It is defined by their ecological niche rather than phylogenetic or taxonomic classification.
Once they can swim on their own, they are classified as nekton. Examples of animals that have a meroplankton stage are corals, sea stars (starfish) , mussels and lobster. Holoplankton are organisms that are plankton their entire lives. Examples include diatoms, dinoflagellates, salps and krill. Examples: The copepod is a type of zooplankton, and a primary food for right whales. Definition: Plankton is the term that generally refers to the floaters, the organisms in the ocean that drift with the currents. This includes zooplankton ( animal plankton ), phytoplankton (plankton that are capable of photosynthesis), and bacteria. Holoplankton are organisms that are plankton their entire lives. Examples include diatoms, dinoflagellates, salps and krill. Examples: The copepod is a type of zooplankton, and a primary food for right whales. Plankton (singular plankter) are a diverse group of organisms that live in the water column of large bodies of water and that cannot swim against a current. They provide a crucial source of food to many large aquatic organisms, such as fish and whales. Within the plankton, holoplankton spend their entire life cycle as plankton (e.g. most algae, copepods, salps, and some jellyfish). By contrast, meroplankton are only planktic for part of their lives (usually the larval stage), and then graduate to either a nektic or benthic (sea floor) existence Phytoplankton /ˌfaɪtoʊˈplaeŋktən/ ˌfaɪtoʊˈplæŋktən are the autotrophic components of the plankton community and a key factor of, oceans seas and freshwater basin. Ecosystems the name comes from The greek words (φυτόν), phyton  meaning , plant and (πλαγκτός), planktos meaning wanderer or. drifter Phytoplankton /ˌfaɪtoʊˈplaeŋktən/ ˌfaɪtoʊˈplæŋktən are the autotrophic components of the plankton community and a key factor of, oceans seas and freshwater basin. ecosystems These organisms include drifting animals, protists, archaea, algae, or bacteria that inhabit the pelagic zone of oceans, seas, or bodies of fresh water; that is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification. Within the plankton, holoplankton spend their entire life cycle as plankton (e.g. most algae, copepods, salps, and some jellyfish). By contrast, meroplankton are only planktic for part of their lives (usually the larval stage), and then graduate to either a nektic or benthic (sea floor) existence One way plankton can be classified is according to how they obtain energy. Zooplankton are animal-like plankton. They are consumers, obtaining their energy by feeding on phytoplankton and other zooplankton. Most zooplankton are eaten by larger zooplankton, fish and even whales. Phytoplankton are plant-like plankton. They are primary producers, using energy from the sun and carbon dioxide to produce their own food. Phytoplankton are the base of the aquatic food web. B acterioplankton consist of bacteria and archaea. They are single celled producers and/or consumers and play an important role in recycling nutrients in the food web. Meroplankton spend only a part of their life as plankton. Many phyto and zooplankton species begin their life as plankton and then transform into an adult form that settles to the bottom or develops a way to swim on its own. This group includes kelp, crabs, fish, clams, oysters, coral, squid and many others. Bioluminescent Noctiluca scintillans (a dinoflagellate). Plankton is composed of the phytoplankton (the plants of the sea) and zooplankton (zoh-plankton) which are typically the tiny animals found near the surface in aquatic environments. Like phytoplankton, zooplankton are usually weak swimmers and usually just drift along with the currents.  Plankton are mostly tiny animal and plant organisms that float or weakly swim in the ocean's surface waters. Some plankton are single-celled while others are multi-celled---wi … th some forming colonies. The word plankton comes from the Greek planktos, meaning drifting or wandering. Zooplankton Meaning 'animal', the prefix zoo denotes a group of animal plankton. Likewise, they cannot swim themselves. These animals are detrivores and omnivores. They eat each other, phytoplankton, and decaying matter. Plankton consists of any drifting organism, such as animals, plants or bacteria. They inhabit the pelagic zone of oceans, seas, or any other bodies of fresh water. See related link below.. These are microscopic organisms, similar to phytoplankton, who consume other plankton and digest waste. Some look like microscopic shrimp and others may look like tiny floating insects, depending on the type
http://marinelife.about.com/od/glossary/g/planktondef.htm http://marinelife.about.com/od/glossary/g/planktondef.htm https://en.wikipedia.org/wiki/Plankton https://en.wikipedia.org/wiki/Phytoplankton https://en.wikipedia.org/wiki/Plankton http://www.teachoceanscience.net/teaching_resources/education_modules/plankton_-_aquatic_drifters/explore/ http://marinebio.org/oceans/zooplankton/index.aspx http://www.answers.com/Q/How_is_plankton_classified
what classifies as plankton