Dr. Reichler’s Bio 301L   MWF 9-10am    Print Name:_____________KEY_____
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 passed on.

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 species recently.

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 symptoms.

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.