Biology 101 - Ch. 12 - Mechanisms of Evolution
While living on the beach for the summer, a college student decides to make several personal changes. First, she goes to the tanning salon to get a good tan. She then visits a tattoo parlor to get a cute tattoo on her wrist. She also frequents a gym, toning her muscles. Lastly, she gets a perm, turning her hair curly. How many changes in allele frequency occurred in the student during this summer of change?
0 Allele frequencies do not change in an individual during its lifetime. pg. 214
Individuals evolve over their lifetime. T/F?
FALSE Alleles can mutate within an individual. pg. 214
Hurricane Irma devastated many islands in the Caribbean in 2017. To escape, many birds tried to fly out and around the unusually large hurricane (400 miles wide at its peak). Which example provides a description of directional selection as a result of the hurricane? Choose one: A. A flock of American flamingos (Phoenicopterus ruber) evacuated to another island ahead of the hurricane, and then returned to their home on the island of Inagua with even mortality rates among size classes. B. The snowy plovers (Charadrius nivosus), a shorebird that is fairly widespread and easily moves from beach to beach, experienced high mortality rates on islands most affected by the hurricanes. C. A flock of Puerto Rican parrots (Amazona vittata), a smaller bird that is listed as "critically endangered," is very sensitive to habitat disturbance. After the hurricane, the few remaining birds congregated in a single forested area; only the very largest birds were able to fly around a hurricane of that size. D. The magnificent frigatebirds (Fregata magnificens), which can fly for weeks on wind currents and are widespread throughout tropical and subtropical waters, were largely unaffected by Hurricane Irma.
(Hint: Directional selection occurs when individuals at one extreme of an inherited phenotypic trait have an advantage over other individuals in a population.) C. A flock of Puerto Rican parrots (Amazona vittata), a smaller bird that is listed as "critically endangered," is very sensitive to habitat disturbance. After the hurricane, the few remaining birds congregated in a single forested area; only the very largest birds were able to fly around a hurricane of that size. Explanation: Although birds that live in the tropics are accustomed to storms, the severity of hurricanes appears to be increasing due to the increased temperature of tropical waters where these storms form. For species that have a widespread distribution and/or ability to physically fly great distances, the impact from a large, powerful hurricane is not selective. For a species like the Puerto Rican parrot, which is already critically endangered, only the largest birds would have any chance of flying around the hurricane and surviving. This means that the survivors would be the larger birds who would be the parents to the next generation, passing on more of those large bird genes. I had thought D. Magnificent frigatebirds are a widespread species throughout the tropics. Given their ability to fly long distances for days, they would have been able to fly around the storm without impacting their population. Directional selection favors one extreme or the other of a phenotypic characteristic. Which scenario describes this? pg. 221
Which of the following mechanisms generates new alleles? Genetic bottleneck Mutation Gene flow Natural selection
CORRECT Mutation Random changes in DNA sequences can lead to new alleles. Mutation is likely the only means by which new alleles are generated. INCORRECT Natural selection Natural selection operates by changing the relative frequency of pre-existing alleles in the population, most often by eliminating traits—not creating them. Genetic bottleneck A genetic bottleneck reduces the genetic variation in a population. Gene flow Gene flow is only a mechanism by which pre-existing alleles are transferred among populations.
A population can only _______ if there is genetic variation. _______, or random errors in the _______ ________, are the source of this variation. If the population is in an __________ where the mutations provide an advantage, the ______ frequency of the population can change. This is ____________.
evolve Mutations genetic code environment allele evolution pg. 216
What did Darwin and Wallace mean when they concluded that species "descend with modification"? Choose one: A. New species arise as separate acts of creation. B. Individuals in a population become modified throughout their lifetime, giving rise to new species. C. New species arise from previous species. D. New species arise only as a result of hybridization between two related species.
(Hint: "Descent with modification" is one of the basic principles of evolution.) C. New species arise from previous species. Individuals do not evolve, only populations evolve. "Descent with modification" is one of the basic principles of evolution. Explanation: The conclusion by Darwin and Wallace that species "descend with modification" means that new species arise from previous species, inheriting many of the traits of the previous species but modifying some traits. These modified traits are those that define the new species. pg. 214
Which statements describe appropriate strategies for preventing antibiotic resistance? Choose one or more: A.As soon as you feel better, you can stop taking your prescribed antibiotics and save the remainder for your next illness. B.Do not ask for antibiotics when your doctor thinks you do not need them. C.Practice good hand hygiene, and get recommended vaccines. D.Antibiotics can treat a wide variety of infections, so it does not matter which one you take.E.It is acceptable to occasionally skip doses when you take antibiotics.
(Hint: Antibiotic resistance is more likely to evolve when resistant bacteria are allowed to survive and reproduce.) B.Do not ask for antibiotics when your doctor thinks you do not need them. C.Practice good hand hygiene, and get recommended vaccines. Correct. Appropriate strategies for preventing antibiotic resistance include practicing good hand hygiene, getting recommended vaccines, and not asking for antibiotics when your doctor says you do not need them. Explanation: Preventing antibiotic resistance starts with avoiding infections by practicing good hand hygiene and getting recommended vaccines. Antibiotics should only be used as prescribed, which means taking only the specific antibiotic prescribed, taking the full course of the antibiotics, and not skipping doses. Antibiotics should not be used when they are not needed; the constant presence of antibiotics is a selective environment for resistant bacteria, and antibiotics can also have harmful side effects. From a medical point of view, taking antibiotics to prevent infection is usually not necessary unless prescribed by your doctor (sometimes antibiotics are prescribed to women immediately before childbirth to prevent infection, for example). pg. 226
Consider the information that is provided in the image, and determine the type of evolution that gave rise to the similar characteristics in marine animals and the type of evolution that gave rise to the similar characteristics in cacti. Drag the type of evolution to the target. The target is positioned between the shark and the dolphins. Note that you will not use one of the labels at all. A - Convergent evolution B - Evolution by common descent See image.
(Hint: Natural selection can result in convergent evolution. How is convergent evolution different from evolution by common descent?) A - Convergent evolution Correct. Natural selection caused two distantly related animals—sharks (a type of fish) and dolphins (a type of mammal)—to look very similar. The three cacti plants evolved from very distantly related plants via natural selection to adapt to life in the desert. These plants, too, are living evidence of convergent evolution. Explanation: Natural selection caused two distantly related animals—sharks (a type of fish) and dolphins (a type of mammal)—to look very similar. These marine animals evolved along very different tracks; they did not share these features initially, and thus this type of evolution is convergent. These three cacti plants evolved from very distantly related plants via natural selection to adapt to life in the desert. These plants, too, are living evidence of convergent evolution. The type of evolution that is exhibited by these organisms happened because the organisms live in a similar environment, but their genetic relatedness is ancient. These organisms evolved separately from one another toward similar characteristics. pg. 216
New Guinea birds of paradise are famous for the courtship displays they use to attract a mate. These adaptations include brightly colored plumage, elaborate songs, and courtship dances. If these adaptations make it more likely for a male to attract a predator, are they being selected against? Why or why not? Choose one: A. If the male is able to attract more females and successfully reproduce more than other males in the population, then these mating adaptations are not selected against. B. If the male attracts predators, resulting in fewer males in the overall population, the males are automatically selected against. C. If these adaptations result in distinct differences between males and females (sexual dimorphism), then these adaptations are selected against. D. If the male attracts predators, the population as a whole is automatically selected against.
(Hint: New Guinea birds of paradise appear to evolve through sexual selection. In sexual selection, what types of traits are selected for?) A. If the male is able to attract more females and successfully reproduce more than other males in the population, then these mating adaptations are not selected against. Correct. If the male can create more offspring, his mating adaptations are not selected against. The male that can create more offspring is the one whose genetic composition is maintained in the evolving population. In the case of sexual selection, it is all about who creates more offspring, and how long the male parent survives is not important. Explanation: Sexual selection is a special type of natural selection. In sexual selection, a trait that increases an individual's chance of mating is selected for even if it reduces the ability of that individual to survive. In the case of sexual selection, it is all about who creates more offspring, and how long the male parent survives is not important. In this example, even if a male bird of paradise attracts predators and lives a short (but productive!) life, if he reproduces more than other males, his traits are selected for in the population. pg. 223
Which example (A, B, or C) depicts disruptive selection? A B C (See image)
(Hint: The names of the different types of natural selection describe how they affect the allele frequencies of the population.) A (see image) Correct. Example A depicts disruptive selection. Disruptive selection occurs when individuals with either extreme of an inherited trait have an advantage over individuals with an intermediate phenotype. This type of selection is the least commonly observed in nature, but one example of a trait affected by disruptive selection is the beak size within a population of birds called African seed crackers. Explanation: In disruptive selection, individuals with either extreme phenotype have an advantage over individuals with an intermediate phenotype. In example A, birds with either small or large beaks survived, but birds with beaks of intermediate size did not survive. Disruptive selection is the least commonly observed in nature, but one example of a trait affected by disruptive selection is the beak size within a population of birds called African seed crackers. pg. 216
Unfortunately, the volleyball player had to be hospitalized to have her infection treated to avoid any permanent damage to her elbow and to prevent the infection from entering her bloodstream. Once in the bloodstream, the infection could cause sepsis, which is life-threatening inflammation as a reaction to the systemic infection. However, after several days of intravenous antibiotics (a combination of methicillin and vancomycin), she is finally cured and on the road to recovery. Which statement best describes what happened to this population? A. The population evolved as a result of natural selection by the environment the volleyball player accidentally created. Only the somewhat susceptible and full treatment bacteria survived and reproduced in the new conditions, causing her infection to recur. B. The population evolved as a result of artificial selection by the volleyball player. Although she did it unknowingly, by not taking the full course of antibiotics, she directly selected which bacteria would survive and reproduce in the next generation. C. Part of the population was already immune to the antibiotic methicillin, so they were the individuals that survived and reproduced. D. Antibiotic resistance is inevitable; the population changed because of new mutations that provided resistance to the antibiotic methicillin.
(Hint: What was different about the bacteria that survived and reproduced, causing a recurrence of the infection?) A. The population evolved as a result of natural selection by the environment the volleyball player accidentally created. Only the somewhat susceptible and full treatment bacteria survived and reproduced in the new conditions, causing her infection to recur. Correct. Taking only a partial course of treatment resulted in killing off the most susceptible bacteria and leaving bacteria that had some resistance to methicillin. The resistant bacteria were able to start reproducing again, producing a new population with a much different genetic makeup. Explanation: By only taking the antibiotics for 7 days instead of 10, the antibiotics only completely killed the fully susceptible bacteria and probably some of the somewhat susceptible bacteria. This allowed some of the somewhat susceptible bacteria and all of the full treatment bacteria to survive. Once she stopped taking the antibiotics, reproduction resulted in the population re-establishing itself but with a much different genetic makeup than the original infection. pg. 214
The volleyball player was prescribed a 10-day course of methicillin to treat her infection. By day 7, her wound appeared to have healed and was no longer inflamed and warm to the touch, so she stopped taking the methicillin thinking that the infection had been eradicated. While most of the bacteria had been killed, there were some still lingering in the wound site. Once she stopped taking the antibiotic, they started multiplying and within two weeks, the wound was once again inflamed, warm to the touch, and very painful. The population had once again reached 1,000 individuals, with 350 of them the SS type and 650 of them the FT type. There were no bacteria left that were fully susceptible to methicillin. Now what is the percentage of each bacterial type? SS ______? FT ______?
(Hint: Your number for the percentages of both types of bacteria should total 100.) SS 35% FT 65% Correct. For somewhat susceptible bacteria, the solution is (350 SS / 1,000 total bacteria) × 100 = 35% of the population. Correct. For full treatment bacteria, the solution is (650 FT / 1,000 total bacteria) × 100 = 65% of the population. Explanation: For somewhat susceptible bacteria, the solution is (350 SS / 1,000 total bacteria) × 100 = 35%. For full treatment bacteria, the solution is (650 FT / 1,000 total bacteria) × 100 = 65%. The population is now predominately S. aureus that are killed only by a full treatment of the antibiotic methicillin. pg. 214
Which of the following are examples of biological evolution? Choose one or more: A.the extinction of certain song bird species due to the loss of forest habitat B.the loss of pesticide susceptibility in a population of mosquitos after beingsprayed with the same pesticide for 3 years in a row C.the flu virus mutating year to year, producing new strains that requiredifferent vaccines than those administered the year before D.a rose bush mutating and producing an allele that makes it resistant toaphid bug infestation E.the deaths of thousands of bats from white-nose fungus, leaving only thoseimmune to the fungus able to survive and reproduce
A, B, C, & E Correct. These are all examples in which the frequencies of inherited traits in a population change over several generations: the flu virus mutating year to year, producing new strains that require different vaccines than those administered the year before; the loss of pesticide susceptibility in a population of mosquitos after being sprayed with the same pesticide for 3 years in a row; the extinction of certain song bird species due to the loss of forest habitat; and the deaths of thousands of bats from white-nose fungus, leaving only those immune to the fungus able to survive and reproduce. Explanation: Populations evolve, not individuals, and in each case selective forces are selecting the individuals who are more fit for the environment (those that survive and reproduce more than other individuals in the populations). pg. 211
2017 saw two major hurricanes move through the Caribbean, Hurricane Irma and Hurricane Maria, both of which were Category 5 hurricanes. The force of the winds from the hurricanes stripped fruit trees bare of their leaves and fruits. After a major stress event like this, it can take two or more years before the trees produce fruit again. Which population would most likely experience genetic drift as a result of a genetic bottleneck after a hurricane? Choose one: A. Puerto Rican parrot, a critically endangered bird that primarily eats fruits but also eats flowers, seeds, and nectar B. flying foxes, large bats commonly called "fruit bats" that eat fruit and are seen on multiple islands in the Caribbean and the Pacific C. Adelaide's warbler, a small songbird that favors caterpillars as the main staple of its diet D. vervet monkeys, an introduced species from South Africa that tend to favor fermented fruits and have become highly urbanized
A. Puerto Rican parrot, a critically endangered bird that primarily eats fruits but also eats flowers, seeds, and nectar Correct. The Puerto Rican parrot is a critically endangered species that relies not only on fruit but also the flowers that produce the fruit and the seeds in the fruit. With population numbers already low, it is likely this bird will experience a genetic bottleneck without its primary food source. Explanation: Catastrophic events like hurricanes can cause rapid drops in the number of individuals of a population. When a population loses too many individuals, reproduction is reduced and genetic diversity is lost, creating a bottleneck. Even if the numbers recover a few years later when the fruit trees start producing fruit again, the genetic diversity is not yet recovered. For the Puerto Rican parrot, its existence is already tenuous after loss of habitat reduced its numbers to a few hundred. For individuals in the wild, the loss of a primary food source is likely to result in another bottleneck in the population. pg. 223
As we noted for Darwin's finches in the Galapagos Islands, beak depth correlates with seed size in African seed cracker birds. In the graph below, the red bars represent birds who survived a dry season, and the blue bars represent those who died. After examining the graph, what could you say about this population of African seed crackers? Choose one or more: A.The population exhibits disruptive selection. B.The population exhibits stabilizing selection. C.The population exhibits directional selection. D.Birds with beaks ~12 mm in width survived. E.Birds with beaks ~16 mm in width survived. F.Birds with beaks ~14 mm in width survived.
A.The population exhibits disruptive selection. D.Birds with beaks ~12 mm in width survived. E.Birds with beaks ~16 mm in width survived. Correct. Birds with smaller and larger beaks survived, while those with intermediate beaks did not. This population exhibits disruptive selection. Disruptive selection occurs when individuals with either extreme of an inherited trait have an advantage over individuals with an intermediate phenotype. This type of selection is the least commonly observed in nature, but one example of a trait affected by disruptive selection is the beak size within this population of birds called African seed crackers. Explanation: In the graph, red bars represent those birds who survived, and blue bars represent those who died. Thus, birds with beaks ~12 mm and ~16 mm in width survived, while birds with beaks ~14 mm in width did not. Because birds with beak sizes at both extremes survived while those with intermediate beak sizes did not, this is an example of disruptive selection. Disruptive selection occurs when individuals with either extreme of an inherited trait have an advantage over individuals with an intermediate phenotype. This type of selection is the least commonly observed in nature, but one example of a trait affected by disruptive selection is the beak size within this population of birds called African seed crackers.With stabilizing selection, individuals with intermediate values of an inherited phenotypic trait have an advantage over other individuals in the population. With directional selection, individuals at one extreme of an inherited phenotypic trait have an advantage over other individuals in the population. Neither one of these mechanisms of evolution would describe the results of the African seed cracker example. See image. pg. 216
Due to pollution, a pond with a multi-colored bottom becomes a dark muted shade, making colorful fish easier for predators to see. A mutation occurs in the gene for skin color of a gold fish. Which of the following possible colors could arise from this mutation? blue mottled gold dark gray red
ALL ARE CORRECT blue mottled gold dark gray red Mutations are random and any plausible outcome in skin color is equally likely in this scenario. Mutations DO NOT arise to meet environmental challenges and could result in more, less, or unchanged adaptiveness to the new environment. pg. 219
During the 1970s, the number of Florida panthers dramatically declined due to hunting and habitat destruction. This left fewer than 10 individuals living in the wild. This is an example of which of the following? Select all that apply. Choose one or more: A.Horizontal gene transfer B.Genetic bottleneck C.Founder effect D.Genetic drift
B.Genetic bottleneck D.Genetic drift Explanation: This is an example of a cause of genetic drift referred to as a "genetic bottleneck," which occurs when a dramatic drop in population size for at least one generation causes a loss of genetic variation.
Which statement best describes why there would be more purple (MRSA) bacteria in the population after passing through the sieve (antibiotic treatment)? Recognize that the sieve is an analogy for the presence of an antibiotic killing some cells (those collected in the sieve) and not killing others (those that pass through the sieve). A. The yellow bacteria are resistant to antibiotic treatment, leaving them to survive and reproduce. B. The yellow bacteria are repelled by the antibiotic treatment. C. The yellow bacteria represent bacteria that are NOT resistant to antibiotic treatment, leaving the purple bacteria (resistant) to survive and reproduce. D. The yellow bacteria could not pass through the sieve.
C. The yellow bacteria represent bacteria that are NOT resistant to antibiotic treatment, leaving the purple bacteria (resistant) to survive and reproduce. Correct. The yellow bacteria represent bacteria susceptible to antibiotic treatment, whereas the purple bacteria represent resistance to the treatment. Explanation: The antibiotic treatment (the sieve) kills all the nonresistant (in this case, yellow bacteria) leaving mostly purple (resistant) bacteria to survive and reproduce in the next generation. This is a vivid example of natural selection, the propagation of a successful genome in the presence of selective pressure, and survival of the fittest. pg. 211
In the case of the Florida panther, a severe genetic bottleneck has resulted in reproductive difficulty for the panthers, with many males having low sperm count and abnormal sperm. Why don't scientists reintroduce genetic diversity back into the population? Choose one or more: A.Scientists can try to reintroduce genetic diversity, but it will not be successfully established in the population without successful reproduction. Since the panthers have reproductive problems, successful reproduction is difficult. B.Scientists are reintroducing diversity through a comprehensive breeding program. C.When the panthers died off almost to extinction, most panther genetic diversity died with those individuals who carried it in their DNA. Therefore, there is no available genetic diversity to reintroduce. D.The original and ultimate source of diversity is mutation, which cannot be safely recreated by scientists for the Florida panther.
C.When the panthers died off almost to extinction, most panther genetic diversity died with those individuals who carried it in their DNA. Therefore, there is no available genetic diversity to reintroduce. D.The original and ultimate source of diversity is mutation, which cannot be safely recreated by scientists for the Florida panther. Correct. Scientists cannot reintroduce genetic diversity into the Florida panther because most of the diversity has already been lost, and it cannot be safely recreated. The original and ultimate source of diversity is mutation, which cannot be safely recreated by scientists for the Florida panther. Explanation: The Florida panther population was on the brink of extinction by the 1970s, with only six wild individuals left alive. Successful breeding programs have increased the population to 80-100 individuals, but most of the genetic diversity of this population died out with the individuals lost before the 1970s. The original source of diversity is mutation, which cannot be safely recreated by scientists. While the loss of genetic diversity in a species is permanent, eventually natural mutations could create new alleles if the species survives. pg. 223
Watch the animation to learn more about the evolution of vancomycin resistance in some populations of bacteria, and then answer the question. Select all of the correct descriptors of what is happening in this picture. (See image) - exchange of genetic information in bacteria - a genetic bottleneck - horizontal gene transfer - evolution - gene flow
CORRECT - exchange of genetic information in bacteria This picture shows bacteria engaging in horizontal gene transfer, which is a mechanism for exchanging genetic information. - horizontal gene transfer Bacteria exchange genes through a conjugation tube in this process known as horizontal gene transfer. - gene flow Horizontal gene transfer is a type of gene flow by which new genes can be introduced into a population. INCORRECT - evolution In this case, an individual bacterium is changing its genetic material. Evolution requires genetic change to a population. Should this bacterium reproduce and increase the proportion of the new genes in the population, evolution will take place. - a genetic bottleneck A genetic bottleneck occurs when genetic diversity is reduced. Gene flow, like the horizontal gene transfer shown in the picture, often increases diversity. pg. 221
Consider the following scenarios: I. In mosquitoes, whether their bites can be felt by humans is a genetic trait of the mosquito. Over time, humans who feel mosquitoes biting swat and kill so many mosquitoes that most of the remaining mosquitoes possess bites that cannot be felt. II. Orchid collectors search the rainforest for rare orchids. Some orchids have alleles that allow their roots to adhere to trees so strongly that they cannot be removed without killing the plant. The collectors leave these individuals alone and collect the others. After a while, most orchids remaining in the forest display the strong adherence trait. III. A person is given a medication to alleviate back pain. After a few months, the person must increase the dosage because the initial dose no longer has the same effect. IV. Your neighbor treats his yard with an herbicide to control weeds. None of the weeds are killed by the herbicide, but the weeds seem to show resistance to the herbicide after the treatment. Which scenario above is an example of evolution?
CORRECT I. Mosquitoes with alleles for causing a sensation in their human hosts during bites are removed from the population, changing the frequency of alleles. This is evolution. II. Orchids with alleles for weak adherence are removed from the population, changing the frequency of alleles. This is evolution. INCORRECT III. An individual person becoming habituated to a pain medication does not qualify as evolution. IV. Since none of the weeds were killed during the treatment, no alleles were removed from the population. Therefore, no evolution has taken place. For evolution to occur, there must be a change in allele frequency in a population. pg. 214
Two populations of the same species of sea urchin, one with mostly long spines and the other with mostly short spines, are separated by an isthmus. A canal is built through the isthmus that connects the two urchin populations. Which of the following outcomes is likely to result after the new canal? The long-spine population will come to have more short-spine individuals. The spines of the long-spine population will become longer. Long-spine urchin individuals will be less frequent in the short-spine population.
CORRECT The long-spine population will come to have more short-spine individuals. INCORRECT The spines of the long-spine population will become longer. The canal opens up gene flow between the populations, which should make the allele frequencies in the two populations more similar. pg. 221-222
Which of the following are attributes of evolution? - occurs only over millions of years - results in genetic change - occurs only in animals - occurs only in populations
CORRECT - results in genetic change Genetic changes must occur for evolution to happen. - occurs only in populations Evolution can only occur in populations. INCORRECT -occurs only over millions of years Evolution can occur on short or long time scales. - occurs only in animals Evolution occurs in all types of organisms and species. pg. 214
Natural selection can, through common descent, produce closely related species that have similarities due to their shared ancestry. Natural selection can also, through convergent evolution, lead to distantly related species appearing very similar. Identify which examples reflect common descent and which reflect convergence. - Hawaiian honeycreepers, with their elongated, nectar-sipping bills, all evolved from a finch-like ancestor. - Many birds and some kinds of bats that feed on plant nectar all have long flexible tongues. - Tree-dwelling primates have prehensile tails for gripping branches. Tree-dwelling opossums also have prehensile tails. - Marsupial mammals throughout Australia show a wide diversity of forms that reflect the habitats in which they live. - Primates use opposable thumbs to help climb. New World monkeys also have prehensile tails, but Old World monkeys do not.
Convergence - Tree-dwelling primates have prehensile tails for gripping branches. Tree-dwelling opossums also have prehensile tails. (Primates and marsupials do not have a recent evolutionary ancestor. Their prehensile tails are a convergent trait due to tree-dwelling habits.) - Many birds and some kinds of bats that feed on plant nectar all have long flexible tongues. (Two very different species of bird and a species of mammal have converged on a similar adaptation to make use of a similar food source.) Common Descent - Hawaiian honeycreepers, with their elongated, nectar-sipping bills, all evolved from a finch-like ancestor. (In this case, the wide, diverse group of honeycreepers all share an ancestor and share homologous traits expected in common descent.) -Marsupial mammals throughout Australia show a wide diversity of forms that reflect the habitats in which they live. (Marsupial mammals exhibit different adaptations in different habitats, but because they all share an ancestor, they retain evidence (including their reproductive pouch) of common descent.) - Primates use opposable thumbs to help climb. New World monkeys also have prehensile tails, but Old World monkeys do not. (Monkeys that share a common ancestor may have different adaptations in different areas, while other traits reveal their common descent.) pg. 219
Which population would be most likely to survive and evolve with a change in the selective environment? A. A large population with low genetic diversity B. A small population with high genetic diversity C. A small population with low genetic diversity D. A large population with high genetic diversity
D. A large population with high genetic diversity Explanation: Large populations with high genetic diversity are the most likely to survive and evolve because they would be best able to respond to changes in selective pressure, such as a change in the environment. The greater the genetic diversity is, the more likely that individuals in the population have traits that help them to survive and reproduce more than other individuals in a changed environment. pg. 216
Individuals at one extreme of an inherited phenotypic trait have an advantage over other individuals in the population. This is what type?
Directional Directional selection is the most common pattern of natural selection, in which individuals at one extreme of an inherited phenotypic trait have an advantage over other individuals in the population. pg. 216-217
Match the correct definition with the pattern of natural selection. Directional Selection Stabilizing Selection Disruptive Selection ____________________________________ One extreme phenotype has advantage over other phenotypes. Extreme phenotypes have advantage over intermediate phenotypes. Intermediate phenotype has advantage over both extremes.
Directional Selection = One extreme phenotype has advantage over other phenotypes. Stabilizing Selection = Intermediate phenotype has advantage over both extremes. Disruptive Selection = Extreme phenotypes have advantage over intermediate phenotypes. Correct. You identified each pattern of natural selection. Directional selection in which individuals at one extreme of an inherited phenotypic trait have an advantage over other individuals in the population is the most common pattern of natural selection. In cases of stabilizing selection, individuals with intermediate values of an inherited phenotypic trait have an advantage over other individuals in the population. Disruptive selection occurs when individuals with either extreme of an inherited trait have an advantage over individuals with an intermediate phenotype. Any of these patterns of natural selection can cause distantly related organisms to evolve similar structures because they survive and reproduce under similar environmental pressures. Explanation: Directional selection in which individuals at one extreme of an inherited phenotypic trait have an advantage over other individuals in the population is the most common pattern of natural selection. In cases of stabilizing selection, individuals with intermediate values of an inherited phenotypic trait have an advantage over other individuals in the population. Disruptive selection occurs when individuals with either extreme of an inherited trait have an advantage over individuals with an intermediate phenotype. Any of these patterns of natural selection can cause distantly related organisms to evolve similar structures because they survive and reproduce under similar environmental pressures. Gene flow is the exchange of alleles between populations and partially provides the genetic recombination to allow pressure on the population to drive evolution. The names of the different types of natural selection describe how they affect the allele frequencies of the population. pg. 216
Natural selection works to increase genetic variation in a population. T/F?
FALSE Natural selection works by changing the relative frequency of some traits that already exist in the population, often by eliminating traits and reducing variation. pg. 215-216
This graph shows the color intensity of feathers for blue birds in the southern Appalachian Mountains in 1900 versus 2000. These fictional data provide an example of which type of selection? (see image (on back)) Stabilizing Disruptive Directional
Disruptive Disruptive selection occurs when individuals with either extreme of an inherited trait have an advantage over individuals with an intermediate phenotype. See image. pg. 216-217
Individuals with either extreme of an inherited trait have an advantage over individuals with an intermediate phenotype. This is what type?
Disruptive Disruptive selection occurs when individuals with either extreme of an inherited trait have an advantage over individuals with an intermediate phenotype. pg. 216-217
A university volleyball player suffers a serious scrape on her elbow after diving to return a serve. Within a week, the scrape becomes red, inflamed, and hot to the touch. After going to the doctor for treatment, she is diagnosed with a Staphylococcus aureus infection. She is prescribed the antibiotic methicillin to treat the infection. Her bacterial population has the following genetic makeup:1,000 individuals total:900 are fully susceptible (FS) to methicillin, meaning they die early in the course of treatment.90 are somewhat susceptible (SS) to methicillin, meaning they have some resistance to methilicillin.10 are killed only by a full treatment with methicillin (FT), meaning they have the greatest degree of resistance. What is the percentage of each type of S. aureus? 900% FS, 90% SS, 10% FT0.99% FS, 0.09% SS, 0.01% FT90% FS, 9% SS, 1% FT90% FS, 10% SS, 1% FT
FT90% FS, 9% SS, 1% (Hint: Your number for the percentages of all three types should add up to 100.) Correct. As much as 90 percent of the bacteria in the volleyball player's infection are fully susceptible to methicillin, while 9 percent are somewhat susceptible, and 1 percent will be killed only with a full course of methicillin. Explanation: For fully susceptible (FS) bacteria, the solution is (900 FS / 1,000 total bacteria) ×× 100 = 90%. For somewhat susceptible (SS), the solution is (90 SS / 1,000 total bacteria) ×× 100 = 9%. For full treatment (FT) bacteria, the solution is (10 FT / 1,000 total bacteria) ×× 100 = 1%. This population of S. aureus is predominately fully susceptible bacteria. pg. 214
A population of birds displays different colors, each of which is associated with its own trait. Blue birds usually fly the fastest. Red birds usually sing the most types of songs. Green birds usually have the most offspring. Black birds usually have the best vision. Which color bird is most likely to be increasing in frequency in the population? Black birds Blue birds Red birds Green birds
Green birds The types of birds that produce the most offspring are the ones that are most likely to be increasing in frequency. pg. 216
The animation depicts material being transferred between the Enterococcus cell and the Staphylococcus cell. What is specifically being transferred that makes this different from usual gene transfer among bacteria? Choose one: A. a single non-mutated strand of Enterococcus plasmid to Staphylococcus B. a single strand of Enterococcus plasmid with vancomycin-resistance gene to Staphylococcus C. various Enterococcus plasmids to Staphylococcus D. a single strand of Staphylococcus plasmid with vancomycin-resistance gene to Enterococcus In the animation, the narrator describes a specific set of conditions that would be conducive to horizontal gene transfer—an infected wound where multiple species of bacteria come into physical contact with one another. Which of these scenarios describes a set of conditions that would also be conducive for a bacterium to become antibiotic resistant through horizontal gene transfer? Choose one: A. the infected wound of a cow living in a high-density feeding operation in close proximity to other cattle on a feedlot B. a basketball player with an open wound not being treated with antibiotics C. an elderly patient with a compromised immune system living in a nursing home D. a chef with a deep cut on her finger working in a large restaurant
PART 1 B. a single strand of Enterococcus plasmid with vancomycin-resistance gene to Staphylococcus Explanation: As organisms that do not sexually reproduce (and therefore recombine genes), bacteria are very effective in sharing genes. In sexually reproducing populations, new alleles are shared through recombination, but bacteria not only accomplish this without sexual reproduction, they also easily share alleles between different species through horizontal gene transfer. Additionally, because bacteria have small genomes, a new allele can have a substantial impact on their ability to survive in any given environment. PART 2 A. the infected wound of a cow living in a high-density feeding operation in close proximity to other cattle on a feedlot Correct. This scenario is the most likely to result in the transfer of antibiotic resistance from one bacteria to another since the wound is open and infected. In addition, proximity to other animals in unsterile conditions makes it likely for other species of bacteria to infect the wound. Explanation: The transfer of antibiotic-resistant genes from one bacterium to another occurs during horizontal gene transfer between a bacterial species that carries the gene (donor) and one that does not (recipient). Of the scenarios described in the question, the one most likely for this to occur is in the infected cow. In addition, the animal is in unsterile conditions (cow manure) and has contact with many other animals because of their confinement on a feedlot. Concentrated animal feeding operations (CAFOs) have been criticized in recent years for being breeding grounds for antibiotic-resistant bacteria. In addition to so many animals being in close proximity (and therefore being more likely to transfer disease to one another), this type of animal agriculture also adds antibiotics to the animal feed on a regular basis to try to prevent disease outbreaks, whether the animals are sick or not. As you learned in this chapter, improper use of antibiotics can lead to antibiotic-resistant strains of bacteria. pg. 211
Individuals with intermediate values of an inherited phenotypic trait have an advantage over other individuals in the population. This is what type?
Stabilizing In cases of stabilizing selection, individuals with intermediate values of an inherited phenotypic trait have an advantage over other individuals in the population. pg. 216-217
Ten frogs live in a pond in your backyard, five are homozygous for an allele that results in dark skin, and five are homozygous for an allele that results in lighter skin. A drought occurs, killing three frogs with light skin alleles. The rest of the population breeds and produces the next generation of frogs. Did the frog population evolve? Y/N?
YES! The allele frequencies of light to dark alleles were 1:1 before the drought. After the drought the frequency of light to dark skin alleles became 3:5. pg. 214
Match each phenotype to the environment for which it is most suited. Environments may have more than one phenotype. habitat with many predators habitat where seeds have very tough shells warmer habitat • duller color in a bird population • stronger beaks in a bird population • larger jaws in a mouse • more active sweat glands in a horse • camouflaged color in a caterpillar
habitat with many predators • duller color in a bird population • camouflaged color in a caterpillar habitat where seeds have very tough shells to open • stronger beaks in a bird population • larger jaws in a mouse warmer habitat • more active sweat glands in a horse Different environments require different traits for organisms to remain successful. Natural selection removes from the population those traits that are not suited for their environment. pg. 215-217
