Midterm 2 A+ Flashcards
{Plato’s concept of the scala naturae}
(a) proposed that the world is composed of a limited number of unchanging essences that are
(b). established a view of the natural world that arranged organisms in a linear sequence
discretely different from one another
( c) paved the way for Darwin’s theory of evolution by providing a clear mechanism that could drive
adaptive evolution: organisms striving for perfection
(d) laid the groundwork for a view of living organisms as being distributed along with the tips of a
branching tree
(e) explained how fossils documented a sequence of increasingly complex, ‘advanced’ organisms in
shallower sedimentary rock deposits
b. established a view of the natural world that arranged organisms in a linear sequence
{If gene A (with alleles A1 and A2) and gene B (with alleles B1 and B2) are found close together on the
the same chromosome}
a. they will still obey Mendel’s Second Law, the law of independent assortment
b. then the mating A1A1B1B1 x A2A2B2B2 will produce a double heterozygote (A1A2B1B2) that will
produce only two types of gametes: A1B1 and A2B2
c. then the mating A1A1B1B1 x A2A2B2B2 will produce a double heterozygote (A1A2B1B2) that will
produce only two types of gametes: A1B2 and A2B1
d. then the mating A1A1B1B1 x A2A2B2B2 will produce a double heterozygote (A1A2B1B2) that will
produce four types of gametes, each equally common: A1B1, A2B2, A1B2, and A2B1.
e. then the mating A1A1B1B1 x A2A2B2B2 will produce a double heterozygote (A1A2B1B2) that will
produce four types of gametes, two of which, A1B1 and A2B2, will be more common, and two of
which, A1B2, and A2B1, will be less common.
e. then the mating A1A1B1B1 x A2A2B2B2 will produce a double heterozygote (A1A2B1B2) that will
produce four types of gametes, two of which, A1B1 and A2B2, will be more common, and two of
which, A1B2, and A2B1, will be less common.
(Mendel’s demonstration that inheritance operates through a particulate mechanism: )
a. was important, because it shows that natural selection can operate as a powerful process of
adaptive evolution
b. explains why, with co-dominant alleles, heterozygotes exhibit a phenotype that is intermediate
between the two homozygotes
c. means that key adaptive mutations are progressively ‘blended away’ each generation, as matings
mix the adaptive mutation with the alleles that dominated the population before the mutation
appeared
d. allows diploid, sexual populations with heterozygote advantage and random mating to produce
100% heterozygous offspring
e. explained why an individual’s genotype can always be reliably predicted from its phenotype
a. was important, because it shows that natural selection can operate as a powerful process of
adaptive evolution
(genetic drift )
a. is a second major mechanism by which evolution produces adaptations
b. is an important mechanism for generating and maintaining genetic variation within populations
c. is a major cause of allele frequency changes that dominates evolutionary processes any time we
have 1/N «_space;s, when N is population size and s is the selection coefficient
d. only operates on strictly neutral traits
e. is a major destroyer of genetic variation within populations
e. is a major destroyer of genetic variation within populations
[A single, clonally-reproducing female snail that produces offspring genetically identical to herself is
allowed to reproduce in nature until she has produced 1000 offspring. If you measure body weight at
maturity among the 1000 offspring then you will likely find:]
a. almost zero variation in body weight, because there is zero genetic variation in the population;
there will also be no response to directional selection
b. a continuous array of trait values, with the distribution of trait values that is approximately bell-
shaped; this population will respond to strong, consistent directional selection for larger weight by
evolving increased body size
c. a continuous array of trait values, with the distribution of trait values that is approximately bell-
shaped; nevertheless, this population will NOT respond to many generations of directional
selection for larger weight
d. snails that exhibit substantial variation in body size, because genetic drift operating on the
the population will create changes in allele frequencies at genes influencing body size
e. snails that vary a lot in body size, because natural selection will favor extreme body size
phenotypes as a way of reducing intraspecific competition
c. a continuous array of trait values, with the distribution of trait values that is approximately bell-
shaped; nevertheless, this population will NOT respond to many generations of directional
selection for larger weight
[ Insecticide resistance alleles: ]
a. are often expressed as dominant traits when the biochemical mechanism involves target-site
insensitivity
b. are often expressed as co-dominant traits when the biochemical mechanism involves target-site
insensitivity
c. are often expressed as recessive traits when the biochemical mechanism involves target-site
insensitivity
d. are often expressed as co-dominant traits when the biochemical mechanism involves detoxication
e. are often expressed as recessive traits when the biochemical mechanism involves detoxication
c. are often expressed as recessive traits when the biochemical mechanism involves target-site
insensitivity
[The core idea behind the high-dose, refuge strategy for managing resistance in insect pests to transgenic crop plants expressing Bacillus thuringiensis-derived protein toxins is that resistance evolution can be blocked because:]
a. the high dose kills all genotypes, including SS, RS, and RR, thereby preventing natural selection
from discriminating between different genotypes
b. persistent immigration of SS individuals from a refuge causes a dilution of the R allele frequency,
thereby preventing resistance allele frequencies from increasing
c. the R gene can be made to function as a functionally dominant trait
d. the RS heterozygotes formed as the offspring of SS x RR matings are themselves susceptible to
the high dose, allowing R alleles to be removed from the population
e. by keeping the population small through the use of a high toxin dose, we can make genetic drift
more powerful than natural selection, and thereby prevent adaptive evolution from occurring
d. the RS heterozygotes formed as the offspring of SS x RR matings are themselves susceptible to
the high dose, allowing R alleles to be removed from the population
[ Predators can suppress local populations of prey ]
a. by attacking and killing prey individuals
b. by causing prey individuals to express costly anti-predator defenses, which may in turn be
associated with a loss of prey reproduction
c. enhancing emigration, as prey choose to leave habitat patches that they judge to be high-risk
locations
d. suppressing immigration, as prey make choices to avoid entering habitat patches that they judge
to be dangerous
e. a – d above are all true
e. a – d above are all true
The Lotka-Volterra model of predator (P) interactions with prey (N) populations is as follows:
a. predator mortality rate
b. predator attack rate on prey
c. the efficiency with which predators convert consumed prey into new predator offspring
d. the carrying capacity of the predator population
e. the equilibrium density of predators in the habitat
c. the efficiency with which predators convert consumed prey into new predator offspring
[Our textbook explains that Darwin got many of his key ideas about genetic variation and selection by]
a. studying fossils that demonstrated conclusively the gradual transition of animals from one form to
another
b. observing the effects of artificial selection on crop plants and domesticated animals like pigeons
c. recognizing that natural selection would be very powerful under a particulate inheritance
mechanism
d. studying mutational processes in finches (birds) found on oceanic islands, like the Galapagos
e. distinguishing between the effects of goal-oriented processes, like selection, versus random
processes like genetic drift
b. observing the effects of artificial selection on crop plants and domesticated animals like pigeons
Does intra-specific (i.e., within-species) competition generally create density-
dependence in the demographic rates (b, d, i, and e) of populations? What kind of
feedback, if any, would you expect to be generated on population growth? Explain your
answer briefly. (6 points)
: Yes. Intraspecific competition generally produces density-dependent birth rates
(often decreasing as density increases), death rates (often increases as density
increases), and sometimes also emigration (increasing in response to intensifying
competition in high-density populations) and immigration (decreasing in response to
intensifying competition in high-density populations). These are all negative
feedbacks, acting to inhibit further population growth once high populations are
reached.
Does cannibalism generally create density-dependence in the demographic rates (b, d, i,
and e) of populations? What kind of feedback, if any, would you expect to be generated
on population growth? Explain your answer briefly. (6 points)
Yes. Cannibalism operates quite similarly to intraspecific competition.
Cannibalism mostly increases death rates as population density increases. It’s
possible that emigration might increase, and immigration decrease. These effects on
d, e, and i are all negative feedbacks, acting to inhibit further population growth
once high populations are reached. (NOTE: cannibalism could elevate birth rates in
surviving cannibals, if the meal increases their reproductive output. This would be a
positive feedback, causing further increases in population growth. We don’t expect
this effect to fully offset the more important increases in death rates in the
cannibalistic population.)
Does inter-specific (i.e., between-population) competition generally create density-
dependence in the demographic rates (b, d, i, and e) of populations? What kind of
feedback, if any, would you expect to be generated on population growth? Explain your
answer briefly. (8 points)
Answer:
Yes, Interspecific competition generates density dependent demographic rates and
positive feedback on population growth of a focal population. If our focal species
(Species A) is present at high density, this will tend to depress densities of its
interspecific competitor (Species B). Lower densities of Species B relaxes interspecific
competition felt by Species A, allowing the density of Species A to get still higher.
This is positive feedback. This is why interspecific competition will (often) lead to
competitive exclusion and local extinction of one of the competing species.
1 Most caterpillars are herbivorous, feeding strictly on plant material. However, in one group
of moths, the caterpillar stage has evolved to become predatory, eating other herbivorous
insects. Using the three conditions that are necessary and sufficient for evolution by natural
selection, explain how a predatory caterpillar might have evolved from an herbivorous
caterpillar. (12 points)
Answer:
(1) Variation in the phenotype: some caterpillars must have been more willing to
consume prey (in this case, other herbivores) than others, which were strictly
herbivorous and rejected opportunities to consume prey.
(2) Inheritance: the offspring of the more predatory caterpillars must have inherited the
propensity to feed as a predator.
(3) Differential mean expectation of reproductive success (or, differential fitness): the
caterpillars that were more predatory must have had a higher reproductive success
(for whatever reason: perhaps insect prey are higher-quality food than plant material,
because insect prey have higher nutrient content or lower levels of chemical defense
against predators).
- You are studying evolution in a plant population that has one generation per year. The
population has two alleles at one locus, B1 and B2, that are equally common: frequency(B1)
= frequency(B2) = 0.5. Although the two alleles do influence the phenotype (B1 causes one
hair to grow on each leaf tip, and B2 causes two hairs to grow on each leaf tip), they are
associated with no difference in mean expectation of reproductive success (that is, they are
strictly neutral). You visit a small population of this plant (100 total individuals; population
size is stable over time) that inhabits a tiny island, where the population is isolated from
immigration. If you track the frequency of the two alleles over a long period of time (say,
1,000 years), do you expect the frequency of the B1 allele to go up, to go down, or to stay
the same? Explain your answer briefly. (10 points)
Answer: The frequency of the B1 allele is likely to change under the influence of genetic
drift, which is likely to be strong because the population is small. It is just as likely to
go up (approximately 50% chance) as it is to go down (approximately 50% chance).
It is very, very unlikely that it would stay exactly the same.
Does cannibalism generally create density-dependence in the demographic rates (b, d, i,
and e) of populations? What kind of feedback, if any, would you expect to be generated
on population growth? Explain your answer briefly. (6 points)
Answer: Yes. Cannibalism operates quite similarly to intraspecific competition.
Cannibalism mostly increases death rates as population density increases. It’s
possible that emigration might increase, and immigration decrease. These effects on
d, e, and i are all negative feedbacks, acting to inhibit further population growth
once high populations are reached. (NOTE: cannibalism could elevate birth rates in
surviving cannibals, if the meal increases their reproductive output. This would be a
positive feedback, causing further increases in population growth. We don’t expect
this effect to fully offset the more important increases in death rates in the
cannibalistic population.)
- Which of the following is NOT one of the assumptions underlying the Hardy-Weinberg
equilibrium:
a. no selection
b. very large population size
c. co-dominant alleles
d. no mutation
e. random mating
c. co-dominant alleles
- Scientific advances in geology helped to lay the groundwork for establishing a theory of
evolution by showing that:
a. the formation of sedimentary rock and erosion are slow processes that must have been
operating over vast periods of time on earth
b. volcanic activity was likely to have caused climate change
c. oxygen availability was essential for photosynthesis in the ancient seas of earth
d. soils contain key nutrients that plants use for growth and reproduction
e. a-d above are all true
a. the formation of sedimentary rock and erosion are slow processes that must have been
operating over vast periods of time on earth
- Mendel’s first law, the law of segregation, says
a. the process of development, during which genes influence the phenotype, operates in a
strictly particulate manner; offspring phenotypes are therefore rarely found to be
intermediate between the phenotypes of their parents
b. the process of development, during which genes influence the phenotype, operates in a
strictly blending manner; offspring phenotypes are therefore universally found to be
intermediate between the phenotypes of their parents
c. the process of inheritance, through which genes are passed down from one generation to
the next, is strictly particulate
d. the process of inheritance, through which genes are passed down from one generation to
the next, is strictly blending
e. genes found close together on the same chromosome segregate independently during
the formation of gametes
c. the process of inheritance, through which genes are passed down from one generation to
the next, is strictly particulate v
The high dose, refuge strategy for preventing insect pests from evolving resistance to Bt-
transgenic crop plants
a. relies on a dose of the Bt toxin that is high enough to kill insects with genotype RS
b. relies on a source of abundant SS immigrants that move into the transgenic crop field
c. relies on the rare RR individuals, which will survive the high dose, subsequently mating
with SS immigrants, producing RS offspring
d. is more likely to be effective when resistance traits are based on target-site insensitivity,
making the R allele likely to be recessive
e. a-d above are all true
e. a-d above are all true
In the Lotka-Volterra model of interspecific competition, if species 1 is a small, seed-eating beetle and species 2 is a large bird that eats exactly the same seeds as the beetle eats, then:
if species 1 is a small, seed-eating beetle and species 2 is a large bird that eats exactly the
same seeds as the beetle eats, then:
a. a12 = a21 = 0.0
b. a12 = a21 = 1.0
c. a12 «_space;1.0 and a21»_space; 1.0
d. a12»_space; 1.0 and a21 «_space;1.0
e. the larger bird is predicted to competitively displace the smaller beetle
d. a12»_space; 1.0 and a21 «_space;1.0
In competitive character displacement exhibited by two species of spadefoot toads
a. the two species diverge in their use of resources in ponds where they are present
together
b. the two species use similar resources in ponds where they are present together, and
more different resources where they are present in ponds alone
c. stabilizing selection acts on each species when they are present in ponds alone
d. disruptive selection acts on each species when both species are present in the same
pond
e. directional selection acts on each species when they are present in ponds alone
a. the two species diverge in their use of resources in ponds where they are present
together
Predators:
a. have their full impact on prey population growth rate by elevating the prey’s per capita
death rate, d
b. can reduce the per capita birth rate of the prey population, b, by causing the prey to
express costly anti-predator behaviors
c. frequently suppress the per capita emigration rate, e, from high-risk prey populations
d. rarely have any influence, either positive or negative, on the prey population per capita
immigration rate, i
e. a – d above are all true
b. can reduce the per capita birth rate of the prey population, b, by causing the prey to
express costly anti-predator behaviors
Vaccination programs implemented in human populations
a. can reduce the risk of infection of the vaccinated individuals
b. can reduce the risk of infection of the unvaccinated individuals
c. must vaccinate a high proportion of the population, >90%, in order to prevent an
epidemic for highly contagious diseases, when the reproductive number, R0, is very high,
>10
d. must vaccinate only a modest proportion of the population, >50%, in order to prevent an
epidemic for a moderately contagious disease, for which the reproductive number R0 =
2.0
e. a – d above are all true
e. a – d above are all true
