5. Shore crabs eat clams to obtain the food energy they need to survive. Crabs f

Question

5. Shore crabs eat clams to obtain the food energy they need to survive. Crabs feed on clams by cracking open the clam's shell with their claws and eating the exposed flesh. The larger the clam, the more edible flesh it contains. The larger the clam, the longer it takes a crab to crack open its shell A. Table 1 displays the results of a laboratory experiment on shore crab feeding preferences. Crabs were offered equal numbers of different-sized clams. Display these data as a histogram (bar graph, 3 points) Table 1. Feeding preferences of shore crabs Size of clam Percent of diet (cm) 10 0.5-1.0 1.0-1.5 1.5-2.0 2.0-2.5 2.5-3.0 3.0-3.5 27 31 10 B. Table 2 displays the rate of energy return a crab gets when eating different-sized clams. The rate of energy return is the amount of food energy a crab obtains from eating the flesh of a clam, divided by the amount of time it takes a crab to crack the clam's shell, and is expressed as the amount of energy obtained per second of handling time. Plot these data as a line graph (3 points) Table 2. Rate of energy return for crabs eating clams Size of clam (cm) Energy return (joules per second) 0.3 0.6 0.8 0.9 0.9 0.8 0.7 2.0 2.5 3.0 4.0 C. Read 14.6-14.8 and Quantifying Ecology 14.2 in your textbook. Write a one -paragraph essay analyzing the data above (Tables 1 and 2) based on your reading. Give one plausible reason why shore crabs in nature might forage differently than the laboratory results would predict (4 points)

Explanation / Answer

A. Histogram is displayed below-

B. Line graph is displayed below.

C. By looking at the first plot above i.e. plot of Percent of diet Vs Size of clam, it is clear that crab prefers to eat small to mid-size clams. this is why clams of size between 1.5 -2.5 cm make up nearly 3/4th (74%) of their diet. The reason why it is the preferable size class of clam for crabs can be understood by looking at the second plot i.e. plot of Energy return Vs Size of clam. In this plot we see that the energy gain goes up as we the size of clam increases beyond 1.0 cm and the energy gain starts to come down as the size of clam reaches higher than 3.0 cm. There is one thing that is also worth noticing in second graph is that eating clam of size-class 3 - 3.5 cm provides as much energy as the size class 2.0 - 2.5 cm, but crabs preferable choice is size class 2 - 2.5 cm. The reason for crab not prefereing the higher size class could be the extra effort that is required to break open the shell of higher size class.

Shore crab in nature might forage differently and would eat more of smaller clams than the larger clams. This would be due to their awareness of the amount of efforts thatwould needed to be put in consuming a bigger clam Vs a smaller clam. Given the choice the would probabbly prefer the smaller clams.

Thanks!

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