Dr. Reichler’s Bio 301L MWF 9-10am Print
Exam #3 November 21, 2005
Read each question carefully and don’t hesitate to
ask if a question seems unclear. If possible, answer each
question in the space provided, but if needed, continue on the
back. If you use a drawing as part of your answer, be sure to
also include a written explanation. These questions have specific
answers, although for some, more than one answer is possible. To
receive full credit you must clearly and fully answer the question
being asked. This exam is worth 103 points with the points for
each question noted in parentheses.
1. Kelly has 10 infertile offspring, and Shannon has 2 fertile
offspring. Who is more evolutionarily successful? What
criteria did you use to make your determination? (4 pts)
Shannnon. Kelly has more
offspring, but they cannot reproduce so her genes will not be passed on.
2. Why is genetic diversity required for natural selection to take
place? (8 pts)
If all individuals have the same
genes, then it does not matter who is able to pass on their genes,
because the outcome will be the same. In other words natural
selection only takes place when different genes are preferentially
3. Using the evolutionary definition of a species, should European
grizzly bears be considered the same species as Yellowstone grizzly
bears? Why or why not? (8 pts)
These bears are separated by great
distance and are not able to share genes, so they are not
evolutionarily the same species. BUT they can likely mate
and produce viable offspring, so this indicates that they were the same
4. Why is formation of an air bubble during water transport
(cavitation) so harmful to the plant? How do plants reduce the
chance of air bubbles forming? (8 pts)
Since water is pulled up from the
top, breaking the connection between water molecules stops the movement
of water. Plants can reduce the chance of cavitation by closing
stomata or by building more xylem by making wood.
5. Why is it critical for plants to respond to far-red light? (8 pts)
This is the wavelength of light
present in the shade of other plants. Since in shade there is
less light for photosynthesis, seeds will not germinate in shade and/or
plants grow taller to compete for sunlight.
6. In a hot environment, close to 37oC, would an ectothermic
(cold-blooded) or an endothermic (warm-blooded) animal have an
advantage? Why? (4 pts)
At this temperature maintaining body temperature would not be an
issue. So the ectotherm would have an advantage because it would
be using less energy.
7. Normally only waste products are found in urine. What problem
might lead to the presence of nutrients in someone’s urine? (8 pts)
An inability to reabsorb the
nutrients after filtration. (This could be due to en excess of
nutrients or a problem with the reabsorption proteins.)
8. How might low body temperature affect digestion of food? (8 pts)
The proteins that chemically digest
food would be less efficient due to the low temperature.
9. Give two examples of increasing surface area in the digestive
system? (8 pts)
The liquefycation/physical breakdown
of food and the undulations/villi/waviness of the small intestine.
10. What two body functions would be disrupted if you were exposed to a
chemical that punched holes in membranes? Why would they be
disrupted? (8 pts)
Any two of: ATP synthesis in
cellular respiration needs membranes to separate the H+ ions prior to
the H+ ions movement through the ATP synthase. Neurons need an
intact membrane to separate the positive Na+ ions to the outside of the
cell…a polar cell. Kidney reabsorption needs an intact membrane
so the nutrients can be transported across the membrane, but the waste
will not be reabsorbed.
11. Two diseases, both caused by viruses, can have very different
effects in people. Once someone is exposed to chicken pox, they
rarely get it a second time. But herpes can recur many
times. Why is it rare for someone to get chicken pox twice and
why does herpes recur many times? (8 pts)
Memory B-cells produced when the
chicken pox first infects someone would protect them from a subsequent
infect. Herpes can integrate its DNA into the cell’s DNA in the
lysogenic cycle, and later it can enter the lytic cycle causing
12. Would T-cells help in protecting someone from a bacterial
infection? Why or why not? (4 pts)
No, T-cells recognize and destroy our
own damaged cells. They cannot recognize foreign cells.
13. What is one similarity and one difference between the channels
along the axon and the channels at the end of an axon? (8 pts)
Similar- signal to open channel
is nearby membrane depolarization.
Difference- along the axon
transport Na+ while at the ends of the neuron transport Ca++.
14. If someone had damage in the rods and cones in their eyes, would
they see darkness or light? Why? (8 pts)
Light. Rods and cones send an
inhibitory signal. In the absence of this inhibition, the
subsequent neurons will send a signal.
Bonus: In the book “Grizzly Years” what is one characteristic
that makes the Bitter Creek Grizzly easy to spot? (Hint:
Using this characteristic you can tell when the Bitter Creek Grizzly
has passed through an area.) What else is unusual about this
grizzly? (3 pts)
The Bitter Creek Grizzly is
pigeon-toed. He has a damaged leg and walks strangely.
Another unusual characteristic is that he is an older, dominant
male. Many of the older, aggressive bears were killed, but the
Bitter Creek Grizzly managed to survive.