: Mutations are permanent changes in the nucleotide sequence of DNA , which may alter a gene product A mutation that changes a gene’s product may have harmful effects Example: Mutations that affect the proteins in hemoglobin reduce blood’s ability to carry oxygen Slide9: Most mutations result from unrepaired DNA errors during DNA replication Some result from exposure to radiation or chemicals Slide10: Radiation (x-rays) breaks chromosomes and produces free radicals Slide11: Radiation (UV light) results in thymine dimers, which lead to skin cancer Environmental Damage: Environmental Damage Some natural and synthetic chemicals cause mutations in DNA Example: Cigarette smoke transfers small hydrocarbon groups to bases in DNA, causing mispairing during replication Slide13: All cells in your body carry the same DNA Some genes are transcribed by all cells, but most cells are specialized (differentiated) to use only certain genes Which genes are expressed at a given time depends on the type of cell and conditions Slide14: DNA carries all the genetic information needed to build a new individual Genetic information consists of base sequences Genes are subunits of that sequence Gene Part of a DNA base sequence Specifies structure of an RNA or protein product Recapitulation From Gene to RNA to Protein: From Gene to RNA to Protein Gene expression involves transcription (DNA to RNA), and translation (mRNA, or messenger RNA, to protein) Gene expression Process by which the information in a gene becomes converted to an RNA or protein product Transcription: Transcription Transcription Process by which an RNA is assembled from nucleotides using the base sequence of a gene as a template Translation: Translation Translation requires the participation of tRNA (transfer RNA) and rRNA (ribosomal RNA) Translation Process by which a polypeptide chain is assembled from amino acids in the order specified by an mRNA Transcription: DNA to RNA: Transcription: DNA to RNA Base-pairing rules in DNA replication also apply to RNA synthesis in transcription, but RNA uses uracil in place of thymine mRNA and the Genetic Code: mRNA and the Genetic Code The information in mRNA consists of sets of three nucleotides (codons) that form “ words ” spelled with the four bases A, C, G, and U Codon In mRNA, a nucleotide base triplet that codes for an amino acid or stop signal during translation mRNA and the Genetic Code: mRNA and the Genetic Code Sixty-four codons , most of which specify amino acids, constitute the genetic code 20 amino acids in proteins; most have more than one codon Genetic code Sixty-four mRNA codons; each specifies an amino acid or a signal to start or stop translation The Genetic Code: The Genetic Code Evidence of Evolution: Evidence of Evolution About Fossils: About Fossils Fossils Physical evidence of organisms from the past Hard fossils include mineralized bones, teeth, shells, spores and other hard body parts Trace fossils include footprints, nests, trails, feces and other evidence of activities Pioneers of Biogeography: Pioneers of Biogeography In the late 1800s naturalists observed patterns in where species live, how they might be related, and how natural forces might shape life Biogeography Study of patterns in the geographic distribution of species and communities Biogeography: Biogeography Similarities in birds on different continents might indicate a common ancestor Rhea South America Emu Australia Ostrich Africa Biogeography : Biogeography Some plants that live in similar climates on different continents have similar features, but are not closely related spiny cactus spiny spurge American Southwest southwestern Africa Comparative Morphology: Comparative Morphology Naturalists studying body plans were also confused by vestigial body parts with no apparent function Comparative morphology Scientific study of body plans and structures among groups of organisms Vestigial Body Parts : Vestigial Body Parts Evolution: Evolution Naturalists suspected that environmental factors affected affect a species’ traits over time, causing changes in a line of descent Evolution Change in a line of descent (in a line from an ancestor) Shared Traits: Shared Traits Extincted glyptodons shared traits with modern armadillos Limited Resources: Limited Resources A population tends to grow until it begins to exhaust environmental resources—food, shelter from predators, etc When resources become scarce, individuals must compete for them Fitness: Fitness In any population, some individuals have traits that make them better suited to the environment than others, and therefore more likely to survive and reproduce Fitness The degree of adaptation to an environment, as measured by an individual’s relative genetic contribution to future generations Adaptation: Adaptation Adaptive traits that impart greater fitness to an individual become more common in a population over generations, compared with less competitive forms Adaptation ( adaptive trait ) A heritable trait that enhances an individual’s fitness Natural Selection: Natural Selection The process of natural selection, through variations in fitness and adaptation, is a driving force of evolution Natural selection Differential survival and reproduction of individuals of a population that vary in the details of shared, heritable traits Slide37: Similarities in structure of body parts are often evidence of a common ancestor Homologous structures Similar body parts that reflect shared ancestry May be used for different purposes in different groups, but the same genes direct their development Slide38: pterosaur chicken penguin stem reptile porpoise bat human elephant Slide39: Some body parts look alike in different lineages, but did not evolve in a common ancestor Analogous structures Similar structures that evolved separately in different lineages Morphological convergence Evolutionary pattern in which similar body parts evolve separately in different lineage Morphological Convergence: Morphological Convergence Slide44: Insects Bats Humans Crocodiles Birds wings wings wings limbs with 5 digits Comparative Embryology: Comparative Embryology Embryos of related species tend to develop in similar ways Similarities in patterns of embryonic development are the result of master genes (homeotic genes) that have been conserved over evolutionary time Slide46: Mouse Slide47: Bat Slide48: Chicken Slide49: Alligator Slide50: Human Slide52: The end Reflections of a Distant Past: Reflections of a Distant Past Events of the ancient past can be explained by the same physical, chemical, and biological processes that operate in today’s world From Evidence to Inference: From Evidence to Inference Scientists infer from evidence such as the K-T boundary layer that an asteroid impact near the Yucat á n 65 million years ago caused the mass extinction of dinosaurs Mass extinction Simultaneous loss of many lineages from Earth Slide58: The K-T boundary layer (formed 65 million years ago at a time of mass extinction) is made up of clay rich in iridium – rare on Earth but common in asteroids Process of Fossilization: Process of Fossilization Layers of sediment cover an organism or its traces – pressure and mineralization change remains to rock Younger fossils usually occur in more recently deposited layers of sedimentary rock, on top of older fossils in older layers The Fossil Record: The Fossil Record Fossils are relatively scarce, so the fossil record will always be incomplete The fossil record helps us reconstruct the lineage of some species, such as whales Lineage Line of descent from a common ancestor Slide64: A A 30-million-year-old fossil of Elomeryx . This small terrestrial mammal was a member of the same artiodactyl group that gave rise to hippopotamuses, pigs, deer, sheep, cows, and whales. Slide66: Fig. 11-7b (3), p. 202 Pronghorn Antelope Rodhocetus Ancient whale Putting Time Into Perspective: Putting Time Into Perspective Transitions in the fossil record, found in characteristic layers of sedimentary rock, became boundaries for great intervals of the geologic time scale Geologic time scale Chronology of Earth history Correlates with evolutionary events The Geologic Time Scale: The Geologic Time Scale Cenozoic = new life The Geologic Time Scale: The Geologic Time Scale Gondwana: Gondwana Certain fossils of ferns and reptiles that predate Pangea are found in similar rock layers in Africa, India, South America, and Australia – evidence of an even earlier supercontinent Gondwana Supercontinent that formed more than 500 million years ago Slide73: Evidence suggests that supercontinents have formed and broken up at least five times The resulting changes in the Earth’s surface, atmosphere, waters and climates have had profound impacts on evolution

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