Quiz 2 With Solutions PDF

Quiz 2 Note that the order of answers (i.e., options A to E) may vary among individual quizzes, so be careful when comparing your answer to those below as the order of the answers, and hence the letter associated with the correct one, may be different. 1. Academic integrity pledge. 2. Choose whic...

Quiz 2 Note that the order of answers (i.e., options A to E) may vary among individual quizzes, so be careful when comparing your answer to those below as the order of the answers, and hence the letter associated with the correct one, may be different. 1. Academic integrity pledge. 2. Choose which, if any, of the following statements is false. In organisms with germ-soma division: a) the soma is produced anew in every individual b) the soma is produced via instructions encoded in the germ cells c) mutations in the soma can be transmitted to germ cells d) the soma serves to support the transmission of germ cells from one generation to the next e) None of the above are false. Answer: C. In organisms with germline-soma division, information flows only from the germline to the soma. This is sometimes called the Weismann barrier. In plants, coral and sponges, a true germ-soma division doesn’t exist as reproductive (germ) cells are derived repeatedly from somatic tissue. Answer E was also accepted because plants, corals and sponges were presented as cases in which somatic mutations can end up in germ cells that are later derived from that soma. 3. Which of the following is true? a) Natural selection is constantly acting for the benefit of species. b) Natural selection helps explain why organisms are generally well suited to survive and reproduce in their environments. c) Natural selection is survival of the fittest. d) An individual can evolve increased reproductive success via natural selection. e) Traits leading to the overexploitation of resources, which are harmful to population survival, cannot evolve via natural selection. Answer: B. A is incorrect as natural selection arising from variation among individuals in their reproductive success relative to other individuals, whether this is good for the species or not. C is incorrect as this definition is a tautology. D is incorrect because individuals cannot evolve – populations evolve. E is incorrect because such traits can (and do sometimes) evolve via natural selection. 4. You are writing a book on the natural history of southern elephant seals. Males of this species defend harems that can contain dozens, sometimes hundreds, of reproductive females. To give readers some insight into this behaviour, you record the number of females in the harem of each male in a population of seals on South Georgia Island. What type of science and what type of study this is? a) Descriptive science, observational study b) Pseudo-science, observational study c) Hypothesis-testing science, observational study d) Descriptive science, manipulative study e) Deductive science, descriptive study Answer: A. This is indeed descriptive as the goal is to characterize the system, not to test of causal explanation for a previously observed pattern, and the study is observational as nothing was manipulated. 5. Which of the following statements concerning homologies is false? a) Homologous traits often share a similar structure between species, even when the trait performs a different function. b) Some homologies are only detectable at a particular developmental stage. c) Homologies are inconsistent with theories of special (i.e. divine) creation. d) Evolution makes sense of homologies – they are due to shared ancestry (i.e. common descent). e) Homologies are a type of transitional form between extant species. Answer: E. Homologies are curious similarities in structure, often of traits performing different functions, that arise from shared ancestry (i.e. inheritance from a common ancestor). 6. Which of the following statements is false? Blending inheritance: a) proposes that traits of the parents are combined into unique, intermediate values in offspring, like two colours of paint being mixed b) results in the loss of phenotypic variation each generation c) proposes that heredity is controlled by genes and every individual has two copies (alleles), one they receive from their mother and the other from their father d) will cause natural selection to become ineffective e) does not allow for traits of parents, that are lost in offspring, to reappear in later generations Answer: C. This is Mendel’s model for inheritance and does not represent blending inheritance. 7. Which of the following is false? a) An individual of genotype Aa is a homozygote. b) Dominance means that genotype cannot always be inferred from phenotype. c) Alleles are variants of a gene. d) A locus is a location on a chromosome. e) A gene can also be referred to as a locus. Answer: A. This individual is a heterozygote, not a homozygote. 8. An evolution experiment was performed using 10 populations of fruit flies (Drosophila melanogaster). Each generation, 500 males and females from a given population were separately introduced into Vial 0 of the maze, which was mounted on a wall. The black lines are tubes. Vials 1-10 on the right contain food, and flies are attracted to them. In moving through the maze, individuals can choose to go up or down at each junction. 24h after being introduced, flies are collected from vials 1-10. For 5 separate Control populations, flies are mixed among vials 1-10 and then 50 males and 50 females are randomly chosen to reproduce. In 5 separate Selected populations, the 50 males and 50 females are chosen preferentially from the lowest numbered vials (i.e., flies are taken from vial 1 first, then vial 2 if needed, on so on until you get 50). The latter creates selection for positive geotaxis (i.e. moving up, against gravity). In each population, the 50 males and 50 females are then allowed to mate and produce offspring, and the process is repeated on the offspring in the next generation. Results, plotted as the average final vial position of all the flies for a given population each generation, are as follows (each line is a single population): Now imagine two different scenarios and, separately for each, explain what you expect would happen in the results of this evolution experiment and why. Your answer should address the conditions necessary for natural selection. The two scenarios are: a) all individuals go through the maze in the exact same way and hence reach the same final vial (2 marks) b) an offspring’s behaviour in the maze is unrelated to the behaviour of their parents. (2 marks) Answer a) Expectation: no difference on average in final vial position of Selected vs. Control populations. (1 mark) Why: selection requires that individuals vary in a trait; if they all behave the same there is no variation and hence no possibility for selection (and hence no evolutionary response). (1 mark) OR No difference in fitness (0.5 mark – There is no variation in fitness BECAUSE there is no variation in the trait, hence only the half mark if the absence of variation in the trait is not mentioned) b) Expectation: no difference on average in final vial position of Selected vs. Control populations. (1 mark) Why: an evolutionary response to selection requires the trait to be heritable (i.e. offspring have to resemble parents to some degree). If the trait is not heritable, there will be no evolution by natural selection. (1 mark) 9. You are designing a study to test whether the intensity with which male praying mantises court females depends on the male’s nutritional status. You rear males on either a low- or high-quality diet and then, once they reach reproductive age, present individual males to a random female. Each male’s courtship intensity is then judged on a qualitative scale from 0 (no courtship) to 10 (intense courtship) by an observer. The experiment is too large for one person to do alone, so you score the courtship of the low-quality diet treatment males and your lab assistant (who you personally train) scores the courtship of the high-quality diet treatment males. Trials of both types of males are performed at the same time each day. Identify (i.e. name) and explain the problem with this design (2 marks), and suggest a better design that would reduce or eliminate this issue without reducing the number of replicate males (1 mark). Answer: Identify problem: there is a potential confounding variable (1 mark) OR there is a difference between the treatment other than nutritional status (i.e. the person doing the observations) (0.5 marks) OR observer bias (0.5 marks: Observer bias is “the tendency of observers to not see what is there, but instead to see what they expect or want to see” (Wikipedia). The issue here is that, by knowing which treatment each person is scoring, they might subconsciously score what they expect. While this is true, there would STILL be an issue with this design even if each observer was blinded to which treatment they are scoring as the two observers may simply score differently, so this isn’t the core problem with the design). Explain: You and your lab assistant may score courtship intensity differently (0.5 marks), and this could produce a difference between treatments that would be interpreted as an effect of (or would alter the effect of) diet (0.5 marks). If observer bias was answered in the first part, an accurate explanation of what this is should receive full marks for this part. Better design: You and your assistant score half of the samples each from each treatment (1 mark) Or: figure out a way to quantify courtship objectively/automatically, such that it is done the same way in both treatments (1 mark) Or: blind the scorers (randomise treatments to score) as to which treatment they are scoring (1 mark; this will remove observer bias, but the problem of difference in scoring remains, but we don’t double penalize so full marks for this) Or: recording all the courships by video and having one person scoring them (1 mark) NOTE: the question stated that one person cannot score all the trials, but a solution that gets around this (like recording them) is reasonable and should get full marks. Or: Do a preliminary study to test whether you and your assistant score the sample samples the same way (0.5 marks only – this is less useful because, even if your preliminary study doesn’t detect a significant difference, one might still exist and it doesn’t tell you what to do if you do find a difference in how you and your assistant score this behavior).