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Chapter 17 Microevolution Designer Pets The many varieties or breeds have been produced through __________________________________ by humans Some _______________________ would have been selected against by nature had it not been for human protection The Great Chain of Being Many of the ancient Greeks, including ____________________________, attempted to explain the natural world by making direct observable By the 14th century, the ancient view of gradual levels of organization from lifeless matter to the most complex organisms had been formalized into the _________________________________ The chain extended from lowest level forms to ________________________ Each being (species) had its fixed place in the __________________________—unchanged and unchanging since creation Biogeography: Questions from Biogeography During the global voyages of the 16th century scientist asked the following questions: Where do all these species “______________” into the great “Chain”? Why were certain species found in only some parts of the________________but not others? How did so many species get from the center of creation to __________________and _________________________________? Comparative Morphology Studies of the _________________________________ of seemingly unrelated animals led to questions of why certain structures should be so similar Example: _________________________ in snakes and ______________________ in humans Questions about Fossils Studies of ____________________ beds revealed that deposits had been laid down slowly, one above the other Fossils: The arrangement of the layers suggested that different ________________________ had lived at different ________________________ De Buffon’s explanation: New Evidence into Old Beliefs Georges Cuvier believed in an ________________________ of all species Cuvier suggested that the abrupt changes in the fossil record in different rock strata reflected the concept of ______________________________ After each catastrophe, ______________________________. The __________________________ were not new species, it was just that their ancestors’ fossils had not been found Lamarck Theory of acquired characteristics is Example: ___________________________________ could not uphold his thoughts on acquired traits Larmarck’s and Darwin &Wallace’s View _________________________________is the father of evolution Voyage on the Beagle Darwin traveled on the _________________________ for five years as ______________________. He collected and studied variety of _____________________________ While on the trip he read Lyell’s book ______________________, which proposed the theory of uniformity – Thus, the earth was________________________ of years old and not thousands of years – evidence of Evolution Darwin’s theory takes form Darwin returned after five years at sea and began pondering the “species problem” what could explain the remarkable diversity among organisms? In Argentina, Darwin had observed extinct _________________________that bore suspicious resemblance to living armadillos; Darwin wondered if the present species had evolved from the extinct one? Variations in Traits _________________________ had suggested that as a population outgrows its resources, its members must compete for what is available. Darwin felt that if some normally variant members of a population bore ____________________ that increased their survival, then ________________ would select those same individuals to ______________________________, and possibly change future populations traits. On the _______________________, the dozen or so species of finches all varied from one another to some extent but resembled the mainland _________________________ to some degree also; perhaps they had descended from _______________________ Darwin’s Finches 1) Finches on the ____________________ resembled a mainland finch but there were more types. 2) Galápagos finch species varied by________________________________ 3) One unusual finch used a twig or thorn to pry out insects, a job normally done by (missing) woodpeckers (Darwin never witnessed this finch behavior). 4) The variation in finches posed questions to Darwin: did they ___________________________ from one mainland ancestor or did islands allow isolated populations to evolve independently, and could present-day species have resulted from changes occurring in each isolated population? Example of Darwin’s Finches Darwin reasoned that a population is evolving when it __________________________ are changing through successive generations. 1858, Darwin received a paper from ______________________, who had developed much the same theory on natural selection but independently of Darwin Darwin and Wallace presented a joint paper but ____________________ published (alone) his ideas in book form in 1859 Individuals don’t evolve –Populations do ___________________________ evolve, not individuals A population is A population exhibits variation among the individual members, but they also hold certain __________________________________________ traits in common. The Gene Pool Individuals of the same __________________ generally have the same number and kinds of __________________ All of the genes in the entire population constitute the _______________________ Each gene exists in two or more slightly different molecular forms called __________________, which offspring inherit and express as___________________________ Each particular mix of alleles depend on these five factors: o o o o o __________________________ create new alleles ________________________ and _____________________ are normal results of meiosis _____________________________ of chromosomes occur in meiosis ___________________________between genetically varied gametes produces “new” combinations of genes Abnormal changes in ____________________________ or number can occur. Stability and Change in Allele Frequencies ______________________________ are a measure of the abundance of each kind of allele in the entire in the entire population Evolution can be detected by a change in allele frequencies from the genetic equilibrium as established by the _______________________________ Hardy Weinberg have five conditions for a Stable population Because of these five conditions are rarely fulfilled in natural populations, any derivation from the reference point established by the “________________________” will indicate _______________________ Microevolution: Mutation Revisited Mutations Mutations are random and the ___________________________ outcome may be neutral, beneficial, harmful, or even lethal to the individual depending on other interactions Mutations are the only source of new_________________ – the genetic foundation for biological diversity Three Types of Mutations Lethal Mutations: Neutral Mutations: Beneficial Mutations: Read Section 17.5 on your own about the Hardy-Weinberg Natural Selection Revisited _______________________________ probably accounts for more changes in allele frequencies than any other microevolutionary process Major Points to Natural Selection Observation: All _____________________have the ___________________________ to increase in numbers over generation Observation: No population is able to _____________________, for its individuals will run out of _______________________________________ Inference: Because more individuals are produced than can survive to ____________________________, the members of a population must compete for the available _____________________ Observation: All the individuals have the same genes, which represent a ______________________ of heritable information Observation: Most genes occur in different molecular forms (__________________), which give rise to differences in _____________________________details Inferences: Because adaptive traits promote ______________________, they must increase frequency over the generation and less adaptive traits must decrease in frequency or disappear Conclusions: Natural Selection: Adaptation Adaptation: Organisms that are adapted to their environment will have the ability to ____________________. ___________________________occurs when an organisms is not adapted to their environment and will not be able to reproduce Organisms have Variations Variations that make adaptation possible are those that are passed on from _____________________ to ________________________. Darwin could not state the cause of variations because___________________ was not yet established. Organisms struggle for existence ________________________proposed that human populations outgrow food supply and death and famine were inevitable. Darwin applied this to ______________________; resources were not sufficient for all members to survive. Therefore, there is a constant struggle for existence; only certain members ________________________________. Organisms Differ in Fitness 1. Organisms whose traits enable them to _______________________ to a greater degree have a greater_____________________. 2. Darwin noted that humans carry out _________________________. a. Early humans likely selected wolf variants; produced the varieties of domestic dogs. b. Many crop plant varieties can be traced to a _______________________________. d. Evolution by artificial or natural selection occurs when more __________ organisms reproduce and leave more _____________________ On the Origin of Species Darwin’s publish book: It waited 20 years to publish his book He used this time to complete experiments to prove his _________________________ What is Directional Selection? ___________________________in a consistent direction Shifts may be in response to environmental pressures or occur as a new mutation appears and proved adaptive Examples: Stablizing Selection Favors the most ________________________ in the population It counters the effects of _________________________________________ Disruptive Selection Favors forms at the _______________________________________________ of variation and selects against the intermediate forms Sexual Selection Most species have distinctively male and female phenotypes – _____________________________________ Sexual selection Usually it is the _______________________ that are the agents of selection when they pick their mates Maintaining two or more alleles A________________________________ on the stabilizing theme in which two or more forms of a trait are maintained in fairly stable proportions depending on survival value in the environment Population is in ____________________ when nonidentical alleles for a trait are being maintained at frequencies __________________________ Sickle Cell Anemia Humans that are ________________________for sickle-cell anemia develop the disease and die at early age BUT Individuals with alleles for both normal hemoglobin and sickle-cell hemoglobin (Heterozygous) have the greatest chances of surviving ________________________ Gene Flow Genes move with individuals when they move out of (________________________), or into (___________________________), a population The physical flow (a result of ____________________________________) tends to minimize genetic variation between population Genetic Drift Is the random fluctuation in _____________________________over time, due to chance occurrences alone Affects: _______________________________ Bottleneck and Founder Effects Bottleneck: Founder Effect: Genetic Drift