Marine Biology Glossary
Science / Marine Biology Glossary
Plankton: Pelagic organisms that float through the water column, not attached to any substrate and unable to move against the currents and tides. Plankton can be further divided into phytoplankton and . . . View Full Definition
Planktotrophic Larva: Planktonic-dispersing larva that derives its nourishment by feeding in the plankton
Planula: The planktonic larval form produced by scleractinian corals and coelenterates
Plate: Major section of the earth's crust, bounded by such features as mid-ocean ridges
Pleistocene: Period of time, going back to approximately 2 million years before the present, in which alternating periods of glaciation and deglaciation have dominated the earth's climate
Pleuston: Refers to plankton that have a float protruding above the sea surface, such as the Portugese man-of-war.
Poikilotherm: An organism whose body temperature is identical to that of the external environment
Polyp: An individual of a solitary coelenterate or one member of a coelenterate colony
Polyphyletic: Refers to a group of species that do not have one common ancestor species
Population: The number of individuals of a particular species that live within a defined area.
Population Density: Number of individuals per unit area or volume
Porifera: The phylum comprising the sponges.
PPT: A measure of the salt content of sea water in terms of kg salt per kg of water, reckoned in parts per thousand. A conductivity version of this measure is the PSU, which differs from PPT by v . . . View Full Definition
Practical Salinity: See PSU
Practical Salinity Units (PSU): A measure of the salt content of seawater (practical salinity), based upon electrical conductivity of a sample relative to a reference standard of sea water, which now happens to be a refere . . . View Full Definition
Precision: Precision is the repeatability of a measurement. A measurement can be precise, but not accurate. See Accuracy and Resolution.
Predation: The consumption of one organism by another
Predator: An organism that consumes another living organism (carnivores and herbivores are both predators by this definition)
Prey: An animal that is used by other animals for food.
Primary Consumer: A heterotrophic, herbivorous organism that feeds directly on a primary producer. Urchins are a primary consumer as they feed on kelp. See also heterotroph, food chain; compare secondary consumer.
Primary Production: The production of living matter by photosynthesizing organisms or by chemosynthesizing organisms. Usually expressed as grams of carbon per square meter per year
Protein Polymorphism: Presence of several variants of a protein of a given type (e.g., a certain enzyme, such as carboxylase) in a population
Province: A geographically defined area with a characteristic set of species or characteristic percentage representation by given species
Pseudofeces: Material rejected by suspension feeders or deposit feeders as potential food before entering the gut
Pteropods: Group of holoplanktonic gastropods
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