In mutualism, both organisms benefit. In commensalism, one benefits and the other is unaffected; in parasitism, one benefits and the other is harmed. Some of these relationships are so close that we speak of the composite of two species as one unit; for example, we speak of the composite of algae and fungi as lichens
<h3>Seafloor sediment consist mostly of terrigenous sediment, biogenous sediment and hydrogenous sediment. Terrigenous sediments form from sediments carried from the land into the ocean by water, wind or ice.</h3>
