Unit 7 Natural Selection Lecture Notes

Unit 7: Natural Selection Topic 7.1 Introduction to Natural Selection 7.2 Natural Selection 7.3 Artificial Selection 7.4 Population Genetics 7.5 Hardy-Weinberg Equilibrium 7.6 Evidence of Evolution 7.7 Common Ancestry 7.8 Continuing Evolution 7.9 Phylogeny 7.10 Speciation 7.11 Extinction 7.12 Variations in Populations 7.13 Origin of Life on Earth Learning Objective(s) EVO-1.C Describe the causes of natural selection. EVO-1.D Explain how natural selection affects populations. EVO-1.E Describe the importance of phenotypic variation in a population. EVO-1.F Explain how humans can affect diversity within a population. EVO-1.G Explain the relationship between changes in the environment and evolutionary changes in the population. EVO-1.H Explain how random occurrences affect the genetic makeup of a population. EVO-1.I Describe the role of random processes in the evolution of specific populations. EVO-1.J Describe the change in the genetic makeup of a population over time. EVO-1.K Describe the conditions under which allele and genotype frequencies will change in populations. EVO-1.L Explain the impacts on the population if any of the conditions of HardyWeinberg are not met. EVO-1.M Describe the types of data that provide evidence for evolution. EVO-1.N Explain how morphological, biochemical, and geological data provide evidence that organisms have changed over time. EVO-2.B Describe the fundamental molecular and cellular features shared across all domains of life, which provide evidence of common ancestry. EVO-2.C Describe structural and functional evidence on cellular and molecular levels that provides evidence for the common ancestry of all eukaryotes. EVO-3.A Explain how evolution is an ongoing process in all living organisms. EVO-3.B Describe the types of evidence that can be used to infer an evolutionary relationship. EVO-3.C Explain how a phylogenetic tree and/or cladogram can be used to infer evolutionary relatedness. EVO-3.D Describe the conditions under which new species may arise. EVO-3.E Describe the rate of evolution and speciation under different ecological conditions. EVO-3.F Explain the processes and mechanisms that drive speciation. EVO-3.G Describe factors that lead to the extinction of a population. EVO-3.H Explain how the risk of extinction is affected by changes in the environment. EVO-3.I Explain species diversity in an ecosystem as a function of speciation and extinction rates. EVO-3.J Explain how extinction can make new environments available for adaptive radiation. SYI-3.D Explain how the genetic diversity of a species or population affects its ability to withstand environmental pressures. SYI-3.E Describe the scientific evidence that provides support for models of the origin of life on Earth. Free Response Practice 2022 #4 Existing isolated brook trout populations in Newfoundland, Canada, were once part of a larger population that was fragmented at the end of the most recent glaciation period about 10,000 to 12,000 years ago. Researchers investigated 14 naturally separated stream populations of brook trout. They found that the populations are all genetically distinct and show differences in morphology. (a) Describe the prezygotic barrier that results in these genetically distinct populations. (b) Brook trout with longer fins are able to swim faster than brook trout with shorter fins. In one of the Newfoundland streams, the main prey of the brook trout evolved to move faster. For brook trout living in this stream, explain the difference in fitness between longer-finned individuals and shorter-finned individuals. (c) If two morphologically and behaviorally distinct populations of brook trout remain isolated for many generations, predict the likely impact on both populations. (d) Researchers claim that there are more genetic differences between any two current brook trout populations than there are between any single current population and the ancestral brook trout population from which all the trout are descended. Provide reasoning to justify their claim. 2021 #4 In 1981 a single immature male Geospiza conirostris finch flew more than 100 kilometers from the Galapagos island of Espanola to the Galapagos island of Daphne Major, where no G. conirostris finches were living. The immigrant finch bred with a female G. fortis, a species of finch common on Daphne Major. The F1 finches and later generations interbred only within their lineage. By 2012 scientists counted 23 individuals, including eight breeding pairs, within this hybrid lineage on Daphne Major. The hybrid lineage became known as Big Bird. Bird with different beak shapes and sizes eat different types of food. The dimensions of the Big Bird beaks relative to the beaks of the major competitor finch species on Daphne Major are shown in Figure 1. (a) The Big Bird lineage became reproductively isolated from G. fortis. Describe one prezygotic mechanism that likely contributed to the reproductive isolation of the Big Bird lineage from G. fortis. (b) Based on the data in Figure 1, explain why the Big Bird population has been able to survive and reproduce on Daphne Major. (c) A virus infects and kills all G. magnirostris on Daphne Major but does not affect the other finch species. Assuming food type and availability stay the same, predict the most likely change in the beak phenotype of the Big Bird population after six more generations. (d) Provide reasoning to justify your prediction in part (c). 2019 #5 A researcher studying the evolutionary relationship among five primate species obtained data from a sequence of mitochondrial DNA (mtDNA) from a representative individual of each species. The researcher then calculated the percent divergence in the sequences between each pair of primate species (Table 1). (a) Based on fossil data, the researcher estimates that humans and their most closely related species in the data set diverged approximately seven million years ago. Using these data, calculate the rate of mtDNA percent divergence per million years between humans and their most closely related species in the data set. Round your answer to two decimal places. (b) Using the data in the table, construct a cladogram on the template provided. Provide reasoning for the placement of gibbons as the outgroup on the cladogram. (c) On the cladogram, draw a circle around all of the species that are descended from the species indicated by the node within the square. 2018 #1 Polar bears are highly adapted for life in cold climates around the North Pole. Brown bears, black bears, and pandas are found in warmer environments. Researchers collected complete mitochondrial DNA sequences from several populations of bears and constructed a phylogenetic tree to represent their evolutionary relatedness (Figure 1). A researcher studying adaptations in bears sequenced the nuclear gene encoding a lysosomal trafficking protein (LYST) in polar bears, brown bears, and panda bears. There are seven inferred amino acid substitutions that are found only in polar bears. Mutations that cause similar substitutions in the human LYST protein are associated with Chediak-Higashi syndrome, an autosomal recessive condition in which pigment is absent from the hair and eyes. The researcher used the inferred amino acid sequences to build the distance matrix shown in Table 1. (a) Use the phylogenetic tree in Figure 1 to estimate the age in hundreds of thousands of years of the most recent common ancestor of all brown bears. Identify the population of brown bears to which polar bears are most closely related based on the mitochondrial DNA sequence comparison. Identify two populations whose positions could be switched without affecting the relationships illustrated in the cladogram. (b) Construct a cladogram on the template to represent a model of the evolutionary relatedness among the bear species based on the differences in LYST protein sequences (Table 1). Circle the position on the cladogram that represents the out-group. (c) A student claims that mitochondrial DNA sequence comparisons provide a more accurate phylogeny of bear species than do LYST protein sequence comparisons. Provide ONE piece of reasoning to support the student’s claim. (d) A researcher genetically engineers a mouse strain by deleting the mouse lyst gene and replacing it with the polar bear lyst gene. Predict the most likely difference in phenotype of the transgenic mouse strain compared to the wild-type mouse strain. Justify your prediction. (e) Describe how the mutation in the lyst gene became common in the polar bear population. If the lyst gene were the only determinant of the fur color, predict the percent of white offspring produced by a mating between a polar bear and a brown bear. 2016 #1 Leucine aminopeptidase (LAPs) are found in all living organisms and have been associated with the response of the marine mussel, Mytilus edulis, to changes in salinity. LAPs are enzymes that remove N-terminal amino acids from proteins and release the free amino acids into the cytosol. To investigate the evolution of LAPs in wild populations of M. edulis, researchers sampled adult mussels from several different locations along a part of the northeast coast of the United States, as shown in Figure 1. The researchers then determined the percent of individuals possessing a particular lap allele, lap94, in mussels from each sample site (table 1). (a) On the axes provided, construct an appropriately labeled bar graph to illustrate the observed frequencies of the lap94 allele in the study population. (b) Based on the data, describe the most likely effect of salinity on the frequency of the lap94 allele in the marine mussel population in Long Island Sound. Predict the likely lap94 allele frequency at a sampling site between site 1 and site 2 in Long Island Sound. (c) Describe the most likely effect of LAP94 activity on the osmolarity of the cytosol. Describe the function of LAP94 in maintaining water balance in mussels living in the Atlantic Ocean. (d) Marine mussel larvae are evenly dispersed throughout the study area by water movement. As larvae mature, they attach to the rocks in the water. Explain the differences in lap94 allele frequency among adult mussel populations at the sample sites despite the dispersal of larvae throughout the entire study area. Predict the likely effect of distribution of mussels in Long Island Sound if the lap94 allele was found in all the mussels in the population. Justify your prediction. 2015 #2 Cellular respiration includes the metabolic pathways of glycolysis, the Krebs cycle, and the electron transport chain, as represented in the figures. In cellular respiration, carbohydrates and other metabolites are oxidized, and the resulting energy-transfer reactions support the synthesis of ATP. (a) Using the information above, describe ONE contribution of each of the following in ATP synthesis. • Catabolism of glucose in glycolysis and pyruvate oxidation • Oxidation of intermediates in the Krebs cycle • Formation of a proton gradient by the electron transport chain (b) Use each of the following observations to justify the claim that glycolysis first occurred in a common ancestor of all living organisms. • Nearly all existing organisms perform glycolysis. • Glycolysis occurs under anaerobic conditions. • Glycolysis occurs only in the cytosol. (c) A researcher estimates that, in a certain organism, the complete metabolism of glucose produces 30 molecules of ATP for each molecule of glucose. The energy released from the total oxidation of glucose under standard conditions is 686 kcal/mol. The energy released from the hydrolysis of ATP to ADP and inorganic phosphate under standard conditions is 7.3 kcal/mol. Calculate the amount of energy available from the hydrolysis of 30 moles of ATP. Calculate the efficiency of total ATP production from 1 mole of glucose in the organism. Describe what happens to the excess energy that is released from the metabolism of glucose. (d) The enzymes of the Krebs cycle function in the cytosol of bacteria, but among eukaryotes the enzymes function mostly in the mitochondria. Pose a scientific question that connects the subcellular location of the enzymes in the Krebs cycle to the evolution of eukaryotes. 2015 #3 The amino acid sequence of cytochrome c was determined for five different species of vertebrates. The table below shows the number of differences in the sequences between each pair of species. THE NUMBER OF AMINO ACID DIFFERENCES IN CYTOCHROME c AMONG FIVE SPECIES E. ferus D. polylepis G. gallus A. forsteri E. africanus E. ferus D. polylepis G. gallus A. forsteri 0 21 0 11 18 0 13 17 3 0 E. africanus 1 20 10 12 0 (a) Using the data in the table, create a phylogenetic tree on the template provided to reflect the evolutionary relationships of the organisms. Provide reasoning for the placement on the tree of the species that is least related to the others. (b) Identify whether morphological data or amino acid sequence data are more likely to accurately represent the true evolutionary relationships among the species, and provide reasoning for your answer. 2014 #2 Mammalian milk contains antibodies that are produced by the mother’s immune system and passed to offspring during feeding. Mammalian milk also contains a sugar (lactose) and may contain proteins (protein A, protein B, and casein), as indicated in the table. MILK COMPONENTS IN DIFFERENT MAMMALS Character Cat Cow Horse Human Pig Lactose + + + + + Protein A + + + + + Protein B ? + + ? + Casein ? + + ? + ? indicates the absence of the character + indicates the presence of the character (a) Using the data in the table, construct a cladogram on the template provided to indicate the most likely evolutionary relationships among the different mammals. Indicate on the cladogram where each of the characters most likely arose in the evolutionary process, and justify the placement of the characters on the cladogram. *Note: part b & c are out of scope* (b) Describe FOUR steps in the activation of the mother’s specific immune response following exposure to a bacterial pathogen. Predict how the mother’s immune response would differ upon a second exposure to the same bacterial pathogen a year later. (c) Predict the most likely consequence for a nursing infant who is exposed to an intestinal bacterial pathogen (e.g. Salmonella) to which the mother was expose three months earlier. Justify your prediction. 2014 #8 A research team has genetically engineered a strain of fruit flies to eliminate errors during DNA replication. The team claims that this will eliminate genetic variation in the engineered flies. A second research team claims that eliminating errors during DNA replication will not entirely eliminate genetic variation in the engineered flies. (a) Provide ONE piece of evidence that would indicate new genetic variation has occurred in the engineered flies. (b) Describe ONE mechanism that could lead to genetic variation in the engineered strain of flies. (c) Describe how genetic variation in a population contributes to the process of evolution in the population. 2013 #3 Fossils of lobe-finned fishes, which are ancestors of amphibians, are found in rocks that are at least 380 million years old. Fossils of the oldest amphibian-like vertebrate animals with true legs and lungs are found in rocks that are approximately 363 million years old. Three samples of rocks are available that might contain fossils of a transitional species between lobe-finned fishes and amphibians: one rock sample that is 350 million years old, one that is 370 million years old, and one that is 390 million years old. (a) Select the most appropriate sample of rocks in which to search for a transitional species between lobe-finned fishes and amphibians. Justify your selection. (b) Describe TWO pieces of evidence provided by fossils of a transitional species that would support a hypothesis that amphibians evolved from lobe-finned fishes. Free Response Scoring Guidelines 2022 #4 Part (a) Scoring Guidelines Topic 7.10 (b) 7.2 (c) 7.10 (d) 7.10 2021 #4 Part (a) (b) Scoring Guidelines Topic 7.10 7.1 (c) 7.1 7.11 (d) 7.1 2019 #5 Part (a) Scoring Guidelines Topic 7.6 (b) 7.9 (c) 7.9 2018 #1 Part (a) Scoring Guidelines Topic 7.9 (b) 7.9 (c) 6.7 (d) 6.7 (e) 5.3 7.1 2016 #1 Part (a) Scoring Guidelines Topic 7.12 (b) 7.12 (c) 2.8 (d) 7.12 2015 #2 Part Scoring Guidelines Topic (a) 3.6 (b) 3.6 (c) 3.6 (d) 7.6 2015 #3 Part (a) Scoring Guidelines Topic 7.9 (b) 7.9 2014 #2 Part (a) (b) Scoring Guidelines Topic 7.9 N/A (c) N/A 2014 #8 Part (a) Scoring Guidelines Topic 5.2 6.7 6.8 (b) 5.2 6.7 (c) 7.1 7.6 2013 #3 Part (a) (b) Scoring Guidelines Topic 7.6 7.6