Practice Problems 1
Answer Key
1.
Louis Pasteur and Francesco Redi performed experiments disproving spontaneous
generation – Redi of animals, and Pasteur of microorganisms.
The other experimental results provide support for the idea that chemical evolution is
possible, and that organic molecules may have arisen spontaneously (or been transported
to Earth from elsewhere in the universe), but did not disprove the possibility of
spontaneous generation.
2.
Several answers are possible; some include
• Its ability to replicate by base-pairing
• Its significance in gene expression
• Its ability to act as both genetic material and a catalyst
• The use of RNA to initiate DNA synthesis (primase uses RNA nucleotides)
• “Vestigial” ribonucleotides in other biological molecules
3.
There are many differences; some include
• They had fatty acid membranes, rather than phospholipid membranes.
• They had RNA, not DNA, genomes
• They relied on basic chemical and physical properties to grow and divide rather than
regulated growth and division
4.
The ER, lysosomes, and the nucleus formed when the plasma membrane invaginated and
pinched off to form internal compartments within prokaryotic cells. In contrast,
mitochondria and chloroplasts arose when free-living bacteria were engulfed by
eukaryotic cells, and incorporated as subcellular structures rather than broken down.
Over time, genes from the mitochondria and chloroplast genomes were transferred to the
genome of the cell, though these structures maintain their own genomes to this day.
5A.
The Miller-Urey experiment did not include all of the gasses that were present on the
early earth. In addition to those gasses included in the Miller-Urey experiment, volcanic
eruptions would have released H2S and SO2 into the atmosphere. In addition, Miller and
Urey were able to detect amino acids and other organic molecules, but not nucleic acids.
When these additional gasses were included in follow-up experiments, additional organic
molecules including nucleotides and lipids were produced. In other words, using “more
accurate” approximations of the early earth’s atmosphere, researchers were able to
produce more of the molecules of life than had previously been possible.
B.
6.
100 million nucleotides per haploid genome corresponds to 200 million nucleotides per
diploid genome. If six coding-sequence mutations were detected, that is 6 mutations per
200 million nucleotides, or 3 per million nucleotides, or 1 per 33,333,333 nucleotides.
This is 0.00000003 (3 x 10-8) mutations per nucleotide.
7.
F (d1) = (2x 100 + 72)/400 = 0.68
F (d2) = (2 x 28 + 72)/400 = 0.32
8.
100 – (20 + 45) = 35
9.
Random mating YES
Founder population NO
No migration YES
Inbreeding NO
10.
There are two isolated populations (“A” and “B”) of an endangered plant species.
Population A has had a constant size of 2,000 plants and population B has had a constant
size of 250 plants.
A.
B.
B; genetic drift
The applicability of HWE is irrelevant; if there only two alleles, and the frequency of one
of them is 0.3, the frequency of the other is 0.7. Thus the frequency of the m allele is 0.7.
F(MM) = 0.32 = 0.09
F(Mm) = 2 x 0.3 x 0.7 = 0.42
F(mm) = 0.72 = 0.49
A number of explanations are possible; some include
• Genetic drift has randomly caused differences in allele frequencies
• The populations may be under different selective pressures so that the M allele is
more favorable/advantageous in population B
• Population B may have arisen from a founder population with a higher frequency of
the M allele
• Population A may have arisen from a founder population with a higher frequency of
the m allele
Regular migration of individuals between the populations would cause the most rapid
change in the frequencies of the m and M alleles in population B. Mutations occur very
slowly, and are unlikely to change allele frequencies significantly in the absence of an
additional factor such as selection. Nonrandom mating changes genotype frequencies,
but not allele frequencies, unless there is another contributing factor, such as selection.
C.
D.
E.
11A.
B.
The frequency of heterozygotes is maximized when allele frequencies are equal, 0.5 each.
At this allele frequency, 2pq = 2 x 0.5 x 0.5 = 0.5
12A.
B.
C.
Clavicle
Ulna
Radius
13A.
B.
C.
14.
Directional selection for smaller individuals
15A.
B.
C.
D.
1
2
3
4
16.
Set A: c is different from the others.
Set B: a is different from the others
17.
B
18A.
B.
Tree 3 is different from the others.
D. simulans is more closely related to D. melanogaster than it is to D. pseudobscura.
TRUE
D. pseudobscura is more closely related to D. melanogaster than to D. sechella.
FALSE – D. pseudoobscura is equally closely related to D. melanogaster and D.
sechella.
D. melanogaster is an ancestor of D. sechella.
FALSE – D. melanogaster shares a common ancestor with D. sechella.
19.
Prezygotic: behavioral
Postzygotic: low hybrid viability
20A.
B.
•
349
Possible answers include
An decreased likelihood for marked fish to survive (for example due to increased
susceptibility to predation)
Differences in the probability of initial capture vs. re-capture
Differences in trap efficacy during the two days, so that the proportion of the population
captures is not constant
•
•
21A.
B.
C.
D.
E.
F.
Regular
Random
Random
Regular
Clumped
Some possible answers for each are:
• The sunflowers may benefit from regular spacing because it provides them with
more access to sunlight, or water, or nutrients in the soil.
• Ants may choose their colony locations based on the availability of food or
suitability of location for building the next. Ant colonies are like small cities,
with different groups of ants playing different roles, so that the ants rely on each
other for survival and would not likely persist in a random or regular dispersion
pattern.
22A.
Rwanda
B.
Germany
23A.
B.
C.
D.
E.
440
80/400 = 0.2
40/400 = 0.1
0.2 – 0.1 = 0.1
The population would increase by 440 x 0.1 = 44 salamanders, for a final population size
of 484 after a second month.
24.
A number of explanations are possible, including
Overfishing by humans
Increase in other predators
Reduction in food availability
Introduction of a competitor (this actually played a huge role – search for Great Lakes +
zebra mussels for more information)
Pollution affecting fertility and/or survival
•
•
•
•
•
25A.
B.
•
•
•
•
•
k-selected
You would expect them to also:
Exhibit slow development
Have a relatively low reproductive rate
Have a relatively late reproductive age
Live a long time
Etc.
26A.
B.
C.
D.
E.
F.
Herbivory
Commensalism
The birds prey on the ticks, and are parasites of the grazing animals
Predation
Amensalism
Mutualism (without knowing more about the benefit to the grasses, it is difficult to say
for sure what type of mutualism it is.)
Mutualism (without knowing more about the benefit to the protozoa, it is difficult to say
for sure what type of mutualism it is.)
Exploitation competition
Defensive mutualism (the wasps kill the caterpillar, protecting the plant, in exchange for
the benefit of easier location of caterpillars); predator
G.
H.
I.
27A.
B.
C.
D.
E.
Crypsis/cryptic coloration
Crypsis/cryptic coloration; aggressive mimicry
Aposematic coloration
The coral snake exhibits aposematism, the other snake exhibits Batesian mimicry
Mullerian mimicry and aposematic coloration
28A.
B.
C.
D.
Yes
No
Yes
Yes