| Pair bonding | The formation of a close and lasting association between male and female animals; used particularly in the cooperative rearing of young. |
| Paleontology | the scientific study of fossils |
| Palp | a fleshy process from the mouthparts, see spiders and insects |
| Palpigradi | microwhip scorpions |
| Pangea | The single, huge landmass during the Permian - Triassic. |
| Papilla | plural = papillae A small, fleshy protuberance on an animal's body (see tardigrada). Papillae often have sensory functions such as detecting food. |
| Parallel evolution | the independent acquisition in 2 or more related descendant species of similar derived character states evolved from a common ancestral condition |
| Parapodium | plural = parapodia A leg-like flap in some worms, used for locomotion or creating a water current. |
| Parasite | An animal that lives on or inside another animal, and feeds on its host, or on food its host has swallowed. Parasites may weaken their host, but usually do not kill them. |
| Parasitic castration | the reproductive death of a host organism resulting from a parasitic infection, e. g. Mermis nigrescens |
| Parasitic male | A dwarf male that lives a parasitic existence attached to the body of its female, usually having well developed reproductive organs, but an otherwise degenerate body form, e. g. Bonella vridis |
| Parasitism | Symbiosis in which members of one species exist at the expense of members of another species, usually without causing their deaths. |
| Parasitoid | A parasite that slowly kills the victim. The death of the victim occurs near the end of the parasite's larval development. |
| Parasitology | the study of parasites and parasitism |
| Parasocial | Bees and wasps. A colony in which all the nest sharing females are of the same generation. |
| Parthenogenesis | reproduction by means of eggs that develop without fertilisation |
| Pathogenic | capable of producing disease |
| Pauropoda | a Class in the phylum Uniramia |
| Peanut worm | an animal in the Phylum Sipuncula |
| Pearly nautilus | Nautiloidea |
| Pea weevil | a beetle in the Bruchidae family |
| Pectinate | comb-like, having comb-like teeth |
| Pectines | a sensory comb-like structure as seen in some scorpions |
| Pedicel | of insects, the slender part of the abdomen best seen in Hymenoptera |
| Pedicellaria | Minute pincer-like organs on the surface of certain echinoderms. |
| Pedipalps | In arachnids the second pair of appendages at the front of the body. They can be used for walking, sperm transfer, or capturing prey, depending on species. |
| Pelagic | living in the upper waters of the open sea |
| Pentastomida | Tongue worms |
| Pentatomidae | Shield bugs |
| Penultimate | last but one |
| Periodicity | the periodic or rhythmic occurrences of an event |
| Peristalsis | waves of contraction of circular and longitudinal muscles passing along a tubular organ (e.g. the gut) having a propulsive effect. |
| Permeability | Having pores or spaces allowing fluid to pass through. The measure of the freedom of entry of new members into a community or society. |
| Pertubation | a disturbance: a departure of a biological system from a steady state |
| Pesticide | a chemical agent that kills insects and other animal pests |
| Petiolate | having a stalk |
| Petiole | A stalk. In Hymenoptera the narrow abdominal segment(s) that form the waist. |
| Petrification | a process of fossilization where the tissues are preserved by impregnation with carbonate or silicate minerals |
| Phagocytosis | the ingestion of solid particulate matter by a cell |
| Pharynx | The first part of the gut from where the gill slits open. The muscular and sometimes eversible first part of the gut. |
| Phasmida | the order of stick and leaf insects |
| Phenology | The study of temporal aspects of recurrent natural phenomena, and their relation to weather and climate, e. g. the first sighting each year of a Bombus terrestris queen in a particular location. |
| Phenotype | the expressed traits of an organism |
| Pheromone | A chemical substance, usually a glandular secretion, which is used in communication within species. One individual releases the material as a signal and another responds after tasting or smelling it. |
| Phoresy | one animal exploiting another by using it as a means of transport, e.g. the mites that hitch a ride on bumblebees |
| Photic zone | The top slice of a body of water where light penetrates sufficiently for photosynthesis to occur |
| Photoreceptor | a cell sensitive to light |
| Photosynthesis | the process whereby plants build up complex organic substances from simple ones using the sun's energy. |
| Phototaxis | A movement away (negative) or towards (positive) light where light is the stimulus. |
| Phylum | one of the major taxonomic divisions of the animal kingdom |
| Phytophage | a plant eater |
| Pieridae | The family of butterflies containing the Whites and Brimstones |
| Pill bug | Actually not a bug at all, but the woodlouse Armadillidium vulgare |
| Placozoa | A phylum of multi-cellular animals |
| Plankton | the small plants and animals living free in the surface waters of lakes and oceans. |
| Plant secondary compounds | They are compounds produced by the plants that have no nutritional value to the particular plant, but often affect the health or welfare of another organism, e.g. a herbivore. |
| Platyhelminthes | Flatworms, flukes and tapeworms |
| Plecoptera | Stoneflies |
| Plumose | feathery - as seen in some insect antennae |
| Pneumostome | the opening to the lung in pulmonate gastropods, most easily seen in slugs |
| Pogonophora | Beard worms |
| Poikilothermic | Animals whose body temperature varies and fluctuates with that of the surrounding environment; cold-blooded. |
| Pollen | The male element of flowering plants. Usually a fine dust produced by the anthers. Pollen is eaten by many insects including bumblebees. |
| Pollen basket | Stiff hairs on the hindmost leg of a female bee arranged so that they form a basket which can be packed with pollen. |
| Pollination | The placement of pollen onto the stigma of a carpel by wind or animal vectors, a prerequisite to fertilisation. |
| Polyandry | mating system of one female with more than one male |
| Polychaeta | bristleworms |
| Polygamy | more than one mate at a time |
| Polygny | A mating system involving one male and many females |
| Polylectic | taking pollen and/or nectar from a wide range of flower species |
| Polymorphic | A population in which 2 or more morphs are present in readily noticeable frequencies |
| Polyp | a simple animal with upwardly-directed mouth, fringe of tentacles, and a simple gut |
| Polyphagous | feeding on a wide variety of different foods |
| Polyphyletic | Pertaining to a taxon whose members were derived from two or more ancestral forms not common to all members. |
| Polyplacophora | chitons - a class of mollusc |
| Polyploid | having more than 2 sets of homologous chromosomes |
| Polyzoa | a.k.a. Bryozoa |
| Pond skater | Gerridae, a water bug in the Hemiptera |
| Population | A group of individuals of one species that live in a particular geographic area. |
| Population biology | The study of the spatial and temporal distribution of organisms |
| Population dynamics | the study of changes within a population, and the factors causing the changes |
| Population genetics | The scientific study of gene pools and genetic variation in biological populations. |
| Porifera | sponges |
| Preadaptation | A structure that evolves and functions in one environmental context, but can perform additional functions when placed in some new environment. |
| Posterior | the rear or tail end |
| Potter wasp | a wasp in the Eumenidae family |
| Praying mantis | an insect in the Dictyoptera order, a mantid |
| Predation | the consumption of one animal (the prey) by another (the predator) |
| Predator | an animal that preys on other organisms |
| Prepupa | A resting (non-feeding) stage that some insects pass through before forming a pupa. |
| Priapidula | A Phylum of marine worm-like animals |
| Prey | Any animal that is eaten by a predator |
| Primary consumers | Herbivores. Organisms in the trophic level that eat plants and algae. |
| Primary producers | Autotrophs. Photosynthetic and chemosynthetic organisms. |
| Primary succession | A type of ecological succession that occurs in an area where there were originally no organisms, e.g. on newly created volcanic islands. |
| Primitive | ancient; little evolved; of characteristics similar to those possessed by the ancestral types |
| Primordial | primitive, primary, original |
| Proboscis | A trunk-like process, sometimes eversible, and usually arising from the head |
| Progeny | the offspring of a single mating, or of an asexually reproducing individual |
| Proglottid | a compartment of a tapeworm's body |
| Profitability of a prey item | A predator will rank items according to their size and quality, against search/handling time. The predator usually consumes those items that have the highest ratio of size, quality : search, handling time; though it will consume some less profitable items as it samples. |
| Prokaryote | Lacking a discrete nucleus in the cell, e.g. bacteria. |
| Prokaryotic | used of an organism lacking a discrete nucleus separated from the cytoplasm by a membrane, e. g. bacteria |
| Prolegs | the soft, unjointed legs found in some invertebrates, e.g. caterpillars |
| Promiscuous | a mating system where neither sex is restricted to a single mate |
| Pronotum | The upper surface of the front segment of an insect's thorax. It may be enlarged to form a shield over the head as in some beetles. |
| Prosobranchia | a subclass of the Gastropods (snails) that have a horny or calcareous plate called an operculum which is used to close the shell opening |
| Prosoma | The front part of the body in some animals, e.g. spiders, where the head and thorax are fused. |
| Prothorax | The front or first of the three segments of an insect's thorax. |
| Protist | A single-celled organism living in water or moist habitats. The cell is usually relatively large and more complex than bacterial cells. Some use photosynthesis to get their energy; others eat. A typical, much-studied protist is Paramecium. |
| Proventriculus | In insects, a muscular dilation of the foregut armed internally with chitinous teeth |
| Proximal | situated towards, or near the point of attachment |
| Pseudocoelomates | Animals whose body cavity is not completely lined by mesoderm, e.g. Nematoda, Rotifera. |
| Pterostigma | A coloured area near the leading edge of some insect wings, e.g. dragonflies. |
| Pubescent | with short, fine hairs |
| Pulmonate | Having lungs, not gills, e.g. pulmonate snails |
| Punctate | having punctures |
| Punctuated equilibrium | A theory of evolution advocating spurts of relatively rapid change followed by long periods of stasis. |
| Pupa | The inactive instar or stage of the holometabolous insect during which development into adult form is completed. |
| Puparium | the case which houses the pupa |
| Pupate | the process of becoming a pupa |
| Pupation | the formation of a pupa by metamorphosis |