The Living World 8th Edition by George Johnson

Exercise 2

The main limiting factor of arthropod size is the
A) inefficiency of open circulatory systems.
B) weight of the muscles needed to move the organism.
C) weight of the thick exoskeleton needed to support very large insects.
D) weight of the entire organism, which if too great would crush the soft body of the arthropod during molting.
A famous evolutionist, when asked the most important thing he has learned, said, "God has an inordinate fondness for beetles." About two-thirds of all the named species on our planet are arthropods. From the arthropod pie chart shown in figure 19.17 , estimate about what percentage of the named species on our planet are beetles.
Figure 19.17 Arthropods are a successful group.
About two-thirds of all named species are arthropods. About 80% of all arthropods are insects, and about half of the named species of insects are beetles.