Glossary Photoorganoheterotrophy A form of metabolism that utilizes light as a source of energy and organic compounds as sources of both reducing power and carbon Photoperiod The length of the daylight period Photoperiod is sensed by green tissues, and is involved in phenological events such as leaf abscission in autumn Photoperiodism The fact of reacting physiologically to changes in the duration of the daylight period Photorespiration A biochemical process in which O2 is assimilated during the oxygenation of Rubisco (Ribulose-1,5bisphosphate carboxylase oxygenase), and CO2 is given off in the metabolism of the products of Rubisco oxygenation Photosynthesis A fundamental chemical process in which green plants (and blue-green algae) utilize the energy of sunlight and other light to convert carbon dioxide and water into carbohydrates, with chlorophyll acting as the energy converter This releases oxygen and is the major source of atmospheric oxygen Photosynthesis provides green plants with their energy requirements, and allows other organisms to obtain nutrients from these plants, either directly or indirectly (by consuming organisms that consume green plants) Photosynthetic Relating to or involved in a process of photosynthesis (see previous) Phototroph An organism utilizing the energy of sunlight or other light for growth Phototrophic Describing energy metabolism based on light energy Phototrophy The ability to obtain nutrition or energy directly from sunlight and other light Phrygana Dwarf shrubland of the eastern Mediterranean Basin, characterized by a dominance of species with seasonal leaf dimorphism Phycobiont See LICHEN Phylesis A line or lines of descent between ancestors and descendants Phyllopod A leaf-like appendage Phylogenetic Having to with or based on phylogeny (see below) Phylogenetic diversity Adjusted diversity measures that take into account the degree of relatedness among a set of species in an assemblage Other things being equal, an assemblage of closely related species is less phylogenetically diverse than a set of distantly related species Phylogenetics The study of evolutionary relatedness among various groups of organisms (e.g., species or populations) Phylogenetic tree See PHYLOGENY (next) Phylogeny The evolutionary relationships among taxa (groups of related organisms), often portrayed with some kind of tree-like branching diagram (phylogenetic tree), with the branches representing speciation events and the lengths of branches representing time since divergence Phylogeography Studies concerned with the principles and processes governing the geographic distributions of genealogical lineages, especially within and among closely related species Phylogram A cladogram (see), especially one interpreted to show terminal taxa and ancestral nodes (intermediate specificity between a generalized cladogram and specific phylogenetic tree) Phylotypes Molecularly differentiated taxa 525 Phylum The highest level of taxonomic division in the animal kingdom, followed in descending order by class, order, family, genus, and species Physiognomy The general appearance of a given area, especially a natural area For example, any desert has a certain recognizable physiognomy, regardless of species composition Physiography The landforms that lend shape and character to the continental landscape, for example, the configuration of mountains and drainage basins Phytochorion (plural phytochoria) A region within which a substantial proportion of the flora is endemic Phytophagous Feeding on plants; herbivorous Phytophagy Plant feeding; herbivory Phytoplankton Plant plankton; i.e., usually single-celled photosynthetic plankton, largely algae and cyanobacteria Phytotoxic Harmful to plants Picophytoplankton The smallest (o mm) size class of photoautotrophic plankton i.e., the picoplankton (see next) Picoplankton A classification of plankton according to size; those plankton of extremely small size (0.2–2 mm) The fraction of aquatic biomass in the size fraction that passes through 3.0 and 0.8 mm filters, and is retained on a 0.1 mm filter Pinniped A member of the Pinnipedia, marine mammals with fin-like limbs including the seals, sea lions, fur seals, and walrus Approximately one-quarter of the known modern species of marine mammals are pinnipeds Pinnipeds are in the mammalian order Carnivora Pioneer One of the first groups of species to colonize a newly formed or denuded habitat Piscivore A predator that consumes fish in aquatic habitats Placenta In most mammals, the organ providing nourishment to the developing fetus via the umbilical cord Placental Having a placenta; see EUTHERIAN Planktivore A predator that consumes zooplankton in aquatic habitats Plankton Small organisms with no or limited powers of locomotion that float freely in the water column of lakes or the ocean and are largely dispersed by turbulence and other water movements Phytoplankton (plant plankton) are plankton with photosynthetic pigments and zooplankton are the animals of the plankton Planktonic Having to with or being one of the many types of small organisms that float freely in the water column Planktotrophic Feeding on plankton to survive and grow This feeding pattern is plankotrophy Planned biodiversity Crops and livestock purposefully introduced and maintained in an agroecosystem by humans, as opposed to the associated natural biodiversity that already exists there (unplanned biodiversity) Plantation An area of land that supports planted forest or food or fiber crops, usually for commercial exploitation Plantation monoculture A plantation forest involving a single species The original biodiversity at the site is not recovered, though the protective function and many of the original ecological services may be reestablished Plant breeding The systematic process of genetic improvement of plants for food and agricultural uses