Which term describes the free-swimming life stage of cnidarians?

Which term describes the free-swimming life stage of cnidarians?

• A. Polyp
• B. Hermatypic
• C. Mysticeti
• D. Medusa

Answer: (D)

Cnidarians typically alternate between two body forms: a sessile polyp and a free-swimming medusa. The free-swimming form is the medusa, which is umbrella- or bell-shaped and moves by pulsating its bell to propel itself through the water. This contrasts with the polyp, which is usually anchored to a surface and can reproduce asexually. The other terms aren’t life stages of cnidarians: hermatypic describes reef-building corals, Mysticeti refers to baleen whales, and while some cnidarians may lack a prominent medusa stage, the term that describes the free-swimming form in the common life cycle is medusa.

Cnidarians typically alternate between two body forms: a sessile polyp and a free-swimming medusa. The free-swimming form is the medusa, which is umbrella- or bell-shaped and moves by pulsating its bell to propel itself through the water. This contrasts with the polyp, which is usually anchored to a surface and can reproduce asexually. The other terms aren’t life stages of cnidarians: hermatypic describes reef-building corals, Mysticeti refers to baleen whales, and while some cnidarians may lack a prominent medusa stage, the term that describes the free-swimming form in the common life cycle is medusa.