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Download biology Ch. 13 Notes Part b Evolution
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biology Ch. 13 Notes Part b Evolution 13.6 Explain how evolutionary trees are constructed and used to represent ancestral relationships. ✍ Darwin was the first to view the history of life as a tree, with multiple branchings from a common ancestral trunk to the descendant species at the tips of the twigs. ✍ Fig. 13.6 Evolutionary Tree http://163.16.28.248/bio/activelearner/17/ch17summary.html ✍ Homologous structures, both anatomical and molecular, can be used to determine the branching sequence of such a tree. ✍ Genetic Code: (A, T, C, G) is a homology shared by all species because they date to the deep ancestral past. ✍ Characteristics that evolved more __________ are shared only within smaller groups of organisms. (Tetrapods all share basic _____ ______ __________ but their ancestors do not. THE EVOLUTION OF POPULATIONS 13.7 Define the gene pool, a population, and microevolution. Gene Pool: The total collection of ___________________at any one time. Used to study evolution at the population level. Population: A group of individuals of _____________species living in the same _________at the same _________. Microevolution: Evolution on its _________scale, occurring in the gene pool of a population. When the relative frequencies of ________in a population change over a number of _______. 13.8 Explain how mutation and sexual recombination produce genetic variation. Mutation: A chance event, not a mechanism (controlled by genes.) New alleles originate by a change (mutation) in the ______________ sequence of DNA. ✍ Ultimate source of genetic variation ✍ Most mutations occur in ______ _______ and are not passed on. ✍ Only mutations in ____________ are passed on. ✍ C________________ mutations: ✍ that delete, disrupt or rearrange many gene loci are usually harmful. ✍ Duplication of part of a chromosome is an important source of genetic variation. o Extra genes that can be mutated. o Olfactory receptor genes in mammals allows for greater range of scent detection. o Mice = 1,300 receptors o Humans = 1,000 receptors Sexual Recombination Fresh assortments of existing alleles: ✍ C______________ during Prophase I. ✍ I____________________________________ Metaphase I of meiosis ✍ S____________________________ ✍ R Mrs. Loyd þ [email protected] Page 1 of 5 4/11/16 http://loydbiology.weebly.com Review Questions: 1. What is the ultimate source of genetic variation? 2. What is the source of most genetic variation in a population that reproduces sexually? Mrs. Loyd þ [email protected] Page 2 of 5 4/11/16 http://loydbiology.weebly.com 1. mutation 2. Unique combinations of alleles resulting from sexual reproduction. 13.8 Explain why prokaryotes can evolve more quickly than eukaryotes. ✍ Prokaryotic mutations can multiply rapidly due to ______ ___________ rate. Bacteria are _____loid, one gene per character, a new allele can have ___________________ effect. ✍ Mutation Rate: o Animals and plants average 1/100,000 genes per generation. o Considered a low mutation rate. o Long time spans between generations, o ___ploid genomes prevent most mutations from significantly affecting genetic variation in plants and animals from generation to generation. MECHANISMS OF MICROEVOLUTION 13.11 Define genetic drift and gene flow. Explain how the bottleneck effect and the founder effect influence microevolution. Genetic _________: A change in the gene pool of a population due to chance. ✍ The __________ the population, the greater the effect. ✍ Alleles may be ________ to the population due to chance ✍ This __________ variation by such losses. ✍ Examples are: o B___________ Effect o F___________ Effect ________________ Effect: ✍ Catastrophe may kill indiscriminately and leave few survivors. ✍ Reduced gene pool variation affects population ✍ Less variation reduces population’s fitness ________________ Effect: ✍ When a few individuals colonize as isolated island or other new habitat. ✍ The smaller the group, the less likely the genetic makeup will represent larger population they left. ✍ Genetic difference between large pop. and founder pop. is founder effect. Gene ______: ✍ Allele frequencies can change as a result of ______ individuals move _____________________a population. ✍ Gene flow reduces _________________ between populations. ✍ Compare to similarities in a closed society like the Amish. 13.11 Explain how genetic bottlenecks threaten the survival of certain species. ✍ Ice age: Human population estimates 600 breeding individuals at one time in S. Africa. Genetic variation between individual humans about 30% less than between individual chimpanzees. ✍ Florida panther ✍ African cheetah ✍ Illinois greater _____________________reduced by agriculture and th development from millions in 19 C. to 50 individuals in 1993. Flocks from neighboring states added into Illinois flock. Regained hatching success from 50% to 90% due to added alleles. Mrs. Loyd þ [email protected] Page 3 of 5 FOUNDER EFFECT example • 1814, 15 people founded British colony, Tristan da Cunha on island in Atlantic. • One of the 15 was a het for retinitis pigmentosa. • In 1960, of the 240 decendants, 4 had RP, 9 were hets. • Frequency 10x higher than parent population. 4/11/16 http://loydbiology.weebly.com 13.12 Explain why natural selection is the only mechanism that leads to adaptive evolution. Chance Events: ✍ G____________ (__________+____________) ✍ G________________ ✍ M________________ Chance + sorting: ___________ ____________ • chance: random collection of genetic variation • sorting: some alleles are favored over others. • sorting makes in adaptive • improves the match between organisms and their environment. • environments change • “fitness” is a moving target • adaptive evolution dynamic process 13.13 Distinguish between and describe an example of: stabilizing selection: ✍ ________ common type ✍ favors _____________ phenotypes ✍ ___________ environment ✍ conditions _________ phenotypic variation ✍ example: human infant weight averages 6.5-9 pounds, extremes have higher infant mortality. directional selection: ✍ shifts the overall makeup of the popul. by selecting against individuals at one of the phenotypic ___________. ✍ example: insects exposed to __________ disruptive selection: ✍ environmental conditions are varied and favors individuals at ______________. ✍ leads to________________________ _________ phenotypes. 13.14 Define and compare intrasexual selection and intersexual selection. Intrasexual selection or within the sex usually between males ✍ “Winner takes _____” ✍ _____ wins territorial rights to a group of ___________. ✍ Usually ____________or ritualized ✍ Example: lions, elk, mountain sheep Intersexual selection or mate choice ✍ between ______ and ____________ ✍ __________ choose ______ ✍ Males display adornments o plumage o courtship dance o song o “Choose Me!” o studies show it relates to overall male health Mrs. Loyd þ [email protected] Page 4 of 5 4/11/16 http://loydbiology.weebly.com 13.15 Explain how antibiotic resistance has evolved. Discovery Channel video clip http://wps.aw.com/bc_campbell_concepts_6/83/21320/545806 3.cw/index.html 13.16 Explain how genetic variation is maintained in populations. ___ploidy: having two sets of chromosomes ✍ helps to prevent populations from becoming genetically uniform. ✍ Recessive alleles hide from selection forces as Hets ✍ Maintains presence of recessive alleles in gene pool _________ Selection: When natural selection maintains stable frequencies of two or more phenotypic forms in a popul. ✍ ________zygote advantage: o homozygotes are selected against o NN = susceptible to malaria/ nn = susceptible to sickle-cell ✍ ________-dependant selection: most common phenotype selected against o scale-eating fish in Lake Tanganika, Africa o attack other fish from behind to steal scales o right-mouthed/left-mouthed o easier to defend against most common attacker o those numbers go down from lack of food o less common #’s go up from greater food 13.16 Explain what is meant by neutral variation. ✍ Mutations that have no effect, + or -, on the individual ✍ Mutation occurs in __________ region of DNA ✍ Occurs but doesn’t change ___________ significantly 13.17 Give four reasons why natural selection cannot produce perfection. 1. Selection can act only on ____________ ____________. a. can use only phenotypes available b. may not be ideal trait for environment c. advantageous alleles do not arise on demand d. extinction happens 2. Evolution is limited by _____________ constraints. a. co-opts existing structures and adapts them to new situations b. Example: environmental changes favor flight; wings would be best but nature must use the parts available. Bats and birds did not evolve a new set of appendages, they changed what they already had. 3. Adaptations are often _______________ a. Each organism must do many different tasks but.. b. …adaptations may be better suited for some tasks than others c. Example: blue-footed booby uses webbed feet to swim after prey well, but they are clumsy on land. 4. Chance, natural selection, and the environment ____________. a. Chance plays a bigger role than once thought. b. Example: a storm blows insects out to sea. A few land on an island, many perish. The few that survived may not be the individuals that would be best adapted to the new environment. Question: Humans owe much of their physical versatility and athleticism to their flexible limbs and joints. But we are prone to sprains, torn ligaments, and dislocations. a. Which one of the four reasons given for why natural selection cannot produce perfect organisms best explains this? b. Explain how your chosen reason applies specifically to humans. Mrs. Loyd þ [email protected] Page 5 of 5 4/11/16 http://loydbiology.weebly.com