Classification of organisms involves identifying and putting them into groups based on distinctive and uniform qualities they possess. This scientific study and activity is referred to as Taxonomy, a branch of science which was first championed and postulated by Carol Linnaeus as a way of classifying organisms into differing groups.
In Taxonomy, organisms are classified based on various qualities and characteristics. And when ways of movements and life patterns are foremost considered, marine organisms are classified in three distinctive groups or classes.
Plankton is a general name used in reference to all sorts of drifting and floating marine organisms, be they animals, plants, archaea, or bacteria. Almost all organisms classified as "Planktonic" share the common characteristics of being able to float and drift at will.
Three further taxonomic groups namely Phytoplankton, Zooplankton and Bacterioplankton exist under Plankton and contain organisms such as diatoms, eukaryotic algae, bacteria, annelids and even jellyfish.
It contains marine organisms that, in contrast to Plankton organisms, are able to resist the activities of ocean currents to some extent and move on their own. Most of them are able to swim as a distinctive characteristic.
Nekton organisms are further classified into three groups and phylum known as vertebrates (examples are sharks, lampreys and the hagfish), Crustacean (containing creatures like crabs, crayfish and barnacles) and Mollusca (also containing squids and scallops).
This is a classification that contains marine organisms living on and within ocean floors. Typical organisms falling in this category are oysters, clams, sea stars and sea anemones. Sub categories of Benthos into which these organisms are further classified based on their sizes are Macrobenthos, Meiobenthos and Microbenthos.
Marine organisms can also be classified into five major kingdoms namely Monera, Protista, Chromista, Metazoa and Fungi.
Sometimes labeled Kingdom Prokaryota, Monera contains marine organisms with no nucleus and certain single celled organisms. The Monera kingdom is, however, less accepted and distinctive as most organisms that fall within it have features that make them qualified to be considered as belonging to the four other kingdoms, most especially Protist or Protista.
5. Protista or Protist
The Kingdom Protista mostly contains marine organisms that are unicellular and cannot be classified under the other kingdoms. Certain multicellular organisms are also included in this kingdom. The Kingdom Protista is further divided into between 30 and 40 phyla.
Examples of Kingdom Protista organisms that live in oceans are water molds, amoebae and bacteria.
6. Kingdom Animalia or Metazoa
It is a large kingdom and contains multicellular organisms that are further grouped into various phyla. Marine organisms belonging to the Kingdom Metazoa have bigger sizes and are also able to move from one place to another.
Examples of marine organisms belonging to this classification are the jelly fish, crabs and sea anemones.
The Kingdom Chromista is sometimes considered a subgroup of Protista but contains distinctive sea organisms like diatoms, algae and water moulds.
Fungi may exist as hyphae, appear upon the fermentation of other organisms, including those living in oceans.