1. Which of the following would be an example of secondary succession?
A. recovery of a grassland from a prairie fire
B. conversion of forest to a pond due to beaver activity
C. decimation of a population of oak trees due to disease
D. answers A and B
2. Assume that you have been studying a population of cattails at the edge of a pond. After 10 years of observations, you notice that the population has remained steady. What is the most likely explanation?
A. The birth rate and death rate are both increasing at the same rate.
B. The pond is drying up.
C. The carrying capacity of the pond has been reached.
D. Nutrient levels in the pond are fluctuating.
3. Assume that each individual of a particular species produces 10,000 seeds over its lifetime. If the population size is stable (not increasing or decreasing), approximately how many of those seeds will (on average) survive to reproduce?
A. 1
B. 10
C. 1000
D. There is no way to know.
4. Ecologists generally separate organisms in an ecosystem into three categories (producer, consumer, decomposer) based on
A. how they obtain their energy.
B. how rapid their metabolism is.
C. the rate of succession in the ecosystem.
D. the size and complexity of the ecosystem.
5. A farmer uses triazine herbicide to control pigweed in his field. For the first few years, the triazine works well and almost all the pigweed dies; but after several years, the farmer sees more and more pigweed. Which of these explanations best describes this observation?
A. The herbicide company lost its triazine formula and started selling poor-quality triazine.
B. The herbicide caused the pigweed to mutate, creating a new triazine-resistant species.
C. Triazine-resistant pigweed has less efficient photosynthesis metabolism.
D. Only triazine-resistant weeds survived and reproduced, so each year more pigweed was triazine-resistant.
6. A farmer uses triazine herbicide to control pigweed in his field. For the first few years, the triazine works well and almost all the pigweed dies; but after several years, the farmer sees more and more pigweed, no matter how often he applies triazine. Which of these actions is most likely to solve the farmer’s problem?
A. buying triazine from a different company
B. trying a different herbicide
C. increasing the amount of triazine he puts on his fields
D. adding triazine more often to his fields
7. Parasitic species tend to have simple morphologies. Which of the following statements best explains this observation?
A. Parasites are lower organisms, and this is why they have simple morphologies.
B. Parasites do not live long enough to inherit acquired characteristics.
C. Simple morphologies have been naturally selected for in most parasites.
D. Parasites have not yet had time to progress, because they are young evolutionarily.
8. Why are some traits considered vestigial?
A. They improve the fitness of an individual who bears them, compared with the fitness of individuals without those traits.
B. They change in response to environmental influences.
C. They existed a long time in the past.
D. They are reduced in size, complexity, and function compared with traits in related species.
9. An example of a vestigial trait in humans is:
A. kidneys
B. cataracts
C. goose bumps
D. There are no vestigial traits in humans.
10. Cystic fibrosis is a genetic disorder in homozygous recessives that causes death during the teenage years. If 4 in 10,000 newborn babies have the disease, what are the expected frequencies of the dominant (A1) and recessive (A2) alleles according to the Hardy-Weinberg model?
A. f(A1) = 0.9996, f(A2) = 0.0004
B. f(A1) = 0.9984, f(A2) = 0.0016
C. f(A1) = 0.9800, f(A2) = 0.0200
D. f(A1) = 0.9604, f(A2) = 0.0392
E. f(A1) = 0.9200, f(A2) = 0.0800
aa = A2A2= 4/10,000 = 0.0004
A2 = 0.02
11. For biologists studying a large flatworm population in the lab, which Hardy-Weinberg condition is most difficult to meet?
A. no selection
B. no genetic drift
C. no gene flow
D. no mutation
E. random mating
12. What does it mean when an allele reaches “fixation”?
A. It is eliminated from the population.
B. It has a frequency of 1.0.
C. It is dominant to all other alleles.
D. It is adaptively advantageous.
13. Male turkeys have a snood, which is a flap of skin that hangs across their beak. Snood length is negatively correlated with parasite load (e.g., males with longer snoods have fewer parasites), and females prefer to mate with long-snooded males. This is an example of:
A. the fundamental asymmetry of sex
B. sexual selection via female choice
C. sexual selection via male-male competition
D. a genetic marker
14. Researchers studying a small milkweed population note that some plants produce a toxin and other plants do not. They identify the gene responsible for toxin production. The dominant allele (T) codes for an enzyme that makes the toxin, and the recessive allele (t) codes for a nonfunctional enzyme that cannot produce the toxin. Heterozygotes produce an intermediate amount of toxin. The genotypes of all individuals in the population are determined (see chart) and used to determine the allele frequencies in the population.
Genotype Frequencies Allele Frequencies
TT Tt tt T t
560 280 160 0.7 0.3
Is this population in Hardy-Weinberg equilibrium? SHOW ALL YOUR MATH!
F(T) = [(560x2) + 280]/2000 = 0.7 f(t) = 0.3
Exp. #: TT = 490 Tt = 420 tt = 90
X2 = 111; this population is NOT in HW
A. yes
B. No; there are more heterozygotes than expected.
C. No; there are more homozygotes than expected.
D. More information is needed in order to answer this question.
15. The researchers had already noted that negligible mutation and migration existed in this milkweed population, and the butterflies that pollinate these plants are not affected by the toxin. Which of the following would be a logical conclusion about this milkweed population based on your answer to question 14 above?
A. Genetic drift and selection are negligible.
B. There is either a heterozygote advantage or inbreeding depression.
C. There is either directional selection or sexual selection.
D. There is either disruptive selection or genetic drift.
E. There is either stabilizing selection or gene flow.
16. Mutation is the ultimate source of genetic variability. Why is this statement correct?
A. DNA polymerase (the enzyme that copies DNA) is remarkably accurate.
B. “Mutation proposes and selection disposes.”
C. Mutation is the only source of new alleles.
D. Mutation occurs in response to natural selection. It generates the alleles that are required for a population to adapt to a particular habitat.
17. Male reproductive success, measured as the number of offspring surviving to adulthood (pupating), is found for two closely related beetle species and graphed below. Which of these statements would you expect to be true of sexual dimorphism in the two species?
A. Species A should have greater sexual dimorphism than species B.
B. Species B should have greater sexual dimorphism than species A.
C. Species A and B should have about equal amounts of sexual dimorphism.
D. Neither species should show any sexual dimorphism.
18. Genetic diversity is required for natural selection to act, but natural selection can reduce or eliminate diversity. What process can restore genetic diversity to a population?
A. genetic drift
B. mutation
C. sexual selection
D. stabilizing selection
19. Which of the following biological processes causes adaptation?
A. mutation
B. migration
C. natural selection
D. genetic drift
E. all of the above
Two populations of birds with somewhat different coloration live on opposite sides of a peninsula. The habitat between the populations is not suitable for these birds. When birds from the two populations are brought together, they produce young whose appearance is intermediate between the two parents. These offspring will breed with each other or with birds from either parent population, and all offspring of these pairings appear intermediate to various degrees.
20. What keeps the two populations separate?
A. temporal reproductive isolation
B. lack of hybrid viability
C. gametic barrier
D. spatial reproductive isolation
E. behavioral reproductive isolation
21. The two populations (in question above) are:
A. different subspecies, under the morphospecies concept
B. different species, under the biological species concept
C. different species, under the phylogenetic species concept
22. Most causes of speciation are slow, except:
A. polyploidy
B. vicariance
C. colonization
D. natural selection
23. Which of the following statements explains why animals are less likely than plants to speciate by polyploidy?
A. Animals rarely self-fertilize, so diploid gametes are much less likely to fuse.
B. Animals have better mechanisms for repairing chromosomes than plants have.
C. Animals are better at recognizing appropriate mates.
D. Animals are more mobile, so populations get separated far less often.
24. Male frogs give calls that attract female frogs to approach and mate. Researchers examined mating calls of pairs of closely related tree frogs in South America. If reinforcement of prezygotic isolation is occurring, what would you expect if you compare the calls of the two species in zones of sympatry and allopatry?
A. Calls would be about the same in both areas.
B. Calls would be more similar in areas of sympatry.
C. Calls would be more different in areas of sympatry.
25. Why are genetic isolation and genetic divergence occurring in soapberry bugs, even though populations occupy the same geographic area?
A. Members of the different populations feed and mate on different types of fruit.
B. One population recently became tetraploid, and hybrid offspring cannot undergo meiosis correctly.
C. A vicariance event occurred when nonnative host plants were introduced.
D. Beak length has changed due to disruptive selection.
26. When the ranges of different species meet, a stable “hybrid zone” occupied by hybrid individuals may form. How is this possible?
A. Hybrid individuals may have intermediate characteristics that are advantageous in a given region, relative to traits in the different species.
B. Hybrid individuals are always allopolyploid and are thus unable to mate with either of the original species. Allopolyploidy forms new species.
C. Hybrid individuals may have reduced fitness and thus be strongly selected against.
D. One species has a selective advantage, so as hybridization continues, the other species will go extinct.
27. Paleontologists studying fossilized therapsids (a group of mammal-like reptiles that are now extinct) would probably be using which of the following species concepts?
A. the biological species concept
B. the morphospecies concept
C. the phylogenetic species concept (accepted either B or C)
D. None of the above; fossil species cannot be classified.
28. The largest extinction, measured as a percentage of species that disappeared, occurred at the end of which geological period?
A. Permian
B. Cretaceous
C. Tertiary
D. Devonian
E. Silurian
29. Which of the following isolating mechanisms are prezygotic and which are postzygotic?
1. Land iguana eggs can’t be fertilized by marine iguana sperm.
2. Mules—horse-donkey hybrids—are sterile.
3. In a forest, one beetle species lives on oaks and another beetle species lives on pines.
4. In closely related bird species, males sing different courtship songs.
5. Hybrid seeds from pollination of one yucca by another yucca species are aborted.
30. Which of the following is most accurate?
A. Mass extinctions are due to asteroid impacts; background extinctions may have a wide variety of causes.
B. Mass extinctions focus on particularly prominent groups, such as dinosaurs; background extinctions affect species from throughout the tree of life.
C. Only five mass extinctions have occurred, but many background extinctions have occurred.
D. Mass extinctions involve at least 60 percent of the species present and extinguish groups rapidly and randomly; background extinctions are slower and result from natural selection.
31. Some birds follow moving swarms of army ants in the tropics. As the ants march along the forest floor hunting insects and small vertebrates, birds follow and pick off any insects or small vertebrates that fly or jump out of the way of the ants. The interaction between birds and ants is an example of what kind of species interaction?
A. competition
B. consumption
C. commensalism
D. parasitism
E. mutualism
32. In the example described in the previous question, what is the specific benefit relationship?
A. Birds benefit from the association but have no impact on the ants.
B. Birds benefit from the association and harm the ants.
C. Birds and ants benefit from the association.
D. Birds do not benefit from the association, but the ants do.
E. Neither birds nor ants benefit from the association.
33. A land developer is arguing with a group of ecologists. Of course the land developer wants the most land possible for building houses, but has to compromise by saving some land for animal habitat. The land developer offers 20 hectares in evenly distributed but isolated 1-hectare portions. The ecologists keep arguing for one 20 hectare area to remain intact. What’s the difference?
A. There really is no difference; they should both work equally well.
B. The isolated hectare plots are better because they spread out the habitat.
C. The isolated plots are more vulnerable to edge effects.
D. The large plot will create more inbreeding in many species.
34. What does the above graph tell you about the definition of a keystone species?
A. A keystone species has little interaction with other species in an environment.
B. A keystone species removed from a community could have drastic effects.
C. A keystone species can be any species.
D. A keystone species added to a community can make it more robust.
35. Which of the following statements regarding extinction is false?
A. Only certain species are immune from extinction.
B. Species are vanishing today faster than at any other time in Earth’s history.
C. Extinction occurs whether humans interfere or not.
D. Extinctions can even be caused indirectly by humans.
36. If a fossil is limited to undisturbed geological strata above the iridium layer created at the boundary between the asteroid that struck the earth at the end of the Meozoic era, then it
A. was abundant on Earth at the time of the asteroid impact.
B. should be embedded in volcanic ash.
C. is less than 65 million years old.
D. existed before the extinction of the reptiles known as dinosaurs.
E. became extinct before the Cenozoic era.
37. Which of the following is the best example of humans undergoing evolution, understood as "descent with modification"?
A. reduction in number of hairs on the head of a balding person
B. widening of the pupils of the eyes when one encounters dimly lit conditions
C. increase in weight over an individual's lifetime
D. increased pigment production by the skin of a person who is exposed to increased UV radiation levels
E. reduction in coarseness of body hair over millennia
38. Over evolutionary time, many cave-dwelling organisms have lost their eyes. Tapeworms have lost their digestive systems. Whales have lost their hind limbs. How can natural selection account for these losses?
A. Under particular circumstances that persisted for long periods, each of these structures presented greater costs than benefits.
B. By the principle of use and disuse
C. Natural selection cannot account for losses, only for innovations.
D. These organisms had the misfortune to experience harmful mutations, which caused the loss of these structures.
E. Both B and D are correct.
39. Looking at the species-area plot above, what can be concluded?
A. Number of bird species increases linearly with island area.
B. Number of bird species is different on various islands.
C. Diversity is independent from island area.
D. Number of bird species increases exponentially with island area.
40. Using the same graph above, if habitable area on an island were reduced from 10,000 km2 to 1000 km2, roughly what percentage of the species would disappear?
A. 0.3%
B. 3%
C. 30%
D. 60%