The Hydra:

The hydra is a member of the Coelenterate phylum, which is characterized by having two cell layers, and a hollow body with only one opening. The hydra is a small organism. It’s one opening, the mouth, is surrounded by tentacles, which move food into the mouth and digestive cavity. The hydra then secretes enzymes into this cavity to partially digest the food particles (extracellular digestion) which are then taken into the cells of the hydra by phagocytosis. Digestion is then finished within the cells of the hydra.

The hydra’s nervous system made up of a web of neurons called a nerve net. Unlike most organisms, nerve impulses can travel both ways along the hydra’s neurons. This causes the whole body to respond to a single impulse. The hydra also has stinging cells called nematocysts, which paralyzes its victims, allowing it to engulf the prey and eat its dinner.

This student chose a hollow, chocolate Easter egg as the body of the hydra and melted gummy worms into the top to represent the tentacles. They also stuck M&M’s on the gummy worms to represent the nematocysts.

(When this student was trying to come up with an edible, hollow, model of the body cavity for her model of the hydra, their first approach was an attempt at coating a balloon with melted chocolate in order to form the model. This is something that they would not recommend, however, since both of them ended up wearing a majority of the results!)