Glossary of Ecology - P

P

• paleoecology - a science which seeks to understand the relationships between species in fossil assemblages
• parasite - an organism which survives with another through a symbiotic relationship with another organism—its host—which it does not usually kill directly but does negatively affect.
• parasitoid - An organism that is a parasite for most of its life and will usually kill its host
• permafrost - permanently frozen layer of terrain found beneath the arctic tundra
• per capita - a measurement indicating "per unit of population"
• pheromone - a chemical which is typically given off into the environment as a signal which causes a natural behavioral response in members of the same species
• phosphorus cycle - the biogeochemical cycle that describes the movement of phosphorus through the environment
• pioneer species - species that first inhabit an environment which was previously unoccupied
• pollination - a type of fertilization and reproduction where the transpoatation of pollen grains from plants to ovure- bearing organs. This takes place by either wind, water, or animal assistance
• pollinator decline -
• population density - the number of individuals of a species living per unit of an area.

• political ecology - a theoretical lens focusing on how political and economic power effects ecology, as well as how ecology can also shape the political economy, by understanding and analyzing environmental influences on social activity.
• population ecology (or autecology) - deals with the dynamics of populations within species, and the interactions of these populations with environmental factors
• population pyramid - a graphic illustration which shows the age structure in a population (typically that of a country or region of the world), which normally forms the shape of a pyramid.
• population size - the number of individuals of a species in a particular geographic range.
• predation - the interaction among populations when one organism consumes another one.
• predator - an organism that lives by killing and consuming another living organism.
• prey - living organisms that predators feed on
• primary producer - an autotroph that obtains energy directly from the nonliving environment through photosynthesis or less commonly through chemosynthesis
• primary production - production of organic compounds from carbon through photosynthesis. This effects all life on Earth either directly or indirectly
• protocooperation - two species interact with each other beneficially
• population distribution - means the pattern of where people and animals live. Throughout the world distribution is uneven for example places which contain small amounts of people are considered sparsely populated whereas places which are densely populated contain many people.