In most insects, gas exchange is accomplished by __________.

One of the key characteristics of arthropods is their jointed appendages. Describe four functions of these appendages in four different arthropods.

SCIENTIFIC THINKING In one of the experiments described in researchers tested the hypothesis that the highly successful arthropod body plan resulted from new genes that originated in the arthropod lineage. Draw a diagram showing the evolutionary relationship between arthropods and velvet worms and use it to explain why velvet worms were a good choice to test this hypothesis. What results would have supported the hypothesis?

The arthropods superficially resemble earthworms in that both groups __________, yet the two are distinctly different because arthropods, but not earthworms, __________.

A major characteristic of arthropods is __________.

In arthropods, molting is necessary because __________.

Sowbugs are really crustaceans, not insects. Therefore, a sowbug does not have __________.

The majority of animal species are __________.

An unidentified species of animal displays the following characteristics: bilateral symmetry, a complete digestive system, an open circulatory system, distinct body segmentation, and a series of molting stages during growth. To which of the following animal phyla does this species most likely belong?