A class of annelid worms with few setae per segment. It includes the earthworms such as Lumbricus and Eisenia.

The flow of water in enviromental bodies of water such as rivers, oceans, water supplies, aquariums, etc. It includes currents, tides, and waves.

Large natural streams of FRESH WATER formed by converging tributaries and which empty into a body of water (lake or ocean).

Animals that have no spinal column.

Number of individuals in a population relative to space.

I'm sorry for any confusion, but "Brazil" is not a medical term or concept, it is a country located in South America, known officially as the Federative Republic of Brazil. If you have any questions related to health, medicine, or science, I'd be happy to help answer those!