KEY
This exam is worth 50 points
in the whole course
Evolutionary Biology
Exam I, Fall 2009
You may take this part
of the exam with you
Part I
A. Multiple Choice Questions. Choose the best possible answer. Use the bubble sheet. (1 pt.
each)
C
1. Which of the following are prokaryotic? (A) animals (B) plants (C) bacteria (D) fungi
(E) viruses.
D
2. Mitochondria... (A) have their own DNA (B) produce ATP (C) probably evolved from
endosymbiotic bacteria (D) all of the above (E) none of the above.
A
3. In DNA, thymine always pairs with... (A) adenine (B) cytosine (C) nucleotide (D) uracil
(E) another thymine.
D
4. If two alleles are identical for a trait, the individual is said to be ______ for that gene.
(A) monohybrid (B) recessive (C) true-breeding (D) homozygous (E) none of the above.
C
5. Mutations that occur in cells other than the gametes are termed... (A) non-genetic mutations
(B) agametic mutations (C) somatic mutations (D) point mutations (E) germ cell mutations.
B
6. Replacement of a single base pair results in a mutation termed a(n)... (A) pyrimidine dimer
(B) base substitution (C) silent mutation (D) base analog (E) chromosomal mutation.
D
7. What was a major difficulty in accepting and understanding Darwin’s ideas on evolution?
(A) cross-over had not been observed (B) DNA had not been identified (C) vestigial organs
had not been studied (D) the basis for variation was not understood (E) ontogeny had not yet
been studied in detail.
D
8. The concept of the inheritance of acquired characteristics is usually attributed to...(A) Plato
(B) Linnaeus (C) Buffon (D) Lamark (E) Darwin.
C
9. Who first suggested that natural populations have enormous reproductive capabilities and
that most individuals do not survive? (A) Darwin (B) Lamark (C) Malthus (D) Plato
(E) Wallace.
E
10. From fossil evidence, Darwin concluded that... (A) living South American species were not
related (B) the biblical account of the flood was true (C) extinct species were
indistinguishable from living species (D) species had not changed since the beginning of
time (E) none of the above.
B
11. Prokaryotes are different from eukaryotes in that they lack... (A) plasma membranes (B) an
organized cell nucleus (C) a cytoplasm (D) cell walls (E) DNA.
C
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12. A nucleotide consists of... (A) an acid, a base, and a six-carbon sugar (B) a single gene (C) a
base, a sugar, and a phosphate (D) an acid, a six-carbon sugar, and two phosphates (E) a
purine and a pyrimidine.
A
13. What is an allele? (A) one of two or more alternative forms of a gene (B) a cross in which
two different genes are considered (C) a gene which masks the effects of similar genes on
different chromosomes (D) a chromosome with the gene for pea color and pod shape (E) an
individual’s visible traits.
C
14. According to Mendel’s first law, the gametes of a heterozygous individual will be (A) all
dominant alleles (B) all recessive alleles (C) half dominant alleles, half recessive alleles
(D) 25% dominant alleles, 75% recessive alleles (E) all heterozygous alleles.
E
15. If a heterozygous individual of genotype Bb is testcrossed to a recessive parent (bb), what
will the genotypic ratio of the progeny be? (A) all bb (B) 3BB:1Bb (C) all BB (D) 1BB:1bb
(E) 1Bb:1bb.
E
16. In dimetrodons (one of the sail-backed reptiles of early Permian times), smiley face (S) was
dominant over sour-puss (s), tall sail (T) was dominant over short (t), and white teeth (W)
were dominant over yellow (w). Assuming that these genes assort independently, in a cross
between a female dimetrodon homozygous dominant for all three traits and a male
homozygous recessive for these same traits, what proportion of the progeny would be
heterozygous for all three traits? (A) 0.00 (B) 0.25 (C) 0.50 (D) 0.75 (E) 1.00.
B
17. Which of the following phrases defines the genetic term “locus?” (A) a gene (B) a specific
place on a chromosome where a particular gene resides (C) a character expressed by a gene
or chromosome (D) a gene with three or more alleles (E) a gene with only two alleles.
D
18. The law of independent assortment only applies to genes that are... (A) dominant
(B) expressed in mammalian cells (C) linked (D) on different chromosomes (E) recessive.
B
19. The D allele codes for high density peas, while the d allele codes for low density peas.
Which of the following genotypes is an example of heterozygosity? (A) DD (B) Dd (C) dd
(D) DD and dd (E) DD and Dd.
D
20. Achondroplasia (A) is a form of dwarfism inherited as a simple monogenic trait. Two
achondroplastic dwarfs marry and have a dwarf child; later, they have a second child who is
normal. What are the genotypes of the two parents in this mating? (A) AA & AA (B) AA &
aa (C) aa & aa (D) Aa & Aa (E) either A or C above.
A
21. If a scientist collects data and then formulates a general hypothesis that explains all of the
observations, then the scientist has engaged in (A) inductive reasoning (B) deductive
reasoning (C) natural selection (D) artificial selection (E) applied research.
A
22. When a scientist talks about a scientific theory, he is talking about something that (A) has
been tested frequently and has a lot of evidence supporting it (B) has been proven to be true
(C) is wild speculation (D) is likely to never change (E) a reasonable guess.
E
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23.According to Darwin’s theory of evolution (A) all individuals have an equal chance of
surviving and reproducing (B) species are immutable (C) tortoises are the modern
descendants of glyptodonts (D) all of the above (E) none of the above.
C
24.Which of the following did not help Darwin formulate his theory of evolution?
(A) fossil evidence that species change over time (B) closely related species on oceanic
islands (C) evidence that the earth was about four thousand years old (D) demonstration of
artificial selection in domestic animals (E) all of the above did help Darwin.
C
25.Structures that have the same evolutionary origin even though they may now have different
structure or functions are said to be (A) endemic (B) analogous (C) homologous
(D) immutable (E) geometric.
D
26. What is the age of the solar system according to radiometric dating? (A) 6,000 yrs
(B) 10,000 years (C) 3.5 million years (D) 4.5 billion years (E) 13.6 billion years.
C
27. Which of the following fossils is transitional between dinosaurs and birds? (A) Biston
betularia (B) Geospiza fortis (C) Archaeopteryx (D) Hyracotherium (E) Drosophila
melanogaster.
C
28. During artificial selection, selection pressure is exerted by (A) the environment (B) predators
(C) humans (D) domestic species (E) other members of the same species.
D
29. As adults, humans have a vestige of a tail. It is called the (A) lanugo (B) vermiform
(C) placenta (D) coccyx (E) cladogram.
B
30. During their early stages of development, the embryos of fish, reptiles, birds and mammals
look very similar. This suggests that fish, reptiles, birds and mammals (A) live in the same
type of environment (B) have a common ancestor (C) have undergone convergent evolution
(D) are no longer undergoing evolution (E) have gotten rid of all their vestigial structures.
C
31. Which situation would most likely result in the preservation of a fossil? (A) footprints along
a riverbed (B) elephant bones on the Serengeti Plains (C) trees covered by volcanic ash
(D) an earthworm that died in its burrow (E) an insect frozen to death in a Buffalo winter.
E
32. The more closely related two species are (A) the more likely it is they will undergo
convergent evolution (B) the more likely it is they will undergo divergent evolution (C) the
easier it is for artificial selection to have an impact (D) the more likely it is that their fossil
record is complete (E) the more similar their DNA is.
A
33. Which organism is a representative of the kingdom with the oldest fossil record? (A) Bluegreen alga (B) Moss (C) Mushroom (D) H1N1 virus (E) Amoeba.
C
34. Areas where ribosomes are assembled in the nucleus are called (A) nuclei (B) cisternae
(C) nucleoli (D) Golgi complexes (E) centrioles.
A
35. An individual who has two of the same allele is said to be (A) homozygous
(B) heteromologous (C) homologous (D) heterozygous (E) dipolozygous.
B
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36. The appearance resulting from a given gene combination is referred to as (A) genotype
(B) phenotype (C) phototype (D) allelotype (E) stereotype.
A
37. If two alternatives for a trait are red and white and red is dominant, the genotype of a
homozygous dominant individual would be expressed as (A) RR (B) rr (C) Wr (D) ww
(E) red.
D
38. When two alternatives for a trait are tall and short and tall is dominant, the genotype of a
heterozygous individual would be expressed as (A) sS (B) ss (C) SS (D) Ss (E) tall.
C
39. Which of the following isotopes is used to date human artifacts? (A)
(D) 87RB (E) 206Pb.
B
40. The function of tRNA is to (A) provide a place for polypeptide synthesis
(B) transport amino acids to the ribosome (C) travel to the ribosome to direct the assembly of
polypeptides (D) transcribe DNA (E) translate DNA.
C
41. The function of mRNA is to (A) provide a site for polypeptide synthesis (B) transport amino
acids to the ribosome (C) travel to the ribosome to direct the assembly of polypeptides
(D) transcribe DNA (E) translate DNA.
B
42. In transcription, the nucleotide sequence CAT in DNA would specify _____ in mRNA.
(A) TAC (B) GUA (C) CAT (D) GTU (E) STOP.
A
43. The genetic code consists of groups of three nucleotides called (A) codons (B) introns
(C) anticodons (D) reading frames (E) triplets.
A
44. In the process of transcription (A) the base sequence of DNA is copied into RNA (B) a
polypeptide is formed as specified by the genes in chromosomes (C) rRNA is specified by
exons in DNA (D) a strand of mRNA is formed with base sequences complementary to those
of DNA (E) mRNA is formed as coded by introns.
A
45. The evolutionary history of a species is referred to as its (A) phylogeny (B) ontogeny
(C) hierarchical organization (D) diversity (E) selection.
E
46. Which of the structures are homologous? (A) wings of a penguin and the wings of a fruit fly
(B) fingernails of Michelle Obama and the heart of her dog (C) spines of a cactus and the
spines of a porcupine (D) flagellum of a bacterium and the flagellum of a human sperm
(E) petals of a rose and the petals of an apple blossom.
E
47. Darwin proposed that the mechanism behind evolutionary change was (A) heterozygosity
(B) genetic drift (C) inheritance of acquired characteristics (D) polymorphism (E) natural
selection.
A
48. Which is the false statement? (A) Prokaryotes have cell walls but eukaryotes don’t.
(B) Eukaryotes have ribosomes and so do eukaryotes. (C) Eukaryotes have chloroplasts and
prokaryotes don’t. (D) Prokaryotes have a circular chromosome and eukaryotes don’t.
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U (B) 40K (C) 14C
(E) Both prokaryotes and eukaryotes have flagella.
A
49. Which is the false statement? (A) Animal cells have mitochondria and plants don’t.
(B) Plant cells can have large vacuoles and animals don’t. (C) Both plant and animals have
endoplasmic reticula. (D) Internal membranes exist in chloroplasts and mitochondria.
(E) Both plants and animals have multiple linear chromosomes.
C
50. Which is the true statement? (A) Meiosis leads to gametes in animals but not in plants.
(B) Mitosis leads to haploid daughter cells. (C) The first step in mitosis and meiosis is the
production of chromosomes with chromatids. (D) Cross-over occurs in Meiosis II.
(E) Meiosis can lead to polyploidy but Mitosis doesn’t.
Part II
Definition Questions: Define the following terms, give an example, and answer the follow-up
questions (5pts each).
1. Define: Cross-over—Cross-over is the exchange of genetic material between two
homologous chromosomes which occurs typically at metaphase in the first meiotic division in
gamete formation.
Example: When the X and Y chromosomes are aligned, occasionally the SRY gene on
the Y chromosome gets transferred to the X chromosome and the individual that receives the Y
chromosome will be XY SRY- and develop as a female as was the case of the Indian runner
discussed in class.
What is the significance of cross-over in evolution? The significance is that cross-over
breaks up chromosomal linkages of genes thereby increasing the variability in the population,
which is the raw material for natural selection.
2. Define: Vestigial organ. A vestigial organ is one that either has no function or has a greatly
reduced function compared to that organ in an ancestral species.
Example: The human appendix, muscles to wiggle the ears and brow, the coccyx, goose
bumps; blind eye of cave animals, wings in ostriches and kiwis, etc.
Why is this concept of great importance to the original controversy between Divine Creationists
and Evolutionists? It is of importance because the evolutionists argued that this was a prime
piece of evidence that evolution had occurred. They said that it made no sense that a creator
would make an organ that did not function. In contrast, evolution could clearly explain
vestigial structures because they were simply remnants of organs that did function in the
ancestral species. That function was lost when the organism was in a different environment
where there was no longer a selective force in favor of that trait so it was slowly lost.
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3. Define: Point mutation. A point mutation is an abrupt change in the genetic material
involving the change in a single nucleotide base unit in DNA, typically occurring during
mitosis or meiosis when the chromosome material is duplicating in preparation for cell
division.
Example. The are three types of point mutation: substitution, such as when instead of
adenine in the DNA strand there will be guanine; addition, for example, when a base like
thymine is simply spliced into the DNA strand lengthening it by one base; or a deletion
(subtraction), say when a base such as cytosine is lost from the DNA molecule shortening it by
one base.
Why are additions more devastating than substitution mutations? Substitutions usually
lead to only one amino acid being substituted for another. This often still leads to a
functioning protein albeit perhaps not as effective as the original. But an addition will cause
all of the subsequent bases to be thrown into different codons arrangements—a frameshiftwhich disrupts all of the amino acids that are coded after the inserted base, thus leading to a
completely non-functional protein.
C. Comment on the validity of the following statements. Use evidence to back up your claims.
Do not be superficial in your answers and use complete sentences (4 points each).
1. The Protestant Reformation played a significant role in the development of scientific
thought.
This is a true statement. The Reformation starting in the early 1500’s initiated when
Martin Luther broke from the Roman Catholic Church and continued into the present
times by the formation of many Protestant religions, brought about the liberalization of
thought no longer controlled by Rome. Thus, people were no longer indoctrinated into
the belief in the infallibility of the church and its position on the formation for the
world or its view on the origin of life or the creation of organisms. People began to
attempt to explain things in secular rather than a religious way, looking for natural
explanations for the physical world rather than inexplicable miracles.
2) Fleming Jenkin’s argument that a beneficial mutation could never take hold in a
natural population was easily dismissed by Charles Darwin.
This is false. Fleming Jenkin’s argument stated that if ever a beneficial variation
turned up in the population, the individual which had the variation would be forced to
breed with one of the other average members of the population. Their offspring would
be a blend of the two parents, thus diluting the beneficial trait. These offspring would
in turn have to breed with the average members of the population and their offspring
would progressively be more and more average. Thus the beneficial trait would be lost
in the ensuing years. Darwin could never answer this criticism because he too believed
in the blending hypothesis of heredity. It wasn’t until Gregor Mendel’s work showed
that that traits are not inherited this way, that Fleming Jenkin’s argument was
defeated.
3) Human intelligence is a polygene trait.
This is correct. A polygene trait is when the expression of the trait depends on several genes,
often on different chromosomes. The way that one can tell if a trait is polygene is if there is a
large variation in the expression of the trait; i.e., the trait will not be either tall or short, it will
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show a basic bell shaped curve in its expression. For example, it will show the same pattern
that we see with human height. A few people are short and a few people are very tall, but most
people are in the middle. If we were to plot the distribution we would show a “normal
distribution” for the trait. Any time we see a trait that shows a bell-shaped curve, then you
know that several genes are involved, i.e. a polygene trait. So looking at intelligence, we see
exactly the bell shaped curve—most of us are rather average and there are few really bright
people and a few dullards.
D. Short Discussion Questions. Use complete sentences to answer and do not be superficial.
Explain what you mean in detail and use evidence to back up your claims.
1. A singe gene has just been discovered that is responsible for producing the interventricular
septum in vertebrate hearts. How does this discovery contribute to our understanding of the
vertebrate evolution?
The interventricular septum is the muscular membrane that exists across the ventricle of some
vertebrate hearts (birds & mammals) which divides the heart into a four chambers.
Reptiles have an incomplete septum and amphibians have none. So what we see in the
vertebrates is that fish have a two chambered heart , amphibians have three, reptiles 3.5, and
birds and mammals four. With this discovery, we note that the transition among these
different hearts is really not as difficult as previously thought. Few genes need to be involved.
In this case, if only one gene is defective, the heart of the mouse will have only a three
chambered heart—the heart of an amphibian.
2. Why was the Galapagos side trip of the Beagle a key turning point in Charles Darwin’s
thinking about biology? Be sure to explain exactly how it changed.
While in the Galapagos, Darwin noted that each island appeared to have closely related
species that differed only slightly from island to island. This included the reptiles (tortoises
and iguanas), birds (meadowlarks & finches), and even plants (cacti). The nearest relative of
these organisms was on the mainland of South America. It seemed to him that it was it was
hard to believe that each of these island species were created by a separate act of creation. It
seemed easier to explain the pattern by believing that a few plants or animals had managed to
get to the islands by chance (storms or wind, etc) and when they arrived on the different
islands that they a specialized for the different environments, than to believe in special
creation on each island. This meant that change through time was occurring; evolution!
3. Biologists claim that whales evolved from land animals related to hippopotamuses. What kind
of evidence is used to support this claim? Be explicit and detailed. There are many lines of
evidence, don’t miss any.
First, the DNA evidence clearly shows that hippos are the closet living relatives—i.e., they
have the most similar DNA to whales of any other organism. They also have some similar
characteristics such as as an aquatic life style, hairless skin, feet adapted to swimming, etc.
If we are to accept evolution, then we know that whales are relatively recent mammals.
Indeed, the first whale fossils are dated to around 55 million years. Since other mammals are
much older and are land animals, we infer that whales evolved from land species.
Further, the anatomical and embryological evidence clearly suggests a land ancestor. 1) There
are a series of recent fossil finds that show a sequence of animals that show trends in their
anatomy where they become progressively more aquatic and less land –based. These include
their leg structure; the progressive loss of the hind limbs. These include the shift in the
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position of the nostrils; they are in the front of the face in the early fossils and progressively
migrate to the top of the head; and the shift in the structure of the ear, from the more land
form to the aquatic.
2 Whale embryology shows the same trend as the anatomy. In the embryo, there is first a
formation of the front limbs and then their loss by the time that the whale is born. There is a
shift in the position of the nostrils, first at the front of the face and then a progressive shift up
the snout until the formation of the blowhole is complete by the time of birth. The ear changes
as well. Also, the whale embryo forms fur and then it is reabsorbed by the time of birth. All of
these patterns suggest that the embryo is retracing the steps of evolution—ontogeny
recapitulates phylogeny-- because the genes are still present form the ancestral stock.
E. Long answer question. Think back to the article that you read in the lab manual at the
beginning of the semester where the question was asked: Why do A. octarticulatus ants sterilize
C. nodosa trees? (8 pts)
1. What was the hypothesis that the author proposed? (1 pt.)
The ants sterilize the plants so that the plants will invest more of their energy in the
production of dormatia (protective structures) than put their energy into reproduction
(flowering and fruiting).
2. What experiment was used to test the hypothesis? (1 pt.)
He cut off the flowers of trees to simulate sterilization of the plants by the ants to see if this
stimulated the growth of the trees.
3. What was the conclusion that was drawn by the author? (1 pt.)
He found that sterilized trees grew faster than non-sterilized trees. He argued that ants
manipulate the trees to form dormatia for them and thus produce larger and more productive
colonies. They do this by deliberate sterilization.
4. Were there any data that did not support the conclusions of the author? If so, how did the
author deal with them? (2 pts.)
Yes, there were differences among prior authors who studied different ants and plants. He
said it was perhaps due to geographic factors and differences among different species of ants.
Also he noted that his use of scissors to cut off the flowers does not really simulate the cutting
of the flowers by the ants in some particular and important way. Further, that the ant species
may have differed in important ways.
5. Was the approach that the author took, inductive or deductive or both? Explain your answer in
detail with supporting evidence. (3 pts.)
The formulation of the hypothesis would have been inductive. Presumably, he would have
come up with this idea by observing the ants and trees for a significant period and then
drawing the observations together to produce a summary statement which was an
amalgamation of all of these pieces. This is induction—reasoning from a set of specific
individual observations and making a generalization.
Given his hypothesis, the author could predict: if the hypothesis is correct, if I cut off the
flowers, then the trees should grow more profusely and produce more protective sites for ants.
This is a deductive process—reasoning from a generalization to a particular case.
The test and the collection of data follow. So what we have is an example of the hypotheticodeductive process that is both inductive and deductive.
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