10. (3 Pts) The Dunkers are
a religious group that moved from Germany to Pennsylvania in the mid-1700s.
They do not marry with members outside their own immediate community. Today,
the Dunkers are genetically unique and differ in gene frequencies, at many
loci, from all other populations including their original homeland. Which of
the following likely explains the genetic uniqueness of this population?
A)
sexual selection and inbreeding depression
B)
heterozygote advantage and stabilizing selection
C)
population bottleneck and Hardy-Weinberg equilibrium
D)
mutation and natural selection
E)
founder effect and genetic drift
11. (2 Pts) Which of these
is NOT true about the Central Dogma of Molecular Biology?
A) DNA
codes for RNA, which codes for Protein
B)
It is a two-way flow of information
C) It
is a one-way flow of information
D)
DNA sequences define the genotype, which then produce the proteins that create
the phenotype
12. (2 Pts) Which of the
following does NOT tend to
promote speciation?
A) founder effect
B) reproductive isolation
C) natural selection
D) gene flow
13. (2 Pts) Which of the
following statements explains why animals are less likely than plants to speciate
by polyploidy?
A)
Animals have behavioral rituals that result in mate recognition.
B)
Animal movement patterns insure gene flow.
C)
Animals rarely self-fertilize, so diploid gametes are much less likely to fuse.
D)
Animals chromosomes are less likely to replicate incorrectly than plants.
14. (3 Pts) The two key
factors responsible for speciation among populations are:
A)
mutation and heterozygote disadvantage
B)
reproductive isolation and genetic divergence
C)
postzygotic isolation and morphological change
D)
mutation and genetic drift
15. (3 Pts) Which of the
following would best be described as a case of speciation in sympatry?
A)
A population of lizards is subdivided by a natural barrier and subsequently
diverges to form two species that cannot interbreed.
B)
Speciation cannot take place in sympatry - only in allopatry, where geography
poses a barrier to gene flow.
C)
A new, isolated population of fruit flies is founded by a small group of
colonists, which then diverge from the ancestral source population.
D)
An individual hermaphroditic plant undergoes meiotic failure, producing diploid
pollen and ovules; these self-fertilize, germinate, and grow into several fully
fertile tetraploid plants.
16. (2 Pts) Applying the
principle of parsimony to the trait "ability to fly," which of the
two phylogenetic trees above is better?
A)
Tree 1 B)
Tree 2
17. (3 Pts) These graphs
show percentage change in three different molecular sequences plotted against
time. Which of these would make a good candidate for a molecular clock?
A)
graph A, because the curve levels off over time
B)
graph B, because DNA is more important to organisms and therefore will give a
more accurate picture of divergence
C)
graph C, because the change in sequence is the most rapid (1 point credit)
D)
graph B or C, because they are straight lines
E)
graph A or C, because amino acid changes in are more likely to be neutral DNA
changes in DNA
18. (2 Pts) Which of these
does NOT describe one way in which the fossil record is biased?
A)
Certain habitats are more likely to produce fossils than others
B)
Soft-bodied organisms are more likely to be preserved
C)
Recent fossils are more likely to be found than older ones
D)
Organisms that lived above ground are more likely to be found than underground
E)
Abundant species are more likely to appear in the fossil record than rare
species
19. (10 pts) It is 3AM. You
are awakened by a phone call. The
mysterious voice asks: ÒWhat are the necessary conditions for natural selection
to occur within a population?Ó I donÕt want the 3-word answer, I want you to
state the conditions more completely.
1. Variation in a trait in the population
2. The trait is heritable, at least to some extent
3. Differential Reproductive success based on that
trait
20. (8 pts) What does it
mean to say Òmutation proposes, selection disposesÓ and what roles do the
genotype and phenotype play in the process?
Mutation is the source of
all variation. It is the only source of new alleles. It is a random event. It
can produce advantageous, neutral, and disadvantageous changes. In essence, it
provides options. Natural selection is not random. It is a filtering process
that eliminates disadvantageous changes in genes from the gene pool (and
increases the frequency of advantageous geneotypes).
21. (5 Pts) What does it
mean when we say Òfitness is relativeÓ?
Fitness is defined in terms of reproductive success relative to others in the population. It is calculated as reproductive success in proportion to the most successful form in the population.
22. (6 pts) What is the
difference between allopatric and parapatric speciation? Why is the latter
rare?
Both are a result of
reproductive isolation. In allopatric speciation, populations are separated by
geographical barriers and reproductive isolation is easy to maintain due to the
physical separation of the populations. The geographic barriers prevent gene
flow and the forces of evolution act independently on each population, leading
to speciation. In parapatric speciation, there is no physical barrier
separating two populations which occur side-by-side (thus ÒparaÓ). Without a
physical barrier to gene flow it is difficult to prevent gene flow and maintain
reproductive isolation making parapatric speciation rare. It usually occurs
because the two adjacent habitats have such different selective pressures that
intermediate forms (the product of inter-breeding between the two populations)
are selected against (at a severe disadvantage).
23. (5 Pts) What is the
Hardy-Weinberg Equation and what are the assumptions of the HW Rule?
The Hardy-Weinberg
equation is p2, + 2pq + q2 = 1. The HW equation is a null model, in that it
predicts GENOTYPE frequencies in a population if no forces of evolution are
working on the population and deals with a diploid population, at a single
locus with only 2 alleles and 3 genotypes.
For a population to be in
Hardy-Weinberg equilibrium, the assumptions are that the population must be
very large to counteract the effects of genetic drift and mutation and very
large randomly breeding population with random mating (no sexual selection)
will ensure sufficient gene flow among a large number of individuals.
Essentially, the assumptions are that there is no selection, no mutation, no drift,
and gene flow within the population.
24. (4 Pts) Which of the
following isolating mechanisms are prezygotic and which are postzygotic?
(Circle either PRE or POST)
+
Land iguana eggs can't be fertilized by marine iguana sperm.
PRE POST
+
Mules-horse-donkey hybrids-are sterile.
PRE
POST
In
a forest, one beetle species lives on oaks and another beetle species lives on
pines.
PRE POST
+
In closely related bird species, males sing different courtship songs.
PRE POST
25. (8 pts) What is
stabilizing selection and how does it differ from disruptive selection and
directional selection? You should include in your answer some explanation of
how the mean value for a trait changes in a population under each type of
selective pressure.
1. Stabilizing
selection selects for the existing mean value of the trait and against extreme
values of the trait. Thus, the mean value does not change over time.
2. Disruptive selection
selects for both extremes simultaneously and against the mean. Thus, the mean
value does not change over time, though the number of individuals with the mean
value decreases. The distribution loses its normal distribution (bell shaped
curve). Eventually, two means may emerge that lead to divergence and, perhaps,
speciation.
3. Directional
selection selects for one extreme only. Thus, the mean value of the trait is
pushed toward that extreme (either increasing the mean, or decreasing the
mean).
26. (6 pts) What is the
difference between homologous traits and analogous traits and use the following
structures as examples: a birdÕs wing, a dogÕs leg, and a flyÕs wing.
Homologous
traits are similar traits shared by two species for which an ancestral form was
present in a common ancestor. Since the species diverged, the differing selective
pressures on the two species generally cause the traits to change in different
ways. A birdÕs wing and a dogÕs leg are homologous traits in that the bone
structure for both was present in a common ancestor. The bone structures now
are used in somewhat different ways. This is divergent evolution. Both the
dogÕs leg and the birdÕs wing were derived traits from a common ancestor.
Analagous
traits are similar traits shared by two species, but no ancestral form was
present in a common ancestor. Similar selective pressures resulted in
convergent evolution to produce similar morphologies. The birdÕs wing and the
flyÕs wing are analogous trait. There is not a common ancestor of both the bird
and the fly that had a ÒwingÓ, but both species gained a selective advantage
through flying, which explains why both have wings.
NOTE:
it is wrong to say ÒAnalagous traits are similar traits in species without a
common ancestorÓ. All species have a common ancestor. The difference here is
whether or not the trait in question was present in a common ancestor.
27. (5 pts) Why can sexual
selection be considered a subset of natural selection, even though
sexual selection often produces exaggerated traits that lower surivorship of
individuals with those exaggerated traits?
Sexual selection is
selection on traits that increase success in competing for mating opportunities
(i.e., mates). Sexual selection is a special case of natural selection, in that
the competition between individuals is for mating opportunities, not survival.
Thus, traits arise through sexual selection that may be detrimental to
survival, but endow the possessor with an advantage in gaining reproductive
success – i.e., differential reproductive success based on that trait. It
has varation in traits, heritability of those traits, and differential reproductive success based
on those traits – the definition of natural selection.
EXTRA CREDIT (2 pts) Give a
3-word definition of Natural Selection
Variable, heritable,
fitness