biology-dictionary_11-06-2009

Peripheral nervous system The sensory and motor neurons that connect to the central nervous system. Peristalsis Rhythmic waves o ...

Phenotype The physical and physiological traits of an organism. Pheromone A small, volatile chemical signal that functions in co ...

Photoperiodism A physiological response to day length, such as flowering in plants. Photophosphorylation The process of generati ...

Phytoalexin An antibiotic, produced by plants, that destroys microorganisms or inhibits their growth. Phytochrome A pigment invo ...

Placental mammal A member of a group of mammals, including humans, whose young complete their embryonic development in the uteru ...

Plantae Plants are major group of life forms and include amiliar organisms auch as trees, herbs, bushes, grasses, vines, ferns, ...

Pneumatic Having cavities filled with air, as the bones of certain birds. Pneumatophores A specialized respiratory root structur ...

Polyandry A polygamous mating system involving one female and many males. Polyandrous Relating to an angiosperm plant that has a ...

Polyphyletic Pertaining to a taxon whose members were derived from two or more ancestral forms not common to all members. Polypl ...

Positional information Signals, to which genes regulating development respond, indicating a cell's location relative to other ce ...

Primary cell walls A cell wall is a fairly rigid layer surrounding a cell, located external to the cell membrane, which provides ...

Primer An already existing short RNA chain bound to template DNA to which DNA nucleotides are added during DNA synthesis. Primat ...

Producer, in ecological systems An autotrophic organism, usually a photosynthesizer, that contributes to the net primary product ...

Prop roots A root that grows from and supports the stem above the ground in plants such as mangroves. Prosimian A lower primate; ...

Protista A kingdom into which all organisms of simple biological organization can be classified. It includes the algae, bacteria ...

Protostome A member of one of two distinct evolutionary lines of coelomates, consisting of the annelids, mollusks, and arthropod ...

Pulmonary artery In birds and mammals, an artery that carries deoxygenated blood from the right ventricle of the heart to the lu ...

Pyramid of energy A diagram of the energy flow between the trophic levels of an ecosystem; plants or other autotrophs (at the ba ...

Racemose Having stalked flowers along an elongated stem that continue to open in succession from below as the stem continues to ...

Raphids One of a bundle of needlelike crystals of calcium oxalate occurring in many plant cells. Reactant A starting material in ...