Question

4) Why is it suggested, by evolutionary biologists, that the teleosts (and the other ray finned fish) share a common ancestor which was freshwater, even though many contemporary teleosts are marine?

a) because the earliest fossil animals are found in freshwater strata, and since teleosts are animals, the earliest teleost must have been freshwater also

b) because, unlike sharks, teleosts are highly-evolved, which means osmoregulating in a wide variety of environments

c) because the bodily fluid osmolarities in teleosts and other ray finned fish are much closer to fresh water than to salt water

d) because the fossil record unambiguously indicates that this is the case

e) because marine teleosts have swim bladders and gills, which are clearly adaptations to a freshwater existence

6) Oxygen has a diffusion constant of 2*10-5 cm2/sec and can diffuse across 10 um in about 20 msec. How long would it take a molecule of HIV to cross the same distance if the diffusion coefficient for HIV is 2*10-8?

a) 0.00002 sec

b) 1 sec

c) 20 sec

d) 20000 sec

e) about 1 year

7) A frog egg before fertilization can be as big as 1 mm. After fertilization, the cells quickly divide by mitosis. After a few divisions, they are about 100 um in diameter. What would the change in surface area / volume ratio be for these cells after this mitosis?

a) 1000 X

b) 100 X

c) 10 X

d) 0.1 X

e) 0.01 X

12) The cell of a goldfish muscle is placed in ocean water that a shark had been happily swimming in. What would happen to the cell?

a) Not much

b) The cell would likely burst

c) The cell would likely shrink in size

d) The cell would develop extensive microvilli

e) The cell would insert aquaporins into its plasma membrane.

Answer 1

4. The correct statement is because the bodily fluid osmolarities in teleosts and other ray finned fish are much closer to fresh water than to salt water.

12. The correct statement is The cell would likely shrink in size. This is because, the goldfish is freshwater fish and shark is found in marine water i.e. salt water. Because the ocean water is hypertonic, the water from the goldfish cell will move out into the marine water which will cause goldfish to shrink.