Urochordata, also known as tunicates, are marine invertebrates with sac-like bodies. They are filter feeders, drawing water through an incurrent siphon. Most are sessile as adults, attaching to substrates in ocean habitats. Their larval stage has a notochord, hinting at their chordate lineage.

Urochordata, commonly known as tunicates or sea squirts, are found in oceans worldwide, from polar regions to tropical seas. They are particularly abundant in shallow coastal waters but can also be found at greater depths.

Tunicates typically inhabit a range of marine environments. They are often found attached to substrates such as rocks, shells, or man-made structures like piers. They thrive in both temperate and tropical climates, with some species adapted to cold-water environments. The water conditions they inhabit can vary from clean to moderately polluted, as some species are quite tolerant.

Urochordata play an important ecological role in marine ecosystems. They are filter feeders, consuming plankton and detritus, and thus help maintain water quality and nutrient cycling. They can also serve as habitat for other marine organisms. Some species form large colonies, which can provide shelter for small fish and invertebrates.