IB150 All 3 Unit Practice Exams

Natural selection can create variation of a heritable trait within a population if none exists, but only when the trait increases the fitness of individuals with this trait.

False

What is the null hypothesis for linkage, what is the prediction it makes, and what is the cross needed to test this prediction?

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What is the null hypothesis for linkage? What data would you require to test the null hypothesis for linkage using data from a genetic cross?

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Choose a species with an adaptation that fascinates you. Explain how the trait you selected may have evolved via natural selection. Include an explanation of how this trait first originated, and inclcude all four postulates of natural selection in your answer.

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Explain why evolution is an inescapable fact of life. Why is it just about guaranteed that a realistic natural population will evolve from one generation to the next? Make explicit reference to which evolutionary mechanisms you need to invoke in your answer.

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If someone placed the lizard and the crocodile into the same clade to the exclusion of all other taxa, based on the character table in the previous question, what kind of phylogenetic mistake did they make? Justify your answer using the cladogram you drew in the previous question, and include which principle you used to determine that a likely mistake was made.

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In a population of Impatiens walleriana (common impatiens), flower color is determined by a single gene that displays incomplete dominance: homozygous genotypes result in either red or white color of blossoms (depending on the allele), while heterozygous individuals have an intermediate, pinkish color. a) Given that bees pollinating flowers are often consistent in the flower color they choose over time, do you expect a population of impatiens to be in Hardy-Weinberg Equilibrium for the gene underlying flower color? b) Which assumption of the Hardy-Weinberg Equilibrium model was violated in this example? c) The starting population of 900 individuals had 300 white, 300 pink, and 300 red individuals. Assuming that bees only pollinate flowers of like color, what proportions of the three phenotypes do you expect in the next generation. Assume the population remains at 900 individuals in the next generation, and that individuals of all three genotypes have equal reproductive success. d) Test whether the offspring generation is in Hardy-Weinberg Equilibrium. SHOW YOUR WORK to get full credit.*) e) Did the population of impatiens evolve? Use the following Chi-square table to help answer Part (d):

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In pea plants, flower color and pollen shape are located on the same chromosome. A plant with purple flowers and long pollen (AaBb) is crossed with one that is recessive for both traits (aabb) and exhibits red flowers and round pollen. You obtain the following phenotypic ratio among the offspring: a) Test whether these two genes are linked or unlinked. Include the p-value of a Chi-Square test to support your conclusion. Show your work to receive full credit! b) How far apart are the two genes in centiMorgan? Show your work to receive full credit! c) Which of the following two diagrams represents a diploid cell of the heterozygous parent in this problem? Justify your answer.

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Using the information on ploidy of different life stages in the organisms above, and based on what you know about the effects of mitosis and meiosis on ploidy, which kind of cell division is responsible for the production of gametes in the three life cycles illustrated above? Mitosis or Meiosis: Fungi produce gametes via: ______________________________ Plants produce gametes via: ______________________________ Animals produce gametes via: ______________________________

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Insects have a unique respiratory system that uses tracheal types that ultimately end at every single cell in their body to deliver oxygen via diffusion. a) Explain why the respiratory anatomy of insects becomes limiting at larger body size, but is perfectly suitable to an insect's metabolic demand at small body size. Make explicit reference to which parts of Fick's Law become limiting as part of your explanation. b) In reality, many insects are partially able to move air by bulk flow as far as the beginning of tracheoles via muscular contractions of their abdomen called abdominal pumping. Which variable in Fick's Law is most directly affected by abdominal pumping? What does this mean with respect to the largest size that insects can attain? Justify your answer. c) Not all insects are capable of efficient abdominal pumping, e.g. many beetles with their harder and more rigid exoskeleton have reduced ability to engage in bulk flow. Yet this group contains some of the largest insects in the world, including the goliath beetle that we saw in lecture. A comparison between the largest beetles such as the goliath beetle and moderately sized and small beetles reveals that these giants are comparatively sluggish as a result of a slower metabolism (slowed rate of cellular respiration). Explain how a slower metabolism allows for a reduced capacity for bulk flow via abdominal pumping. Make sure you trace a full chain of cause and effect in your justification. (Why is does reduced metabolic rate important/which variable does it affect; which variable is directly affected by this; what is the causal connection to bulk flow?)

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Male pattern baldness is caused by a recessive allele of a gene M on the X-chromosome. a) Draw the diploid Karyotype of Bruce Willis, who displays phenotypic symptoms of male-pattern baldness, showing the locus and allele(s) associated with the gene M responsible for male-pattern baldness. Only show the sex chromosomes for the cell for simplicity. b) Draw a Pedigree that shows Bruce Willis and his parents, and his grandparents. Indicate Bruce's genotype using the XY and superscript notation for the alleles of gene M, and determine as much as you can about the genotypes of his parents and grandparents. Leave any alleles you cannot identify definitively with a blank: __ c) Is it possible that Bruce Willis inherited male pattern baldness from his father? Use the pedigree in (b) to demonstrate why or why not. d) Is it possible that Bruce Willis inherited male-pattern baldness from his maternal grandfather (his mother's father). Use the pedigree in (b) to demonstrate why or why not.

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The following figure shows the karyotype of an unusual individual from a population of the freshwater fish Characidium zebra. a) What is the karyotype formula for this individual (e.g. the karyotype formula for humans is 2n = 46). b) Members of this species are usually diploid. Something went wrong during the meiotic divisions that produced the gametes that fused to give rise to this individual. What must have been the ploidy of each of the two gametes that fused to produce this individual? Gamete 1: ___________________________ Gamete 2: ____________________________

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The human population has grown faster than exponentially over the last 200 years. Already humanity is using almost all arable land to produce food to sustain this growing population, raising concerns about future world food security as we are approaching 9 billion people by 2050. Explain why an increasing worldwide shift to a western, meat-dominated diet is heightening concerns about food security. Your answer should include: a) Explain which trophic level (plants, cows, or humans) stores more chemical potential energy, making reference to the Second Law of Thermodynamics. b) Identify what additional processes might lead to energy loss along the path from sunlight to work done in your cells. c) Based on these considerations, what changes to world diet would you propose that might have the biggest impact on increasing future food security in the face of continued population growth?

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The mosquito species Anopheles gambiae is the main vector of the malaria parasite, a widespread, deadly disease in tropical regions. One attempt to reduce malaria infections is thus tied to the control of mosquitoes of this species using pesticides such as DDT. Resistance to the pesticide DDT in Anopheles mosquitoesis associated with a dominant allele of the gene GSTe2. Biologists exposed a sample of 400 Anopheles mosquitoes to DDT to evaluate how common this dominant allele is in mosquito populations. They discovered that 231 of the mosquitoes in the experiment survived prolonged exposure to DDT. a) The biologists want to make a first, rough estimate of how common the allele leading to DDT-resistance is in Anopheles mosquitoes. Assuming the Anopheles population is in Hardy-Weinberg Equilibrium with respect to the gene GSTe2, determine how common the dominant allele associated with DDT resistance is in this population. b) Alarmed by their estimate for the abundance of this allele, these biologists decide that spending the money to take a closer look at the genetic structure of the Anopheles population is warranted to investigate the threat posed by DDT resistance in countries with high incidents of malaria. Their next step is to find out whether Anopheles populations are evolving with respect to the gene GSTe2, and whether the resistance-conferring allele is becoming more common in Anopheles populations over time. To do so, they extract DNA from a small tissue sample from the mosquito carcasses and use it to sequence the gene GSTe2 in all 400 Anopheles individuals from their original sample in order to determine their genotype. Here are their results: # of DD: 67 # of Dd: 164 # of dd: 169 What do you conclude: Is this population of mosquitoes evolving with respect to the gene GSTe2? Show your work. *) c) Based on the scenario described above, what is the likely evolutionary mechanism that is at work in this population? What is a prediction you would make about the frequency of the resistance-conferring allele if your hypothesis is true? d) Are the data the biologists collected consistent with the prediction based on your hypothesis for the evolutionary mechanism? Hint: compare the allele frequencies you determined in parts a) and b). Think about why these values are not the same. Is the direction in which they differ consistent with the scenario you proposed in part c)? Use the following Chi-square table to help answer Part (b):

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Two species of seed-eating finch live on islands in the Pacific. On some islands, either species occurs on their own, and on some other islands both species co-occur. The niches with respect to the preferred seed size in their diet overlap extensively on islands where these two species occur on their own (see graphs below). a) What process resulted in the shift in preferred seed size when both species co-occur on an island? Include a full explanation how this process allows these species to co-occur in the same habitat and avoid competitive exclusion. b) Give the seed size ranges that correspond to the fundamental niches and the realized niches for both species living on the same island. c) The two finch species differ in their beak size, which changes the seed size each is more efficient in handling and cracking. Drought conditions on these islands decrease seed abundance, while in wet years copious amounts of seeds of all sizes are produced. Identify whether the pattern shown in panel 3 with both species coexisting is likely more or less pronounced during drought years and provide a full explain why, by assuming that both birds compete for seeds solely through exploitative competition, and individuals of both tend to choose the seed size of the seeds currently available that each species finds easiest or quickest to manipulate, crack, and consume.

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Use the data in the character table below to construct a cladogram that shows the most parsimonious relationships among the taxa:

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Use the data in the table above to give: - your best estimate of the carrying capacity for this population - your best estimate for rmax of this population - the year where ∆N is greatest - an explanation of what information you would like to have about this population to improve your estimate of rmax for this population

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a) Label the appropriate structures that are associated with the following variables in Fick's Law in panel (a) of the above figure: A, L, P1, P2; and list which medium that D is associated with in the case of a lugworm. b) For which variables of Fick's Law do you find evidence that they are optimized in the case of the lugworm based on information in the figure above? Justify your answers for each variable you identified with 1 sentence. c) Smaller species of annelid than lugworms do not have gills. Explain why these small worms do not need gills to obtain sufficient oxygen. d) In many of the lugworm gills, the blood flows in the opposite direction to the current of water passing over them. Explain the advantage of this arrangement, making explicit reference to how it optimizes an aspect of Fick's Law. e) All annelid worms like the lugworm have blood which contains hemoglobin, However, the strength with which hemoglobin binds oxygen in the respiratory capillaries varies by species. Marine annelids that live in the intertidal zone have to survive in their burrows when the tide is out and oxygen concentrations in the remaining water drops to extremely low levels. Annelid species that live in open marine sediments have continual access to freshly oxygenated water. Predict whether you would find hemoglobin with a stronger affinity (stronger binding) to oxygen in intertidal annelid species like the lugworm or in open marine annelid species. Justify your answer by referring to variables in Fick's Law.

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A species of mice can have gray or black fur and long or short tails. Many crosses between black-furred, long-tailed mice and gray-furred, short-tailed mice all produce black-furred, long-tailed offspring. How many distinct genotypes will be found among the gametes of the black-furred, long-tailed P1 mice (i.e., the original parents)?

1

In fruit flies, eye color is a X-linked trait, and red eyes are dominant to white eyes. In a cross between a white-eyed female fruit fly and red-eyed male, what percent of the female offspring do you expect to have white eyes?

0%

If you assume this is a recessive, X-linked trait, what is the probability that individual 2 in the third generation (III-2) is a carrier of this allele? NOTE: Carriers are NOT indicated on this pedigree. In pedigrees, males are always indicated by squares, females by circles.

0.0

If a couple has exactly three children, what is the probability that they all will be girls?

0.125

If the couple of generation III with the blood group A and O phenotypes have two more children, what is the likelihood that both children will have the blood type O phenotype?

0.125

The human ABO blood group is controlled by a single autosomal gene with three alleles, IA, IB and i. Individuals with either the IAIA or IAi genotypes have blood type A; those with IB IBor IBi have blood type B; those with IAIB have blood type AB; and those with ii have blood type O. Imagine a mother with type-A blood, and a father with type-B blood have a baby with type-O blood. What is the probability that any given child of this couple will have type-O blood?

0.250

A population of 500 jackrabbits has two alleles, FBand FW, for a locus that codes for fur color. FBFBindividuals have black fur, FBFW individuals have gray fur,FWFWindividuals have white fur. 250 individuals are black, 150 individuals are gray and 100 individuals are white. What are the observed genotype frequencies in this population?

0.50, 0.30, 0.20

A species of seagulls exists as a large number of different populations on separate islands of the Azores archipelago. Both black and white gulls are present. The black-colored seagull is due to a dominant allele (M). Mm and MM individuals are black, and mm individuals are white. During a storm, two males and two females are blown 300 miles West, to an isolated island uninhabited by seagulls. They reproduce and found a new population. They cannot disperse back to the original habitat, nor can any new seagulls cross to the new island. Three of the original colonists were white-colored gulls and one was black. Genotyping shows the single black gull to be heterozygous. What is the frequency of the recessive (m) allele in this new population?

0.875

Explain at least TWO different mechanisms by which populations of two different species that compete for a shared resource in their environment are able to evade competitive exclusion, and can co-exist in the same habitat.

1) Their niches might not completely overlap. Even if they compete for exactly the same food resources, they each might be more efficient at doing so in a different aspect of their niche, for example with respect to the parts of their habitat in which they are less prone to predation. 2) Their populations may be kept far lower in their habitat by predation or pathogens than their theoretical carrying capacity at which resource limitation would set in and cause competetive exclusion.

In 2-3 sentences, explain how presence of a predator can allow two competing prey species with very similar niches avoid competitive exclusion.

1) Their niches might not completely overlap. Even if they compete for exactly the same food resources, they each might be more efficient at doing so in a different aspect of their niche, for example with respect to the parts of their habitat in which they are less prone to predation. 2) Their populations may be kept far lower in their habitat by predation or pathogens than their theoretical carrying capacity at which resource limitation would set in and cause competetive exclusion.

In lecture we saw that competition between two Paramecium species in their "petri-dish habitat" resulted in the competitive exclusion of one species. Propose specific changes that you could make to their petridish habitats that might have allowed both species to co-exist (other than introducing a predator).

1) feeding on food in different areas or give each a food that the other cannot utilize 2) make one habitat different in a different way (such as PH level) so that one area is limited to a species

Imagine Genes A and B are linked on one chromosome type, and Genes C and D are linked on another. For an individual heterozygous at all four genes (i.e., AaBbCcDd), how many distinct gamete genotypes are possible for this individual? (Ignore mutation and crossing-over.)

4

An individual has the following genotype for 7 genes: Aa bb Cc Dd ee FF Gg Genes A, B, C and D are all located on chromosome type 12, while genes , F, and G are all located on chromosome type 20. Assuming genes A through D and genes E through G are so tightly linked on their chromosome (so close together) that crossing-over between them is so unlikely that we can assume a recombinant frequency of 0% between all linked genes shown here, how many unique gamete genotypes can this individual produce? If on the other hand all linked genes are far enough apart to allow for measurable rates of crossing-over between them, how many unique gamete genotypes can this individual produce?

4, 16

Predict what happens if you set up the same cross (Aa Bb x Aa Bb), but this time you know that the two genes are linked with a distance of 40 cM between them. You further know that the two double heterozygous parents you used were both produced from the same cross of the 2 true-breeding lines: AA BB and aa bb, what is the phenotypic ratio you expect then?

59 : 16 : 16 : 9

In a species of mouse, there are two alleles (A1 and A2) of a single gene that control coat color. A1A1 individuals have white coats, A1A2 individuals have brown coats, and A2A2 individuals have black coats. A breeding pair of brown mice produce 12 offspring. How many of those offspring do you expect to be brown?

6

The human lung contains about 150,000,000 alveoli. The large number of alveoli maximizes which term of Fick's Law of Diffusion?

A

Explain multiple ways in which a deleterious allele can persist in a population: I only thought of one way, and I am not even sure if what I proposed is accurate, but I have inbreeding depression, where a deleterious allele can persist in a population because of considerably less genetic diversity due to the smaller number of genotypes being passed from generation to generation, as well as the higher chance for mutations that arise due to random chance to be passed on. Is this method correct, and what are the other ways that we need to know?

A deleterious recessive allele is immune from selection in a carrier (selection only acts on the phenotype, and the recessive phenotype is not displayed in carriers). If population size becomes very small, drift becomes ever more important, and can even trump selection so that a previously rare, deleterious allele can even become fixed in a population just by chance during a founder event or bottleneck event. Those are the main two ways this has come up.

Explain what makes an organism a good model organism. What properties makes the fruit fly Drosophila melanogaster a great model organism for studying genetics?

A good model organism displays the general properties we are interested in studying, and should be relatively easy to raise and manipulate in order to test predictions on. For investigating basic genetic principles, the fruit fly Drosophila turned out to be a fantastic model organism. The high number of mutants available, and the ease of raising populations, fast generation time, and the very high number of offspring per pair that we are crossing all aid in genetics experiments. (there are many other reasons that could be listed that make Drosophila a great model organism - depending what we are interested in studying - for example, we have the entire genome of this organism sequenced, the embryonic development of Drosophila is well known, and can be studied relatively easily, etc).

Define what a null hypothesis is. What is the null hypothesis for evolution? What is a prediction associated with this null hypothesis that you can test for a population? What kind of data do you need to collect to test this hypothesis?

A null hypothesis describes what would happen if only random processes are at play. The null hypothesis for evolution is that a population is not evolving, because all alleles are equally likely to be passed on, as all individuals are equally likely to reproduce, and pass their alleles on in the same proportions, while mating with a partner of random genotype for the gene under observation. The PREDICTION associated with this null hypothesis is that genotype frequencies will be in Hardy-Weinberg proportions in the next generation, if (and only if) the null hypothesis is true for a given gene in a population.

In which of the following scenarios would you expect allele frequencies in a population to shift dramatically in just one generation?

A severe flood kills 90% of an insect population.

In which of the following scenarios is the rapid fixation of an allele most likely?

A small population of plants that establish themselves on an island previously uninhabited by this plant

What aspect of fitness is NOT represented by the two shown selection pressures in the graphs above? (Graph 1 goes down, graph 2 goes up)

Ability to produce viable and fertile offspring

Which of the following is NOT a possible outcome of genetic drift over time?

Adaptation

What type of variation in finches is passed from parent to offspring?

All characteristics that are genetically determined.

Imagine two genes, one that controls eye color (either black or orange), and one that controls feather color (either white or green) in a bird species. Several thousand crosses are performed between males that are heterozygous for both genes and females that are homozygous recessive for both. These crosses produce the following four phenotypes in approximately equal proportions: 1) black eyes and green feathers, 2) orange eyes and white feathers, 3) black eyes and white feathers, and 4) orange eyes and green feathers. Which of the following best explains these results?

Alleles of these genes are assorting independently.

K-strategists such as humans typically have slower intrinsic rates of population growth (r) than r-strategist. Explain what property of the concept "carrying capacity" can nevertheless lead K-strategists to exceed their long-term carrying capacity.

Although K-strategists are far less likely to exceed the carrying capacity through increasing their population size from one generation to the next, carrying capacity is not fixed, and a growing population of a K-strategist might cause sufficient environmental degradation to reduce the carrying capacity of the environment below the current population size of the species, leaving the current population "high and dry" above the new carrying capacity of its habitat.

Marfan syndrome is one of the most common inherited disorders of connective tissue. Marfan syndrome is caused by mutations in the FBN1 gene. There is a wide variability in clinical symptoms in Marfan syndrome with the most notable occurring in eye, skeleton, connective tissue and cardiovascular systems. It is an autosomal dominant condition. In the US, one in every 10,000 individuals displays symptoms associated with Marfan syndrome. Assuming the US population is in Hardy-Weinberg equilibrium with respect to the gene FBN1, what do you predict is the frequency of the disease-causing allele in the US? SHOW YOUR CALCULATIONS TO RECEIVE FULL CREDIT.

Be careful with this problem: the disease-causing allele is dominant! That means among the 1/10,000 individuals, some will be homozygous dominant and some will be heterozygous, which we cannot distinguish based on phenotype. Homozygous recessive individuals will not show the disease, however, and we know the frequency of this genotype in the population. If (and only if) we can assume that the US population is in Hardy Weinberg Equilibrium as the problem states, the frequency of homozygous recessive (wild-type) individuals will be q2. so: q2 = 9,999/10,000 = 0.9999 the frequency of the wild-type recessive allele is q, which we can estimate by taking the square root of q2: q = 0.99995 so we know that the frequency of the dominant allele associated with Marfan syndrome in the US population is p = 1-q = 0.00005.

Which one of the following populations would most quickly lead to two groups with few shared traits? The answer is disruptive selection and I think I know the reason, but why can't directional selection be the answer?

Because directional selection moves allele frequencies of the entire population in one direction, rather than separating the population into two genetically distinct subpopulations as disruptive selection would.

Which of the following diagrams correctly labels the alleles of a diploid organism that is heterozygous for three genes (A, B and C)? Genes are depicted as solid black lines crossing the chromosome, and allele labels are immediately adjacent to them. Dominant alleles are shown in upper case, recessive alleles in lower case. Not all genes or alleles are labeled.

C

All organisms release heat primarily released by metabolic reactions during cellular respiration associated with the organelle mitochondria. Compare the following two images of cells: Which if these cells most likely belongs to an endotherm?

Cell B.

Which of the following is NOT a good explanation for why crocodiles possess a Foramen of Panizza?

Crocodiles inherited this structure from their common ancestor with all other reptiles.

How did the different beak types first arise in the Galapagos finches?

Changes in the finches' beaks occurred by chance, and when there was a good match between beak structure and available food, those birds had more offspring.

If you want to test your prediction in the preceding question, which of the following data would you need to collect to directly measure the fitness of male guppies in this population?

Count the number of offspring produced by male guppies

What process or processes listed below can result in allele fixation?

Directional selection

All phenotypic traits of an organism are adaptations.

False

Which process contributes the largest amount of genetic diversity to offspring of a pair of unrelated individuals, and why: mutations, independent assortment, recombination, fertilization.

Fertilization. Mutations are rare enough that for any given couple this process will not contribute much to the genetic variation among their offspring. independent assortment and recombination can result in different combinations of the alleles of all the genes that each parent carries, contributing a large amount of variation in the offspring. the greatest contributor is likely fertilization though, where two gametes from unrelated individuals fuse (syngamy), simply because this allows many alleles from an individual not shared with the unrelated other parent to merge with those from the other parent, contributing to combinations of alleles of different genes that may have never occurred in the past.

Depending on their beak size and shape, some finches get nectar from cactus flowers, some eat grubs from bark, some eat small seeds, some eat large nuts. Which statement best describes the interactions among the finches and the food supply?

Finches compete primarily with closely related finches that eat the same kinds of food, and some may die from lack of food.

Which process is most likely responsible for the frequency of the deleterious allele to be more common in the boxer population?

Genetic Drift

Which of the following graphs shows the overall fitness of male guppies with different phenotypes in this environment?

Graph B (graph goes up, has a peak, then goes down, like an "n" shape)

Rana aurora (red-legged frog) breeds in fast-moving, temporary streams, whereas its relative Rana catesbiana (Bullfrog) breeds in permanent ponds. What is the isolating mechanism between these Species?

Habitat isolation

Consider the following two genetic disorders (descriptions modified from Wikipedia): Huntington's disease is caused by an autosomal dominant allele of a gene called Huntington. It is a degenerative disorder that affects muscle coordination and leads to cognitive decline and dementia. Physical symptoms of this particular variant of Huntington's disease usually begin between 35 and 44 years of age. Tay-Sachs is caused by an autosomal recessive mutation on the HEXA gene. Its most common variant causes a deterioration of mental and physical abilities that usually results in death by the age of four. Using only this information, could either of these genes be in Hardy-Weinberg equilibrium (HWE) in the US population (>300 million people)?

Huntington's could be in HWE, but not Tay-Sachs

Which reproductive isolating mechanism operates after the zygote is formed?

Hybrid sterility

You sequence the gene TTN in a sample of individuals taken from the boxer population, and discover that the genotype frequencies in the boxer populations are as follows, Where 'T' and 't' represent the dominant and the recessive alleles for gene TTN: First, test the null hypothesis that this population is in Hardy-Weinberg Equilibrium for this gene, and state your conclusion. Refer to the following Chi-Square table to obtain the associated p-value:

I reject the null hypothesis, with a calculated p-value of <0.001

What information do you need to determine if two birds are the same species using the biological species concept?

If they can produce fertile offspring

Mammals are endotherms, and use an elevated rate of cellular respiration in all their cells to maintain a higher body temperature than their surroundings (as compared to ectotherms). The actual body temperature results from the balance of heat production during cellular respiration and heat loss from the body surface. Small mammals such as mice have to engage in much higher rates of cellular respiration in each of their cells to maintain the same internal body temperature than big mammals such as elephants. How can you explain this observation? Make sure you include a full description of how the relevant concept works.

In mammals, production of body heat is proportional to body volume because the number of cells that each release heat increases by the volume. The loss of heat to the environment (when the environment is colder than the body temperature) is proportional to the surface area of the organism. Smaller organisms generally have a higher SA:V than larger mammals, so were they to have the same metabolic rate as a larger mammal, they would lose heat to their environment proportionally faster than they would produce it. A higher metabolic rate in smaller mammals allows them to balance the relatively higher rate of heat loss.

Which of the following is NOT true regarding bulk flow?

It is an exergonic (energetically favorable) process that releases energy

Inbreeding depression is not observed in species like Mendel's garden peas, where self-fertilization has occurred routinely for many generations. Why not?

Inbreeding exposes deleterious recessive alleles to selection. After many, many generations of inbreeding, deleterious recessive alleles can be lost from the population. Once this occurs, a self-fertilizing population will not exhibit reduced fitness under additional generations of inbreeding.

The pedigree below does not indicate carriers. Assume that individuals not directly descended from the original two parents are homozygous dominant. Using the phenotype information indicated on the pedigree, which of the following individuals must be a carrier?

Individual B

Imagine a recessive autosomal genetic disorder that causes death before sexual maturity. Which of the following best helps explain why such alleles persist in populations for long periods of time?

Individuals that are carriers of the allele have the same fitness as individuals without the allele

Why does gene flow make speciation by reproductive isolation less likely?

It prevents populations from diverging

When an animal of same size grows, its respiratory surface area increases faster than expected for a body of the same shape. Which of the following is the most likely pattern and explanation for this pattern that we observe as an animal grows?

Maintaining a constant SA:V ratio keeps the supply rate of oxygen in line with the demand of oxygen as the animal grows.

Male guppies are quite colorful fish, while female guppies tend to have a tan coloration. Guppies live in pools at the edges of streams that harbor predatory fish that hunt prey by sight. Furthermore, female guppies show a strong preference for male coloration when selecting a mate, while males tend to court and attempt to copulate with any female they encounter in their environment. According to the information in the scenario above, which of the graphs above represents selection pressures on male versus female guppies: (Graph 1 goes down, graph 2 goes up)

Males experience BOTH selection pressures, females experience selection pressure 1

Explain why the SA:V ratio of respiratory surfaces and the body volume does not become limiting in large multicellular animals.

Multicellular organisms have methods of transport like tubes and vessels that carry materials from one part of the organism to another. These transport systems make close contact with cells, such as those of exchange surfaces.

Purebred boxers are one of the dog breeds that have an elevated likelihood to suffer from heritable cardiomyopathy (abnormal heart rhythms caused by a pathological ventricle) that can lead to premature death, and is caused by the presence of a recessive allele of the gene TTN, which codes for the protein titin. Titin provides structure, flexibility, and stability to muscle cells. Genetic testing confirms that the deleterious allele responsible for this condition is unusually common in boxers compared to other dog breeds and compared to wolves (wild ancestors of dogs). Which process is most likely responsible for the frequency of the deleterious allele to be very low in ancestral wolf populations?

Natural Selection

Based on the scenario described at the beginning, and a comparison of the observed number of individuals to the expected number of individuals if the population were in Hardy-Weinberg Equilibrium, which of the following processes is the most likely to be currently acting on this population of boxers?

Non-random mating - positive assortative mating

Based on the data presented in the previous question, what do you know for sure?

One or more of the five violations of Hardy-Weinberg must have been acting on this population within the last generation to cause its genotype frequencies to deviate from Hardy-Weinberg proportions.

These images are electron micrographs of two single-celled organisms. Assume the volume of each cell is equal, and that the only way in which they differ is their shapes. Which of these organisms has a lower surface-area to volume ratio?

Organism 2

Which of the following is NOT one of the fundamental properties of life?

Organisms require oxygen.

Use the following parameters of Fick's Law of Diffusion to indicate which parameter differs between the two diagrams below.

Phigh-Plow and L

In which of the following situations would it be impossible for the indicated mechanism to cause divergence between two populations of flowering plants?

Pollinators have no preference for flower color and routinely visit flowers in both populations

What causes insecticides (man-made chemicals intended to kill insects) to become less effective over time?

Regular use of an insecticide kills almost all individuals except those with alleles that allow them to tolerate the insecticide.

I was wondering if we have to know about gene segregation. If so, can you please clarify what this refers to?

Segregation is one of the two laws of Mendel. Segregation simply refers to that traits (alleles as we now understand them to be) do not just blend together irreversibly when you cross two parents of different versions of those traits, but remain separate, and can be reconstituted among some of the offspring.

How do sexual selection and inbreeding differ?

Sexual selection can change allele frequencies, inbreeding cannot.

Compare and contrast expected changes in allele frequency in a population depending on if that allele is under selection versus experiencing drift: Is this saying that when a population is under selection, allele frequencies will change based on the fitness of individuals and of the genotypes and phenotypes in the population, whereas in a population experiencing drift, all changes in allele frequency depends on random chance alone? Or is there some other aspect of this that I am missing?

That's exactly it.. so as a consequence the allele frequencies modified by drift go up and down through time in an unpredictable manner - whereas alleles under selection follow very strong and predictable trends in how their frequency changes over time in a population.

Justify why traits/behaviors for the "good of the species" (but at the cost of an individual's fitness) would not be favored by natural selection: Is this because natural selection does not have a brain and cannot choose which trait or behavior is more or less beneficial for the species? So, the only factor that plays into natural selection would be the individual's fitness, and if the fitness is lowered by the trait or behavior, the natural selection would work against it.

That's exactly right. and it is measured by the INDIVIDUAL's fitness... not at the population level. Because only the individual's fitness in that environment determines which alleles get passed on more than others.

Why do the circulatory systems of land vertebrates have separate circuits: one to the lungs and the other to the rest of the body?

The decrease in blood pressure as blood moves through the lungs may prevent efficient circulation to the rest of the body without passing the heart a second time.

Making specific reference to the relevant parameters of Fick's Law of diffusion, describe how the complete division of the ventricles of the mammalian heart improves the ability to perform cellular respiration in body cells (e.g., a muscle cell in the legs) relative to vertebrates that do not have a single ventricle that is not fully divided (e.g., frog).

The complete division of the ventricles prevents the mixing of oxygenated blood returning to the heart from the lungs with deoxygenated blood returning to the heart from the body. By not mixing the two, the blood that reaches the body has a higher concentration of oxygen (P2) when it reaches the cell, relative to an organism without a fully divided ventricle. This maximizes the (P2 - P1) term, and giving a higher rate of oxygen diffusion from the blood into the cell. This oxygen is required by the cell as an input for aerobic cellular respiration.

What caused populations of birds having different beak shapes and sizes to become distinct species distributed on the various islands?

The finches were quite variable, and those whose features were best suited to the available food supply on each island reproduced most successfully.

I was wondering if you could clarify the difference between assortative mating (non-random mating) and inbreeding. Is assortative mating a type of inbreeding?

The other way around. Inbreeding results in a form of positive assortative mating, because close relatives of an individual are more likely to share their genotype for a gene than a random, unrelated individual.

Why is meiosis 2 more close to mitosis than meiosis 1?

The processes in Meiosis I are wholly different from Mitosis. Homologous chromosomes meet up, form a synaptonemal complex, exchange genetic material between homologous chromosomes, and at the end, the ploidy of the cell is halved, going from diploid to haploid as homologs are separated. Meiosis II on the other hand proceeds generally like Mitosis, where sister chromatids of all chromosomes currently present in the cell are simply separated into the resulting daughter cells. The only difference between Mitosis and Meiosis II really, is that Mitosis generally proceeds for a diploid cell (at least for organisms that follow the life cycle of animals), while meiosis II proceeds for a haploid cell.

In the finch population, what are the primary changes that occur gradually over time?

The proportion of finches having different traits within a population change.

You are given the following cross for two genes: Aa Bb x Aa Bb You determine the gametes both parents can produce and set-up a Punnett Square. You predict a phenotypic ratio of 9:3:3:1 for the offspring of this cross by counting the offspring fields associated with each phenotype. What assumption(s) did you make when you counted the fields of the Punnett Square to obtain this ratio?

The two genes are unlinked The two genes both display complete dominance The two genes are reshuffled via independent assortment

If you observe significant deviations in genotype frequencies for ALL genes from Hardy-Weinberg Equilibrium expectations in a population, that result in higher frequencies of homozygotes than expected, what is likely occurring in this population?

There is a lot of inbreeding in this population

Characterize how the biotic interactions of interspecific competition and predation and abiotic factors of an organisms' s environment result in selection pressures from that interaction can that affect intraspecific competition of individuals of different genotypes: I do not understand what this one is asking exactly.

This is a connection between Unit 1 and this Unit: environmental variables from the abiotic environment (temperature preferences of different genotypes etc etc) and how they fare in competition or predatory interactions with other individuals are all components of the environment where some genotypes in the population may end up having higher fitness than other genotypes exposed to the same environmental pressures. Those environmental pressures thus act as selection pressures on the population.

If a trait evolves convergently more than once, what is most likely true?

This trait is most likely adaptive.

Discuss the causes of heritable variation and the consequences of differential survival and reproduction for variation in a population: Are the two causes of heritable variation mutations and recombination of alleles through fertilization, and do differential survival and reproduction result in variation in a population because individuals who survive and reproduce will pass on their genotypes to the next generation whereas individuals who either do not survive or do not reproduce will not pass on their genotypes, creating variation?

Variation is initially added through mutations. sexual reproduction then results in a great number of different ways this variation in different traits can occur (which coat color with which fur length for example, etc). All of this variation is then subject to natural selection - which of these phenotypic variants in the population have the highest reproductive success on average - and whatever alleles are associated with those traits are going to become more and more over represented. This one is keying in part into the contrast between where variation comes from (mutations) and why particular phenotypic variants become more common in a particular environment that result in adaptations (natural selection).

Finches on the Galapagos Islands require food to eat and water to drink.

When food and water are scarce, some birds may be unable to obtain what they need to survive.

In mammalian embryos, developing into the male body-plan it initiated if the individual possesses a copy of the SRY gene, which is located on the Y-chromosome. Not inheriting a copy of the SRY gene retains the female body plan. Interestingly, this means that in mammals the female body plan is the ground plan, from which the male body plan is modified away from during develop. What is the resulting inheritance pattern of sex determination in mammals (including humans)?

Y-linked

Explain why we essentially never see the appearance of a brand-new structure "from scratch", but rather tinkering with pre-existing structures that can be co-opted for new functions.

You inherited a set of developmental genes from our ancestors. As it turns out, most animals share similar developmental genes, all inherited from deep ancestors - at least for early embryonic developmental stages. It is unlikely that you will evolve completely new developmental genes that will cause structures to develop that increase the fitness of an individual with these from the get go - that is like creating a hopeful monster - very low likelihood. But in order for this structure to be selected for, it has to increase the fitness at every step along the way. A more likely scenario is to take pre-existing developmental programs and modify them slightly - often simply by changing where and when and for how long different developmental genes are turned on - to result in differences in the structures that develop from these. And that seems to be what is happening in nature. An example of this can be seen in your limbs for example, which still use exactly the same developmental program (genes) as the fins in lobe-finned fish such as the lung fish, but expressing these at different times and locations to result in your limb with hands rather than a fin lobe with fin rays.

What is the relationship between maintaining homeostasis and reaching chemical equilibrium with the environment for a living cell?

a cell needs to maintain homeostasis in order to perpetually keep itself out of chemical equilibrium

Which of the following describes a phylogenetic constraint?

a developmental pathway in a group of organisms that can be modified by natural selection but that is difficult to reverse

a) Explain what inbreeding and assortative mating are. b) Explain what the effect of both is on allele and genotype frequencies, and why neither on their own would lead to evolutionary change in the population. c) Most individuals in the human population (the same is true for many other species) are carriers of an estimated 7 recessive alleles that - if present in the homozygous condition - would be fatal. Based on your answer to part (b) above, suggest a hypothesis for how both inbreeding and assortative mating might indirectly lead to enhanced selection against recessive alleles in a population where either inbreeding or assortative mating is frequent.

a) Inbreeding refers to matings between close relatives, whereas assortative mating refers to matings between individuals that are of like phenotype (and more likely than not genotype). b) Both matings between close relatives and assortative matings make it more likely that individuals are of like genotype. In these cases, homozygous genotypes will become increasingly common among successive offspring generations, and heterozygotes increasingly rare. However, allele frequencies are not necessarily affected by this (just their distribution among genotypes). Given that biological evolution is defined as a change in allele frequency across successive generations, inbreeding or assortative matings do not necessarily lead to evolutionary change in the population. c) However, the increased likelihood of producing homozygous individuals reduces the chances that a deleterious recessive allele can "hide" in heterozygous carriers. SInce homozygous recessive individuals display the effect of deleterious recessive alleles phenotypically, the increased occurrence of homozygous recessive individuals among the population can result in stronger selection against the recessive allele in populations that experience inbreeding or assortative mating - and can ultimately lead to the loss of these recessive alleles from the population.

Many patterns of the distribution and abundance of different organisms on the Earth are a direct consequence of basic limitations set up by basic Laws of Physics. Explain how physical limitations of our universe set up energetic constraints on life at three different levels of organization. Make sure to relate your answers to each part of this question back to the Second Law of Thermodynamics: a. Explain why life could not exist without access to an "outside" source of energy. What is this energy needed for, and why do all organisms die if they lose access to an energy source? Include in your answer which of the "characteristics of life" are affected by this absolute requirement to access to an external energy source. b. Organisms rely on chemical potential energy stored in C-H bonds of organic molecules like carbohydrates and respiratory bases such as oxygen to oxidize these molecules and make the stored energy biologically available. All organisms rely on diffusion to obtain these respiratory gases, and some on bulk flow. Identify which of these two processes requires no energy input to do work, and explain why this process is favorable under the Second Law of Thermodynamics. c. Explain how the Second Law of Thermodynamics forces the carrying capacity (in terms of energy stored in the total biomass) of each successive trophic level to be lower than of the next lower trophic level.

a) Most of the 6 characteristics of life involve endergonic reactions, including the ability to reproduce, to grow, to react to the environment, to maintain homeostasis and an internal environment that is distinct from the external environment, and being highly organized. (Only the fact that life evolves does not inherently require endergonic reactions). The second law of thermodynamics requires that the universe overall move toward increasing disorder (which is in part achieved by the release of heat to the environment). As a consequence, the only way for non-spontaneous processes to proceed that result in increased order (for instance inside a cell or the body of an organism overall; maintaining homeostasis far away from equilibrium), is if they are coupled to favorable exergonic reactions that provide the cell or organism with an external energy source to do work. b) c) One of the consequences of the second law of thermodynamics is that there needs to be an overall NET release of free energy from the system we look at to the surroundings (the rest of the universe). This is just a fancy way of saying that no transfer of energy can ever be 100% efficient; some energy is always lost to the environment, usually as heat. Thus, it is physically impossible for organisms on a higher trophic level to obtain all of the energy stored in the chemical bonds of the biomass in the previous trophic level. (The above is a sufficient answer. However, for completion sake, we should remember that a second reason for this trophic pattern is that organisms at each trophic level use a large fraction of the energy they consumed to power their own endergonic reaction with cellular respiration. This portion of the consumed energy is not available to be incorporated into the organic molecules that make up the tissues of that organism, and hence are not available to an organism on the next higher trophic level to consume.)

a) Explain what the benefits of asexual reproduction are. b) Explain what the benefits of sexual reproduction are. c) Parthenogenesis (reproduction via asexually produced eggs without fertilization) is comparatively common in some lizard species. There is evidence that currently asexually reproducing species are all relatively young, whereas sexually reproducing species are on average older (have persisted for longer). This seems to indicate that while asexually reproducing species readily evolve and are successful at quickly increasing their population sizes, their populations do not seem to persist for as long, on average, as sexually reproducing species before dying out again. (i) Based on your answers to (a) and (b) suggest a hypothesis that might explain this pattern. (ii) What is a prediction based on your hypothesis that you could use to test your hypothesis with?

a) Since in asexual reproduction, every individual in the population produces or gives birth to offspring, asexually reproducing individuals display faster population growth than sexually reproducing individuals. b) Sexual reproduction leads to high genetic variability among sexually reproduced offspring by exchanging (and sharing) alleles with other individuals. Higher genetic variability provides increased phenotypic variation. Particularly in a variable environment, or when competing with other species or dealing with evolving parasites, disease agents or predators, the resulting phenotypic variation may allow more of your offspring to be successful down the road, than if all individuals were genetically (and phenotypically) identical - or if acquisition of new genetic variation in a family lineage were to depend entirely on new mutations. c) Asexually reproducing individuals in a population tend to thus have higher fitness and can hence rapidly outcompete sexually reproducing individuals in the short term, explaining why asexually reproducing species or populations can evolve, if some mutation pops up by chance that allows a female individual to reproduce parthenogenetically. However, populations of parthenogenetically reproducing females have only acquisition of new mutations to provide genetic variation among individuals, reducing the ability to evolve in the face of changing environmental conditions and hence changing selection pressures. This reduces the ability of these species to respond to environmental changes, increasing their likelihood of going extinct compared to sexually reproducing species. If this hypothesis is true, then I should expect that parthenogenically reproducing species have lower genetic variation among individuals (fewer alleles in the population) than in related, sexually reproducing species.

Which of the following is true about both of the following mutations: a substitution that causes a nonsense mutation a three-nucleotide insertion mutation

both would have no effect on the translated amino acid sequence

Endothermy come with trade-offs. Based on the information on endotherms in the previous questions, select all choices below that are likely to be benefits to being an endotherm:

c. Having more energy available to support faster growth e. Able to engage in longer strenuous physical activity

This diagram depicts four chromosomes of a diploid organism. The loci of three genes (Gene A, Gene B, and Gene D) are shown. Each gene has two alleles, indicated as upper- and lowercase letters. Dark bars crossing chromosomes represent gene loci, and alleles are labeled immediately adjacent to them. Which of the following accurately describes the processes that can create combinations of alleles of these three genes that were not present in this individual's parents?

crossing over but not independent assortment

A woman who is a carrier for an X-linked genetic disorder is expected to pass the allele associated with the disorder to what proportion of her children?

half of her daughters and half of her sons

Consider the following graph of body size in a population of insects in 2008 and 2012: (2008 graph makes "n" shape, 2012 makes "u" shape) What type of selection is depicted?

disruptive

Consider the following graph of body size in a population of insects in 2008 and 2012: What type of selection is depicted? (2008 makes n shape, 2012 makes u shape)

disruptive

'Maximum parsimony' is a general principle with broad application in science, which states that:

in the absence of additional information, the explanation that makes the least unsupported assumptions is the most likely.

A species that possesses only a single chromosome type is not capable of which process to generate additional genetic diversity?

independent assortment

Which of the following (by itself) will NOT change allele frequencies of a single gene within a population?

independent assortment

Prof. Berlocher, a well-known biologist at the University of Illinois who is working on mechanisms of speciation, found two populations of very similar looking flies in the genus Rhagoletis that live side-by-side on the fruits of hawthorn and apple trees in the same geographic area. He would like to test whether these two populations are in fact separate species, that is, they do not mate with each other to produce viable offspring. Taken individually, he notices that each population (apple and hawthorn population tested separately) is in H-W equilibrium. He is planning to test whether flies from both populations combined are in Hardy Weinberg Equilibrium. He points out that if a group of flies sampled from both populations and combined in the analysis is NOT in Hardy Weinberg Equilibrium, this result would be consistent with the two populations representing distinct species. Why can he make this prediction? - Which assumption of the Hardy-Weinberg principle would be completely violated if the two populations are separate biological species?

individuals choose other individuals at random to mate with

Species in a polyphyletic grouping likely have ....

many analogous characters that were mistakenly assumed to be shared derived characters

Below are segments of mRNA sequences transcribed from the DNA of a single gene in two different individuals. The original sequence is that found in most members of the species, and the new sequence has been recently discovered in a single individual. Original mRNA sequence: AUGUAUUGGCCU New mRNA sequence: AUGUAUCGGCCU This mutation would be classified as a _____________________ mutation.

missense

Which of the following statements justifies why mutation is a random process, but evolution by natural selection is a nonrandom process?

mutation is an error that occurs during DNA replication, but selection results from differences in fitness

A small population of wolves was reintroduced to southern New Mexico 20 years ago. Within the population at that time were two different alleles (A1 and A2) for a particular gene that affects coat color. A recent analysis shows that there is only one allele (A2) in that population today, after only three generations. Which of the following mechanisms are potential reasons for this observation?

natural selection AND/OR genetic drift

Recombination of alleles is caused by the exchange of genetic material between ____________.

non-sister chromatids of homologous chromosomes

A virus killed most of the seals in the North Sea (e.g., reduced the population from 8000 to 800).What is this an example of?

population bottleneck

Which answer correctly describes the order of events that can occur during the process of speciation?

reduced gene flow, selection, reproductive isolation

Which of the following differences would you expect between an ectotherm (cold-blooded animal) and an endotherm (warm-blooded animal) of equal size?

the ectotherm consumes O2 at a lower rate than the endotherm

In a plant, the allele that results in violet flowers (V) is dominant to one that results in white flowers (v); at another locus, the allele that makes prickly seed capsules (P) is dominant to one that results in smooth capsules (p). A plant with white flowers and prickly capsules is crossed with one that has violet flowers and smooth capsules. The resulting seeds were planted and yielded 50 plants with white flowers and prickly capsules, 46 plants with white flowers and smooth capsules, 45 plants with violet flowers and prickly capsules, and 47 plants with violet flowers and smooth capsules. What are the genotypes of the two parents?

vvPp and Vvpp

In humans the blood groups A, B, AB, and O are determined by three alleles of an autosomal gene I: IA, IB, and i. Alleles IA and IB are codominant to each other, and allele i is recessive to the other two. The blood type phenotypes of some individuals in the pedigree below are indicated. Empty symbols represent individuals whose phenotype is unknown.

type A, type B, and type O