To what phylum do the water bears belong?

Match the structures of the water vascular system to the image below.   

What does metamerism mean?

To what class do the leechs belong?

Echinoderms have a reduced ___________ system, a complete ______________ system, and an absent ______________ system. 

Look at the image below. The posterior end of two roundworms (Ascaris lumbricoides) is shown below. What structure is indicated by the red arrow?  

I conduct a study on the effect of a low carb diet on weight loss among people with a mobility issue. I use their weight that was recorded in the OT hospital clinic today and then measure their weight using my bathroom scale form home 4 weeks later. This could cause a threat to internal validity known as:

To what subphylum do the crabs, crayfish, shrimp, isopods, copepods, lobsters, etc. belong?

To what class do the centipedes belong?

Which of the following is CORRECT concerning echinoderms?