Exam 2

What causes genetic drift?

- independent assortment of alleles - random variation in survival - random variation in mating success - random variation in fecundity

What is a species?

A species is a group of potentially interbreeding organisms.

Which type of selection is most common?

All appear equally common.

Activity: Write a figure legend - Thermoregulation

As the cost of thermoregulation increased, animals thermoregulated less accurately until they became thermoconformers," or animals that conform their body temperature to the air temperature.

How are these organisms thermoregulating?

Changing in different directions to change surface area exposed to sun

All individuals of a species express the same degree of plasticity. T/F?

False

True or False? A herring gull and a black-backed gull are different biological species

False

True or False? An enzyme maintains a rigid structure while catalyzing a reaction.

False

True or False? Given unlimited food, shrews should enter torpor on cold nights.

False

True or False? In this experiment, the cost of thermoregulation was a risk of predation.

False

True or False? To maximize its energy gain, the bird should remain on one tree.

False

PE 3.3b The loss of genetic variation likely stemmed from an increase in the mutation rate. T/F?

False (A higher mutation rate would increase genetic variation).

PE 3.3b The population was more likely to experience genetic drift before hunting than it was after hunting. T/F?

False (A larger population would be less likely to experience genetic drift).

PE 4.3b. All else being equal, a shaved shrew loses less heat by convection than an unshaved shrew. T/F?

False (A shaved shrew would lose more heat by convection because hair insulates an animal.)

PE 3.3b Following the decline of cheetahs, the population would more likely adapt to environmental change. T/F?

False (A small population, with less genetic variation would respond slowly to phenotypic selection.)

PE 4.2. Genotypes from populations at 16°C performed best when raised at 16°C and tested at 25°C. T/F?

False (Adaptation to a constant temperature should favor genotypes that develop and perform best at that temperature.)

PE 4.5. If a mutation occurred, causing the daughter of two pygmies to grow taller than usual, this daughter would likely reproduce at an even earlier age than her parents did. T/F?

False (Allocating more energy to growth early in life would reduce the energy available to reproduction, causing the daughter to mature at a later age.)

PE 3.2. If the X chromosome crosses over with the Y chromosome, the resulting gametes are likely to generate healthy offspring. T/F?

False (Crossing over between two different chromosomes will generate gametes that do not have a full set of genes, which is likely to cause the death of offspring.)

PE 4.3b. As a control, the unshaved shrews would have to be handled by researchers but would not have to see a razor. T/F?

False (Everything about the treatment should be the same, except that the razor should have something to block the blades from cutting hair. Shrews should be handled for the same time, while seeing, feeling, and hearing the razor. Otherwise, one cannot tell whether the stress of shaving, rather than the loss of hair, caused a change in physiology.)

PR 4.2. Genotypes from all populations displayed the same degree of plasticity. T/F?

False (Flies from populations at fluctuating temperature were able to change the flight performance adaptively during development, whereas flies from other populations only performed well when raised and tested at a single temperature.)

PE 3.2. An allele at locus A is more likely than an allele at locus B to remain linked to the allele for barred eyes. T/F?

False (Genes that are closer together are less likely to be recombined through crossing over.)

PE 3.3. Genetic drift cannot eliminate a beneficial allele from a population. T/F?

False (Genetic drift can cause a beneficial allele to decrease in frequency, meaning that rare beneficial alleles or weakly beneficial alleles can be lost by genetic drift.)

PE 3.1. Over many generations, the population of snakes should evolve toward striped snakes that flee by turning or checkered snakes that flee straight. True or False?

False (Instead, the population of snakes should evolve toward striped snakes that flee straight or checkered snakes that flee by turning.)

PE 4.3. Between 9 am and 5 pm, the lizard spent energy to thermoregulate but avoided any risk of predation. T/F?

False (Minor fluctuations in body temperatures indicate that the animal moved between sun and shade repeatedly, which could attract a predator as well as burn calories.)

PE 3.3. On average, genetic drift will increase the frequency of a deleterious allele. T/F?

False (On average, genetic drift causes no change in the frequency of an allele; alleles are equally likely to drift toward higher or lower frequency).

PE 4.5. African pygmies are likely to reproduce earlier because they lack sufficient food to continue growing. T/F?

False (Pygmies grow as fast as other humans and must have energy to continue growing if they are able to reproduce instead of grow.)

PE 4.3b. Given unlimited food, a shrew should continue to drop its temperature on cold nights. T/F?

False (Shrews drop their body temperature on cold nights to save energy. If shrews can access unlimited supply of food, they could afford to spend the extra energy needed to produce enough heat to thermoregulate on cold nights.)

PE 4.1. If adaptation occurred, genotypes remaining at the end of the experiment should outcompete their ancestors at 37°C and at 42°C. T/F?

False (The genotypes remaining should perform better at 42C and worse at 37C than the ancestor does.)

PE 4.3. Between 9 am and 7 pm, the lizard likely used endothermy to maintain a high, stable temperature. T/F?

False (The lizard shuttled between sun and shade as evidenced by the dramatic warming in early morning and minor fluctuations in body temperature throughout the day.)

PE 4.2. The sample size in this experiment is the number of flies in each treatment. T/F?

False (The sample size would be the number of populations, since this experiment addresses an evolutionary question.)

PE 3.4. Ensantina klauberi and Ensatina eschscholtzii should be considered different biological species. T/F?

False (The two population can exchange alleles by gene flow that occurs between the other pairs of populations (i.e., alleles that flow around the ring of populations).)

PE 4.1. To replicate this experiment, researchers only needed one population of bacteria, because bacterial populations contain millions of individuals. T/F?

False (The unit of evolution is the population; therefore, the researchers needed multiple populations to replicate the experimental treatment.)

PE 3.3. Genetic drift cannot occur in the same generation as natural selection. T/F?

False (This is a common misconception. Genetic drift, which depends on chance events that influence reproductive success, can occur at the same as natural selection, which depends on phenotypes that influence reproductive success. Any gene can be influenced by a combination of genetic drift and natural selection, as well as mutation.)

PE 3.2. The allele at locus B is likely to be lethal when combined with the allele for barred eyes. T?F?

False (We know that the Bar eye allele sits very closely to locust B, which mean after cross-over, the Bar allele and locus B are likely still together (combined) and we know that offspring are produced with Bar eyes- so it is not lethal or there would be no offspring to observe the bar-shaped eyes.

PE 4.4. Species 1 more closely matched its mating time to the optimal mating time. T/F?

False - A tangent line drawn from the beginning of the search time will intersect the curve for species 2 at a point very close to the observed time, but will intersect the curve for species 1 at a point well before the observed time.

PE 4.4. The rate of fertilization increases with the time that a male spends mating. T/F?

False - The rate decreases toward a maximum, which is probably the number of eggs that the female has produced.

True or False? Stabilizing selection occurs more often than disruptive selection.

False.

True or False? If the slope of the relationship between the phenotype and fitness is positive, natural selection would decrease the phenotype over generations.

False. A positive relationship would lead to an increase of the phenotype over generations.

True or False? Acclimation benefits an organism the most when the environment changes quickly and the phenotype changes slowly.

False. Acclimation benefits an organism most, when it immediately adapts to a changing environment.

True or False? Acclimation involves a change in the genotype triggered by a change in the environment.

False. Acclimation involves a change in the phenotype. There's no change in the genotype.

True or False? Genetic drift cannot eliminate beneficial alleles.

False. Genetic drift can eliminate beneficial alleles.

True or False? The longer the light remained lit, the greater the cost of thermoregulation.

False. It would be the opposite

True or False? The sample size equals the number of fish in each stream

False. The sample size is the stream (the different streams)

What is the appropriate control for a treatment in which one shaves a shrew?

Handling the shrews as if they were being shaven

Activity: Write a figure legend.

In warmer vents, tube worms were more likely to have allele 90, which enhanced function at high temperatures.

What if animals must learn to catch food?

Initial rate of return would be slower

Activity: Write a figure legend

Triangles represent guppies from control sites, dark circles represent guppies from transplant sites. They measure the energy used to reproduce as a percentage. What they're looking at is how much of that energy budget is diverted into reproduction? Most of the energy that guppy uses is going to maintenance or to activity, some of it's going to its body to grow, and the very small fraction left over after all of that, is what's going to produce new offspring. Guppies transplanted to safe sites evolved to reproduce less early in life compared to guppies that remained in control sites.

True or False? An endotherm is more likely than an ectotherm to have a narrow thermal niche.

True

True or False? As the risk of death increases, an organism should reproduce earlier and more often.

True

True or False? Genetic drift should have a bigger effect on the evolution of small populations.

True

True or False? If Mendel had compared traits controlled by genes on the same chromosome, his results would not have matched the predictions of his model.

True

True or False? If a parent passes one copy of each chromosome to offspring, alleles on the same chromosome would be inherited together.

True

True or False? If each tree contained fewer insects, the bird should spend more time feeding on a tree before searching for a new tree.

True

True or False? If energy gain remained constant over time, the bird would maximize energy gain by staying on the tree forever.

True

True or False? If the parameter for the squared term is negative, natural selection will likely stabilize the phenotype at an intermediate value.

True

True or False? In a rapidly changing environment, a population would likely benefit more from sexual reproduction than from asexual reproduction.

True

True or False? The enzymes of animals in old vents should be more flexible than those of animals in young vents.

True

True or False? The observed increase in CTmax likely reflects greater swimming performance at 4°C.

True

True or False? Two species mate but their offspring die before reaching adulthood. A more efficient way to prevent interbreeding would be to have incompatible genitals.

True

PE 3.3.b Prior to hunting, the population likely had more alleles for the 47 genes. T?F?

True (A decrease in population size would enhance the loss of genetic variation by drift.)

PE 4.1. If adaptation occurred, genotypes remaining at the end of the experiment should have had more rigid enzymes than their ancestors had. T/F?

True (At high temperatures, rigid proteins will function better than flexible ones.)

PE 3.1. Although the researcher estimated fitness by survival, he could have also used another proxy for fitness, such as mating success. True or False?

True (Both survival and reproduction are common proxies of fitness used to quantify phenotypic selection.)

PE 3.4. The genes of Ensatina eschscholtzii should be more similar to the genes of Ensatina xanthoptica than they are to the genes of Ensantina klauberi. T/F?

True (E. eschscholtzii and E. xanthoptica should have more similar genes because they interbreed directly rather than indirectly.)

PE 4.3. Between 7 and 8 am, the lizard was likely exposed to solar radiation. T/F?

True (Ectotherms, such as lizards, can only warm when gaining heat from the environment. In the early morning, solar radiation is the most common source of heat.)

PE 3.2. If the chromosomes crossed over equally, the resulting gametes would likely have the same number of genes. T/F?

True (Equal crossing over usually recombines alleles without destroying the structure of genes along a chromosome.)

PE 3.3. If a population doubles in size, a deleterious allele should become less likely to drift to a higher frequency. T/F?

True (Genetic drift occurs more slowly in larger populations; therefore, any allele will drift less after a population doubles in size.)

PE 3.3b If the population of cheetahs continues to decline, genetic drift would be more likely to eliminate new alleles resulting from mutation. T/F?

True (Genetic drift will more likely eliminate an allele in a smaller population.)

PE 3.3. Genetic drift occurs whenever a random event causes a genotype to reproduce more than others in a population. T/F?

True (Genetic drift, as the name implies, is the random movement of the gene pool caused by random events in which some genotypes reproduce more than expected from their phenotype.)

PE 4.5. If a pygmy were to mate with an African of normal size, the offspring would likely be intermediate in size. T/F?

True (Height is a quantitative trait resulting from the effects of many alleles; therefore, alleles from the two parents would effectively blend.)

PE 4.1. To control for stress, the researchers should have frozen some bacteria at the end of the experiment and defrosted these descendants along with their ancestors before comparing their thermal niches. T/F?

True (If one set of populations is frozen, the other must be frozen to control for potential stress.)

PE 4.2. Flies would likely have benefitted less from acclimation if the temperature had changed several times per generation instead of once every generation. T/F?

True (If temperatures fluctuated several times per generation, flies that developed a certain way would only enjoy the benefits during some portions of their life and would suffer the costs during other portions; for example, a fly that acclimated to 25°C during development would suffer each time the temperature switched to 16°C during its life.)

PE 4.1. Assuming that the ancestral populations and the evolved populations were compared under the same environmental conditions, any difference in fitness at 42C would more likely result from adaptation than plasticity. T/F?

True (If the environments are controlled, a difference in fitness likely reflects a genetic change.)

PE 4.5. African pygmies are likely to live in risky environments, where the probability of survival is low compared to other environments where humans live. T/F?

True (Low survival favors the evolution of early reproduction at a smaller size.)

PE 4.3. After 7 pm, you would expect the body temperature of this animal to decrease sharply. T/F?

True (Once the animal leaves the surface it can no longer absorb solar radiation; consequently the animal will cool to the temperature of the air in its burrow.)

PE 3.4. If the population of Ensantina klauberi and the population of Ensatina eschscholtzii remain in contact, natural selection would likely favor a prezygotic isolating mechanism. T/F?

True (Prezygotic isolating mechanisms reduce the chances of hybridization, which saves a genotype time and energy that would otherwise be wasted on offspring that cannot survive or reproduce.)

PE 4.3b. To reduce the energetic cost of thermoregulation, a shrew could remain in its burrow instead of foraging on the surface; however, this behavior would impose an opportunity cost. T/F?

True (Shrews that remain in a burrow would avoid the cool air that causes convective heat loss; however, these shrews would miss opportunities to forage for food or conduct other activities while in the burrow.)

PE 4.5. Pygmies likely evolved because individuals who reproduced early in life were more fit than individuals who reproduced later in life. T/F?

True (Small size at maturity results when individuals grow slower or reproduce earlier; since pygmies don't grow much slower than normal, their size must reflect selection for earlier reproduction.)

PE 3.2. After crossing over, both chromosomes will contain new alleles at the point of crossover. T/F?

True (The DNA at the point of crossing over will be a stitch between two previous pieces of DNA; therefore, any gene at that point would become an allele made from a combination of the two alleles that crossed over.)

PE 3.1. The strength of selection for a color pattern is greater in snakes that flee by turning than in snakes that flee straight. True or False?

True (The absolute value of the slope of the relationship represents the strength of selection, which is greater for snakes that flee by turning (i.e., greater negative slope.)

PE 3.4. If biologists consider Ensantina klauberi and Ensatina eschscholtzii to be different species, they would likely argue that postzygotic isolating mechanisms had reinforced speciation. T/F?

True (The inability to produce viable and fertile hybrids is a postzygotic isolating mechanism.)

PE 4.3b. After lowering its body temperature, a shaved shrew would lose less heat by convection. T/F?

True (The loss of heat by convection depends on the difference in temperature between the animal's surface and the surrounding air. If the animal cools, the difference in temperatures decreases, and thus heat loss by convection decreases.)

PE 4.3. Between 9 am and 5 pm, the lizard was likely moving repeatedly between sun and shade. T/F?

True (The only way for an ectotherm to maintain a stable temperature is to shuttle between sun and shade as it cools or heats too much.)

PE 3.4. Ensantina klauberi and Ensatina eschscholtzii could be considered different morphological species. T/F?

True (The original distinction between these species was based on morphological differences.)

PE 3.2. If the researchers are correct, the X chromosomes likely cross over at the locus that controls normal or barred eyes. T/F?

True (The phenotype must be caused by a new alleles that arise from crossing over in the middle of a gene.)

PE 3.1. Regardless of escape behavior, the color pattern of snakes will be influenced by directional selection. True or False?

True (The relationships between color pattern and relative fitness are linear, regardless of the escape behavior.)

PE 3.1. A snake with stripes would be more likely to survive by fleeing predators in a straight line. True or False?

True (The relative fitness, estimated by survival, was greater for striped snakes that moved straight.)

PE 4.2. Flies from populations at fluctuating temperatures should have evolved the greatest capacity for acclimation. T/F?

True (These populations experienced conditions that changed slowly and predictably, this favoring genotypes that develop the appropriate phenotype each generation.)

PE 4.4. A male that mates for longer than the optimal time may miss an opportunity to mate with another female. T/F?

True - The cost of mating too long is that the male cannot mate with a second female while he is still mating with the first.

PE 4.4. This model depicts an opportunity cost of searching versus mating. T/F?

True - The model depicts an opportunity to mate and an opportunity to search, which trade off against one another.

PE 4.4. A male that mates for the optimal time will not fertilize all of the eggs carried by a female. T/F?

True - The optimal mating time will maximize the number of eggs fertilized by the male, not the number of eggs fertilized in one female.

True or False? Directional selection is more likely to be weak than strong.

True.

True or False? On cloudy days, neither species thermoregulated, likely because solar radiation was absent.

True. Both species don't thermoregulate on cloudy days because they can't thermoregulate without the presence of solar radiation. That's the only thing that can heat them up above their ambient environment.

True or False? Given a limited supply of energy, fish acclimated to a high temperature should outperform fish acclimated to a low temperature, when tested at high temperatures.

True. Only the fish acclimated to the testing temperature should be the ones that perform well. Everyone else should've paid some cost of being acclimated to some other temperature. So, if I now apply it to this example that the fish at high temperature should outperform the fish acclimated to low temperature when they're tested at high temperature.

True or False? Natural selection will likely eliminate deleterious alleles more quickly with sexual reproduction than with asexual reproduction.

True. Sex works in both directions. It helps to speed the evolution, the spread of beneficial alleles, and it helps speed the disappearance of deleterious alleles

True or False? When an organism moves from sun to shade, it reduces heating by conduction.

True. When you move into the shade, you are standing on much cooler ground, because that ground is in the shade. So not only are you gaining less radiation, you're also gaining less heat by conduction.

Which type of organisms should evolve the most rigid enzymes? a. Desert organisms b. Nocturnal organisms c. Aquatic organisms d. Polar organisms e. I don't know the answer

a. Desert organisms

Organisms such as the Antarctic fish can swim at extremely low temperatures. Which mechanism best describes how they do this? a. They modify their proteins to be more flexible. b. They modify their proteins to be more rigid. c. They do not use proteins. d. They warm their bodies through metabolism. e. They live in a frozen state. f. I don't know the answer

a. They modify their proteins to be more flexible.

All else being equal, an organism that grows more in a given period will reproduce less during that period. a. True b. False c. I don't know the answer

a. True

If your professor in the video were behaving optimally, he should have opened a new bag of potato chips instead of eating crumbs from an old bag. a. True b. False c. I don't know the answer

a. True

Speciation occurs more often between allopatric populations than it does between sympatric populations. T/F?

a. True

When biologists use an optimality model to predict foraging behavior, they assume that animals behave in a way that a. maximizes energy gained over time. b. maximizes reproductive success over a lifetime. c. maximizes immediate reproductive success. d. maximizes the probability of survival. e. I don't know the answer.

a. maximizes energy gained over time.

Allopatry occurs when _________________. a) populations become separated geographically. b) populations exchange alleles by migration. c) populations become two separate species. d) populations go extinct.

a. populations become separated geographically

The primary cost of tanning is ______________________. a. the energy needed to produce melanin b. the time needed to lay in the sun c. the money needed to purchase sunblock d. All of the above are equally costly e. I don't know the answer

a. the energy needed to produce melanin

The thermal niche of a desert organism __________________. Yes, that's correct! a. will differ from that of a polar organism. b. will include very low temperatures. c. will include the critical thermal maximum of a polar organism. d. is unlikely to include high temperatures. e. is unlikely to limit its distribution on Earth. f. I don't know the answer

a. will differ from that of a polar organism

Which type of chemical bond will stabilize an enzyme's structure the most? a. Hydrogen b. Covalent c. Ionic d. Metallic e. I don't know the answer

b. Covalent

Most organisms grow as much as possible throughout their lives. a. True b. False c. I don't know the answer

b. False

The net benefit equals the benefit divided by the cost. a. True b. False c. I don't know the answer

b. False

Which of the following observations provides the best experimental evidence that populations diverge during allopatry? a) Hybrid offspring of cold-adapted and saline-adapted genotypes were more viable than purebred offspring. b) Hybrids of offspring cold-adapted and saline-adapted genotypes were less viable than purebred offspring. c) Exposure to cold enabled populations to evolve better performance at low temperatures. d) Exposure to salt enabled populations to evolve better performance at high salinity.

b. Hybrids of offspring cold-adapted and saline-adapted genotypes were less viable than purebred offspring.

When populations become geographically separated for a period and then come back into contact, they __________ become different species. a) always b) sometimes c) never

b. Sometimes

An organism that invests more energy in reproduction will likely ______________. a. live longer b. die earlier c. be unaffected by this decision d. I don't know the answer

b. die earlier

The range of environmental temperatures in which a genotype can persist is one aspect of its _________. a. habitat b. niche c. behavior d. phylogeny e. I don't know the answer

b. niche

Which is the best description of the niche of a salmon? Yes, that's correct! a. the Columbia River b. salinities between 0 and 3000 ppm c. March through September d. All of the above are equally good descriptions of the niche. e. I don't know the answer

b. salinities between 0 and 3000 ppm

Plasticity is most adaptive when the environment changes __________ throughout an organism's life. a. rapidly and predictably b. slowly and predictably c. rapidly and unpredictably d. slowly and unpredictably e. I don't know the answer

b. slowly and predictably

The age at maturity is the age at which an organism ______________________. a. completes embryonic development b. starts to reproduce c. is killed or dies d. leaves its parents e. I don't know the answer

b. starts to reproduce

An organism that invests energy primarily in growth, likely lives in a. an aquatic environment b. a terrestrial environment c. a safe environment d. a risky environment e. I don't know the answer

c. a safe environment

The fact that one can find fish in both tropical and polar waters implies that _______________. Yes, that's correct! a. a single fish can swim in just about any body of water on Earth. b. tropical and polar waters provide similar selective environments. c. different species of fish have adapted to different environmental conditions. d. most fish migrate between tropical and polar waters. e. I don't know the answer

c. different species of fish have adapted to different environmental conditions.

Phenotypic plasticity occurs when one __________ produces multiple __________. a. allele / proteins b. protein / alleles c. genotype / phenotypes d. phenotype / genotypes e. I don't know the answer

c. genotype / phenotypes

The optimal strategy maximizes the ___________. a. benefit b. cost c. net benefit d. net cost e. I don't know the answer

c. net benefit

When modeling foraging behavior, biologists assume that food occurs only in ___________. a. kitchens b. soil c. oceans d. patches e. forests f. I don't know the answer

d. patches

The niche of a fish is defined by ______________. Yes, that's correct! a. temperature b. salinity c. pH d. other species of fish e. All of the above f. I don't know the answer

e. All of the above

Which of the following environmental factors can affect the phenotypes expressed by a genotype? a. Atmospheric oxygen b. Diet c. Solar radiation d. Humidity e. All of the above cause plasticity f. I don't know the answer

e. All of the above cause plasticity