|Lamellibranchs arose from protobranchs which became filter feeders by consuming detrital particles and microorganisms trapped in their gills as the ventilating currents of water passed through their shells. This type of feeding freed lamellibranchs from depending on deposit material for food. Lamellibranchs are the biggest group of mollusc. Most species live in soft substrate, exploiting the protection offered by a subterrenean life in marine or freshwater sand and mud while trapping food brought in from the water above. Others now live in habitats and follow ways of life that would have been unsuitable for their protobranch ancestors.