Which Began First

question 51

Multiple Choice

Which began first?

• A)Multicellular life in the ocean
• B)Multicellular life in fresh water
• C)Plants colonizing the land
• D)Animals colonizing the land

---

Definitions:

Sponges

Simple aquatic animals belonging to the phylum Porifera, characterized by porous bodies through which water flows.

Echinoderms

A phylum of marine animals including sea stars, sea urchins, and sand dollars, characterized by radial symmetry and a unique water vascular system.

Nematodes

A phylum of worm-like organisms known as roundworms, which can be found in various habitats and play diverse ecological roles.

Cnidarians

A phylum of aquatic invertebrate animals that includes corals, jellyfish, sea anemones, and hydras, characterized by their cnidocytes, stinging cells used for prey capture and defense.