FRESHWATER BIOLOGY (207) Name:
Exam 2 (Oct 31, 1995)
1) You are a reckless young copepod and you stumble into the tentacles of a Hydra.
No problem you say, but suddenly you find yourself unable to swim away.
(2 points each)
a) why can't you escape and what is your fate?
b) before you meet your fate you notice that the Hydra is green. How will you help to keep it green?
c) could it survive without careless zooplankton like you? Explain.
2) If you were a clam that brooded young and released juvenile, rather than larval clams, how would this reproductive mode be: (2 points each)
a) an advantage?
b) a disadvantage?
3) The sturgeon has an inferior mouth.
a) describe where the mouth is on the fish (1 point)
b) explain WHY the mouth is inferior (2 points)
4) Snail populations are abundant in the Little River where we sampled. (3 points each)
a) based on this fact alone, would you expect the periphyton growth on aquatic macrophytes to be abundant or not and why?
b) if higher levels of fertilizer from the golf course and surrounding farm lands get into the River, would you expect the snail populations to increase or decrease and why?
c) would you expect the periphyton populations to increase or decrease in the River if it were stocked with more predatory sunfish and why?
5) Rotifers can change their body form in response to predators.
a) what is a typical change they show? (1 point)
b) how do they benefit from such a change? (2 points)
c) how might this "cost" the rotifer? (2 points)
6) Why is a minnow able to hover almost effortlessly - and without much fin movement - in the water of an aquarium and not sink? (2 points)
7) Flatworms are flat for several reasons.
a) give 2 explanations (2 points)
b) would a flatworm with symbiotic algae tend to be positively or negatively phototactic and why? (3 points)
c) could there be a risk of this behavior? Explain. (1 point)
8) Lake Ontario populations of Pacific salmon, alewives, zooplankton, and phytoplankton are interconnected members of the food web. What might happen to the abundance of each of these populations if:
a) more nutrients were allowed to enter the Lake via sewage or agricultural runoff? (4 points)
·salmon -
·alewives -
·zooplankton -
·phytoplankton -
b) zebra mussel populations increased? (4 points)
·salmon -
·alewives -
·zooplankton -
·phytoplankton -
c) people were allowed to catch as many salmon as possible (in other words, throw out the fishing regulations!)? (4 points)
·salmon -
·alewives -
·zooplankton -
·phytoplankton -
9) For both larval and adult salamanders, water is very important. For most species:
a) which life stage is more dependent on water? (1 point)
b) what conspicuous morphological adaptation does this life stage have that the other does not, and what is this used for? (2 points)
10) If you were a hermaphroditic worm, how would this reproductive mode be an advantage? (2 points)
11) You've collected 2 different, live fish in a lake; one a streamlined-shaped fish in the surface layer of the lake, and the other a depressiform fish from the lake bottom. For each fish you measure its weight as well as its total gill surface area. From this you calculate a ratio of the gill area (GA) to the fish weight (W), shown as GA/W. For one fish you find a ratio value of 50 and for the other fish a value of 1. a) Which value belongs to the surface fish and which to the benthic/demersal fish? (1 point)
b) why? (2 points)
12) Oligochaete worms eat and move/mix sediments.
a) why don't they have many body projections sticking out from their bodies? (2 points)
b) is the sediment they eat more, or less rich in organic food material after they process it and why? (3 points)
13) Your summer job is to sample bivalve populations in small streams. One stream contains water flowing out of an eutrophic lake, whereas a neighboring stream of similar size, flow, and temperature drains a forested watershed. (3 points each)
a) in which stream are you likely to find an abundant clam population and why?
b) for the stream with abundant clam populations, plot the concentration of food (arbitrary units OK) sampled from the upstream to the down- stream end of the bed, measured just above the clams.
c) for this same stream, plot the body size of the clams (arbitrary units OK) found, from the upstream to the downstream end of the bed.
14) How do bryozoans:
a) protect themselves? (1 point)
b) if you prevented half of a colony's zooids from feeding for a few days (but let the others feed) will they die? Why or why not? (3 points)
15) Sponges typically have ostia with openings of about 50 µm. Given this, do sponges filter-feed mainly on phytoplankton or zooplankton (like copepods, rotifers, cladocerans) or both, and why? (3 points)
16) Some fish get parasitic infections on their fins, which can render the fins functionless (the fins get chewed up, essentially). How would the movement of a salmon be affected if it lost the function of: (2 points each)
a) its caudal fin?
b) its dorsal fin?
c) both of its pectoral fins?
d) its adipose fin?
17) If you removed all planktonic rotifers from a lake, what other lake organisms would: (2 points each)
a) benefit and why?
b) suffer and why?
18) Some bivalves have a hinge ligament that tends to hold the 2 valves agape. How does the animal benefit from this? (2 points)
19) Define 10 (ONLY 10!) of the following 14 terms (1 point each):
a) barbel (not the kind you lift) -
b) counter-current flow -
c) anadromous -
d) caviar -
e) operculum (not the kind on a fish!) -
f) radula -
g) piscivore -
h) hermaphrodite -
i) lophophore -
j) nematocyst -
k) corona -
l) parthenogenesis -
m) cyclomorphosis -
o) oscula -