Biology Graphing Questions

The following two graphs show sea urchin availability and consumption by otters.

What trend and/or relationship do you see in both of these graphs?

• Larger urchins are found near Attu Island, and smaller urchin are rarely consumed near either island.

• Larger urchins are found in Amchitka, and smaller urchin are rarely consumed near either island.

• Similar sized urchins are found in both islands, and urchins are consumed evenly regardless of size.

• Similar sized urchins are found in both islands, and only small urchins are consumed.

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What do these graphs suggests in regards to which sized urchins are preferred by otters?

• Otters prefer to eat small sea urchins.

• Otters prefer to eat mid-sized to large urchins.

• Otters do not have a preference for urchin size.

• Otters refuse to eat medium sized urchins.

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This graph shows the relationship between the size of a sea urchin (diameter) and the thickness of its protective shell for two different species.

What does this graph reveal about sea urchins?

• Purple urchins have a greater thickness than red urchins.

• Red urchins have a greater thickness than purple urchins.

• Both urchins have the same thickness.

This graph shows the relationship between the size of a sea urchin (diameter) and the thickness of its protective shell for two different species.

How might the size of a sea urchin affect the sea otters' choice of prey?

• Otters would not prefer the larger prey, because it would take too long to eat

• Otters would prefer the larger prey, because they provide more energy.

• Otters would prefer smaller prey, because they are easier to digest

• Otters would have no preference based on size

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This graph shows the relationship between the size of a sea urchin (diameter) and the thickness of its protective shell for two different species.

How might the thickness of the urchin's shell impact the otters' choice of prey?

• Otters would prefer thinner shells, because they will be easier to open.

• Otters would prefer thicker shells, because they would be harder to open.

• Otters would prefer thicker shells, because they would be easier to open

• Otters would not have a preference based on shell thickness

Sea otter consumption of different species of prey in the wild.

Based on this graph which species of prey do the sea otters prefer?

• Purple urchins

• Red urchins

• Kelp

• Crabs

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Sea otter consumption of different species of prey in the wild.

Based on the data from the graph, how do the otters impact the two species of sea urchins?

• By eating more purple sea urchin, this population is decreased the most.

• By eating more red sea urchin, this population is decreased the most.

• By eating the same number of both species, the two populations decrease the same.

• Otters do not impact sea urchin populations.

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Relative sea urchin size (diameter in cm) in an area without sea otters (A) and an area with sea otters (B).

What trends do you see in the graphs?

• Sea urchins are bigger in areas without sea otters.

• Sea urchins are smaller in areas without sea otters.

• The presence of sea otters does not seem to affect sea urchin size.

• Sea urchins are bigger in areas with sea otters

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Relative sea urchin size (diameter in cm) in an area without sea otters (A) and an area with sea otters (B).

What do you think would happen to the average sea urchin size if the sea otters in (B) were removed?

• The average size of sea urchins would increase

• The average size of sea urchins would decrease

• The average size of sea urchins would stay the same

• The average size of sea urchins would not be affected

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Relative sea urchin size (diameter in cm) in an area without sea otters (A) and an area with sea otters (B).

Based on the evidence from the graph, why are sea otters considered a keystone species?

• They eat all of the small urchins to keep them from overpopulating

• They eat the medium to larger sea urchins to keep the population in balance

• They are eaten by the sea urchins for energy.

• Sea otters do not eat sea urchins.

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