BIOB51 - Review
Explain the variable on the Y-axis in this graph. Why is this 'relative testes size' rather than simply 'absolute' testes size? What hypothesis was tested in this study? What type of analysis?
1. It is already known (demonstrated) that testes weight increases with body weight across taxa. This analysis is asking whether there is additional variation explained by mating system. Thus the Y-axis is testes weight relative to body weight. Notes: If the value is '0' then testes weight is as predicted by body weight, if the value if positive, then testes weight is higher than expected if the value is negative, it is lower than expected. 2. The hypothesis was that the evolution of testes size depends on the intensity of sperm competition in a given taxon. Since increased testes size allows for the production of more sperm, when sperm competition is high, then larger testes evolve because they increase success in the competition for fertilization. This was tested by comparing taxa with different mating systems. Single male or Monogamous systems have low sperm competition (B) and are predicted to have relatively small testes, but multi-male systems (A) have high sperm competition and are predicted to have relatively large testes. 3. Comparative method
1. Using the data and information above about Hoekstra, Drumm and Nachmann's work, and assuming these populations are in Hardy‐Weinberg equilibrium, determine the frequency of alleles Dand d in all mice living on light‐coloured substrates. Freq(D) =16% Freq(d) = 84% 2. If the populations on light‐coloured substrate are in Hardy‐Weinberg equilibrium, what are the genotype frequencies on this substrate? 3. Use a similar approach to determine the frequency of theDD, Ddand dd genotypes for mice on the dark-coloured substrate if the populations are in Hardy-Weinberg Equilibrium. 4. Compare the genotype frequencies of Rock Pocket Mice on the two different substrates (assume any differences of 10 or more are significant). Given what you know about selection on the rock pocket mouse, provide a hypothesis to explain your findings.
1. See slide 2. Freq(dd) = 71% (already calculated above) Freq (Dd) = 2pq = 27% Freq(DD) = p2 = (0.16)2 = 2% OR: Freq(DD) = 1 ‐ (Freq[Dd] + Freq[dd]) = 1‐(0.98) = 0.2 or 2% 3. Freq(DD) on dark = 61% Freq(Dd) on dark = 34% Freq(dd) on dark = 5% 4. Comparison: The DD genotype is the most common genotype on the dark substrate (61%) whereas it is the least common genotype on the light‐coloured substrate (2%); the opposite is true for the dd genotype. Hypothesis. This is consistent with the idea that there is selection for one allele as a function of the visibility of the mice to predators on the substrate on which they live. The D allele is favoured on the light‐coloured substrate, but the d allele is favoured on the light‐coloured substrate.
1. Puerto Rico, Cuba, Jamaica, and Hispaniola have different species of anole lizards with distinct body types, called ecomorphs. Ecomorphs are species that occupy a similar niche and have similar morphology and behaviour. Each island has a number of different ecomorphs which are also found on other islands. Anole ecomorphs differ in key morphological traits that are adaptations to survival in the different niches in which they live on each island. What are these morphological traits? (there is more than 1 correct answer)
;e.g. length and toe pad size
15. What was the Cambrian explosion (570 million years ago)?
= sudden explosion of diversity in animal body plans Genetic basis of body plan evolution Fossils show major changes in animal body plans over time. This section focuses on how these changes may have occurred.
mutation
A mutation is a change in the sequence of nucleotides in the DNA of an organism.
9. Anole lizards communicate with rivals and with potential mates using dewlap signals. Briefly explain how the dewlap signal may evolve differently in anoles adapted to live on the trunks of shady trees compared to those adapted to life on bushes in open areas, and how this might affect speciation.
Anoles that live in open areas may evolve darker dewlaps because they are more visible than light colours in that environment, similarly, those that live in shady areas may evolve light‐coloured dewlaps. If dewlap colour is important for mate choice, then a change in dewlap colour between shade‐living and open‐living anoles may mean that they do not interbreed if they come in contact. Thus the populations could speciate since there is no exchange of genes through mating.
Suppose you are studying a recently discovered population of rock pocket mice with dark- colored fur that lives on volcanic rock. You take a DNA sample from a member of this new population and determine the DNA sequence of a gene known to play a role in fur color. The sequence you get is identical to that of the same gene in another rock pocket mouse population with dark- colored fur that lives on a different patch of volcanic rock. Which of the following could explain this observation? a. The mice in the two populations evolved from the same ancestral population. b. The volcanic rock caused the same mutation in each rock pocket mouse population, resulting in dark coloration. c. The same mutation spontaneously arose in the two different populations. d. Both (a) and (c) are possible. e. All of the above are possible.
Answer: Both (a) and (c) are possible. (Additional Explanatory Note: This question asks which answers could be consistent with your observation, not which you think is more likely. Thus the similar genes could either be the same due to inheritance [i.e., they may be homologous], or they may have arisen independently by chance [i.e., they may be homoplasious or analogous—the result of convergent evolution]. We will discuss homology & homoplasy in future lectures, but you may also recall these terms from your high school or first year introductory courses, and recall that homoplasy or analogy is expected to be less common than homology. Nevertheless, both are consistent with these data).
Question 10 You decide to move a group of the light-colored rock pocket mice from the newly-discovered population in Arizona to the population in New Mexico that was described in the video. Recall that the mice from New Mexico also live on dark-colored volcanic rock. You also move a group of dark- colored mice from the New Mexico colony to the Arizona colony. You monitor the populations for five years and observe the following. Summarize the data in two or three sentences. Then provide an explanation for these observations in a few sentences. Be sure to include the following key words in your answer: "selection" (or "selective"), "fitness" (or "fit"), and "survival" (or "survive").
Answer: Description: In New Mexico, the number of dark mice increases while the number of light mice decreases over time, (or: the proportion of dark mice in the population increases over time). In Arizona, the number of light mice and dark mice remain constant over time (or the proportion of light and dark mice remains the same over time). Explanation: In New Mexico, there is a selective advantage to dark fur since dark mice are less visible to predators and visually-hunting predators are common there. Dark mice are thus more fit than light mice in this habitat and are more likely to survive and have the opportunity to reproduce. In Arizona, there is apparently no selective advantage to dark-coloured fur. Therefore dark and light coloured mice are equally fit which means they survive and reproduce at similar rates and their frequency in the population does not change significantly over time. Additional note: the fact that the dark mice in Arizona have a larger population size overall does not mean that dark fur is favoured by selection in that population. Remember that you took some white mice and moved them out of Arizona (thus reducing the number of white mice) and that you took some black mice from New Mexico and moved them to Arizona (thus increasing the number of white mice). Essentially—you created 'migration'. Once the migration is complete, in the absence of selection (or other mechanisms of evolution), the proportion of white and black mice should remain constant over time (as observed here).
Near the end of the film, Dr. Sean B. Carroll states that "while mutation is random, natural selection is not." In your own words, explain how this is possible.
Answer: Natural selection acts on phenotypic traits as a function of whether they allow individuals to survive and reproduce at a higher rate than others in a population. So the traits favoured by natural selection are not random, they are specifically those that confer higher fitness. However, natural selection can only act if there is variation in the population, and mutation is a source of that variation. Mutation leads to a variety of phenotypes, not just those that are most fit in a given environment. So mutation is random with respect to the traits that would increase fitness in a given environment.
As you saw in the film, rock pocket mice evolved to have darkcolored fur in certain habitats. In three to five sentences, explain how this trait increased in frequency in the population. Include the following key terms: "fitness" (or "fit"), "survival" (or "survive"), "selection" (or "selective"), and "evolution" (or "evolve").
Answer: Populations of rock-pocket mice included many individuals with light-coloured fur, and a few with dark-coloured fur. Rock pocket mice with dark-coloured fur were more fit on dark-coloured volcanic rock because visual predators could not see them well. This means that natural selection favoured individuals with dark- coloured fur in these habitats; that is, more of the dark-coloured mice survived and reproduced. Since dark-coloured fur is caused by a different allele than light-coloured fur, this resulted in more dark-coloured mice being born in the next generation. This process was repeated over many generations in areas with dark-coloured volcanic rock. This caused the population of rock pocket mice to evolve from one that was mostly mice with light-coloured fur, to one where most individuals had dark-coloured fur.
Suppose you are studying a new population of rock pocket mice in Arizona. These mice live on a recently discovered patch of dark-colored volcanic rock. You observed the following numbers of light- and dark-colored mice on this new patch of rock over several years of observation. Describe what the data show in one or two sentences, then outline one possible hypothesis that could explain the observed data. Be sure to include the following key words in your answer: "selection" (or "selective"), "fitness" (or "fit"), and "survival" (or "survive").
Answer: The data show that both light and dark-coloured mice are maintained in the population in similar numbers. It appears that both dark and light coloured mice have similar fitness, so natural selection does not change the frequency of these traits. Hypothesis: I hypothesize that, in this new population, fur colour does not affect survival because there are fewer (or no) flying predators that hunt using vision. [there may be other reasonable hypotheses proposed here, as long as they focus on why there is no advantage to black or to white fur, they may be good answers. Post to the discussion board or come to my office hours if you have questions about whether your hypothesis is a good answer]. Additional Note: 'Does not change the frequency' means 'does not lead to statistically significant changes in the frequency of the traits'. There can be fluctuations in the frequency of the different morphs from year to year (as seen most clearly here for light coloured mice), but these are not the same as substantial, systematic changes in frequency. All biological systems (all natural systems) show fluctuations around average values. We will discuss how to determine whether there is statistically significant change when we talk about methods of evolutionary analysis and population genetics.
Is the following statement true or false? Justify your answer in one or two sentences: "The same mutation could be advantageous in some environments but deleterious in others."
Answer: True. If a mutation affects the phenotype, then it may be advantageous or deleterious depending on whether the new phenotype allows organisms that possess it to perform better (increase their lifetime reproductive success) relative to others in the population in that particular environment. Thus the mutation that causes black colouration is advantageous in habitats where lava flows have made the surface dark, but is deleterious in habitats where light-coloured sand is more common.
Recall Darwin's postulates (see Lecture 2 if you need a reminder). Does the example of evolution of furcolour in the Rock Pocket Mouse fit Darwin's postulates? State each postulate and briefly describe how this example relates to each postulate.
Answer: Yes, this example fits Darwin's postulates. Postulate 1. There is variation in the population. This example: Some mice have light-coloured fur, and some have dark-coloured fur. Postulate 2. Some of the variation in inherited. This example: dark-coloured mice have different alleles than do light-coloured mice. (Additional Explanatory note: the particular alleles that cause dark colouration may differ between populations, as described in the video. In the New Mexico population, a mutation in the MC1R gene causes dark colouration, in other populations in the Southwest, different alleles cause the same outcome. If you image that dark colouration arises through a series of physiological steps, different mutations that affect different steps may yield similar phenotypic outcomes). Postulate 3. Not all individuals survive and reproduce. This example: Some mice are killed by predators and do not reproduce, or produce fewer offspring than others which survive. Postulate 4. Individuals with particular traits have greater success in the struggle to survive and reproduce. This example: Mice with fur colour that allows them to be cryptic (hard to see) in their environment survive and reproduce at a higher rate than those that contrast with their environment. (Additional note: Since the particular traits that confer higher fitness are also heritable, in this case we predict natural selection will lead to evolutionary change, and this has occurred, as shown in the video).
Levine & McGinnis tested Lewis' hypothesis using the Antennapedia gene in Drosophila. What did their new technique demonstrate?
Antennapedia (which controlled leg development) was normally expressed / turned on in the thorax of developing embryos. They showed that Antennapedia was like a master switch that was turned on in areas that would become insect thorax. Genes like antennapedia could be the architects of body plans—turning on genes in the wrong place would lead to radical changes in body plans, and provide variation on which natural selection could act.
20. What do 'architect' (Hox) genes suggest about evolution of body plans across taxa?
Apparently animals use a very similar set of 'architect' genes to build bodies. This suggests evolutionary conservation of mechanisms for building body plans among animals. That is, the 'architects' turn on other genes—these other genes may have been modified over evolutionary time (e.g., mouse eye versus a Drosophila eye)--but the architects are very similar across taxa. 'Architect' genes were likely inherited from common ancestors to most organisms with complex body plans. The evolution of new body plans could be fueled by relatively simple changes in these genes or pattern of activation of these genes.
9. What did Gingerich discover about Basilosaurus that was not previously known, and what did this suggest about the origin of this animal?
Basilosaurus had a pelvis, complete set of leg bones, and toes, unlike modern whales. This strongly suggested terrestrial origins.
Describe what this graph shows about beak length in soapberry bugs.
Beak length was more variable in the 1800 and early 1900's (ranging from about 5.5 to 9mm in size), than after about 1930 when variation decreased quite a bit. After this time, the largest beaks were about 7.5mm and the average size would thus be lower.
16. Organisms show a pattern of repeating segments, and there are sometimes errors or repetition of segments. Bateson studied developmental 'errors' where body parts developed in the wrong place. What did these developmental errors suggest?
Errors suggested some underlying 'blueprint' for animal development might exist. This might sometimes be disrupted to lead to misplaced body parts. This was inferred because the body part was built correctly, suggesting it was not the gene for building those parts that caused the problem, rather the error was in something else that determined where those parts would be built. These novel arrangements of body parts introduced radically different variants to populations. These variants might sometimes be viable and trigger the evolution of diverse of body plans.
What would you need to know to determine if evolution occurred in soapberry bugs in Lake Wales?
Evolution is a change in allele frequencies for a given trait over time. To determine whether the change in the frequency of smaller beak sizes is an evolutionary change, I would need to know whether the alleles that affect beak size had changed in frequency. NOTE: the average beak size could also change due to environmental effects. For example, the new fruit could affect developmental pathways in a way that leads to smaller beaks (e.g., no change in alleles).
Is the following statement true or false? Justify your answer in one or two sentences: "Mutations are caused by selective pressure in the environment."
F: Answer: False. Mutations are not caused by the environment or by selection. Mutations occur randomly. (Additional Explanatory note: Although mutations are not induced or caused by selection, they do generate new phenotypes on which selection can act. So mutations lead to new phenotypic variants, and once these variants exist, natural selection can act to make them more or less common in the population over generations.)
T or F: Lamarck's hypothesis about the Evolution of Acquired traits did not provide an explanation for Adaptation.
False. Proposed an idea, just a bad one.
What types of organisms did Gingerich expect to find if Darwin's hypothesis was correct?
He expected to find a series of related organisms appearing in sequence in the fossil record. These should show the changes in traits necessary to go from the wolf-like ancestor found in Pakistan to the modern whale.
6. Gingerich sought transitional forms to test predictions of Darwin's hypothesis. What transition was Gingerich seeking to understand?
He was seeking to understand the transition from land mammals to aquatic mammals.
6. The anole‐introduction experiment shown in the film was a representation of a large‐scale experiment Losos and colleagues conducted in the 70's and 80's. In these experiments, they placed 5 to 10 male and female lizards on each of 14 different islands that had been 'hurricane scrubbed' (had no lizards) and tracked the traits of the resulting populations over 10 years. The graph below shows: morphological characteristics of the original population (x = mean; + = individuals) as well as the mean trait values for the 14 populations that were introduced to new islands (solid circles and triangles) that primarily contained brush and twigs. Briefly state the hypothesis Losos was testing in this experiment. 2. . Assume that any differences between population means are statistically significant. Describe what the data show, the conclusions you can draw from these data, and the process that lead to this outcome.
He was testing the hypothesis that the anoles introduced to these islands would evolve in a way that made them more well‐adapted to moving/foraging/resting on the twigs that were most common on those islands. In this case this means the evolution of reduced leg length and reduced toe pad size. 2. Data show: Populations of lizards on the islands have evolved shorter legs and smaller toe pads on average. This can be seen by comparing the mean values on each island after 10 years (solid triangles and circles) to the mean of the original population (x). I would conclude that this is support for the hypothesis that the anoles adapt to conditions on the island with respect to their locomotion on twigs. Process: There is reasonable evidence that this is evolution by natural selection. The original population is variable (+ on graph) for toe pad size and leg length. The video showed that anoles with smaller leg sizes do better when trying to move across twigs. Assuming the introduced populations had similar variation as the original, natural selection would arise because individuals with smaller legs/toe pads would have higher lifetime reproductive success, likely because they were better at running after/catching prey and/or running away from predators. If the offspring of smaller‐legged anoles also have smaller legs on average than the offspring of larger‐legged anoles, then there would be change in the population over time (in this question I tell you nothing about inheritance of this trait, but the video does).
Two important measures of genetic diversity within populations are mean heterozygosity and the percentage of polymorphic loci. Outline the difference between these two measures.
Heterozygosity. Proportion of people in a population that are heterozygous per locus OR proportion of genes that are heterozygous in the genotype of a typical person. This measure focuses on how variation is arrayed within individuals % Polymorphism. Fraction of genes in a population with at least 2 alleles. This measure of variation focuses on how much variation is in a population as a whole.
13. What new hypothesis about tetrapod evolution did Clack propose?
Hypothesis: limbs evolved in an aquatic ancestor and only later were used on land.
14. What key features of the early tetrapod skeleton discovered by Clack supported her new hypothesis about tetrapod limb evolution?
It was a 'fish with fingers'. It had a complete, paddle-like hand—tetrapod hand bones on appendages, but it also had a fish- like tail and gills, so was clearly aquatic.
1. What is a 'Great [evolutionary] transformation'?
Key evolutionary change in a lineage that opens the door for new ways of life and new forms of life. Here we focus on 3 great transformations: A. Evolution of whales B. Evolution of Tetrapods C. Evolution of Animal Body plans
17. Lewis proposed an initially controversial hypothesis about body plan development. Under his hypothesis, why could relatively few mutations lead to big differences in body plans?
Lewis proposed that development of each body segment or area (e.g., insect head or abdomen) is directed by a single gene ('architect' gene), so a small set of genes are responsible for the layout of an entire body plan. These genes turn on other genes that are appropriate to the body part being constructed (so they are like 'architects' in the sense that they direct the construction of the body). Even small errors in 'architect' genes or in turning on 'architect' genes can lead to substantial differences in body plans as a result of relatively few mutations. (NOTE: these 'Architect' or Homeobox (or Hox) genes are developmental regulatory genes - these regulate the transcription of other genes in embryos. Homeobox products provide positional information in a multicellular embryo and induce the formation of particular parts or structures in the right position. They do not contain the information necessary to build the structure itself, but they do 'turn on' the genes that then create the structure.
10. Which of the following were major changes in body plan in the transition series leading to modern whales? (select all correct answers)
Loss of legs** Origin of a swim bladder x Movement of nostrils to top of the head** Streamlining of body shape** NOTE: As we discussed in class, it is not necessary that every organism was a 'link' in a chain that led in a direct line of descent to modern whales. There might also be some organisms that showed transitional features (some adaptations for land in addition to some adaptations for aquatic life) which left no living descendants but are nevertheless evidence that the predicted evolutionary sequence is plausible.
Briefly outline one piece of evidence that environments have changed substantially over time.
Many possibilities here. One is: fossilized whales are found in the Sahara Dessert, this shows that this area was once under water (from the Great Transformations video). Whale femur (eventually became part of penile tissue)
D: Survival and reproduction are random processes. YES or NO
N; Survival and reproduction is more likely for organisms that have traits that allow them to perform better than their competitors in a given habit. Thus, survival and reproductive are not random.
12. Would this study on Brassica have been more convincing if the researchers had used a phylogeny in their analysis of flowering time in Brassica rapa? Why or why not?
No. This was a microevolutionary study. The hypothesis they were testing was that flowering time of B. rapa would change as a result of selection via the drought. This was a hypothesis about natural selection within a single species, and within one population. There is no need to use a phylogeny in this study (and in fact, it is hard to imagine how it would be used at all!).
Why are some taxa useful for testing evolutionary hypotheses, but others are not?
Page |6 To test an evolutionary hypothesis, we need to find taxa that have the same evolutionary 'starting point' (i.e., a recent common ancestor) from which they evolved, where there is a change in the 'X' variable of interest during divergence. Taxa that are not sister to each other (more recent common ancestor with each other than with other taxa) are not useful because changes may have occurred in the distant past and been simply inherited. Taxa that do not differ in the 'X' variable of interest are not useful because they do not show the change in the proposed causal variable of interest.
Measures of Polymorphism and Heterozygosity may be equal or may be unequal in the same population. If these measures are not equal, which one will be greater than the other?
Polymorphism will be greater than Heterozygosity if they are not equal.
What is the evidence for 'architect' genes in other organisms?
The 'eyeless' gene controls eye development in Drosophila A very similar gene is present in the mouse, and is involved in eye development. Transplanting the 'eye control' gene from the mouse to Drosophila leads to development of a normal (compound) insect eye. Conclusion: same gene directs eye growth in both flies and mammals. This 'architect' gene turns on other genes that direct eye development (i.e., the gene itself does not determine eye structure, since the Drosophila did not develop a mouse eye). Rather, the gene turns on other genes that are necessary for eye growth.
4. Our understanding of whale evolution was aided by the discovery of the fossil of a wolf-like skull of a terrestrial organism (in the 1980's). Why was this fossil important to the study of whale evolution?
The distinctive shape of the inner ear on this fossilized skull is found only in modern and extinct whales. This suggested this terrestrial animal was related to, and likely an ancestor of, modern whales.
12. The discovery of a fossil of an aquatic animal with a tetrapod shoulder contradicted old hypotheses about tetrapod evolution. Why?
The old hypothesis was that fish moved onto land, then, fins evolved into legs to allow terrestrial movement. Under this hypothesis, aquatic animals should not have limbs (or tetrapod shoulders).
For rock pocket mice, which of the following contributes to selection favoring dark-colored fur? There may be more than one correct response. a. The presence of visually-hunting predators. b. Genetic mutations affecting fur colour. c. Colour of the rock on which the mouse lives d. Distributionoffoodplantsthatdeterminethetypesofpigmentsproduced during development.
The presence of visually-hunting predators Colour of the rock on which the mouse lives (Additional Explanatory Note: Genetic mutations produce the variation on which selection acts, but in itself, mutation does not cause selection. That is, the change in gene sequence (=mutation) does not yield differences in lifetime reproductive success; rather, gene expression can lead to variation in phenotype, and a changed phenotype under a given set of conditions may lead to changes in lifetime reproductive success)
3. One of these two trees illustrates the most likely hypothesis for how the different species evolved on the Caribbean islands given the data currently available. State which one, and the key evidence from the film that supports your answer.
The tree on the left is actually the one best supported by the current data. Gene sequence analysis shows that the different ecomorphs on each island are more closely related to each other than they are to the same ecomorph on the other islands. This is surprising because it means that the different ecomorphs have evolved repeatedly and thus their similarities on different islands is due to convergent evolution. Thus the similar traits in each ecomorph on different islands are Homoplasies. This is NOT the most parsimonious hypothesis, but it is best supported by the data.
Darwin: The variations among individuals are not passed from parent to offspring. Y or N?
The variations among individuals are not passed from parent to offspring. NO: Although not all variations are passed on to offspring, some of them are. It is these inherited (heritable) traits that can be the focus of evolution by natural selection as proposed by Darwin.
2. Why is the evolution of whales puzzling?
Whales are mammals, mammals evolved on land [approx 200mya]. Whales are aquatic but evolved later, after the evolution of terrestrial mammals. (note: mya = million years ago) Puzzle = How/when did mammals return to an aquatic existence? How did marine mammals evolve?
3. What was Darwin's hypothesis about whale evolution?
Whales evolved from terrestrial mammals.
When distantly related taxa share similar traits, it is likely these traits are (homologous OR homoplasious). This type of trait (is OR is not) useful in building phylogenies.
When distantly related taxa share similar traits, it is likely these traits are homoplasious. This type of trait is not useful in building phylogenies. Extra notes: The wings of insects and birds are Homoplasies. These are traits that are similar because of convergent evolution—the process by which similar traits arise in response to similar types of selection in different taxa. This type of similar trait does NOT reflect evolutionary relatedness because these different taxa evolved them independently; they were not inherited from a common ancestor. Thus these traits are not helpful in building phylogenies because they do not reflect relatedness.
Darwin: Individuals within populations are variable. Y or N?
Y
Darwin: Some individuals are better at surviving and reproducing. YES or NO
Y
11. How does swimming differ between fish/sharks compared to whales/dolphins, and how do these compare to movement patterns of terrestrial mammals?
a) Fish/Sharks: flex spine from side to side b) Whales/Dolphins: undulate spine up and down (dorso-ventral) c) Terrestrial mammals moving on land or in the water: undulate spine up and down (dorso-ventral) when running or swimming d) Movements of Whales/Dolphins is most similar to: Terrestrial mammals (e.g., compare otter swimming and dog running to whales/dolphins)
22. In humans, Rh‐incompatibility occurs if an Rh‐negative mother has an Rh‐positive baby. Assume that this is controlled by a single gene (this is an over‐simplification) and that Rh‐positive is a dominant trait. A) Show the possible genotypes and phenotypes of the mother, father, and baby in a case of Rh-incompatibility. B) If the Rh+ child is a boy who grows up and has children with an Rh-negative woman, should they expect any Rh-incompatibilities with their children? If so, what percentage of their offspring will be affected?
a) Let Rh‐positive allele = R Let Rh‐negative allele = r Rh‐incompatibility: Mother: rr; phenotype: Rh negative Baby: Rr; phenotype: Rh positive (not RR because must have received 'r' allele from Mother) Father: RR or Rr; phenotype: Rh‐positive c) Son: Rr; woman rr. Yes, they should expect some Rh‐incompatibilities. c) About 50% of their children will suffer from Rh-incompatibility.
You are studying a trait controlled by two alleles at one locus. One allele is M, the other is N. In a population of 3100 mice, you find that 1101 are MM, 1496 are MN and 503 are NN. A) Calculate the frequencies of alleles M and N in this population. B) Calculate the expected number of individuals with each of the three genotypes if the population is in Hardy-Weinberg equilibrium. C) Given your calculations, how would you determine whether the population is in Hardy-Weinberg equilibrium?
a) freq(M) = [1101 + 0.5(1496)] 3100 = 0.60 freq(N) = 1‐0.60 = 0.40 NOTE: you are not told the population is in HW equilibrium, so you cannot use the HW frequencies to calculate allele frequencies, instead you must use your knowledge of the types of gametes produced by individuals of each genotype (as the frequencies of the alleles in the population = the frequencies that would go into the gene pool). b) Expected number of MM = expected freq(MM)* # individuals = [freq(M)]2*(3100) = 1116 Expected number of MN = expected freq(MN) * # individuals = 2[freq(M)*freq(N)] *(3100)= 1488 Expected number of NN = expected freq(NN) * # individuals = [freq(N)]2(3100) = 496 b) I would do a statistical test to see if the difference between the observed (given in the question) and expected numbers (calculated in b) of each genotype is significant. If the test shows that P 0.05, then the observed population is not in Hardy‐Weinberg equilibrium (the observed numbers are significantly different from the expected numbers).
8. Why did Gingerich seek transitional forms that would be informative about whale evolution in the Sahara Desert? (there may be more than one correct answer)
a. Fossils are more likely to be well-preserved in the hot-dry dessert compared to an aquatic habitat. b. The Sahara Desert was a sea 40 million years ago.*** c. One lineage of the wolf-like ancestor of all whales migrated to the Sahara Desert prior to the evolution of whales. d. There is evidence that terrestrial ancestors of whales lived in the Sahara Desert millions of years ago. Although the Sahara is currently a desert, it was a sea 40 mya. There is an area there called 'whale valley' that contains the remains of many whale-like animals.
5. In the film, Jonathan Losos placed a male and female (long‐legged) trunk‐ground anole on an island that did not have any trees but had short grass and shrubs (with thin branches and twigs). Losos and colleagues visited the island in the following several years. What happened to the anole population? a. The two anoles died because there were no trees for them to live in. b. The two anoles reproduced and their surviving descendants had shorter legs than their parents. c. The legs of the two anoles got shorter and their descendants inherited shorter legs. d. The two anoles reproduced and the legs of their descendants remained similar from one generation to the next. e. The descendants of the two anoles had darker dewlaps than their parents.
b The two anoles reproduced and their surviving descendants had shorter legs than their parents.
4. A population of mice has two alleles at a locus for fur colour. Allele R is dominant and produces red fur. Allele r is recessive and produces yellow fur when homozygous. You are studying a population that consists of 96 yellow mice and 54 red mice. When these mice produce gametes, R alleles are converted to r alleles by mutation at a rate (μ) of 0.03 per generation. Assume adults mate randomly. A) How many adult mice in this population are heterozygous? B) What is the frequency of R and r alleles in the gene pool after mutation? C) What is the frequency of each genotype in the next generation?
c) Genotype frequencies in next generation: RR = q2 = (0.806)2 = 0.650 Rr = 2pq =2*(0.806)(0.194) = 0.312 rr = p2 = (0.194)2 = 0.038 Note that random mating means that the alleles in the gene pool are 'picked at random' to form the next generation. Thus you can use the post‐mutation allele frequencies and plug them into the HW genotype frequency formulas to calculate the adult genotype frequencies. You can only do this because you calculated the allele frequencies in the gene pool AFTER mutation.
4. Losos proposed that lizards diversified on each island because of selection for adaptation to the different niches present on each island. What variable aspect of the available niches imposed selection on anole morphology? a. the presence of predators. b. the amount of ambient light. c. the physical structure of the material across which the lizard had to move. d. the frequency of hurricanes. e. the types of prey that were available.
c. the physical structure of the material across which the lizard had to move.
8. According to the species concept used in the film, when are organisms considered to belong to different species? if they have different phenotypes, such as different color or leg lengths. if they live in different geographical areas, such as different islands. if they eat entirely different types of foods. if they do not mate or produce fertile offspring.
if they do not mate or produce fertile offspring.
What is the synapomorphy of E, F, G in this graph?
large eyes
In this study, researchers tested whether flowering time had evolved in response to drought using seeds. To test their hypothesis, the researchers had to control for at least one potentially confounding factor. What was the confounding factor, and how did they control for it? NOTE: Researchers had seeds from the original population and from the current population (after the drought). They could grow the seeds and assess flowering time to determine whether that had changed over time. Answer: The seeds from the ancestral population (before
the drought) were older and had been stored for some time. If they found a difference, it could have been caused by the age of these older seeds. To control for this, they raised one generation from the ancestral and descendant seeds under common conditions, then used the fresh seeds (produced in the same year) to raise plants and gather their data.
. The video describes two types of evidence that were used to reconstruct whale evolution. Which of the following types of evidence were important?
the fossil record - mechanics of swimming
Anole species representing each of several ecomorphs live on each of four caribbean islands. The phylogenetic trees in the figure illustrate two hypotheses for how these types of lizards may have evolved. Using parsimony only, which tree is more likely? (See slide)
tree on right
