Evolution
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Lamarck/ vs. Darwin
Evidence
Homologous vs. Analogous
Mechanisms
– Natural Selection
– Genetic drift
– Gene Flow
– Mutations
– Non-Random Mating
In what way
are these
organisms
displaying
examples of
convergent
evolution?
2. Mice that are homozygous for a lethal recessive allele die
shortly after birth. In a large breeding colony of mice, you find
that a surprising 5% of all newborns die from this trait. In
checking lab records, you discover that the same proportion of
offspring have been dying from this trait in this colony for the
past three years. (Mice breed several times a year and have
large litters.) How might you explain the persistence of this
lethal allele at such a high frequency?
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Homozygous recessive mice have a reproductive advantage.
A large mutation rate keeps producing this lethal allele.
There is some sort of heterozygote advantage and perhaps
selection against the homozygous dominant trait.
Genetic drift has kept the recessive allele at this high frequency
in the population.
Since this is a diploid species, the recessive allele cannot be
selected against when it is in the heterozygote.
3. Genetic analysis of a large population of mink inhabiting an island
in Michigan revealed an unusual number of loci where one allele
was fixed. Which of the following is the most probable explanation
for this genetic homogeneity? *
– The population exhibited nonrandom mating, producing homozygous
genotypes.
– The gene pool of this population never experienced mutation or gene
flow.
– A very small number of mink may have colonized this island, and this
founder effect and subsequent genetic drift could have fixed many
alleles.
– Natural selection has selected for and fixed the best adapted alleles
at these loci.
– The colonizing population may have had much more genetic
diversity, but genetic drift in the last year or two may have fixed these
alleles by chance.
4. Increased UV irradiation causes the skin of
humans to become more darkly pigmented over a
period of days. The notion that the offspring of
such tanned individuals should consequently
inherit darkened skin from their parents is
consistent with the ideas of
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Charles Darwin.
Carolus Linnaeus.
Alfred Wallace.
Jean Baptiste Lamarck.
Charles Lyell.
5. A biologist studied a population of squirrels for 15 years.
Over that time, the population was never fewer than 30
squirrels and never more than 45. Her data showed that
over half of the squirrels born did not survive to
reproduce, because of competition for food and
predation. Suddenly, the population increased to 80. In a
single generation, 90% of the squirrels that were born
lived to reproduce. What inferences might you make
about that population?
– The amount of available food probably increased.
– The number of predators probably decreased.
– The young squirrels in the next generation will show greater levels
of variation than in the previous generations because squirrels that
would not have survived in the past are now surviving.
– All three of these are reasonable inferences.
– Only B and C are reasonable inferences.
6. In a hypothetical environment, fishes called pike-cichlids
are visual predators of algae-eating fish, i.e., they locate
their prey by sight. If a population of algae eaters
experiences predation pressure from pike-cichlids, then
which of the following should not be observed in the
algae-eater population over the course of many
generations?
– Coloration of the algae eaters may become drab.
– The algae eaters may become nocturnal (active only at
night).
– Female algae eaters may become larger, bearing broods
composed of more, and larger, young.
– The algae eaters may become sexually mature at smaller
overall body sizes.
– The algae eaters may become faster swimmers.
7. When chemicals are used to control unwanted
organisms, then the wisest application strategy, in
light of natural selection and assuming that
chemicals generally have negative effects on the
environment, is to apply
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a large dose of a single chemical.
a small dose of a single chemical.
a moderate dose of a single chemical.
large doses of several different chemicals.
moderate doses of several different chemicals.
8. As adults, certain species of whales possess baleen
instead of teeth. Baleen is used to filter the whales'
diet of planktonic animals from seawater. As embryos,
baleen whales possess teeth, which are later replaced
by baleen. The teeth of embryonic baleen whales are
evidence that
– all whales are the descendants of terrestrial mammals.
– baleen whale embryos pass through a stage when they
resemble adult toothed whales.
– baleen whales are descendants of toothed whales.
– ontogeny recapitulates phylogeny.
– among ancient whales, baleen evolved before teeth.
1. A botanist identifies a new species of plant that has 32
chromosomes. It grows in the same habitat with three
similar species: species A (2n 5 14), species B (2n 5
16), and species C (2n 5 18). Suggest a possible
speciation mechanism for the new species.
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allopatric divergence by development of a
reproductive isolating mechanism.
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change in a key developmental gene that causes the
plants to flower at different times.
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autopolyploidy, perhaps due to a nondisjunction in
the formation of gametes of species B.
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allopolyploidy, a hybrid formed from species A and C.
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Either answer c or d could account for the formation
of this new plant species
• The following question refers to this
information: In the year 2500, five male
space colonists and five female space
colonists from Earth settle on an uninhabited
Earthlike planet in the Andromeda galaxy.
The colonists and their offspring randomly
mate for generations. All ten of the original
colonists had free ear lobes, and two are
heterozygous for that trait. The allele for free
ear lobes is dominant to the allele for
attached ear lobes
2.After many generations, the population on
this planet has an unusually high frequency
for the incidence of retinitis pigmentosa,
relative to Earth's population. This is most
likely due to
– the founder effect.
– sexual selection.
– the inheritance of acquired characteristics.
– mutations.
– the bottleneck effect.
The restriction enzymes of bacteria protect the
bacteria from successful attack by
bacteriophage, whose genomes can be
degraded by the restriction enzymes. The
bacterial genomes are not vulnerable to these
restriction enzymes because bacterial DNA is
methylated. This situation selects for
bacteriophage whose genomes are also
methylated. As new strains of resistant
bacteriophage become more prevalent, this in
turn selects for bacteria whose genomes are
not methylated and whose restriction enzymes
3.Over the course of evolutionary time, what
should occur?
– Methylated DNA should become fixed in the
gene pools of bacterial species.
– Nonmethylated DNA should become fixed in the
gene pools of bacteriophage.
– Methylated DNA should become fixed in the
gene pools of bacteriophage.
– Methylated and nonmethylated strains should
be maintained among both bacteria and
bacteriophage, with ratios that vary over time.
– Both A and B are correct.
4. A balanced polymorphism exists through
diversifying selection in seedcracker finches from
Cameroon in which small- and large-billed birds
specialize in cracking soft and hard seeds,
respectively. If long-term climatic change resulted in
all seeds becoming hard, what type of selection
would then operate on the finch population?
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diversifying selection.
directional selection
stabilizing selection
sexual selection
No selection would operate because the population
is in Hardy-Weinberg equilibrium.
• A biologist discovers two populations of wolf spiders
whose members appear identical. Members of one
population are found in the leaf litter deep within the
woods. Members of the other population are found
in the grass at the edge of the woods. The biologist
decides to designate the members of the two
populations as two separate species. Which species
concept is this biologist most closely utilizing?
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Ecological
Biological
Morphological
Pluralistic
genealogical
2. The formation of a land bridge between North and
South America about three million years ago should
have resulted in which of the following?
I. allopatry of marine populations that were
previously sympatric
II. sympatry of marine populations that were
previously allopatric
– I III.
onlysympatry of terrestrial populations that were
– II only
previously allopatric
– III only
– I and II
– I and III
3. If two subspecies, A and B, are not considered
separate species even though they cannot
interbreed, then
– they are groups that are endemic to isolated
geographic regions.
– they have eliminated postzygotic barriers but not
prezygotic barriers.
– gene flow between A and B may exist through other
related subspecies.
– gene flow has ceased and genetic isolation is
complete.
– their diploid gametes are produced by
nondisjunction.
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Populations (Hardy Weinberg)
Speciation, Reproductive isolation
Adaptive Radiation
Modes of Natural Selection
AP Labs and Essays
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Lab 8
1992, # 4
1996, # 4
1997, # 4
2001, # 2
2004, # 3