Question

How does the movement of cnidaria, like jellyfish, compare to mollusks, like bivalves? what specific body parts, if any, are used to aid their movement?

Answer 1

Jellyfish, a cnidarian, use their medusa form for movement based on jet propulsion by expelling water, while bivalves, a type of mollusk, typically use a muscular foot to move or burrow. Cnidarians have nematocysts for defense and capturing prey, aiding their movement and survival.

Step-by-step explanation:

Comparing the movement of cnidarians like jellyfish to mollusks like bivalves reveals significant differences. Jellyfish, a type of cnidarian, use their bell-shaped body, or medusa, to move. They fill their umbrella section with water and push it out forcefully, propelling themselves by the conservation of momentum. This action causes the jellyfish to move in the opposite direction. In contrast, mollusks such as bivalves primarily rely on a muscular foot for movement. However, other mollusks like squids use a form of jet propulsion similar to jellyfish but can control their direction using a nozzle.

Jellyfish's ability to move was a useful innovation as it allowed them to swim the world's oceans, find food, and escape predators. Jellyfish and other cnidarians have specialized cells called nematocysts that are used for both defense and capturing prey. These cells can deliver stings to would-be predators or prey, aiding their survival.

Examples of Cnidarians

• Jellyfish
• Coral
• Sea Anemones