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Transcript
Evolution Biogenesis Abiogenesis Before the 1600s, it was generally thought that organisms could arise from nonliving material by spontaneous generation Francesco Redi Redi showed in 1668 that rotting meat kept away from flies would not produce new flies Maggots appeared only on meat that had been exposed to flies Lazzaro Spallanzani Spallanzani showed in the 1700s that microorganisms would not grow in broth when its container was heated and then sealed This seemed to indicate that microorganisms that cause food spoilage do not arise from spontaneous generation but, rather, are carried in the air Louis Pasteur Pasteur used a variation of Spallanzani’s design to prove that microorganisms are carried in the air and do not arise by spontaneous generation Fossil Record Fossils A fossil is a trace of a long-dead organism The law of superposition states that new geologic strata are deposited on top of older strata The history of Earth and its life-forms can be inferred by examining the fossil record Fossil Record The fossil record shows that new lifeforms have arisen continually during the history of life on Earth Biogeography The study of biogeography shows that organisms arise in areas where similar, now-extinct organisms once lived Theories of Evolution Jean Baptiste de Lamarck Lamarck proposed that species evolve over time He incorrectly hypothesized that species modification is the result of acquired characteristics and that these characteristics can be passed on to offspring Charles Darwin began his work on evolution when he was employed as a naturalist for a voyage of the H.M.S. Beagle Uniformitarianism Darwin was influenced by Charles Lyell, who proposed the principles of uniformitarianism, which hold that the structure of Earth results from cycles of observable processes Adaptive Radiation Darwin found evidence of species modification in both modern and extinct species Darwin hypothesized that related species, such as the Galapagos finches, descended from a common ancestor Natural Selection Darwin wrote The Origin of Species, in which he proposed that natural selection is the principal driving force behind evolution Adaptation A population of organisms adapt to their environment as their proportion of genes for favorable traits increases So what exactly is evolution? Evolution is the change in genetic makeup of a population over generations Can you create the perfect habitat for each of these wild canines? HOMEWORK!!! Using magazine clippings, crayons, and markers, illustrate a habitat you think each canine is well suited for. Life in the Grasslands… The maned wolf is well adapted for life in the tall grass plains or pampas of South America. Their stilt-like legs aren't for running -- this canine is no speedster. Instead, long legs help maned wolves peer over tall grasses to spot each other and their prey. Life in the Desert… The fennec fox makes its home in the desert. Pale fur reflects the sun's rays, and extends over the soles of its paws to protect against burning desert sands. When fennec foxes overheat, they shunt or send blood to their large ears to rapidly dump the excess body heat into the environment. Life in the Arctic… Not many wild canines can survive the frigid temperatures of the arctic. The arctic fox is the only year-round small canine resident of this harsh environment. Its fur goes from white in winter to brown-gray in summer, keeping in line with the seasonal change from white snow cover to brown tundra. To keep warm, it has thick fur that even covers the soles of its feet and tiny ears to reduce heat loss when the temperature dips far below zero. Life in the Forest… The gray fox has a unique adaptation for life in the forest. In addition to small body size and short legs that make it easy to move through the underbrush, the gray fox is the only climbing canine. Using its somewhat curved claws, it scampers up trees to avoid predators as well as to forage for food such birds or their eggs. Evolution in Process Body Structures Evidence supporting evolution is found in the body structures of living organisms Homologous structures have a common structure Analogous structures are similar in function but have different structure A species with vestigial structures probably shares evolutionary origins with a species that has a functional forms of the structure Homologous Structures Analogous Structures Vestigial Structures Embryological & Molecular Evolution Similar embryological development among species indicates a common evolutionary history Similarity in macromolecules such as RNA, DNA, and proteins indicates a common evolutionary history Coevolution In coevolution, two or more closely associated species, such as a predator and its prey, change in response to each other Convergent Evolution In convergent evolution, organisms that are not closely related resemble each other because they have responded to similar environments Divergent Evolution In divergent evolution, related populations become less similar as they respond to different environments Adaptive radiation is a type of divergent evolution Disruption of Genetic Equilibrium Genetic Equilibrium Shifts Evolution can take place if the genetic equilibrium of a population is disrupted Immigration Nonrandom mating Genetic drift Stabilizing selection Directional selection Disruptive selection Sexual selection Immigration & Emigration Immigration can bring new genes into a population, causing evolution Emigration is the movement of individuals out of a population Nonrandom Mating Nonrandom mating can alter the genotypes of a population, but does not affect allele frequencies Genetic Drift Genetic drift operates in small populations; the contribution or lack of contribution of the genes of one or a few organisms can change the population’s gene pool significantly Stabilizing Selection Stabilizing selection encourages the formation of average traits Directional Selection Directional selection encourages the formation of more-extreme traits, such as a very long tongue in anteaters Disruptive Selection Disruptive selection selects for extreme traits rather than average traits Sexual Selection In sexual selection, the development of traits that may seem harmful can actually enhance reproductive fitness if they encourage mating Formation of Species Species Definition According to the biological species concept, a species is a population of organisms that can successfully interbreed and cannot breed with other groups Speciation Speciation means species formation, and it always begins with a population that has become isolated Geographic Isolation Geographic isolation results from the division of an original population Reproductive Isolation Reproductive isolation results from barriers to successful breeding Prezygotic isolation occurs before fertilization Postzygotic isolation occurs after fertilization and results in wasted gametes