Dr. Reichlerıs Bio 301          Print Name:_________KEY________________

Exam #2   Oct. 31st, 2003


            Answer each question as succinctly as possible in the space provided.  If needed, continue on the back.  If you use a drawing as part of your answer, be sure to also include a written explanation.  Read each question carefully and donıt hesitate to ask if a question seems unclear.  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.  Each question is worth 6 pts, unless otherwise noted, for a total of 103 points possible for this exam.


1.     Researchers often determine what grizzly bears eat by looking at their feces.  Are they getting an accurate view of the bearıs diet?  Why or why not?  (8pts)

Probably not.  Bears are not good at digesting plant material, so much of it passes undigested into their feces, but animals would be fully digested by the bears, and therefore not be visible in the feces.


2.     What time of year do grizzly bears need to eat the most?  Why?

EitherŠSpring after they emerge from their dens and need to gain weight lost during the winter.  OR  In Fall, to gain weight prior to entering the den.


3.     Why are plants green?

Plant pigments absorb blue and red light reflecting green.


4.     You are eating a Snickrunch bar with chocolate, rice, and nuts.  Your friend is eating a Krunch bar with only chocolate and rice.  Why is the Snickrunch healthier for you than the Krunch?

The Snickrunch has all of the essential amino acids provided by nuts and rice.


5.     If your stomach were removed so that your esophagus was directly connected to your small intestine, how would your eating habits need to change?  (8pts)

EitherŠOnly eat small quantities at a time, the stomach is not present to store food.  OR  Be careful about the sterility of food, the stomach acids are not killing pathogens on the food.


6.     You are walking in the woods and come across a grizzly bear.  Your fear causes you to empty the contents of your large intestine.  What was expelled?

Undigested food.  Also possibly unreabsorbed water.


7.     Grizzly bears have been seen eating rotting animals that have been dead for weeks and that are covered in bacteria.  Why do the bears NOT get sick?

EitherŠTheir stomach acids kill the bacteria.  OR  Their short digestive systems do not allow much time for the bacteria to multiple and infect the bear.


8.     How can the immune system protect you from cancer?

T-cells monitor and destroy abnormal cells such as cancer cells.


9.     How can antibodies be used to determine previous exposure to a pathogen?

The presence of antibodies or memory cells against that pathogen would indicate previous exposure to that pathogen.


10.  How much genetic information do gametes (sperm or eggs) have compared to other cells?  Why?

1/2.  Gametes are combined with two halves of the genetic info to make an offspring with a full complement of genetic info.


11.  Why is it impossible for a female grizzly to become pregnant the first time she has intercourse, while human females can get pregnant the first time they have intercourse?  (8pts)

Female grizzlies only ovulate after copulation.  Female humans ovulate periodically irrespective of copulation.


12.  Why does the body need both excitatory and inhibitory neurotransmitters?

Excitatory neurotransmitters are needed to signal other neurons or for muscle contraction.  Inhibitory neurotransmitters are needed for signaling the opposing muscle to relax so that movement can take place.


13.  What is similar between ATP production in mitochondria and the transmission of a signal from one end of a neuron to the other?  (8pts)

ATP production involves the pumping of H+ across the membrane and ATP production as the H+ diffuses thru channels back across the membrane.  Neuron signaling involves pumping of positive ions across the membrane, and the signal occurs as these positive ions diffuse thru channels back across the membrane.


14.  What are two ways that we rely on plants for our survival?

Any two of:  Plants fix CO2 into sugar so we can use the sugar in cellular respiration.  Plants have bacteria in their roots that fix nitrogen from the atmosphere into useable forms.  Plants absorb phosphate from the soil, and make it available for other organisms.


15.  Without humans killing other organisms, why do other species go extinct as the human population grows?  (8pts)

More humans use more resources reducing the resources availability for other species.



Bonus:  When are male grizzlies most aggressive, and why are they so aggressive at this time?  When are female grizzlies most aggressive, and why are they so aggressive at this time?  (3pts)

Males- Aggressive in the late spring/early summer when looking for mates.  They are competing with other males for the ability to reproduce with females because only about 1/3 of the females are without cubs and available for mating.  Females- Aggressive when they have cubs.  Male bears will kill cubs and try to mate with the females, so females are aggressive in protecting their cubs.