Marine life appeared in the form of fish, which live exclusively in water. Some of these evolved into amphibians which spend portions of their lives in water and portions on land. Other fish evolved into land mammals and subsequently returned to the ocean as seals, dolphins or whales. Plant forms such as kelp and algae grow in the water and are the basis for some underwater ecosystems. Plankton, and particularly phytoplankton, are key primary producers forming the general foundation of the ocean food chain. Marine invertebrates exhibit a wide range of modifications to survive in poorly oxygenated waters including breathing tubes (see
Osmotrophy Osmotrophy Osmotrophy is the uptake of dissolved organic compounds by osmosis for nutrition. Organisms that use osmotrophy are osmotrophs. Some mixotrophic microorganisms use osmotrophy to derive energy. The organisms that used osmotrophy are known to be an osmotrophs which are usually found in protists and fungi although exclusively osmotrophic feeding in contemporary ecosystems are restricted to microscopic bacteria thereby used the process of osmosis for the movement of food although some macroscopic animals like molluscs, sponges, corals, brachiopods and echinoderms used osmotrophic feeding as a supplemental food source. Osmotrophy is a means of gathering nutrients in microscopic organisms that relies