Download Print Name: UNR I.D. Number: BIOL 191 SPRING 2005 Midterm 1

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BIOL 191 SPRING 2005 Midterm 1 Form A
IMPORTANT: Be certain to indicate on your answer card (scantron) the form letter that
appears above (Form A or B).
Part 1, Multiple Choice (50 points); Choose the single best response (A,B,C,D or
E) to each question
1. According to Lamarck’s theory of evolution,
A. hereditary information is encoded by particulate factors that do not blend in
offspring.
B. individuals in a population vary in characteristics that affect their ability to survive
and reproduce.
C. genetic drift causes maladaptation in large populations.
D. organisms develop heritable adaptations through the use and disuse of
characters.
E. the DNA replicator is the fundamental unit of evolution.
2. Scientific evidence indicates that
A. HIV-infected individuals who are heterozygous at major histocompatibility (MHC)
loci survive AIDS longer than do individuals who are homozygous at MHC loci.
B. HIV frequently evolves resistance to several of the drugs administered to an
AIDS patient.
C. HIV, an RNA virus, inserts a DNA version of its genetic material into the genome
of its human host.
D. wild-type (non-drug-resistant) HIV strains re-evolve in patients after the patients
stop taking anti-AIDS drugs for several weeks or months.
E. (All of the above)
3. In some regions of tropical Africa, the allele responsible for sickle cell anemia
occurs at a frequency of approximately 20%, despite being nearly lethal in the
homozygous condition. The allele is maintained at this relatively high frequency in
African populations by
A.
B.
C.
D.
E.
a high mutation rate from the wild-type allele to the sickle cell allele.
gene flow.
genetic drift.
inbreeding.
heterozygote superiority.
Form A, page 1
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4. In a population that is in Hardy-Weinberg equilibrium for two alleles, 49% of the
individuals show the recessive trait. What is the frequency of the dominant allele in
the population?
A. 0.15
B. 0.30
C. 0.49
D. 0.51
E. 0.70
5. Many nucleic acid sequences present in the human genome have their origin in
parasitic retroviruses that have lost their capacity for transfer to a new host. Such
retrovirally-derived sequences
A. are likely to have become less virulent to their hosts through the generations.
B. are likely to have become more virulent to their hosts through the generations.
C. exhibit a method of transmission that is best described as horizontal.
D. exhibit a method of transmission that is best described as vertical.
E. (Both A & D)
6. Differential reproductive success resulting from competition between members of
one sex to achieve matings and/or fertilizations
A. always favors traits that enhance survival.
B. is a concept first proposed by Darwin that is currently rejected by the
scientific community.
C. is called Haldane’s Rule.
D. typically occurs through the mechanisms of direct male competition or
female choice.
7. Laboratory experiments and molecular genetic analyses have revealed that, in the
presence of pesticides, houseflies carrying an allele, R, on the third chromosome
have higher rates of survival and reproduction than individuals homozygous for an
alternative allele, r. Field studies have shown that, since the 1940s, the gene
frequency of the R allele has increased five-fold in agricultural regions characterized
by high pesticide use. These studies
A. demonstrate that evolution has occurred in housefly populations.
B. illustrate how biological evolution can be shown to be an observable process,
that is, a fact.
C. suggest that natural selection is at least partially responsible for the change in
gene frequency.
D. (All of the above)
Form A, page 2
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8. The school of systematics that aims to erect a classification based strictly on
recency of common ancestry is called
A. Cladistics
B. Evolutionary systematics
C. Informatics
D. Phenetics
E. Taxonomics
9. Grasses growing near mining sites in Wales are becoming reproductively isolated
from ancestral populations in the surrounding pastures by means of
A.
B.
C.
D.
E.
allopatric speciation.
allopolyploidy
soil-generated changes in flowering time (phenology).
sympatric speciation.
allelopathic speciation.
10. Pseudoscorpion individuals from populations in Panama and Ecuador freely mate
with one another yet all embryos produced by between-population crosses die
during early development. This provides an example of
A. heterozygote superiority.
B. postzygotic reproductive isolation.
C. postcopulatory sexual selection.
D. prezygotic reproductive isolation.
E. sympatric speciation.
Form A, page 3
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Part 2, Definitions (50 points) Use complete sentences to provide detailed definitions (or
descriptions) of the following terms or phrases:
1) Negative frequency dependent selection: occurs when the fitness of a genotype
(or phenotype) decreases as it becomes more common and increases as it becomes
more rare (5 points). Alternatively, and more concisely, frequency dependent
selection occurs when the fitness of a genotype is inversely proportional to its
frequency.
2) Gene flow: refers to the movement of alleles between populations as a result of the
migration of individuals (5 points).
3) Evolution: refers to a change in the genetic composition of a population through
time or across generations (5 points). Alternatively, a change in gene frequency
through time.
4) “Good genes” model of sexual selection: according to this model, exaggerated
male traits provide an honest signal of male genetic quality because they are costly
to exhibit or maintain. Females exhibiting a preference for males bearing such traits
therefore acquire high quality genes for their offspring (5 points). Alternatively,
sexually selected traits signal heritable genetic quality, and are therefore preferred
by females (5 points).
5) Sympatric speciation: refers to speciation in the same place, that is, the evolution
of reproductive isolation in the absence of geographic barriers (5 points). Examples
include polyploidy in plants and host-shifts in insects (e.g., Rhagoletis flies). (Give 2
points for example only)
Form A, page 4
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6) Haldane’s rule of speciation: states that in crosses between individuals from
different populations or species, it is the heterogametic sex that is more likely to be
inviable or infertile (or exhibit reduced viability or fertility) (5 points). Males are the
heterogametic sex in mammals and most insects (XY), and females are
heterogametic in birds and butterflies (ZW). (Note, students don’t need to include
this latter statement but it could compensate partially for a poor definition (up to 2
points).
7) Allopatric speciation: refers to speciation in a different place, that is, the evolution
of reproductive isolating mechanisms between populations that are isolated by a
geographic barrier (5 points).
8) Paraphyletic unit: is a group that includes a common ancestor and some but not all
of its descendent species (5 points). An example is not required but give 2 points for
reptiles.
9) Polyandry: a mating system in which a female mates with more than one male (5
points).
10) Meiotic drive: occurs when one allele has a greater probability of being transmitted
to offspring than alternative alleles at a locus (4 points). In meiotic drive systems
(e.g., t-locus in mouse), sperm carrying the drive allele sabotage sperm carrying
alternative alleles (1 point).
Form A, page 5
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Part 3, Extra Credit (12 points)
1. Using words and/or labeled graphs, compare and contrast directional, stabilizing
and disruptive selection. Provide an example for each type of selection.
For each type of selection, assign 3 points for describing and/or graphing the
selection type and 1 point for an example.
Examples:
Directional: selection for greater insecticide resistance; survival after food depletion
in swallows (selection for larger size)
Stabilizing: selection for heterozygotes; selection on birth weight in mammals
Disruptive: selection for wide and narrow beak depth in seed-cracking birds;
selection on gametes favoring tiny sperm and large eggs
Form A, page 6