Flatworms were the first organisms to evolve specialized cells for excretion (flame cells). What specific purpose does an excretory system serve?

A coelom in a segmented worm also serves as a hydrostatic skeleton.

What feature do Tardigrades and arthropods share?

Ecologically, sea stars are at what trophic level?

Crustacea are biramous, meaning they possess

The segments of crustaceans are covered with a dorsal plate or _____________ and a ventral plate or ______________.

When a parasitic insect is itself parasitized by another insect,

A sea star feeds by absorbing food through the

Copulatory spicules function to

Arthropods are successful because they have