There are 120 species of mammals including whales, dolphins, porpoises, seals and sea lions which have evolved to adapt to their aquatic environment by developing small appendages (ears and flippers), a generally large size, hydrodynamic (mechanical properties of liquid) body shapes and different methods to cope with extreme changes in temperature.
The ocean provides habitat for a wide variety of animals, some of which are flying-fish, sharks, narwhals, sting-rays, whales, tarpon, tuna, sardines and jellyfish. One tiny shrimp-like animal known as the phaeton is a key species floating freely in the ocean. Many fish and marine mammals feed on it, and in turn carnivorous predators such as sharks, orcas and electric eels tear apart their prey, allowing pieces to fall to the sea floor and decompose, providing a rich fertilizer.
Fish are able to obtain oxygen through their gills, a specialized structure in which blood comes into contact with the water over a very large surface.
Animals such as flatworms, sea stars, giant isopod (wood louse) sole and flounder have adapted to living in the deepest ocean trenches where the pressure can be over one thousand atmospheres.
Mammals such as whales, dolphins, porpoises, manatees, dugong, seals, walrus, otters and even polar bears swim effortlessly through their watery environment, diving and swimming with ease. For example, the sperm whale cleans out its lungs to get rid of old carbon dioxide and load up with fresh oxygen in its swimming muscles before diving as low as 8,200 feet as it hunts for food. At this depth, the pressure is tremendous and a human would suffer from the “bends” if not properly pressurized. Sperm whales routinely hold their breath for as long as one hour before returning to the surface to repeat the process.
The watery environment is not conducive to strong vision because of light absorption, and as a result some marine mammals have evolved to rely upon echolocation.
Toothed whales (dolphins, porpoises, river dolphins, orcas and sperm whales) send out a series of high-frequency clicks in the direction their head is pointing and listen to the echoes of those calls as they return from various objects in their environment. The different rates of click production are heard as barks, squeals and growls in the bottlenose dolphin. Some of the smaller toothed whales have a tooth arrangement that aids in echolocation.
Plankton converts inorganic carbon into sugars that are stored in its cells. They are in turn eaten by zooplankton, filter feeders and baleen whales. Zooplankton are eaten by small fish which in turn are eaten by salmon, tuna, seabirds, marine mammals, and so on.
There are thousands of seabirds that depend heavily on the ocean in order to survive. Birds in general have evolved to have hollow bones for flying, lightweight toothless bills for eating and strong waterproof feathers. Many seabirds (frigate birds, albatross, gulls) have developed large wingspans so they can travel long distances and take advantage of food sources different from terrestrial birds (cormorants are divers; penguins live in Antarctica where other birds don’t and cannot fly but are excellent swimmers; gulls are coastal scavengers).
Ducks have developed webbed feet for swimming. Many birds have light-coloured plumage to protect them from being seen by predators, whereas divers have light colour on their fronts and dark colour on their backs to make them less visible.
Birds’ bills have evolved to suit their specific food preference. For instance, pelicans have a huge pouch to scoop up fish; albatrosses have very large nostrils allowing them to smell food from a great distance; ducks have long, flat bills to strain small plants and animals from the water, whereas herons and kingfishers have spear-like bills adapted for fishing.
Seabirds must return to land to nest and generally choose remote cliffs to protect them from terrestrial predators. Many eggs are cone-shaped so that they don’t roll off the cliffs.
Plankton is a term used to describe organisms that float in the oceans, but which rely upon currents to move, and can be either plant or animal. Most are found in the pelagic zone and very important to life on Earth. They support many of the animals higher up in the food chain, all the way up to humans. Plankton also greatly assist in photosynthesis (process by which organisms turn carbon dioxide and water into carbohydrates and oxygen), and thus are vital to maintaining our atmosphere. Plankton require a balanced environment and nutrients in order to survive.
Plant life includes seaweed, algae, dark star, sea-cactus, fungi, ocean lilly, Cimarron, yorma bulb, red tide.