Glossary: P

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

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living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

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The Pleistocene Epoch began approximately 1.8 million years ago and ended about 11,000 years ago.


organisms that prefer or require to live on ice for at least one phase of the life cycle. For example, seals that breed or raise young on coastal or sea ice.


the roof of the mouth in vertebrates. The palate can either completely or partially separate the nasal and oral cavities and consists of a hard palate (bony or cartilaginous part) and a soft palate (soft tissues).

  1. Argentinian steppe grasslands; 2. grassland created by burning and cattle occupation.

An area on the Brazil-Bolivia-Paraguay frontier that covers more than 100,000 sq km (38,000 sq mi) and is best characterized by its low degree of land relief and annual flooding; swampy savanna.

  1. A small round or conical projection on the skin, at the root of a hair or feather, or at the base of a developing tooth. 2. One of the small, rounded projections of the upper tongue surface of vertebrates that contain taste buds.

Alpine meadow of northern and western South American uplands.


Referring to a group of organisms with a single, common ancestor, but not containing all of the descendants of that common ancestor within the group.

See Also: monophyletic
parasagittal gait

Limbs move parallel to the vertebral column (in the parasagittal plane) and are held vertically, rather than sprawling to the side, as in primitive amniotes. Synapomorphy of the Mammalia+Cynodonts+"Early Therapsids". Also a synapomorphy for the birds+"Dinosauria", although it arose separately in the mammal and the bird lineages.


an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death

paratenic host

an intermediate host which may be needed for the parasite to complete the lifecycle, however, the parasite does not grow or metamorphose into another life stage.


in many invertebrates, the spongy mass of vacuolated mesenchyme cells filling spaces between viscera, muscles, or epithelia. Also, the specialized tissue of an organ as distinguished from supporting connective tissue.

parenchymula larva

the flagellated, solid-bodied larvaa of some sponges (Phylum Porifera).

parental care

all of the help that a parent gives to its offspring, including (in some cases) feeding, sheltering,and protecting them from predators.

parental investment

the commitment of energy and resources in order to enhance the survival or number of offspring


Referring to a female who has produced offspring.


development takes place in an unfertilized egg

partly divided circulation

The two atria of the heart are completely separate compartments in all reptiles, but the ventricles are not completely partitioned, except in crocodillians. Laminar flow patterns through the heart keep oxygenated and deoxygenated blood from mixing, however, so reptiles have a functionally divided circulation. Synapomorphy of the Tetrapoda+Eusthenopteron+Dipnoi.


The process of giving birth.


A social organization based on livestock raising as the primary economic activity.


An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).

pentaradial symmetry

symmetry in five planes: a body symmetry involving five or more parts arranged concentrically around a central axis made up of an oral/aboral pole. Animals with pentaradial symmetry are echinoderms (Phylum Echinodermata, sea stars, brittle stars, sea urchins, and others). Synapomorphy of the Crinoidea + Asteroidea + Ophiuroidea + Echinoidea + Holothuroidea.


the area around the mouth in many invertebrates which sometimes is modified to assist in food collecting. An example is the first segment of polychaete worms, the protostomium, which is variously modified with hardened jaws, palps, or ciliated to collect food.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.


an adjective which describes a form that is similar to a flower petal.


the body cavity in vertebrates between the mouth and the esophagus and trachea, it serves as a passageway for both food (on the way to the esophagus) and respiratory gases (on the way to the trachea). The corresponding region in invertebrates is also referred to as the pharynx. Synapomorphy of the Anthozoa.


concerning descriptions of characteristics without regard to shared ancestry or independent evolution. Animals are typically described as being most closely related to each other if they are most similar.


Referring to the physical make-up of an individual, or the expression of a particular trait, such as skin color, that may vary between individuals of similar genetic make-up.

See Also: genotype

chemicals released into air or water that are detected by and responded to by other animals of the same species


Referring to an animal that has a tendency to return to or stay in its home area, or to return yearly to the same area to breed.


generates and uses light to communicate


A method of observing hard-to-see animals by taking their pictures automatically, using remote cameras triggered when the animal interrupts an infrared light beam.


the period each day of daylight; daylength.


a sensory cell or group of cells which responds to light. Usually containing a pigment which changes chemically when exposed to light, triggering a nerve response.




Referring to the pattern of evolutionary descent.

See Also: systematics; taxonomy

photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)


flattened cells which make up the dermal epithelium of sponges (Phylum Porifera).

pinhole eye

Simple eye without a lens.


see brachia


an animal that mainly eats fish


An internal organ providing nourishment to and removing waste products from the blood of an unborn young. The unborn young's blood is conveyed to the placenta via the umbilical cord.


Ectodermal thickenings that give rise to sensory structures during development. Synapomorphy of the Craniata.

placoid scales

These scales are found on sharks and many rays and chimaeras. They consist of a plate-like base just under the skin, with a spine projecting from the back of the plate onto the surface of the skin. Like mammalian teeth, placoid scales have a hard, enamel-like outer layer that surrounds a pulp cavity supplied with blood vessels. Placoid scales do not get larger as the fish grows, but instead increase in number.


an animal that mainly eats plankton


small, free-floating, aquatic plant (phytoplankton) and animal (zooplankton) organisms that serve as food for many larger organisms (planktivores.)

plant exudates

Substances produced by trees at the sites of insect and other damage.


Relating to an animal that walks on the sole of its feet with the heel touching the ground; as opposed to digitigrade.

planula larva

Free-swimming cnidarian larvae, uses cilia for locomotion, composed of ectoderm and endoderm. Synapomorphy of the Cnidaria. These are usually flattened and oval.


the coat of feathers of a bird


filled with air pockets


a external pore found on the right side of the mantle in land snails and slugs. Air-breathing gastropods use it for respiration.


A process of soil formation, especially in humid regions and often under coniferous or mixed forest , involving principally leaching of the upper layers with accumulation of material in lower layers and development of a group of soils (the soils are called podzols) that have an organic mat and a thin organic-mineral layer above a gray leached layer resting on a dark illuvial horizon enriched with amorphous clay.


any substance which is harmful to the health of a living organism.


an animal which has a substance capable of killing, injuring, or impairing other animals through its chemical action (for example, the skin of poison dart frogs).


the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.

polarized light

light waves that are oriented in particular direction. For example, light reflected off of water has waves vibrating horizontally. Some animals, such as bees, can detect which way light is polarized and use that information. People cannot, unless they use special equipment.


act of carrying pollen to other flowers, helping plants to reproduce.


Referring to a mating system in which a female mates with several males during one breeding season (compare polygynous).


Referring to a female that has two or more estrus cycles in one breeding season.


A mating system where an individual has more than one mate per breeding season.


the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.


having more than one female as a mate at one time


"many forms." A species is polymorphic if its individuals can be divided into two or more easily recognized groups, based on structure, color, or other similar characteristics. The term only applies when the distinct groups can be found in the same area; graded or clinal variation throughout the range of a species (e.g. a north-to-south decrease in size) is not polymorphism. Polymorphic characteristics may be inherited because the differences have a genetic basis, or they may be the result of environmental influences. We do not consider sexual differences (i.e. sexual dimorphism), seasonal changes (e.g. change in fur color), or age-related changes to be polymorphic. Polymorphism in a local population can be an adaptation to prevent density-dependent predation, where predators preferentially prey on the most common morph.

See Also: sexual dimorphism
polymorphic gene

A gene at which the most common allele has a frequency of occurrence of less than 0.95.


the sedentary stage of the life cycle of cnidarians (Phylum Cnidaria, jellyfish, anemones, and corals). Made up of a cylindrical body cemented at one end to a substrate, with a mouth surrounded by a ring of tentacles at the other end. Synapomorphy of the Non-Trachyline Hydrozoa+Scyphozoa+Cubozoa+Anthozoa.


Referring to an animal that feeds on many kinds of food.


Referring to a group of organisms that do not share a common ancestor.

See Also: monophyletic

having more than one syllable, or notes, separated by brief pauses during a single utterance


A group of animals of the same species that occupies a particular area; usually refers to a group that is somewhat separate from other groups of the same species.


Referring to fish that live entirely within fresh water.


offspring is able to locomote and feed or care for itself soon after birth/hatching, often to a limited extent. In birds, covered with down and able to move about soon after hatching.

See Also: altricial

an animal that kills and eats other organisms for food.


Capable of, or adapted for, grasping.


An animal that is eaten by other animals.

prey swamping

an anti-predator strategy in which organisms produce large numbers of offspring synchronously so that the resident predator population cannot significantly impact the prey population.


A long, flexible nose or trunk.


Referring to a mating system where a member of one sex mates with more than one member of the other sex, and each relationship is ephemeral and terminates after mating without a social bond being formed.


condition of hermaphroditic animals (and plants) in which the male organs and their products appear before the female organs and their products


condition of hermaphroditic animals (and plants) in which the female organs and their products appear before the male organs and their products


Singular: protonephridium. A primitive osmoregulatory or excretory organ made up of a tubule ending at a flame bulb, or solenocyte.


the developmental pattern of animal blastula whereby the blastopore ultimately develops into the mouth, cleavage is typically spiral, and the coelom forms from by splitting.. This pattern is typical of many invertebrate groups (the "Protostomia"), including acoelomate, pseudocoelomate, and coelomate animals. These groups include flatworms, rotifers, nematodes, arthropods, molluscs, annelids, and many others.


Referring to an organ or appendage that can be quickly extended or thrust out, such as the mouth of many fishes.


providing nourishment


describing a postion close to the body, compare to "distal".