| Oceanic zone |
the region of open waters beyond the continental shelf and lying over deep areas |
| Ocellus/ocelli |
One of the 3 simple eyes of adult insects, located on or near the centre line of the dorsal surface of the head. |
| Ommatidium |
One of the basic visual units of the insect compound eye. The ommatidia are bounded externally by the facets that together make up the glassy, rounded outer surface of the eye. |
| Omnivore |
An animal that eats both plant and animal food |
| Ootheca |
plural = oothecae An insect egg case (see cockroach). It may have a thin covering as in cockroaches, or the eggs may be embedded in a fast-hardening foam, as in mantids. |
| Open circulatory system |
An arrangement of internal transport where the blood bathes the organs directly. |
| Operculum |
a calcified flap or plate which closes the opening of some gastropod shells |
| Optimal foraging |
a type of foraging behaviour that mamimizes the ratio of energy intake to expenditure |
| Opithosoma |
the posterior body (abdome) in arachnids and pogonophorans |
| Oral |
of the mouth |
| Order |
the major taxonomic division of a class |
| Organ |
A structure of the body composed of several kinds of tissue that carries out specific tasks, e.g. heart |
| Organelle |
A membrane-bound body in a cell, e.g. mitochondria. An organelle performs a specific function. |
| Osculum |
the excurrent opening in sponges |
| Osmoregulation |
the maintenace of a suitable internal salt/water concentration in a cell or body |
| Osmosis |
the process whereby water passes across a membrane from the weaker to the stronger solution |
| Ossicles |
the small, separate pieces of echinoderm skeleton |
| Ostia |
a pore through which water enters the body (as in sponges), or through which blood enters the heart |
| Ovary |
the structure producing female gametes and reproductive hormones |
| Oviduct |
In invertebrates, a tube passing from the ovary to the vagina |
| Oviger |
the egg carrying leg in the pycnogonids |
| Oviparous |
Reproducing by laying eggs |
| Ovipositor |
The egg laying tube in some female insects. In some bees and wasps it has been modified to become a sting. |
| Paleontology |
the scientific study of fossils |
| Palp |
a fleshy process from the mouthparts, see spiders and insects |
| 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. |
| 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. |
| 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. |
| 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 |
| 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 |
| Peristalsis |
waves of contraction of circular and longitudinal muscles passing along a tubular organ (e.g. the gut) having a propulsive effect. |
| Pharynx |
The first part of the gut from where the gill slits open. The muscular and sometimes eversible first part of the gut. |
| 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 |
| 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. |
| Pneumostome |
the opening to the lung in pulmonate gastropods, most easily seen in slugs |
| 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. |
| 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 |
| Polygamy |
more than one mate at a time |
| Polygny |
A mating system involving one male and amny females |
| 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 |
| Polyphyletic |
Pertaining to a taxon whose members were derived from two or more ancestral forms not common to all members. |
| Population |
A group of individuals of one species that live in a particular geographic area. |
| Population genetics |
The scientific study of gene pools and genetic variation in biological populations. |
| Preadaptation |
A structure that evolves and functions in one envronmental context, but can perform additional functions when placed in some new environment. |
| Posterior |
the rear or tail end |
| Predator |
an animal that preys on other organisms |
| Prepupa |
A restin (non-feeding) stage that some insects pass through before forming a pupa. |
| 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 |
| Proboscis |
A trunk-like process, sometimes eversible,
and usually arising from the head. |
| 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. |
| Prolegs |
the soft, unjointed legs found in some invertebrates, e.g. caterpillars |
| 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. |
| 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. |
| 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. |
| Pulmonate |
Having lungs, not gills, e.g. pulmonate snails |
| 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 |
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