Download Key for Exam 1 Part 2 - Evolutionary Biology

EXAM I 2016
EVOLUTIONARY BIOLOGY – PART II
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Name
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TA Name
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Lab Day & Time
Negative Points
Positive Points
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TOTAL
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B.
Fill in the blank with the correct answer. Be as specific as possible. (1 pt each)
_______Two_____________ 1. An Australian ant species has only two chromosomes in the cells
of its heart. What is the diploid number for this species?
________True____________ 2. True or false? Evolution by natural selection changes the
population but not the individual.
_______Ribosome_________3. What is the name of an organelle that is found in
eukaryotes and prokaryotes?
both
_______Protein____________4. Viruses are composed of a nucleic acid surrounded by a coat of
(4).
_____Cell wall____________5.Name the outermost structure surrounding an Archaea
_Any bacterium or Archaea__6. Name an organism without mitochondria
_____False______________ 7. Analogous structures (homoplasies) are useful in
determining phylogenies? (True or false)
__Polygene trait___________8. What do we call it when several genes code for a trait, such as
the height of people
__Mitochondrion__________9. Which cell organelle uses oxygen?
__Co dominance__________ 10.What do we call it when there is not complete dominance of
one allele over the other, but instead both alleles are active and
control the expression of the trait?
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C. Definition Questions. Define the following terms or phrase giving an example and answer the
follow up question. Do not be superficial in your responses; give details (5 pts. each)
1. Define the term vestigial structures
A vestigial structure or organ is one which whose function and size is much reduced or absent compared
to ones present in its ancestor. Example: wings in flightless birds, eyes in cave animals, etc.
The human appendix is often cited as a vestigial structure and is thus considered as part of the evidence
for evolution. But the appendix does perform functions as part of the immunological system, so
creationists say this negates the argument for evolution. Does it? Explain.
No, this does not negate its use as evidence for evolution, because although the appendix still has residual
function, its function in the digestive system is much reduced compared to its near relatives.
Creationists have no way of explaining the presence of vestigial organs, especially those with no
apparent function at all (such as the non functional eyes of cave animals); they are confronted with
the problem of why a creator would create an organ without function. Evolutionists have no problem
explaining vestigial organs; they argue that the function of the organ has become reduced by natural
selection over time because the environment as changed or the life style of the organism has altered,
thus reducing its selective advantage and so it is slowly disappearing.
2. Explain Ernst Haekel’s Ontogeny Recapitulates Phylogeny (“Biogenic Law”)
This “law” simply states that the embryology of an organism repeats its evolutionary history.
Examples: humans embryos have structures such as gill supports, body hair, and a tail, all absent in
adults; this suggests there were stages in our evolution when we did have such structures. Similar
patterns occur in all animals such as whale that show the nostrils in the normal position at the end of
the snout and then moving to the top of the head to form the blow hole.
How is this principle used in support of the theory of evolution?
The patterns alluded to in the “biogenic law” cannot be reasonably explained using the model of
creationism because there is no apparent reason why a creator would create structures in embryos
that are reminiscent of past lives. However, the evolutionary model provides a very good explanation
for these features; they are remnants of the evolutionary history that still exist. The genes are still
there.
3. Define the term consilience
Consilience means that evidence about a particular controversy comes from a variety of different sources
or disciplines and converges toward the same answer; i.e. multiple sources agree on a single answer.
For example, the data from geology, chemistry, physics, and biology all agree that the age of the
earth is millions of years old.
Why is this principle important in the field of science especially when controversy exists?
It is important because whenever a controversy exists, the more evidence that is brought into
support a particular side of the argument (especially when it is from different fields), the
more confidence one can have that the conclusions are correct.
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D. Short Answer Questions (3 pts each) State whether the statement is true or false and then
give the evidence supporting your claim
1. The use of radioactive elements to determine the age of the earth is seriously flawed
because there is no reason to believe that the rate of decay is the same today as it was in
the past.
False. There is no reason to believe the method is flawed. (1) Experiments show that the
radioactive decay is constant regardless of the environmental conditions. (2) The methods
have been tested against objects with known ages and found accurate. (3))When several
methods are used on the same material they agree.
2. Prokaryotes evolved first and eukaryotes evolved later.
True. The fossil evidence supports this showing that prokaryotes existed at least 3.5 billion years
ago and eukaryotes don’t show up in the record until just prior to 2 bya. Also, the
prokaryotes are small and their cell structure much less complex than eukaryotes which have
many membranous organelles (mitochondria, chloroplasts, Golgi, ER, etc.) and a nucleus,
exactly what you would expect on the basis of evolution, going from simple to complex.
E. Long Questions
1. Many bacteria have become resistant to antibiotics. 1st explain how a Lamarckian would
explain this event, and then explain how Darwin would explain it.
a. Lamarck’s explanation (3 pts)
Lamarck would argue using his acquired characteristics mechanism, saying that the bacteria
were exposed to the antibiotics and thus acquired immunity by the direct exposure and that
this characteristic was passed on the next generation of bacteria and thus the environment
affected the heredity.
b. Darwin’s explanation (3 pts)
Darwin would argue that there was variability it the population of the bacteria to start with;
individuals would have a range of susceptibility to the antibiotic. So, when the population
was exposed to the antibioltic, although most of the bacteria would die, some of them wee
naturally resistant. And those would be the ones that would reproduce and form the core of
the next generation. So, the population susceptibility to antibiotics would now be much
reduced.
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3. Gregor Mendel established the “Particulate Theory of Inheritance.” First describe what that
theory is. Second, give an example. Third, explain how this undermines Fleming Jenkins’
criticism of Darwin’s view that natural selection can give rise to new species. (Obviously, a good
answer would first explain Jenkins’s criticism before turning to how Mendel’s work would have
an impact. (6 pts.)
The Particulate Theory of Inheritance states that traits are passed from parents to children via the sperm
and eggs as distinct individual units or factors (particles) and are not fused together or blended.
Example: Mendel’s experiments with purple and white flowered pea plants. When these plants were
interbred, there were not intermediate colors produced but distinctly either purple or white.
Fleming Jenkins criticized Darwin’s evolution by natural selection argument by stating that new species
could not arise by this method. He argued that even if a new better characteristic arose in a
population by chance (say a faster running rabbit than the previous rabbits), that this trait could
never cause the improvement of the whole population. This was because the individual with the good
trait would still have to breed with average individuals and thus the children of this mating would be
less successful than the “good parent.” And the same thing would happen in each succeeding
generation as the characteristics would be blended together and the population would thus not
change over time.
4. The hypothetico-deductive method (often called the scientific method) is held up as the standard
of all excellent science. Knowing what you know about Mendel’s work, can you identify those
steps in his approach? First, state what the hypothetico-deductive method is, then show how it
may apply to Mendel’s work. Give examples where appropriate. (7 pts.)
The hypothetic-deductive method breaks down into these steps; observation, question, hypothesis,
prediction (deduction), experiment (observations), and conclusion.
We see them clearly in Mendel’s approach to inheritance.
Observations and Question: Mendel clearly had experience as a farm boy with plants and had
observed plants growing in his monastery garden and thus the fundamental question driving his
further work was how are traits passed from parent to offspring? Are there rules that guide this
process?
Hypothesis: His preliminary work must have prompted him to make the hypothesis that there
were rules that guided the passing of traits from generation to generation.(He was guided in this
assumption because of his physics experience where there were definite rules or “laws.”)
Experiments: All of Mendel’s work focused on detecting the underlying rules of inheritance. He
chose to work with the traits of pea plants, cross breeding them himself transferring male pollen
to female reproductive organs to effect fertilization. Then by cataloging the exact numbers of
plants of each type, he was able to detect certain principles. This was only possible because he
focused on single traits rather than the whole plant and because he chose 7 traits that seemed to
follow clear patterns.
Conclusions: After 8 years of work and 29,000 pea plants Mendel noted three key conclusions.
(1) Participle Theory of Inheritance: Factors which determine traits are passed as distinct
particles or factors from parents (via sperm or pollen and egg)) to offspring (2) His Law of
Segregation –which states that his hereditary factors do not blend but remain distinct during
breeding—thus, disproving the blending theory.
3) His Law of Independent Assortment –which states that character traits are not connected but
are inherited independent of one another. (This law was to be soon to be modified)
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