Echinoidea, commonly known as sea urchins, are spiny, globular marine animals. They inhabit ocean floors worldwide, from shallow waters to deep sea. Sea urchins have a hard shell, called a test, covered in spines. They feed on algae and play a crucial role in their ecosystem by controlling algae growth.

Echinoidea, commonly known as sea urchins, are found in oceans worldwide. They inhabit a wide geographical distribution that includes the Atlantic, Pacific, Indian, and Southern Oceans. They are prevalent along coastlines and continental shelves from the Arctic to the Antarctic, with a higher concentration in temperate and tropical waters.

Sea urchins predominantly inhabit marine environments, ranging from the intertidal zones to deep ocean floors. They are typically found on rocky substrates, coral reefs, sandy bottoms, and seagrass beds. The environmental conditions they thrive in include clear, saline waters with varying degrees of temperature, depending on the specific region. Sea urchins can be found in shallow waters where they are exposed to tidal changes and waves, as well as in deeper waters where conditions are more stable.

Echinoidea play a crucial role in marine ecosystems as both grazers and prey. They feed primarily on algae and detritus, helping to control algal growth and maintain the balance of marine plant life. In turn, they serve as a food source for a variety of predators, including fish, sea otters, and humans. Some species of sea urchins have adaptations that allow them to survive in specific niches, such as burrowing into rock or sand to avoid predation, or developing spines for protection.