Download BIOL212Experience1keyAPR2012

First Experience Key – April 2012
BIOL212
See separate .pdf for the answers to the multiple-choice questions.
47.) Explain the significance, if any, of Archaeopteryx lithographica to the Theory of Evolution.
(10 points)
A. lithographica was the first (and a very clear) example of an organism with both reptilian and avian
characteristics. With feathers, “by definition” a bird, but otherwise skeletal structures looked reptilian. Often
referred to as “the missing link” between reptiles (dinosaurs) and birds. (Discovered in 1861 and ~ 145 million
year old.)
Avian features:
-
(Asymmetrical) feathers
curved claws on feet
lacked major flight muscles
(supercaracoidius muscle)
fused bones
Reptilian features:
- single occipital condyle (cranium-vertebra joint)
- single ear bone
- multiple bones in lower jaws
- tarsal ankle
- similar scales
{- yolked eggs
- female birds & many reptiles
hetero gametic sex
- nucleated red blood cells} – not visible in
Archaeopteryx (or other fossils)!!
Looking for clear statement of intermediary with features both avian and reptilian – points off for feature not
possibly visible in a fossil.
48.) What are the five (5) conditions necessary for Hardy-Weinberg equilibrium? (5 points)
large population
random mating
no mutations
no natural selection pressure
no migration (or no gene flow)
49.) Explain why natural selection can or cannot make new genes. (5 points)
Natural selection is a “pressure” that can only act on things (alleles) already present. It
does not “make” anything.
50.) Explain the strengths and weaknesses of the biological species concept. (5 points)
Strengths:
- interbreed in nature
- producing viable,
- AND fertile offspring
- do nor breed successfully with other populations
“reproductively isolated”
Weaknesses:
- fossils
- asexual organisms
- gene flow between distant species
-
51.) What is a lipid? (1 point)
- fats, oils, waxes
- long chain hydrophobic “energy storage” molecules
First Experience Key – April 2012
BIOL212
52.) What is a carbohydrate? (1 point)
Sugars & starches
53.) What is a protein? (1 point)
long chain molecules (polypeptides) of amino acids, includes enzymes
54.) What is a nucleic acid? (2 points)
The components (other than sugar backbone) of DNA & RNA
(for the four above, key has minimum answers.)
55.) How does the concept of descent with modification explain both the unity and diversity of
life? (10 points)
Unity: all organisms have similar cell structure, protein synthesis, membrane transport, cell
division mechanism, organelles, development, etc., etc., hence ~ 50% of genes are
conserved, or very similar from bacteria to humans. The genetic code is stored in DNA.
(Since diversity comes from alleles, DNA is especially important.)
Diversity: natural selection (descent with modification) acts on the alleles present (DNA)
allowing organisms to become more fit for their current environment (habitat, niche) allowing
exploitation of all, or nearly all, available niches
56.) Explain how the following statement is inaccurate: “Antibiotics have created drug
resistance in MRSA.” (5 points)
Since natural selection can only put pressure on what is there, it cannot “create drug
resistance”. What happens is, since only the individuals that already have drug resistance
live to reproduce (most fit for the new environment – the presence of antibiotic - ) subsequent
generations after exposure to antibiotic, the new population, all have the alleles for resistance
to that antibiotic.
First Experience Key – April 2012
BIOL212
Vocabulary:
57.) convergent evolution
58.) vestigial structures
59.) genetic variation
60.) cline
61.) gene pool
62.) genetic drift
63.) gene flow
64.) blastula
65.) cephalization
66.) founder effect
57.) d
58.) f
59.) a
60.) g
61.) b
62.) e
63.) j
64.) c
65.) h
66.) i
a.) differences among individuals in the composition of their genes or other
DNA segments.
b.) all the copies of every type of allele at every locus in all members of a
population
c.) multicellular, usually a hollow ball, stage of development following
cleavage
d.) the independent evolution of similar features in different lineages
e.) chance events cause allele frequency to fluctuate unpredictably between
generations
f.) remnants of features that served a function in an organism’s ancestors
g.) a graded change in a character (trait) along a geographic axis
h.) sensory organs concentrated at anterior end of organism incl. a central
nervous system in the head
i.) a few individuals become isolated from larger population and establish a
new population
j.) transfer of alleles into or out of a population due to the movement of fertile
individuals or their gametes
k.) a drastic change in environment that drastically reduces the size of a
population
Extra credit:
67.) Explain directional selection, disruptive selection and stabilizing selection (6 points)
Directional: shifts the overall expression of a trait favoring one variant.
Disruptive: shifts the expression of a trait toward to extremes.
Stabilizing: favors the intermediate trait type removing extremes of the type from the population. (The
intermediate type is “concentrated”!)
(Important note: esp. when alleles are recessive, the absence of the expression of an phenotype does not mean
an allele is lost from the population – remember, in another environment, that phenotype might be more fit and
the other phenotype could become common again!)