According to our most recent data, the invertebrates most closely related to the vertebrates are members of phylum

A sea star suffers from an infection that affects its ampullae.  Due to the infection, the ampullae no long function.  What do you predict will be the effect on the sea star?

What class/phylum of animals has the fewest number of species among these choices? 

How does an open circulatory system differ from a closed one? 

Describe the route of water through a sponge. 

Your colleague is studying a newly-discovered organism.  She is becoming increasingly convinced that the organism is an arthropod.  You find that you must respectfully disagree when you note that the organism has a set of distinctly non-arthropod characteristics.  The features that cause you to exclude the organism from the arthropod grouping are 

Suppose you discover a new species of animal that does not have body segments, but is triploblastic, pseudocoelomate, and cephalized. Under the molecular phylogenetic scheme, you would allocate it to which phylum? 

Butterflies and moths are members of order Lepidoptera.

Members of phylum Echinodermata include all of the following EXCEPT:

In your observations of a new rotifer species, you note that diploid females can lay diploid eggs that in turn become diploid female adults.  What do you conclude about this behavior?