Dr. Reichlerís Bio 301L       Print Name:____________KEY__________
In-class Exam #3  15 November 2001

 Answer each question as succinctly as possible in the space provided.  You may use the back if you need more space.  If you use a drawing as part of your answer, be sure to also include a written explanation.  Each question is worth 4 pts, unless otherwise noted, for a total of 100 points possible for this exam.  Read each question carefully, and donít hesitate to ask if a question seems unclear.

1. a.  If you were looking at some cells under a microscope, what is one characteristic that you could see that would indicate that the cells are bacteria?
Any one of:  No nucleus, no internal organelles, circular DNA, 3 of 4 points for gram staining (only visible on gram positive)

b. Heterotrophic organisms produce energy by taking in organic molecules.  What type of heterotrophic bacteria were prevalent when life was first forming?  How is this different than the current situation?
Anaerobic were prevalent, now there are mostly aerobic

c. What type of bacteria were responsible for the change in 1b?  Explain.
Photosynthetic, they use CO2 and produce O2

2. a.  What is one difference between the Archaebacteria and the Eubacteria?
Any one of:  Archae do not have peptidoglycan in the wall, general differences at the DNA level

b. Some Archaebacteria live at high temperatures (80oC).  What is one problem they must overcome to live at these high temperatures and how do they overcome this problem?
Problem-  proteins denature.  Solution-  maintain 3-D structure of proteins by covalent bonds

c. Where is one place you might find Methanogens, and what are they doing there?
Any one of:  Stomach of cow or termite, digesting cellulose; Swamp, decaying dead material

3. a.  What is one good and one bad interaction that humans have with a heterotrophic bacteria?  Be specific.
Any one of:  Good-  Outcompete Bad bacteria on skin, Help digest food, make vit K, Fix N, Decay dead material.
Bad-  Food poisoning, skin infections, STD's, internal infections, spoil food.

b. Describe another way that bacteria are helpful to humans.
Any different one of:  produce O2, fix N, protect skin from infectious bacteria, help digest, make vit K

c. What are two ways that antibiotics kill bacteria, and what are two mechanisms by which bacteria can be resistant to antibiotics? (6pts)
Any two of:  Kill-   Stop wall production, stop transcription or translation, inhibit replication
Resistance-  Change enzyme so antibiotic no longer recognizes it, enzyme binds and deactivates antibiotic, bacteria pump antibiotic out of cell.

d. Mutations that give rise to antibiotic resistance in bacteria are uncommon, but bacteria that are resistant to antibiotics are becoming abundant.  Why is this?
Over-exposure to antibiotics is causing the selection of only bacteria that can survive in the presence of antibiotics.

4. a.  One way plants defend themselves after a viral infection is to kill the cells surrounding the infected area.  How would this stop the virus from spreading?
Viruses need living cells to replicate.  If the plant kills the surrounding cells, the virus will not be able to get into cells and reproduce.

 b. What is happening if a virus enters the integrative (lysogenic) cycle?  Describe how the integrative cycle is or will be harmful to the infected organism.
The virus is inserting its DNA into the DNA of the host cell.  Can be harmful if it inserts into or near a gene and disrupts the gene OR if the DNA de-integrates and enters the lytic cycle.

c. What viral protein is necessary for HIV (the virus that causes AIDS) to reproduce, what does this protein do, and why does HIV need it? (6pts)
Reverse Transcriptase.  It codes from RNA into DNA..  HIV carries RNA, so it needs to make the DNA so it can make more virus.

5. (For a and b choose from mouth, esophagus, stomach, small intestine, or large intestine)
b. What part of the digestion system could a human lose and still survive?  How would they survive without it?
Any of:  Mouth- place food directly in stomach, only use soft foods; Esophagus- place food directly in stomach, only use soft foods; Stomach- eat a little constantly, chew food very well, drink liquids with foods; large int.- drink lots of liquids, need to get rid of wastes constantly

b. What part of the digestive system would be fatal if it was completely removed?  Why would it be impossible to survive without this part?
Small intestine- needed to chemically digest and absorb food

c. Why is the heart so susceptible to being harmed by a diet high in fats and lipids?
Fats and lipids are transported directly from the small int. to the heart via the lymphatic system.  This means that there is no monitoring or control of the amount of lipids that reach the heart.

d. What role does the liver play as part of the digestive system?
It monitors and controls how much of the nutrients are released to the rest of the body.

6. Why does the Venus flytrap "eat" bugs, and where do most plants get what the Venus flytrap is getting from eating bugs?
To get inorganic nutrients such as N or P.  Most plants get these from the soil.

7. a.  In what type of blood vessel does exchange take place, and why does it only occur in this part?
Capillaries, they are subject to low pressure and can be permeable while arteries and veins are impermeable.  Also, each capillary is small and therefore offers a large surface area.

c. Blood pressure is high in arteries and lower in the capillaries.  Why is this?
Capillaries have a high area, the same volume (quantity) of blood in a larger area leads to lower pressure.

d. Why is lying immobile for long periods of time bad for circulation?
Muscle movement is required to squeeze the blood in veins or lymph fluid in lymph vessels through the one-way valves.  Without this fluid builds and can not return to the heart.

e. The lymph vessels return extracellular fluid to the blood, and blood vessels carry blood around the body.  Describe one other difference and one similarity between these systems.
Any one of:  Difference-  lymph open system, blood closed system; blood passes to body and lumgs, lymph only to body;
Similar-  both use muscle movement and one-way valves; both function in immune response; both carry materials for exchange with cells

8. a.  What are two characteristic of skin that allows it to act as a barrier to foreign material entering the body?
Any two of:  dry, dead cells with little nutrients, other bacteria to compete with

b. How is the stomach related to protecting us from disease?
Acid in the stomach kills whatever may enter.  Hair and mucous in nose and throat pass foreign objects into stomach to be killed.