Concept explainers
(a)
To draw: A graph depicting the phenomenon of no selection with a range of
Introduction: The phenomenon of natural selection is based on the evolutionary changes that occur within the population.
(b)
To draw: A graph depicting the phenomenon of “stabilizing selection” with a range of phenotype (e.g. height) on the x-axis and number of the individual on the y-axis.
Introduction: The phenomenon of natural selection is based on the evolutionary changes that occur within the population. The mechanism of natural selection can be classified into three kinds: stabilizing selection, directional selection, and disruptive selection.
(c)
To draw: A graph depicting the phenomenon of “directional selection” with a range of phenotype (e.g. height) on the x-axis and number of the individual on the y-axis.
Introduction: The phenomenon of natural selection is based on the evolutionary changes that occur within the population. The mechanism of natural selection can be classified into three kinds: stabilizing selection, directional selection, and disruptive selection.
(d)
To draw: A graph depicting the phenomenon of “disruptive selection” with a range of phenotype (e.g. height) on the x-axis and number of the individual on the y-axis.
Introduction: The phenomenon of natural selection is based on the evolutionary changes that occur within the population. The mechanism of natural selection can be classified into three kinds: stabilizing selection, directional selection, and disruptive selection.
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EBK BIOLOGY
- Phenotypic trait (2) Phenotypic trait (z) Phenotypic trait (z) Identify the type of selection indicated by the three graphs. O A = stabilizing selection; B = directional selection; C = disruptive selection O A = directional selection; B = disruptive selection; C = stabilizing selection O A = directional selection; B = stabilizing selection; C = disruptive selection O A = disruptive selection; B = stabilizing selection; C = directional selection houanbay Kouenbe Kouerbelarrow_forwardVISUAL SKILLS Consider a population in which heterozygotes at a certain locus have an extreme phenotype(such as being larger than homozygotes) that confersa selective advantage. Compare this description to themodels of selection modes shown in Figure 23.13. Doesthis situation represent directional, disruptive, or stabilizing selection? Explain your answer.arrow_forwardThe evolution of a qualitative trait in reponse to natural selection is described by the following equation, R=h2 S a) What is h2 and what does it measure? b) Describe a study that would allow you to estimate h2 for a real populationarrow_forward
- When we take, say, 100 individuals of a species of beetle from the wild and place them in a new environment that is not so different that they are unable to thrive but different enough so that they are experiencing a new selective regime, say, a lower temperature, what typically happens? A - Sexual selection causes some larvae to be able to survive in the cooler temperatures and other individuals to be unable to survive because they need warmer temperatures. B - We are unable to measure phenotypic selection, presumably because we do not have much variation among individuals for how they handle temperature. C - The founder event assures us that the new population will be strictly representative of the source population (especially if we took all the 100 from the same location rather that from throughout the range of the species). D - The population evolves to be tolerant of the lower temperature; it can do this because of latent variation already in the 100 founding individuals. E -…arrow_forwardRecall that the Hardy-Weinberg model makes the following assumptions: No mutations Extremely large population No gene flow No selection You score flower colour in a very large natural population where flower colour is a co-dominant trait where white and red are homozygotes (CWCW and CRCR) and pink are heterozygotes (CWCR). Taking your observed phenotypes and genotypes, you apply the Hardy-Weinberg principle and find an excess of homozygous individuals (that is, individuals with either white or red flowers). Give two plausible explanations for this excess of homozygotes in the natural population.arrow_forwardImagine that you travel around the world and find two populations of fish that look very similar, but one one population lives in a cold climate and is very cold-resistant (produces an antifreeze protein), while the other population lives in warm climate and is not cold-resistant (and does not produce the antifreeze protein). This is the kind of example that biologists try to explain, and think about whether it is due to phenotypic plasticity or selection. Let's think through this with a series of questions. Which of the following are true about phenotypic plasticity? answer choices A-A change in the phenotype through phenotypic plasticity allows organisms to adapt to their current environment (for example, from not being cold-resistant to being cold-resistant) B-The difference between the two phenotypes in question is based on an allelic difference between the two (for example, cold-resistant and not cold-resistant are based on two different alleles of the same gene) C-…arrow_forward
- Consider the roles of different types of selective pressure. Part A: Compare and contrast sexual selection, artificial selection, and natural selection. Part B: Give examples of traits that may be favored in sexual selection, artificial selection, and natural selection. For each, explain if the trait would be favored by one type of selection but selected against by another type of selection. BI 1000 MacBook Air O00 F1 F2 F3 F4 F5 F6 F7 F8 $ % & * 2 3 4 6.arrow_forwardPINE TREE NEEDLES Variation among members of a population can lead to natural selection, but only if two conditions are met: First, the trait must be relevant to an individual's survival and/or reproductive rate. Second, variation in this trait must be heritable, that is, at least partly controlled by genes. a. How might you design an experiment to determine the importance of needle length in determining survival and reproduction? b. How might you test the extent to which needle length is heritable?arrow_forwardNatural selection and artificial selection or selective breeding can both cause changes in animals and plants. The difference between the two is that natural selection happens naturally, but selective breeding only occurs when humans intervene. Changes in genetic traits have occurred over generations through both natural selection and selective breeding although the occur through different means. What characterizes only artificial selection? Choose all that apply. A) chickens that lay larger eggs are favored B) selection increases the chances of surviving C) selection make a species stronger and fit for survival D) selection favors the desired characters in the new organismsarrow_forward
- To analyze: Imagine the length of the maize ears which has narrow sense heritability (h²) of 0.70 A population yields ears that have an average length of 28 cm, and a breeder selects a plant harvesting 0.70 cm ears from this population and cross by self-fertilization. Find the expected selection differential (S) and the response to selection (R) for this cross.arrow_forwardFor each of the following situations, indicate if it is best explained by (A) directional selection; (B), stabilizing selection; or (C) disruptive selection. Put the correct letter (A, B, or C) in each box. a. A paleo-zoologist studying the fossils of a particular lineage of fish noticed a steady increase in the number of teeth over time; the oldest fossils had the fewest teeth, while more recent fossils had more teeth. Extant members of the same group had the most teeth. b. A population of poisonous frogs was examined. Researchers discovered that individual with lower poison levels were more likely to be preyed upon during their larval stage, while individuals with higher poison levels had decreased fertility. After measuring the poison concentrations of a large sample and graphing the results, they found most individuals were clustered around a fairly narrow band of values. c. A population of tropical fish is mostly composed of individuals with either bright yellow or bright red…arrow_forwardConsidering the Hardy-Weinberg theorem’s assumptions, which of the following statements is NOT correct? (Recall that there are certain assumptions that must be true in order for the Hardy-Weinberg theorem to accurately predict genotype ratios in the next generation.)a) The population must be very large so there random genetic drift will not occur.b) No natural selection can occur.c) Mating must be random.d) Individuals must migrate into and out of the population so that gene flow will occur.e) Mutations must not occur.arrow_forward
- Biology (MindTap Course List)BiologyISBN:9781337392938Author:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. BergPublisher:Cengage Learning