clams found in tidal pools. A crow grabs aclam with its beak, then flies upward

Question

clams found in tidal pools. A crow grabs aclam with its beak, then flies upward and drops the clam onto therocks below

to break the shell. If successful, the crowcan dine on the clam’s inner soft parts. If the shell doesnot break, the crow

flies up and drops the clam again and againuntil the shell breaks. The higher the bird flies, the fewer numberof drops

required to break the shell. Thus, a crowcan either (1) drop the clam from lower height, but having to flyup more times,

or (2) break the shell with fewer drops, butfrom higher up. Both options require lots of effort on the part ofthe crow.

The researcher hypothesized that height andnumber of drops would influence feeding behavior in crows.He

predicted that crows would, on average, flyto a middle (optimal) height requiring fewer drops than a lowerheight, but

also not requiring to bird to fly toohigh.

To test this prediction, the researcher putup a 15 meter (15m) pole and dropped clams from differentheights

(2m, 3m, 5m 7m, and 15m). At each height, herepeatedly dropped a clam onto a rock surface and recorded thenumber

of drops required to break the shell. Headded replication to his experiment by dropping 20 clams from eachheight and

averaging the number of drops from thecombined results of these 20 clams. He used clams of the same size,made

drops under uniform weather conditions, anddropped clams onto the same rock surface. Finally, for each height,he

calculated a measure of overall effortrequired to break shells by multiplying the number of drops by theheight (see

Table 1). The researcher also observed crows feeding and foundthat on average crows flew to a height of 5.2 m.

Explanation / Answer

Well if you were to put a control into this experiment it would bean undropped clam, because the undropped clam has no othervariables and/or changes to the clam.

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