Dr. Reichlerís Bio 301L    Name:____________________________
In-class Exam #3  27 April 2001

 Answer each question as succinctly as possible.  You may use the back if you need more space than is provided below the question.  Each question is worth 3 pts, unless otherwise noted, for a total of 70 points, which along with your 30 point take-home gives a possible 100 points for this exam.  Read each question carefully, and donít hesitate to ask if a question seems unclear.

1.  Describe one of the lines of evidence that links humans to other related species?
Any one of:  genetic similarities, morphological similarities, fossil evidence

2. Next to the part of the digestive system listed below write what is happening to the food.  The number in parenthesis denotes how many points each part is worth AND how many things you need to mention.
Mouth (2):
Any two of:  moistening food by saliva, macerating food, digestion of carbos by amylase

Stomach (2):
Any two of:  acidifying food, further liquefying, digestion of proteins by pepsin, churning, storage

Small Intestine (2):
Any two of:  neutralize food by adding bicarbonate, digestion, absorption of digested material

Liver (1):
Any one of:  monitoring of nutrients that pass from sm. int., storage of amino acids

Lacteals (1):
passing fats and lipids from sm. int. to blood near heart

Large Intestine (2):
Any two of:  absorption of water, absorption of salts, production of vit. K by E. coli, expulsion of non-digested material

3. In humans what is meant by an essential amino acid?
An amino acid that the human body can not produce so we need to eat foods that contain this amino acid

4. a.  What does hemoglobin do, and how is its function affected by changes in the pH of the blood?  (4pts)
Hb carries oxygen from lungs to body, at basic pH it binds oxygen very well, at lower pH it releases oxygen (binds less well)

b. What are 2 conditions that humans need to maintain in the lungs to facilitate gas exchange?  (4pts)
Any two of:  large surface area, moisture, concentration gradient

5. a.  What causes blood to move through the veins as it returns to the heart?
Muscle movement squishes the blood through the veins, and one-way valves keep it moving toward the heart

b. Where does lymph fluid come from?
As blood moves from arteries to capillaries the blood pressure forces some liquid to squeeze out of the blood vessel, this is interstitial fluid that is collected and returned to the blood via the lymph vessels

6. How does an endotherm react to cold temperatures differently than an ectotherm?
endos:  increase metabolism, ectos:  can't change metabolism

7. a.  Why is it critical for humans to maintain a set concentration of salts in our body fluids?
Too much or too little salt effects the 3-D structure of proteins and causes them to function less efficiently

b.  After the blood is filtered in the Bowman's capsule, what is removed before excretion?  Give 4 specific examples.  (4pts)
Any four of:  water, some salts, vitamins, lipids, amino acids, some minerals, sugars, nucleotides

8. a.  What are 3 characteristics of skin that allow it to act as an effective barrier?
Any three of:  dry, dead so not much to eat, good bacteria, sweat, tears, oils

b. HIV, the virus that causes AIDS, directly affects T-cells, but leads to an overall weakening of the immune system.  Why?
There is a connection (a hormone signal) between the helper T-cells and activation of B-cells.  Without T-cells the B-cells do not react very well.

c. Would the cell mediated (T-cells) or humoral (B-cells) immune response be most effective against an infection of the flu virus?  Explain your answer.  (4pts)
Either answer is ok as long as supported well.
T-cell:  virus infects cells to reproduce, so T-cells would kill infected cells.
B-cell:  antibodies would bind virus keeping it from entering cells, and/or attracting WBCs to engulf and destroy

d. What is it about HIV that makes it difficult to create effective anti-HIV drugs?
HIV has a high mutation rate so can develop resistance to drugs and it is difficult to make vaccines due to constant changing of outer proteins, membrane surrounding virus makes it difficult to get anything inside

9. a.  What characteristics does a neuron have at rest, and how does the neuron maintain these conditions?
The membrane is polarized, more positive ions outside and more negative ions inside.   This is maintained by pumping positive ions out of neuron

b.  In the nervous system, what is the function of neurotransmitters?
Transmit signals between neurons.  Receptors on the receiving neuron perceive presence of neurotransmitter and activate depolarization of membrane.

c. What does calcium do when released into muscle cells?
Calcium binds tropomyosin removing tropomyosin from actin so that myosin can bind to and move actin

10. a.  What are 2 differences between the formation of eggs and sperm in humans?  Focus on the actual production of the gametes.  (4pts)
Any two of:  Sperm made constantly, Eggs only produced once a month/  mieosis for sperm produce 4 cells, eggs only one/  sperm produced throughout life, all  eggs produced before birth/  sperm production controlled by testosterone, eggs by estrogen, progesterone

11.  Briefly describe one of the environmental responses of plants discussed in class.  List the environmental signal and then how plants respond to it.  (4pts)
Any one of:
Light:  grow toward light, and/or grow taller in light filtered by other plant
Gravity:  shoots up, roots down
Touch:  mechano-stimulated plants grow shorter and stockier
Injury:  produce protease inhibitors, plant-wide and plant to plant signals
Pathogen:  kill infected cells
Temperature:  change membrane content, make antifreeze compounds