BIO 3400 (Bush) - Exam 1-7 Questions - Mizzou
(exam 7) A food chain consists of phytoplankton, which are eaten by small fish, which are eaten by big fish, which are eaten by walruses. For every 50 calories of energy in the body of a walrus, how much energy must be present in the phytoplankton?
50 walrus 500 big fish 5,000 little fish 50,000 phytoplankton
(exam 6) The Evening Bat (Nycticeius humeralis) and Keen's Bat (Myotis keenii) are similar in size and resource requirements. Both species are found in eastern North America. Dr. S and Dr. J disagree with each other about the likely outcome of competition between the two species. Dr. S thinks that the Evening Bat will always outcompete the Keen's Bat, whereas Dr. J thinks that both species will exist in a stable equilibrium. To explore the likelihood of these possibilities, they calculate the Lotka-Volterra Zero Growth Isoclines of the two species. On the axes below, draw the isoclines if a) Dr. J is correct, and b) Dr. S is correct. (Save axes c for the next question.) Be sure to label your lines with E (for Evening Bat) and K (for Keen's Bat). Dr. S and Dr. J find that they are both wrong. Their research suggests that the two species exist in an unstable equilibrium. Draw & label the zero-growth isoclines representing this conclusion on axes c.
A. line E above line K, intersect B. line E (above) parallel w/ K --> never cross C. line K above line K, intersect
(exam 3) You find a fossil in a local stream and show it to your grandfather, who has never had an opportunity to learn about evolution. In the course of your conversation, he says, 'evolution is just a theory, after all.' Based on our discussion in class, describe a respectful response that an evolutionary biologist would use to address this misconception. (2-3 sentences)
Although in everyday language, the word theory is often used to mean a hunch, a formal scientific theory is very different. In science, a theory is a broad explanation - it pulls together and explains a diversity of observations. For an explanation to rise to the level of a formal scientific theory, there will be lots of evidence supporting it. We use the word 'theory' when describing the Theory of Gravitation, Cell Theory, and the Theory of Plate Tectonics, none of which is 'just a hunch.' BTW, there's nothing wrong with the assertion that evolution is a theory; the problem is the context of statements like 'it's just a theory.'
(exam 5) According to your reading assignment, is light colored skin homologous or analogous between people of European and East Asian ancestry? What is the evidence? (1 sentence)
Analogous, based on the observation that different genes cause the reduction in pigment in people of European vs Asian ancestry. Note: the question asks for the evidence, i.e. how do we know this?
(exam 2) Among shorebirds, some species have a flat bill and others have a little nub, or bump, on top of the bill. The phylogeny of shorebirds is based on DNA and is labeled according to bill shape of the species. Is it more likely that the most recent common ancestor of all species in the tree had a flat bill or nubbed bill? Explain your answer. (1 sentence)
Based on maximum parsimony, it is more likely that the common ancestor of all species in this tree had a nubbed bill. If the common ancestor had a nubbed bill, it would require a minimum of 3 transitions (to flat bills) to achieve the distribution of bill types illustrated by the tree; if the common ancestor had a flat bill, it would require at least 4 transitions
(exam 4) Based on our classroom discussion, what disease is sometimes characterized as 'a loss of multicellularity?'
Cancer. Multicellularity requires that individual cells hold down their own reproductive rates. Cancer is the loss of this control.
(exam 4) There is abundant evidence that the earliest cells used RNA rather than DNA as their information storage molecule. According to your reading assignment, what was the advantage of switching to DNA?
DNA is a more stable molecule than RNA.
(exam 4) Bearded dragons - lizards that are popular in the pet trade - have a fringe of spines around their necks. Louise attempts to increase the average length of the spines through artificial selection: she measures a population of lizards, breeds together only the lizards with the longest spines, then measures the spines of the offspring generation. Histograms of spine length in the parent pop are shown on top (with individuals chosen to breed shaded in gray) and the first offspring generation below. Louise is surprised to find that in addition to an increase in average spine length, the offspring generation includes some individuals with much longer spines than occurred in the parent lizards. Given that none of the parents had such long spines, she attributes these very long spines to the luck of new mutations. Would you agree or disagree with this interpretation? Explain your answer (1-2 sentences)
Disagree. The more likely explanation is that spine length is under the influence of multiple genes. New combinations of alleles of those genes (in the absence of new mutations) can generate longer spine lengths.
(exam 3) Why is it more challenging to accurately date fossils found in caves than fossils found embedded in rock? (1-2 sentences)
For fossils that are deposited in sediments (i.e NOT in caves), if you can determine the age of the rocks directly above and below that sedimentary layer, you can estimate the age of the fossil - it is younger than the rocks below it but older than the rocks above it. With fossils found in caves, however, the rocks both above and below the fossil are older than the fossil, because the cave existed prior to the animal dying (or being deposited) there. Fossils found in caves are therefore expected to be younger than the cave itself, but it's difficult to determine the age more precisely than that.
(exam 6) Think about the experiments by Park with flour beetles (called them species a and b), as described in your reading assignment. Which of the possible outcomes of the Lotka-Volterra classwork exercise would correspond to Park's results? One sentence.
In Park's experiments, one species always drove the other to extinction, but it appeared to be random which one would prevail; this corresponds to an unstable equilibrium.
(exam 6) According to the Demographic Transition Model of population growth, birth rates equal death rates in both stage 1 and stage 4. How are stage 1 and stage 4 different from each other? 1 sentence
In stage 1, both birth and death rates are high and population size is low; In stage 4, both birth and death rates are low and population size is high.
(exam 5) Michael studies sturgeon (fish) populations. To estimate the size of a population, he catches 20 sturgeon in a stream, attaches a tag to the dorsal fin, and releases them where he caught them. A few weeks later he returns and catches 18 sturgeon, 2 of which have tags. Based on this information, approximately how many sturgeon are in the population?
In the second catch, 2 of 18 sturgeon were marked. This means he marked 1 out of every 9 fish in the population. Given that he marked 20 fish, and 20 x 9 = 180, there are approximately 180 fish in the population.
(exam 6) A midwife toad population's growth curve is shown to the right. Females begin breeding at 10 months old. r=.03 and K=460 in this population. Draw a curve representing a pop in an identical habitat, but females begin breeding at 12 months old, and label the line 'a.' Now draw a curve in which females breed at (the original) 10 months, but there is more food available for the animals to eat, and label the line 'b.'
Line B starts w/ normal line then goes above Line A starts at origin w/ normal line then goes below but plateus out w/ normal line
(exam 2) When comparing ecological speciation and mutation-order speciation, which one results from selection for similar phenotypes?
Mutation-order speciation --> In mutation-order speciation, selection favors the same phenotype (e.g. a change to darker fur color) across the distribution of the species. Two populations may experience different mutations, both of which generate that favorable phenotype, but in different ways. So, the two populations end up looking the same, but are genetically different. If those genetic differences are significant enough to interfere with reproduction, then the two populations may evolve into separate species.
(exam 5) Wood ducks sometime lay eggs in the nests of other wood ducks. A field guide says that the 'foster parents' accept these eggs because it's good for the species if they cooperate to increase their numbers. Would you agree or disagree with this statement? Explain your answer.
No animals engage in a particular behavior because it's good for the species. Animals behave in ways that maximize their own fitness, i.e. the number of copies of their own alleles that are passed to future generations.
(exam 2) According to the tree, did sooty shearwaters evolve from storm petrels? (circle one): yes no
No living species is descended from another living species.
(exam 2) Does one of the living species in the tree most closely resemble the species at the arrow? If so, which one?
- There is no way to know whether one of the species in the tree most closely resembles the species at the arrow. - All of the extant species have been evolving for the same amount of time since their common ancestor was alive. - Just because there is a straight line from the arrow to belted kingfishers doesn't mean that the species at the arrow resembled a belted kingfisher. - Remember that the tree to the right cannot be interpreted to mean that the ancestors of echinoderms resembled humans. - Any line that is passing through time will exhibit evolutionary change, even if there are no nodes depicted on the tree.
(exam 5) In the space to the right, draw an age structure diagram for a human population that is likely to decline in size in the future. Label the levels of the diagram.
--> If a population has more individuals in the current reproductive than pre-reproductive age class, then in the future, there will be future people reproducing than there are today. Even if those people produce just as many offspring per person, on average, the population will decline because fewer people are having babies. Note: some people drew diagrams that didn't come to a close at the top. Although I didn't take off points, please recognize that people need to die at some point.
(exam 1) Kalutas are mouse-sized marsupials that live in Australia, where they feed on insects and small vertebrates. They have thick tails, where they can store up to 6.0 g of fat as an energy reserve. The ancestors of kalutas had thin tails that were capable of storing only 0.3 - 0.5 g of fat. List the four postulates of natural selection; for each postulate, indicate how it applies to the evolution of thick tails in kalutas.
1. Individuals vary in their traits: fat storage capacity in ancestral kaluta tails ranged from 0.3 to 0.5 g. 2. Some of the variation is heritable: the ability to store fat in the tail is a heritable trait, meaning it can be passed on to offspring. 3. More offspring are born than will survive to reproduce: some kalutas will die before having an opportunity to pass on their alleles to the next generation. 4. Some individuals are more likely to survive and reproduce than others: kalutas with the capacity to store more fat in their tails were more likely to survive periods of food shortage and had more energy available for reproduction than kalutas with less capacity to store fat in their tails.
(exam 2) Why are there no green mammals? Propose two possible explanations based on two of the three limitations on natural selection in your reading. Explain the limitation in the context of the mammal question. 1 sentence each.
1. Trade-offs: although there may be benefits to having green fur, perhaps there are disadvantages that outweigh the benefits 2. Lack of genetic variation: selection can only act on alleles that exist in populations. If there has never been a mutation that generates green fur, then there is no way for this trait to spread through the population. 3. Historical constraints: physiological structures evolve without planning or forethought and are largely based upon the manipulation of existing structures; moreover, no physiological structure exists in isolation: all structures interact with other structures, either at the cellular/molecular level or at higher levels of bodily organization
(exam 1) The rhinoceros beetle is named for the horn that grows at the back of its head. Two scientists disagree about the evolutionary mechanism that is responsible for the horn. Dr. R argues that the horn evolved through natural selection and is used for digging burrows and fending off predators. Dr. E argues that the horn evolved through sexual selection. Describe an experiment you could perform to test Dr. E's assertion that the horn is sexually selected. Be sure to indicate what you would measure and which results would support Dr. E's position.
One possibility would be to perform a similar experiment to the one we talked about regarding tail length in barn swallows. Take a group of male beetles and alter the lengths of their horns: trim the horn shorter on some beetles, then glue the 'cut offs' onto other beetles to give them longer horns than they had before; create a control group by cutting the horn and then gluing it back on. You now have three groups of beetles that differ in horn length. Put them with females and measure how quickly they are chosen as mates. If males with the elongated horns are chosen more quickly, this would provide evidence that horn length is a sexually selected trait.
(exam 7) You are the manager of a marine wildlife preserve where your goal is to maintain biodiversity. Each year, many of the fish and dolphins in your preserve are eaten by sharks. Some members of your team argue that sharks should be excluded from the preserve in order to maintain the population sizes of their prey species. Other people disagree and argue that the sharks should be permitted to hunt in the preserve. What would be your decision? Explain your answer on the basis of ecological principles discussed in class.
Some communities appear to be very strongly under top-down control, i.e. higher-order predators are important for maintaining the structure of the community. If the sharks are eliminated, the populations of their prey may grow to such large numbers that competition among prey for resources results in the loss of some of the prey species from the preserve through competitive exclusion. If the goal of the preserve is to maintain biodiversity, the sharks should be allowed to continue hunting in the preserve.
(exam 7) At the end of the paper on salmon, the author states that 'the estimated 80-90 percent reduction in salmon returning to streams over the last 100 years...will have ecosystem-level consequences for the remaining forests.' What does he mean by this? What might the consequences be, based on the information in the paper? (1-2 sentences)
The bodies of salmon contribute large quantities of nutrients, such as nitrogen, to the inland forests. The salmon obtain their nutrients primarily in the ocean, then swim upstream, where they are eaten by bears and other predators. These animals eventually spread the salmon's nutrients throughout the forest whenever they die or poop in the forest. If the salmon disappear, the forests may see a drop in nutrient availability.
How does an analysis of energy flow through ecosystems support the argument that it would be better for the environment if we reduce our consumption of meat? (1-2 sentences)
The loss of energy as it moves up trophic levels means that more individuals can typically be supported at lower trophic levels than at higher trophic levels. As a result of this energy loss, therefore, much more land needs to be allocated to food production to support our meat-eating habits than is necessary to support our plant-eating habits.
(exam 3) In the evolution of the vertebrate eye, what was the advantage of the pinhole eye over the cup eye?
The pinhole eye provides an image, a cup does not.
(exam 1) According to the reading on modes of selection, 'If the preponderance of directional and stabilizing selection is real, however, it creates a puzzle.' Write one sentence that explains the puzzle (or question) that is generated.
The puzzle is that both directional and stabilizing selection reduce genetic variation in populations, and yet variation persists; what maintains this variation?
(exam 2) Many decades ago, Lake Apopka in Florida became contaminated with high levels of pesticides that interfered with the reproductive system of alligators; few alligators succeeded in breeding and the population declined to a very small size. Pesticide levels have been reduced and the alligator population has grown again to a large size. Alligators living in Lake Kissimmee were not affected by the chemical spill. Suppose you take a random selection of genes and compare the diversity of alleles between alligators in the two lakes. What would you most likely find? Explain your answer. (1-2 sentences)
The question asks how the diversity of alleles will compare between the two lakes. Lake Apopka, which experienced a bottleneck, is likely to exhibit far less diversity in alleles compared with Lake Kissimmee. When the population of Lake Apopka was reduced to a small size, it is highly unlikely that all of the alleles that were present in the original population were still represented among the relatively few surviving alligators. This is an example of genetic drift. (Note: we're talking about a random selection of genes that were used in this comparison, not specifically genes that might have allowed those alligators to survive the chemical spill; we're not talking about selection here.)
(exam 5) Reptiles have three bones on either side of their lower jaw, but mammals have only one. What happened to the other two bones? (1 sentence)
Two of the bones became smaller and migrated into the ear, where they transmit vibrations.
(exam 6) What is the likely outcome of the situation in which the two bat species exist in an unstable equilibrium? What would you expect to find when you look at bats in these regions? One sentence.
You are likely to find one species or the other, i.e. not a mixture, but it is random which species will be there.
(exam 1) What is the standard scientific definition of evolution?
a change in allele frequencies in a population over time
(exam 4) a. In Andalusian fowl, a single gene determines feather color. Individuals are either white (aa), gray (Aa), or black (AA). The table gives the observed numbers for each phenotype in a wild population of 1460 birds. Calculate actual allele frequencies, and the numbers of birds expected for each phenotype if the population is in Hardy Weinberg equilibrium for this locus. Use 3 decimal places in your calculations and show your work in a way that I can follow it. Draw boxes around the answers to each calculation. Number --> Black (AA) = 865, Gray (Aa) = 306, White (aa) = 289 b. Is the population in Hardy-Weinberg equilibrium for this locus? Explain your answer (1 sentence)
a. Allele frequencies: Freq. A: [2(865) + 306] / 2(1460) = 2,036/2920 = 0.697 Freq a: [2(289) + 306] / 2(1460) = 884/2920 = 0.303 Expected genotype frequencies: p2 = A2 = (0.697)2 = 0.486 2pq = 2Aa = 2(.697)(.303) = .422 q2 = a2 = (.303)2 = .092 Expected counts: Black: 0.486(1460) = 710 Gray: 0.422(1460) = 616 White: 0.092(1460) = 134 b. The population is not in HWE. The expected counts are very different from the observed accounts.
(exam 7) 2a. In the figure above, what happens to the energy that is 'used up?' a. It is destroyed through metabolic processes. b. It moves down to lower trophic levels. c. It is transformed to heat energy. d. It is incorporated into the tissues of the animal. 2b. Which box or boxes represent(s) energy that is available to animals at the next trophic level?
a. --> c. It is transformed to heat energy. b. --> Body gain. The only energy available to higher trophic levels is the energy that is stored in the chemical bonds of the molecules that make up the bodies of the organisms in the trophic level immediately below them.
(exam 6) A biologist is studying the population dynamics of midwife toads and calculates the life table shown below for a cohort of 500 toads. Use the life table to answer the questions a. Use the axes to the right to construct a survivorship curve for this population b. What is the life expectancy of a toad that is 4 years old?
a. ??? b. 2.6 * 2 = 5.2 years (e^x value = 2.6, age classes vary by 2 years)
(exam 3) Based on your reading assignment, what is the Zero Force Evolutionary Law? a. Complexity will always increase over evolutionary time, even in the absence of natural selection. b. Because natural selection tends to favor the evolution of new traits, evolution typically proceeds from 'less complex' to 'more complex' over time within a lineage. c. Complex traits tend to degenerate into simpler traits as genes mutate, resulting in alternating periods of increasing and decreasing complexity within lineages.
a. Complexity will always increase over evolutionary time, even in the absence of natural selection.
(exam 3) It is argued that the thumb of a human and the thumb of a panda are analogous rather than homologous structures. A) explain what this means (1 sentence), and b) describe one piece of evidence you could look for to either support or refute this hypothesis. (1-2 sentences)
a. If the two thumbs are analogous, it means that humans and pandas evolved their thumbs independently of each other rather than both inheriting thumbs from a common ancestor. b. There are multiple possible answers. Evidence for analogy would include: the thumbs are derived from different bones during fetal development; the development of the thumb is under the influence of different genes; the fossil record shows that the most recent common ancestor of pandas and humans lacked a thumb
(exam 2) Which of the following is an accurate interpretation of the tree to the right? a. a hippo is more closely related to a dolphin than to a rhino b. a hippo is more closely related to a rhino than to a dolphin c. a hippo is equally related to a dolphin and a rhino d. a hippo is related to a rhino but not to a dolphin
a. a hippo is more closely related to a dolphin than to a rhino --> According to this tree, hippos share a more recent common ancestor with dolphins (red dot) than they do with rhinos (blue dot); therefore, hippos are more closely related to dolphins than they are to rhinos.
(exam 2) Is a storm petrel more closely related to a northern loon or a cattle egret? a. a storm petrel is more closely related to a northern loon. b. a storm petrel is more closely related to a cattle egret. c. a storm petrel is equally related to northern loon and cattle egret.
a. a storm petrel is more closely related to a northern loon. --> Storm petrels share a more recent common ancestor with northern loons (blue dot) than they do with cattle egrets (green dot).
(exam 1) Given our discussion and readings on heritability, why is the heritability of a trait not constant over time in a population? a. because the extent to which the environment impacts the trait can change over time b. because new alleles are constantly arising in a population as mutations occur c. because the percentage of alleles that come from the mother vs the father is not constant d. because genes will have a bigger influence on traits in individuals with dominant alleles than recessive alleles
a. because the extent to which the environment impacts the trait can change over time --> Heritability is the proportion of variation that is due to genetic vs environmental factors. Some environments may have little impact on a trait, whereas other environments may have a significant impact on the same trait - and yet the genes haven't changed. The heritability of the trait will be reduced in situations in which the environment is impacting the trait more than before.
Based on your reading assignment, what do the Hoxa-13 and Hoxd-13 genes do in mice? And in fish?
a. mice: control the growth of paws/wrists, or endochondral bone b. fish: control the growth of fins/fin rays, or dermal bone
(exam 4) The Hardy-Weinberg equations are only expected to hold true if a long list of assumptions is met. What is the significance of these assumptions? Why are they important to the equations? a. they eliminate the forces that can cause allele frequencies to change b. they ensure that only a single locus is being included in the calculations c. they remove possible sources of measurement-error that could confound the results d. they prevent dominant alleles from obscuring the impact of recessive alleles on phenotypes e. they ensure that any equilibrium that is reached in a population is stable rather than neutral.
a. they eliminate the forces that can cause allele frequencies to change
(exam 5) In a particular species of dandelion, large seeds generally survive better than small seeds because they contain more nutrients to nourish the seedling before it begins photosynthesizing. Very small seeds exhibit a small increase in survival, however, because they catch the wind easily and are therefore unlikely to land close to the parent plant, where they must compete for survival. According to the data below, which seed diameter is optimal for these plants?
answer = 2.3 mm --> For each seed diameter, you need to multiply the number of seeds per plant by the percent surviving; selection will favor the seed diameter that results in the highest number of surviving offspring. 2.3: 400 * 0.04 = 16 * highest * 2.6: 300 * 0.02 = 6 2.9: 200 * 0.06 = 12 3.2 100 * 0.08 = 8 Be careful with your numbers. The Y axis on the second figure is percent surviving; for accurate calculations, you needed to convert them to decimals.
(exam 7) Why are mutualistic relationships between different species often unstable over evolutionary time? a. It is common for one species in a mutualistic relationship to find another species that is a 'better match,' and thus shift its relationship to the other species. b. Selection favors abandoning the relationship if the other species evolves mechanisms allowing it to over-exploit the relationship. c. The two species in a mutualistic relationship end up transferring genes to each other, eventually merging genetically into a single species. d. The two species are usually competing for the same resources, and one ends up driving the other to extinction, thus ending the mutualistic relationship.
b. Selection favors abandoning the relationship if the other species evolves mechanisms allowing it to over-exploit the relationship.
(exam 2) Virginia Sneezeweed is an endangered wildflower with populations in both Virginia and Missouri. Which of the following characteristics would make the Missouri population particularly prone to genetic drift? a. The flowers are pollinated by only one species of bee. b. The population consists of just 42 plants. c. The plant is not closely related to any other species of wildflower in Missouri. d. The plant is the preferred food of young deer. e. The plant grows best in areas with limestone bedrock.
b. The population consists of just 42 plants. --> Genetic drift has its greatest impact on small populations.
(exam 2) Which species (if any) is equally related to all other species in the tree? a. greater scaup b. belted kingfisher c. dusky grouse d. all species in the tree are equally related to each other
b. belted kingfisher --> The most recent common ancestor between the belted kingfisher and all of the other species in the tree is the same - it's the one indicated by the arrow. Therefore, the belted kingfisher is equally related to all other species in the tree
(exam 3) Given the information in the question above, these moths probably most closely resemble moths located: a. on Pacific islands that have a similar climate b. in Brazil c. on the Canary Islands, which are off the Atlantic coast of Africa d. it's impossible to say: distributions of species are largely unpredictable
b. in Brazil --> A common pattern in biogeography is that island endemics are most similar to the species found on the nearest mainland
(exam 7) In a predator-prey cycle, which population fluctuates in size due to variation in carrying capacity? a. the prey b. the predator c. both the predator and the prey d. neither the predator or the prey
b. the predator --> Remember that carrying capacity is determined by resource availability. The predator population fluctuates because its main resource (the prey) fluctuates. The prey fluctuates independently of its carrying capacity, though - the prey fluctuates due to variation in predation, and drops well below carrying capacity when predation pressure is high.
(exam 1) A species of grasshopper occurs in the central valley of California as well as on the surrounding mountains. Individuals living in the valley are significantly larger than individuals living on the mountains. Some researchers argue that this size difference is an adaptation (i.e. an evolved trait). Which of the following statements would provide the strongest evidence that this body size difference is an evolved trait? a. When valley and mountain individuals are raised together, they all grow to be the same size. b. When valley individuals are moved to the mountains, they don't grow as large as they would in the valley. c. When mountain and valley individuals are raised in the same environment, valley individuals still grow to a larger size than mountain individuals. d. Individuals living in the mountains have higher fitness than individuals living in the valley.
c. When mountain and valley individuals are raised in the same environment, valley individuals still grow to a larger size than mountain individuals. --> if the size difference is an adaption, there must be genetic differences between the two populations that cause valley grasshoppers to grow larger than mountain grasshoppers, i.e. the difference in size isn't just due to physiological effects of climate or food. To test whether the difference is genetic, you can raise them in the same environment. If the valley grasshoppers still grow larger than the mountain grasshoppers, this would provide evidence that body size is an adaption, i.e. an evolved trait, rather than simply a physiological response.
(exam 2) Is a dusky grouse more closely related to a bald pate or to a greater scaup? a. a dusky grouse is more closely related to a bald pate. b. a dusky grouse is more closely related to a greater scaup. c. a dusky grouse is equally related to a bald pate and a greater scaup.
c. a dusky grouse is equally related to a bald pate and a greater scaup. --> The most recent common ancestor of the dusky grouse and the bald pate is the same as the most recent common ancestor of a dusky grouse and a greater scaup. (red dot)
(exam 4) The vertebrate jawbone evolved from what structure in fish? a. lateral extensions of the neck vertebrae b. temporal bones that wrap around the sides of the skull c. bones that support the gills d. bones that serve as the attachment site of the tongue
c. bones that support the gills --> The gill arches are bones that the gills are attached to, with each arch separated by a gill slit where the water flows through (and then over the gills). Two of the gill arches developed hinges that enabled them to fold, resulting in the first vertebrate jaws.
(exam 5) According to your reading assignment on human pygmies, what life history trait is favored by natural selection in these populations? a. small offspring size b. iteroparity c. early reproduction d. small offspring number
c. early reproduction --> The authors argue that pygmy stature evolves when there is a high risk of death. In such circumstances, individuals that reach sexual maturity early are more likely to pass on their genes (including genes that influence timing of maturation) compared with individuals who reach sexual maturity later; so, selection favors early sexual maturity/reproduction. The small stature is a side effect of reaching maturity early, since humans typically stop growing shortly after hitting puberty.
(exam 6) 2. Look at the logistic growth equation below and identify the valid interpretation of the equation: Nt+1 = [1 + r - rN/K ] Nt a. population size at time t+1 is always greater than population size at time t b. populations with a high intrinsic rate of increase will overshoot carrying capacity c. the growth rate decreases as the population size approaches carrying capacity d. carrying capacity declines as the population size increases
c. the growth rate decreases as the population size approaches carrying capacity
(exam 5) A paleontologist isolated fragments of collagen (a structural protein abundant in bone) from an 80 million-year old fossil dinosaur. She compared the amino acid sequence of the protein fragments to collagen in the bones of living organisms. Given your understanding of evolutionary relationships, rank the following organisms with regard to how much you would predict the dinosaur amino acid sequence to resemble collagen protein in living organisms, with 1 indicating most similar and 4 indicating least similar. Dog, chicken, tuna fish, salamander
chicken = 1 dog = 2 salamander = 3 tuna fish = 4 --> To answer this question, you need to think about the how closely related the various animals are based upon common ancestry among vertebrates, as shown in the tree to the left. Given that birds evolved from dinosaurs, which were reptiles, we would expect the dinosaur's amino acid sequence to most closely resemble that of a chicken. The most recent common ancestor of birds and reptiles is marked with *. If we go further back in time, we pull in the common ancestor with mammals (including dogs), marked with an X. Going further back in time, we pull in the common ancestor with amphibians (e.g. salamanders), marked with #. The earliest tetrapods (marked with %) evolved from fish. So, dinosaurs are most closely related to birds, then to mammals, then to amphibians, then to fish.
(exam 1) In a population of minnows living in a stream, individuals with long bodies are able to swim faster than minnows with shorter bodies. A large predatory fish invades the stream and begins feeding on the minnows. Over time, the average length of the minnows in the population increases. Why? a. Minnows are born with longer bodies than their own parents had. b. The new predator creates a need for longer bodies, so they evolve. c. The presence of the predator causes a mutation in the minnows, leading to longer bodies. d. Minnows with long bodies are reproducing more than minnows with short bodies.
d. Minnows with long bodies are reproducing more than minnows with short bodies. --> a. no - minnows inherit their genes from their parents. Even if it would be beneficial for your offspring to be longer than you are, there's no way for parents to influence their offspring in this way. Offspring resemble parents. b. Natural selection isn't about fulfilling a need. It's simply that some individuals pass on more copies of their alleles than other individuals, and those alleles therefore become more common in the next generation. c. Mutations occur randomly; the predator doesn't cause them.
(exam 4) Which observation would provide the best evidence for the endosymbiosis hypothesis? a. Mitochondria and chloroplasts, but not bacteria, have telomeres at the ends of their chromosomes resembling the telomeres of eukaryotes. b. Mitochondria, chloroplasts, eukaryote cells, and prokaryote cells are all built from organic molecules with a carbon backbone, and all use the same genetic code during translation to build proteins. c. Lysosomes, which are found in eukaryotes but not prokaryotes, break down old and defective mitochondria and chloroplasts. d. N-formyl-methionine is the 1st amino acid in every protein in bacteria, mitochondria, and chloroplasts, whereas methionine is the 1st amino acid in typical eukaryotic proteins.
d. N-formyl-methionine is the 1st amino acid in every protein in bacteria, mitochondria, and chloroplasts, whereas methionine is the 1st amino acid in typical eukaryotic proteins. --> You are looking for evidence that ties together mitochondria and chloroplasts with prokaryotes. This is the only option that indicates a feature that mito, chlor, and prokaryotes share with each other, but that is different from the rest of the eukaryote cell
(exam 5) The figure to the right represents the hypothetical evolutionary history of rabbits, hares, and rodents. Key: RH=rabbits & hares, MS=marmots & squirrels, C=cavies, B=beavers, RM=rats & mice. What happened at the time marked by the arrows? a. There was a burst of rapid speciation. b. There was a reduction in the number of genes in most mammals. c. The animals became smaller in body size. d. There was a mass extinction. e. The animals became confined to smaller geographic ranges
d. There was a mass extinction. --> We looked at a similar tree representing all vertebrate groups. The widths of the branches represent the diversity in the group, i.e. how many different species are estimated to have been alive at that time. A restriction at a single time point represents a mass extinction event.
(exam 5) A hominin fossil has been found along with several tools that have been manufactured from stone. You can probably assume all of the following characteristics of this hominin EXCEPT: a. it walked on two legs b. it had opposable thumbs c. it had good depth perception d. it had controlled-use of fire
d. it had controlled-use of fire --> Evidence suggests that controlled use of fire among Hominins arose much later than manufacturing of stone tools. All of the other options represent physical trait that evolved much earlier: opposable thumbs and good depth perception are general characteristics of all primates (monkeys, apes, humans). Walking on two legs evolved shortly after our ancestors diverged from those of chimps.
Suppose you want to determine whether the Virginia Sneezeweed plants in Missouri are really the same species as the Virginia Sneezeweed plants in Virginia. According to the Biological Species Concept, you would most likely answer this question by: a. comparing DNA sequences of plants from the two populations b. comparing various morphological characteristics of the plants, such as petal number, leaf arrangement, pollen shape, etc. c. comparing the habitats of the two populations to identify the strongest selection pressures in each location d. producing hybrids of plants between the two populations and seeing whether the seeds grow into healthy plants e. constructing a phylogenetic tree and determining how recently the two populations shared a common ancestor.
d. producing hybrids of plants between the two populations and seeing whether the seeds grow into healthy plants --> According to the Biological Species Concept, two organisms are considered the same species if they are capable of reproducing and having live, fertile offspring. None of the other options will tell you whether the plants are able to reproduce with each other
(exam 7) Based on your reading assignment, what behavior performed by sloths is beneficial to moths? a. building nests of leaves b. licking their fur c. scraping bark from trees d. frequent copulation e. pooping in a hole
e. pooping in a hole
(exam 3) Most moths have ears that detect ultrasonic sounds produced by hunting bats. When a moth hears a bat-call, the moth dives to the ground where the bat is unable to locate it. A particular species of moth lives on an island off the Atlantic coast of Brazil. There are no bats living on the island. These moths have the ear-structures that function to detect bat-calls in other moths, but the ears are not connected to the moths' brains. The moths are therefore deaf. The ears in these island-dwelling moths are an example of: a. adaptive traits b. the universality of the genetic code c. constructive evolution d. the unpredictability of natural selection e. vestigial traits
e. vestigial traits
(exam 6) A group of 15 Majorcan midwife toads has been introduced into a stream in an attempt to establish a new population of this endangered species. The population grows exponentially over the next 100 years with an intrinsic growth rate of 0.044. Given that Nt=N0ert , calculate the population size over the time periods indicated in the table to the right
year 1 --> N = 15 year 25 --> N = 45 year 50 --> N = 135 year 75 --> N = 407 year 100 --> N = 1,222
