Rock Platforms: Spray Zone - Results from the Barnacle Experiment

Examine the graph and then answer the following questions.

How does the growth rate of Catomerus vary with increasing height above sea level?

no difference

increases

decreases

try again

Check the height of the columns in the graph for each zone and try again. (The differences are significant.)
Well... Look at the size of operculae reached by Catomerus in one year in the spray zone and the intertidal zone again. (That is a measure of growth rate.) Try again.
Yes. Operculae in 1-year-old Catomerus are smaller in the spray zone than the intertidal zone, ie. growth rate decreases with increasing height above sea level.
barngraph.swf barnacle barnacle barnacle barnacle barnacle

Examine the graph by moving the mouse over it.

This bar shows the size of barnacles from the intertidal zone. The intertidal zone is generally inundated twice each day (a hazard for the zoologists measuring them).

This bar shows the size of barnacles from the lower part of the spray zone. This area was covered by water a number of times each month.

This bar shows the size of barnacles from the spray zone. The site was only sprayed with water and not covered at extreme high tides.

Height above sea level is measured relative to a physical marker, as sea level varies with the tides

This is the mean width of a sample of barnacles' opercula reached in the first year of adult life, ie. it is a measure of growth rate.