When an animal mimics, or copies the appearance of another animal in order to gain an advantage, like camouflage or a better defense. A good example is the marine fish, Mimic tang . There are many different forms which may be soft, leathery, or even those producing hard skeletons. Hatching may occur internally or external to the mother. The 'pinnules' which are found on many octocorals are small side branches of the polyp tentacle which give it a 'pinnate' appearance.
Pelagic organisms have the ability to swim around or move in some fashion.
Benthos and benthic refers to living on or under substrate at the bottom of the ocean. Sessile means the organism is attached to the substrate. The process by which organisms, usually plants, use the energy contained in light, usually sunlight. Although they may have some form of locomotion they are mostly carried by water currents. The microplankton is divided into zooplankton, tiny marine animals, and phytoplankton, or plants.