AP BIOLOGY

Detailed explanation-1: -Polyp forms are sessile as adults, with a single opening (the mouth/anus) to the digestive cavity facing up with tentacles surrounding it. Medusa forms are motile, with the mouth and tentacles hanging down from an umbrella-shaped bell. Figure 28.6 Cnidarian body forms.

Detailed explanation-2: -Arthropods have an open circulatory system (without blood vessels) that consists of a tube that is the heart and an open hemocoel, the coelom of the animal, in which blood pools. Arthropods also have a complete gut with two openings, the mouth and the anus.

Detailed explanation-3: -The members of phyla Platyhelminthes, Porifera, and Cnidaria have many things in common. They are all multicellular animals that are heterotrophic, meaning they do not create their own food. None of these phyla have a respiratory system, and they perform gas exchange through diffusion through their external layers.

Detailed explanation-4: -Complete Digestive System Porifera, Cnidaria, and Platyhelminthes all have a digestive cavity with a single opening that serves as both a mouth and an anus. The presence of separate openings allows specialization of regions along the digestive tract.