Anal appendages: Male odonates possess one (in dragonflies, in which animals also possess an epiproct) or two (in damselflies) pairs of appendages at the base of the abdomen, which are used as claspers for holding the female during copulation. The shape of the upper and/or lower appendages may be an important diagnostic feature in some species.
Anal triangle: In many dragonflies, triangular section of the hindwing base, consisting of two or more cells. The number of cells is a guide to identification in some species.
Casque: A structure protruding from the top of the head, frequently bearing a loose resemblance to a helmet (as in chameleons and some birds). Casques take a variety of forms and are found on many vertebrates; including cassowaries, many lizards and a number of frogs. Casques are also characteristic of many hadrosaurs, a lineage of plant-eating bipedal dinosaurs, where they exhibit perhaps their most varied and extreme shapes.
Canthus rostralis: In reptiles and amphibians, the line connecting the tip of the snout with the top of the eye orbit, generally present as a ridge. The shape of the canthus rostralis is often a useful guide to identifications. In chameleons, the canthus is often strongly angled and distinct from the rest of the head, where it is known as a rostral crest.
Caudal lamellae: Three leaf-like structures protruding from the abdomen of damselfly larvae; these provide the primary means of respiration and may also be involved in defence. The shape, relative lengths and patterning of caudal lamellae are important features in species identification. The singular form is lamella.
Choanae: One of the defining features of terrestrial vertebrates, choanae are the openings in the roof of the skull that form one end of the nasal passages, the other being the nostrils.
Cloaca: In non-mammalian vertebrates, a single opening at the underside of the body near the tail base (in reptiles, fish, tailed amphibians and birds) or the urostyle (in frogs). The cloaca is involved in both reproduction and waste excretion. The cloaca is often referred to simply as the vent.
Costa: The leading edge of the insect wing.
Crest (in chameleons): The head shape of chameleons is often a valuable guide to identification, and the presence and form of several types of crest is used to distinguish many species; most also have crests of spines or enlarged scales along the back, and sometimes the belly. This can make chameleon taxonomy seem complex and daunting at first. Terminology important in identification includes:
Dorsal crest: The crest down the centre of the back, which may continue along the tail. Often composed of spine-like triangular scales.
Gular crest: A row of small spines running down the centre of the throat.
Lateral crest: A ridge extending from behind the eye to the base of the casque on each side of the head; where both a lateral and rostral crest is present, they form a single continuous crest. Occasionally
this entire ridge may be referred to as the lateral crest.
Parietal crest: The central ridge down the front of the casque. Not always present.
Rostral crest: A ridge of enlarged scales along the canthus rostralis. When a lateral crest is present,
this is a continuation of the rostral crest. Rostral crests are normally present; whether or not they meet at
the snout tip is important in identification of some species.
Ventral crest: A row of small spined or conical scales running down the centre of the belly. When present, the ventral crest may or may not be continuous with the gular crest.
Cuticle: Any external protective layer in an organism, including among other examples wax layers of plant leaves, layers of dead skin above living tissue, or perhaps most commonly the external skeletons of arthropods.
Dermal: Relating to the skin.
Dermal fringe: A fringe or flap of skin running along part of the body. Examples include fringes running along the limbs of some frogs, or the extensible fringes or flaps of skin between the limbs in some gliding reptiles
Dorsolateral: Relating to both the upper (dorsal) surface of an animal and sides. The term is often used to describe anatomical features that occur at the border of the dorsum and flanks, though can also refer to features, such as patterns, that extend across both the upper body and sides.
Dorsolateral folds: A diagnostic feature in many frogs, particularly members of the family Ranidae (typical or "true" frogs). These frogs typically have paired dorsolateral folds, one at either side of the back, which are visible as raised ridges of skin that run down part or all of the length of the back.
Pelophylax lateralis, a frog with prominent, orange-brown dorsolateral folds
Epiproct: Spine-like plate projecting from the final abdominal segment in dragonflies. The shape is an aid to larval identification. In males, a projection beaneath the base of the epiproct mayu also be useful in distinguishing species.
Fin (in fish): The fins of fish are defined by their position on the body; the shape, size and structure of different fins is often useful as an aid to identification. Most fins are present in all fish, but some groups have lost particular fins as they have evolved.
Anal fin: A fin on the underside of the body, behind the vent.
Caudal fin: The tail fin; the shape of this fin is an important feature in distinguishing many groups of fish.
Dorsal fin: Usually a single fin, although up to three may be present, found in both bony and cartilaginous fish, that rises from the animal's back. The most famous dorsal fins are of course the triangular fins of sharks. A dorsal fin is present in most fish; however, it is lost or reduced in rays.
Pectoral fins: A pair of fins extending from the side of the body, one on each side, just behind the head. The 'wings' of rays are enlarged pectoral fins.
Frons: The upper section of a dragonfly's face, immediately in front of the eyes, which often sports dark patterning. When used to distinguish between species, the frons generally refers to the shape and size of this pattern.
Gular: Relating to the throat.
Hemipenes: Male lizards and snakes possess dual penises, which they use alternately when mating. When not engaged in mating activity, the hemipenes are contained within the body, creating a distinct hemipenal bulge at the base of the tail which can be used to sex animals.
Interpleural stripe: A black, line close to the centre of the thorax when viewed in profile, a common feature of many damselflies The interpleural lies between two prominent sutures, the humeral (upper, below any antehumeral stripe) and metapleural (lower). The stripe extends from close to the wing base.
Labial: Relating to the lips, such as a marking along the lip.
Labium (also labial mask or mask): Toothed feeding apparatus in dragonfly and damselfly larvae, held against the front of the head as a 'mask' when not in use, covering the mouthparts. The halves of the mask are the labial palps, each edged with a row of teeth. The labium can be projected forwards to capture prey on the teeth or prehensile hairs.
Lamellae: Enlarged scales on the underside of the toe in some lizards, principally geckos. Gaps between the lamellae act as hooks that perform the function of climbing aids.
Lateral: Relating to the sides; the flanks.
Maxillary teeth: In vertebrates, the teeth of the upper jaw. Whether or not maxillary teeth are present can be an important factor in classifying frogs.
Metatarsal tubercle: An important diagnostic feature in many frogs, consisting of a typically hardened protrusion from base or heel of the hindfoot. The presence or absence of a metatarsal tubercle, its shape and size, and occasionally the number of turbercles (most frogs have at most one) can all be useful in identifying species. Burrowing species such as spadefoot toads often have enlarged metatarsal tubercles adapted for digging, which may be referred to as the spade.
Nuchal: Relating to the neck (for instance, the nuchal crest in some lizards extends along the neck).
Nuptial pads: Thickened, often hardened, pads on the fingers of many adult male frogs, with which they clasp females while breeding. Nuptial pads may be present year-round, in which case they are frequently smaller and less conspicuous outside the breeding season, or may develop only during the breeding season. Males of some species, especially those that don't engage in amplexus, lack nuptial pads altogether.
Ocelli: Spots or circular markings in an animal's patterning.
Parotid (or parotoid) gland: A diagnostic feature of the frog family Bufonidae (true toads), consisting of a round or roughly oval gland at the back of the head, behind the eye; parotid glands are always paired, one either side of the head. The size and shape of this gland may be a guide to species identity. The function of the gland is to secrete a latex-like toxin to deter predators, and which can be lethal if ingested.
Plastron: The lower half of the carapace in turtles, consisting of a number of bony plates.
Prothorax: The frontal segment of an insect's thorax. The upper surface is generally protected by an armoured section, the pronotum, which is important diagnostically feature in some groups. In beetles, the pronotum is expanded to protect the entire thorax.
Pruinosity/Pruinescence: A light, powdery or waxy coating over the surface of part of an organism. Most commonly, pruinosity is associated with plants, but is also found in some animals. The abdomens and, on occasion, other features of many dragonflies are pruinose, for example; in this case the powdery covering is typically a light blue or grey in colour.
Pterostigma: Typically dark cell on the leading edge of each wing in some insects, most conspicuously in dragonflies and damselflies. In some groups, this may be absent, or it may be less distinct and divided by crossveins (a pseudopterostigma). The pterostigma acts to stabilise the tip of the wing in flight.
Rostral: Relating to the snout (rostrum). Often used to describe features towards the front of the head in relation to the snout. Many lizards and a small number of frogs and snakes possess rostral appendages, often shaped as a spike and so sometimes called rostral spikes or horns. in this context, 'rostral' refers to features projecting from or ahead of the snout itself.
Scale (in reptiles): Body covering composed
of keratin arranged as numerous adjoining plates. The shape, arrangement and
number of scales is an important taxonomic feature in distinguishing reptile
species and higher-level groupings. Scales are named according to their
location on the body; scales which are important in identification include:
Labial scales: The scales immediately above (supralabials) and below (infralabials) the mouth, i.e. bordering the lips. Labial scales are often larger or more elongated than surrounding scales, and form a recognisably discrete row above and another below the mouth.
Loreal scale: A scale that separates the scale behind the nostril from the preocular, the scale immediately in front of the eye. Absent in some groups of snakes, and the presence or absence of a loreal scale is thus a useful taxonomic feature.
Mid-body scale rows: Counted at the widest point of a snake's or lizard's body, the number of mid-body scales or scale rows is the number of scales on the flanks and upper body combined (i.e. all but the ventral scales) in cross-section.
Parietal scales: Large, paired scales at the base of the head, behind the scales surrounding the eye. The two parietals surround a smaller scale called the interparietal. In some lizards, notably skinks, an important taxonomic feature is whether the parietal scales are whole or fragmented (broken into several smaller scales), and whether the two parietals are in contact with one another behind the interparietal or are wholly separated from each other by it.
Preocular: The scales
bordering the front of the eye, above the upper labials. Postocular
scales border the rear of the eye orbit.
Subcaudals: Literally "beneath the tail". Subcaudals are the small ventral scales of the tail, which typically occur either as a row of single scales or in paired rows (in which case the scales are said to be divided). Whether or not the subcaudals are divided is a diagnostic feature in some snakes.
Supraciliary scales: Row of small scales between the scales bordering the top of the eye (supraocular) and the scales at the top of the head.
Ventral scales: Those on the animal's belly. In snakes, these typically form a longitudinal row of large, single scales and the number of ventrals is often an important diagnostic character.
Tubercle: Descriptive term for an enlarged, rounded or spined scale, which may be found on any part of the body, often giving a pebbly or prickly texture to the skin.
Scutes: Individual plates of the carapace in turtles.
Setae: Superficially hair-like structures along body segments in arthropods; when especially dense, these can give the animal a furry appearance. The distribution of setae on different parts of the body is often important in classification.
Spiracle: A body opening in certain animal groups which is involved in respiration, by allowing air or water to pass into or out of the body. In larval amphibians, these are exits for water taken up during respiration. Tadpoles possess one or two spiracles, and the number and position of these on the body is diagnostic. Conversely, in elasmobranchs and some primitive bony fish, a spiracle behind each eye serves the reverse function, allowing water to enter the body and oxygenate the gills while the animal itself is motionless.
Stridulation: Sound produced by rubbing two body parts, such as wing cases, spines or hairs, together. The most familiar example is sound production by grasshoppers
Supraocular cone: In several species of Malagasy leaf chameleons (genus Brookesia), these are the forward-facing, broadly triangular structures jutting out from above the eye socket. Supraocular cones are absent in a number of leaf chameleons, and so provide a useful aid to identification.
Supratympanic fold: A glandular structure in frogs that curves around and above the tympanum; where the supratympanic fold is thick and fleshy, the tympanum itself may be partially or completely concealed.
Thorax: In insects and crustaceans, the central section of the body. The thorax is the point of attachment of the animal's limbs and (if present) wings, and the site of vital organs such as the heart.
Toe discs: Enlarged disc-shaped swellings at the base of the toes and fingers in many groups of frogs. The presence and size of toe discs is a good guide to a species' behaviour, as enlarged toe discs are generally an adaptation for a climbing lifestyle.
Tympanum: The ear opening in reptiles and amphibians (in amphibians, normally covered by a circular membrane). Snakes and some lizards lack a tympanum.
Underwings: The underside of a butterfly's wings, as seen when the animal is at rest with wings closed. Not to be confused with the hindwings, the second (rear) pair.
Upperwings: The top side of a butterfly's wings as seen when the animal is at rest with wings open; typically (but not always) the most colourfully-patterned face of the wings. Not to be confused with the forewings, the front pair of wings.
Ventral: The underside of a bilaterally symmetrical animal; the belly.
Vocal sac: The calling apparatus in most male frogs, consisting of a pouch beneath the chin or, less commonly, two pouches either to the sides of or beneath the chin, which can be inflated with air from the lungs.
Vomerine teeth: In frogs, a small row of teeth located in the roof of the mouth. Whether vomerine teeth are present and where they are located is a character used in species classification.
Wing sheaths: In exopterogyte insects, the wings develop as externally visible buds or sheaths in larval instars; these grow in relative size as the animal develops, before becoming fully-functional wings in adults.
Aestivation: A state of environmentally-induced dormancy in many animals, in which animals enter dormancy in response to high temperatures, low humidity and, frequently, lack of prey. Animals may aestivate for prolonged periods, a state similar to hibernation, or only briefly to survive warm spells.
Crepuscular: Active around dawn and/or dusk.
Tandem: The mating position adopted by most dragonflies, in which the male clasps the female around the head and thorax with his anal appendages, so that the two are joined in flight with the male leading the female. Once in tandem, copulation takes place in the wheel position, in which the female's tail curls round to make contact with the male genitalia at the base of the abdomen.
Biome: On a global scale, a biome refers to all biological systems of a specific type; a biome may represent a division as coarse as 'rainforest' or 'tundra', but in conservation is generally used to describe systems with particular climates, vegetation, fauna and characteristics found nowhere else, usually defined at continental scales or below, such as Bornean peat-swamp forest or the Argentinean pampas. Tthe terms 'biome' and 'ecosystem' are sometimes used interchangeably, although in biogeography the term 'ecosystem' is more often confined to smaller-scale biological systems; an ecosystem in this context can be thought of as being representative of a particular biome.
Disjunct: Describing the distribution of a species which is not continuous throughout its range, but where two or more centres of distribution exist which are separated by areas where the species is absent. Some species naturally occur in this pattern, often due to historical changes in climate or geography in intervening areas, but more usually disjunct distributions are a consequence of recent human-induced extinctions in part of a species' range, are due to poor knowledge of species occurrence, or arise from inadequate taxonomy when two or more species are erroneously included within a single named form.
Endemic: Used to describe a species that only occurs in a particular region; most often used at the scale of countries, islands or smaller geographical features to describe species confined to relatively small areas, but the term may also be used to describe species that are restricted to particular habitats; a species might, for instance, be endemic to rainforest, but may occur in rainforests covering a comparatively large area. Endemic species are often of particular conservation concern as, while they may often be common where they occur, their dependence on small areas or particular types of habitat makes them vulnerable to the effects of human activities.
Eurasia: The world's largest continental plate, consisting of the traditional 'continents' Asia and Europe.
Gondwana: The southern portion of the former supercontinent Pangaea, following its break-up in the early Mesozoic (200-180 Mya). For much of this period, Gondwana was a single landmass connecting the Southern Hemisphere continents, with Antarctica forming the bridge between South America, Africa, Australia and a landmass consisting of what are now India and Madagascar. Both as the larger of the two continents that followed the breakup of Pangaea and for its influence (through the collision of India with Asia) on Northern Hemisphere faunas and floras, Gondwana is of particular importance for understanding modern biogeographical patterns, as many major groups of plants and animals evolved during the Gondwanan period. Gondwana itself broke up throughout the Cretaceous, with India-Madagascar, Africa, South America and finally Australia separating from Antarctica. Note that in a biogeographical context, Gondwana only refers to the southern continent that existed following the breakup of the supercontinent. This is in contrast to the usage of the term in geology, in which Gondwana or Gondwanaland also refers to a continent that preceded the creation of Pangaea, long before multicellular life colonised the land.
Neotropics: The tropical areas of the New World, encompassing Mexico, Central and tropical South America.
Pangaea: The 'supercontinent' that existed during the Paleozoic era, from 545 Mya to the beginning of the Triassic period 200 Mya. During this time, Pangaea was the Earth's only major landmass, containing all the continents that exist today. This was the landmass on which the first terrestrial life forms - invertebrates, plants and terrestrial vertebrates - evolved and diversified, making Pangaea an important source of biogeographical information.
Radiation: An evolutionary term for a rapid (in evolutionary time, meaning typically thousands to millions of years) speciation event within a single lineage. A group of organisms may undergo a radiation if it develops a particularly advantageous trait (as with the radiation of flowering plants), or if it is newly introduced to a region without competitors
Sympatry: A description of a species' distribution relative to others; if one species is sympatric with another, the two occur together.
Amplexus: Reproductive 'embrace' used by many frogs, in which one or occasionally more males physically grasp females with their forelimbs while mating. Amplexus can sometimes last for hours or even days.
Amphibian reproductive strategies: Pond- and stream-breeding amphibians can broadly be divided into explosive breeders, species with a short breeding season (often no more than several days) which congregate in large numbers around the breeding site and (in frogs) typically call in loud choruses, and protracted breeders in which animals breed in smaller numbers throughout the season, and may have a more extensive aquatic phase. Most familiar frogs of disturbed areas are explosive breeders; salamanders are typically protracted breeders.
Caudal autotomy: The ability, common in several families of salamanders and lizards, to shed part or all of their tails as a defensive mechanism, by severing it at a weak point when grabbed by a predator. Nervous impulses in the severed tail cause it to twitch for a short time, sometimes several minutes, and this will often distract predators for long enough for the animal to escape. The tail will subsequently regrow, but these regenerated tails are shorter and more brittle than the original tail. In species with unusually-shaped tails, such leaf-tailed geckos from Madagascar and Australia, the regrown tail usually loses these features and instead resembles a more typical lizard tail.
Dimorphism: Literally, "two forms". Used to describe a species in which a portion of the population exhibits consistent differences from the rest, created two distinct types within the one species that differ in size, colouration or other attributes. Most commonly used in the context of sexual dimorphism, in which males may be bigger than females (or vice versa) or exhibit other differences, but other forms of dimorphism can occur. In a number of bird species, for example, both black and white forms may exist that readily interbreed and belong to the same population, but in which neither sex is consistently one colour or the other. In some cases of sexual dimorphism, members of one sex may sometimes exhibit colouration or other features typical of the other sex. Such individuals are termed andromorph (where a female imitates a male) or gynaeomorph (where a male resembles a female).
Direct development: In frogs, direct development is the term used to describe a life cycle without a tadpole stage. Eggs are laid, commonly in most habitats on land, and the young grow directly into froglets within the egg, before emerging fully-formed. Direct development has evolved in numerous lineages of frogs and occurs in much of the world; particularly diverse radiations are associated with the "eleutherodactyline" frogs of South and Central America (Family Brachycephalidae and allies), the Asian tree frog genus Philautus (family Rhacophoridae), a lineage of true frogs in South-east Asia and New Guinea (Platymantis, family Ranidae) and the highly diverse radiation of narrow-mouthed frogs in New Guinea (family Microhylidae).
Ecdysis: The act of moulting in arthropods and related animals with a hardened exoskeleton, enabling growth which would otherwise be inhibited by the rigid cuticle. After separation from the body of the animal within (apolysis), the exoskeleton breaks along weak points (points of ecdysis) allowing the soft-bodied animal to emerge and expand before a new cuticle forms. The discarded exoskeleton is known as an exuvium (plural exuvia or exuviae).
Electroreception: A sense possessed by some groups of, predominantly aquatic, animals that enables them to hunt by homing in on the electrical activity of their prey. This is often an adaptation for hunting in low-visibility environments.
Endopterogyte: An insect with internal (rather than external) wing buds in the larval stage. Larvae of endopterogyte insects often look very dissimilar from adults, and all undergo eventual metamorphosis during which external wings develop. Endopterogytes include the most abundant, diverse and evolutionarily 'advanced' insects, the most familiar being the beetles, flies, wasps and their relatives, and moths and butterflies.
Exopterogyte: An insect in which externally visible wing sheaths are present during larval development, often thought of as 'primitive' insects. Larvae characteristically resemble adult animals (although this resemblance may be rather slight, for instance in dragonflies and damselflies), and maturation occurs without metamorphosis. Familiar exopterogytes include grasshoppers and their relatives, true bugs, dragonflies and mayflies.
Hibernation: The term used to describe a, usually fixed, period of dormancy in mammals, a response to low external temperatures in which most metabolic processes are slowed considerably, including respiration and maintenance of body temperature. In 'true' (mammalian) hibernation, animals typically remain dormant in this state for most or all of this period, without emerging to feed. The term is used more broadly to describe any form of overwinter dormancy, and is often applied to insects, amphibians, reptiles and other animals as well as mammals.
Holometabolous: Description of the life cycle of endopterogyte insects, such as beetles, flies, moths and wasps, in which the animal undergoes metamorphosis from a larval stage into a distinct, and often winged, adult form. The alternative life cycle, in which no metamorphosis takes place, is known as hemimetabolous.
Masting: A life history strategy used by many trees, in which seeds are produced in large numbers at irregular multiyear intervals. During a masting event, all members of the species in the woodland or patch will set seed simultaneously, overwhelming the ability of seed predators to consume the entire harvest. Masting is most associated with tropical forest trees, especially in the Asian rainforest family Dipterocarpaceae, but also occurs in temperate regions such as European beechwoods.
Melanism: The condition caused by an excess of the pigment melanin, resulting in an animal whose skin, hair or feathers are entirely black.
Metamorphosis: In the life cycle of many animals the transition from one form to another, typically from a larval form to an adult. This type of metamorphosis is particularly familiar from amphibians and many insects, though occurs in other animal groups including crustaceans, fish and molluscs. The products of metamorphosis have different names depending on the organisms; for example, newly-metamorphosed frogs are known as froglets or metamorphs, while newly-emerged dragonflies may be described as teneral.
Oviparity: A reproductive system in which a female lays eggs that develop to term outside the mother's body.
Ovipositing/Oviposition: The act of laying eggs. A structure adapted for releasing eggs is referred to as an ovipositor.
Ovoviviparity: A reproductive system in which eggs develop fully within the mother's body, with the young inside feeding off the yolk sac until shortly before birth. The eggs hatch inside the mother, and live young are born shortly afterwards. This distinguishes ovoviviparity from true viviparity (live-bearing), in which developing animals obtain some or all of their nutrition directly from maternal tissues.
Paedomorphism: The situation in some species with complex life cycles, notably the axolotl, whereby the animal grows and reaches maturity in its larval form, without undergoing metamorphosis. In some cases it is possible to induce metamorphosis by altering environmental conditions; this may be a natural response, or as in the axolotl may only occur in captivity. Partial paedomorphis, in which some juvenile characteristics are retained into adulthood, is known as neoteny.
Parthenogenesis: A state in populations of many sexual organisms in which females are able to reproduce asexually, laying fertile eggs in the absence of males. In some cases, parthenogenesis may require ovulation to be stimulated by another female engaging in courtship behaviour; in others a single female may produce young without any contact with other animals. Offspring are necessarily clones, and are themselves invariably female. Parthenogenesis may be facultative, in which females are able to reproduce clonally in the absence of males, but will produce offspring sexually when males are available. However, some parthenogenic species altogether lack males; in others, especially species introduced to areas outside their native range, only certain populations lack males. Many effective colonisers, including several species of tropical gecko and the blind snake Rhamphotyphlops braminus, exhibit parthenogenesis.
Pupa: In holometabolous insects, the final stage before sexual maturity. The larval form moults into a sessile pupa, often nondescript in colour and attached to vegetation, within which the animal's tissues are reorganised in the process of metamorphosis.
Teneral: The soft-bodied stage between ecdysis and the hardening of a new exoskeleton in arthropods and their relatives. This is the period during which an animal grows as fluid expands its tissues. In some animals, such as odonates, changes in colouration and aspects of physical appearance such as the development of wings or enlarged eyes, also take place during this period.. In dragonflies, the term is usually used to refer only to the period immediately after the adult form emerges from the final larval instar.
Thermoregulation: The act of maintaining body temperature at a level that allows for continued activity. Mammals, birds and some other organisms possess the ability to maintain their internal temperature at a constant level using energy from the breakdown of food. Most animals rely instead on regulating their body temperature behaviourally, for instance by basking in sunlight and retreating to the shade in warm periods.
Univoltine: Describing a species that produces only one brood of offspring in a year; species with multiple broods may be described as bivoltine, trivoltine etc. Most often used to describe insects, such as butterflies. Conversely, animals that exhibit slower rates of voltinism may be described as semi- (taking two years to complete development) or partivoltine (longer periods).
Viviparity: Often known as 'live-bearing', truly viviparous species are those in which mothers both give birth to live young, and provide nourishment for offspring as they develop in the mother's womb. This form of reproduction is known from most mammals, and occurs to a lesser extent in a number of other animal groups, including some sharks and insects.
Anthropogenic: Literally 'human-created'. When used to describe habitats, the term refers to environments that are predominantly man-made, and typically associated with regular human presence - examples include urban areas, parks and gardens, and agricultural land. More broadly, anthropogenic disturbance can refer to any form of habitat modification with a human cause, such as selectively logged forest or secondary regrowth following land clearance.
Benthic: The deep-water environment, including the base or floor of a waterbody. The term can be applied to both freshwater and marine environments.
Crypsis: Used to describe an animal in relation to its surroundings, a cryptic species is one which blends in well with its background, due to camouflage or simply dull colouration.
Ecosystem: An ecosystem is the product of all interactions between animal and plant species and inorganic components of their environment, such as nutrients. Ecosystems can be defined on a range of spatial scales. A full description of an ecosystem includes not only the characteristics of the habitat and the species which inhabit it, but also the processes involved in transferring nutrients and energy through the system (ecosystem processes).
Ecosystem engineer: A species whose behaviour alters their environment in such a way that the occurrence, abundance and/or relationships between other species are indirectly affected (i.e., not simply reducing the abundance of a prey species). The best-known ecosystem engineers are beavers, whose dams create ponds that provide habitat for a range of aquatic species.
Eutrophic: A system is eutrophic if it is 'overloaded' with nutrients, a condition that, in aquatic environments, can promote the growth of algae which block sunlight and limit the diffusion of oxygen into the water column. On land eutrophication (typically in the form of nitrogen deposition) can promote the spread of 'weed' species at the expense of other plants. Eutrophic habitats can occur naturally, but are most often considered in the context of agricultural and industrial pollution, especially the runoff of nitrogen and phosphorous into freshwater. Eutrophic habitats are hostile to many organisms.
Fossorial: Used to describe a species adapted to living underground. Most commonly the term refers to species that burrow into or live beneath or within leaf litter, sand, mud or other surface cover.
Interspecific: Relating to individuals between species, such as in the context of biological interactions (e.g. interspecific competition is competition between species)
Intraspecific: Relating to individuals within a species, often in the context of interactions between members of a single species (e.g. intraspecific competition) or physical differences between members of a species (intraspecific variation). Contrasts with interspecific.
Microhabitat: Within a broad habitat type (such as a forest), microhabitat defines particular elements of that habitat's structure and climate upon which species depend, such as favoured perch types (tree, rock, leaf litter etc.), moisture regimes, breeding or foraging sites.
Nutrient: The generic name for any inorganic materials that are required for the functioning of biological processes. Nutrients may be required in either large (macronutrients) or small (micronutrients) quantities, and most are ultimately produced by the breakdown of rocks through weathering and chemical erosion. The most important nutrients for plant growth, and hence for sustaining ecosystems, are nitrogen and phosphorous.
Nutrient cycling: A fundamental ecosystem process that describes the transfer of nutrients through soil, plants and other organisms. Nutrients are removed from the soil by plant roots, and are ultimately released back into the soil by the decomposition of plant and animal material. In many nutrient-starved ecosystems (those that receive few nutrients from outside the system, and/or that have thin soils that provide few nutrients of their own), such as tropical rainforest, nutrient cycling provides most or all of the nutrients that sustain the ecosystem.
Pelagic: The open-water environment, in either the sea or freshwater. The description of a species as pelagic indicates that it spends the majority of its time away from shore. Colloquially large marine creatures with a pelagic lifestyle, such as marine turtles and many sharks, are often referred to by divers simply as pelagics.
Primary (habitat): The term used to describe areas of the landscape with little or no apparent sign of disturbance or human activity. In the specific case of primary forest, the term refers more specifically to areas dominated by large, slow-growing old-growth trees, in contrast to areas of recent regrowth where trees are typically faster-growing and with a more open canopy.
Succession: A process of gradual habitat evolution and replacement over time, classically from an area of bare ground to a woodland through a process of rock weathering, soil development and establishment by progressively longer-lived, larger plant species. In practice, succession is a more dynamic process, with interactions between species (such as browsers preventing tree establishment) and natural disturbance preventing many ecosystems from reaching any 'final' successional state. Succession can be a useful way of understanding colonisation and competitive processes in both plants and animals, with early pioneer species characterised by rapid dispersal, tolerance of poor environmental conditions and fast growth rates followed by slower-colonising species that prefer less extreme, well-vegetated habitats and that may outcompete the pioneers in time.
Amniote: A tetrapod characterised by the possession of an amniotic egg in the primitive condition. This egg consists of a yolk sac, a central cavity surrounding the embryo filled with amniotic fluid, a moist albumin (protective membrane) and a watertight shell. Paralleling the evolution of seeds in plants and hard egg cases in insects, the development of the amniotic egg was the vertebrates' most critical adaptation to a fully-terrestrial lifestyle. Living amniotes include the reptiles, mammals and birds, but not the amphibians.
Anura: The major living order within the Amphibia in Linnean taxonomy, containing all tail-less amphibians (i.e. frogs and toads). In a biological sense, the term anuran is synonymous with 'frog' (a term which also encompasses all animals commonly known as 'toads'), but is often preferred to avoid confusion with the common usage of 'frog' (i.e. excluding toads).
Arthropod: Literally, 'jointed-foot'. Treated as a phylum in Linnean taxonomy, this enormous grouping contains all animals with exoskeletons and jointed limbs, including the major lineages Hexapoda (insects and six-legged relatives), Crustacea and Arachnida (spiders, mites, scorpions, horseshoe crabs and relatives). Centipedes and millipedes (the Myriapoda) are also arthropods, and genetic evidence places the velvet worms (Onychophora) at the evolutionary base of this group.
Binomial nomenclature: The system of giving organisms scientific names according to Linnean taxonomy. Each binomial consists of a specific name for a species, in lower case, and the name of the genus of related species to which it belongs, which always begins with a capital letter, with each species receiving a unique combination of the two. In formal taxonomic use, the full binomial is followed by the name of the author of the paper or book in which the organism was first described (the authority) and the date of its publication. This is often omitted in non-taxonomic studies. For example, the full name of the Asian common bush frog is Polypedates leucomystax Gravenhorst, 1829, usually referred to as Polypedates leucomystax (the genus name can be abbreviated to its first letter after the first use in a document, so P. leucomystax will often be seen relating to this species). The origin of species and genus names is often a classical European language, principally Latin or Greek, but Latinised forms of place names, cultural groups or people, or words in non-European languages are also frequently used.
Cladistics: The modern application of taxonomy to identify evolutionary relationships. Cladistic taxonomy traces the evolution of specific characters (traits), and aims to define groups of related species (clades) based on the extent to which these features diverge from those of ancestral forms. In practice, major clades are generally assigned to existing levels in Linnaean taxonomy; for example a single family of frogs may represent a clade. However, cladistics is able to identify many more levels of evolutionary divergence than traditional taxonomy allows, and has the ultimate goal of defining all organisms as monophyletic groups.
Cryptic species: As used in taxonomy, a cryptic species is one that resembles another so closely that both have traditionally been considered a single species. Sometimes these species can be distinguished by close scrutiny, and in these cases the crypsis is an artefact of a poor state of knowledge regarding particular species; often in these cases it is known or strongly suspected that multiple species are involved, but one or more await formal description. Alternatively, populations may be genuinely indistinguishable on the basis of external characters, and the presence of additional species can only be established using genetic analysis. Commonly, a single described species represents a complex of multiple cryptic species, rather than simply two species. Note that this use of 'cryptic' is different from the term's meaning in ecology, where it refers to an animal's ability to camouflage itself to match its surroundings.
Diapsid: One of two major amniote lineages that first appeared in the Carboniferous period (360-300 million years ago), diverging from a common ancestor with the synapsids. Diapsids are characterised by the possession of a large opening (fenestra) at either side of the skull although several lineages, including turtles, appear to have since lost this trait. The surviving diapsids are reptiles and birds.
Elasmobranch: A member of the major surviving group of cartilaginous fish, a group of vertebrates characterised by skeletons made of dense connective tissue instead of bone. Sharks first appear in the Devonian Period, 400 million years ago, and the group is today represented by around 1,000 species of shark, skate and ray.
Eutherian: The largest and most widespread of the three major groups of mammals, the eutherian or placental mammals occur on every continent (represented by bats and rodents in Australia, and by seals and whales in Antarctica). They are distinguished from the egg-laying monotremes in giving birth to live young, and from the marsupials in having an extended development period within the womb and a more complex, better-developed system of placental tissue.
Extant: Used in opposition to extinct; i.e. an extant species or group of species is one with living members.
Linnaean system: The system of biological classification pioneered by the 18th Century botanist Carl Linnaeus. Organisms are grouped into one of six major levels - species, genus, family, order, phylum and kingdom - representing a hierarchy of similarity: organisms that appear identical to one another or nearly so belong to a single species, with groups of similar species contained within the same genus, genera within families and so on. Although increasingly superseded by cladistics, the named levels of the Linnaean taxonomy are still a convenient way of representing evolutionary relationships, albeit relatively crudely. The most lasting contribution of the Linnean system is the use of binomial nomenclature for giving species scientific names.
Odonate: A member of the insect order Odonata, dragonflies and damselflies.
Marsupial: Marsupials or metatherians are a group of mammals that occur today in Australia, South and North America, and are most famously represented by the Australian kangaroos. Several hundred species of living marsupial exist, mostly in Australia and New Guinea. Young marsupials are born at an earlier stage of development than those of placental mammals, and are carried by the mother once they leave the womb, either in a pouch or pockets on her skin, or clinging to her body.
Monotreme: A small group of mammals with the unusual habit of laying eggs rather than giving birth to live young. Today the monotremes are represented by one species of platypus in Australia, and several of echidna (spiny anteater) in Australia and New Guinea, although the oldest fossil platypus are known from Argentina.
Phylogenetics: The practice of constructing family trees to represent evolutionary relationships between organisms. The resulting phylogenies effectively represent hypotheses about the relatedness of different organisms, with the goal of identifying monophyletic groups, clades which contain all organisms descended from a given common ancestor. In practice, many phylogenies represent groups which are either polyphyletic (including one or more unrelated species, and therefore in which organisms are not all derived from one common ancestor), or paraphyletic, in which all species descend from the same common ancestor, but some species that are also descended from that ancestor are excluded from the group. A classic example of the latter is the class Reptilia. By convention, the definition of a reptile excludes birds, although no taxonomic features are known to exist which reliably distinguish birds from theropod dinosaurs, classified as reptiles. The discipline of cladistics is an effort to resolve these issues and produce wholly monophyletic phylogenies for all organisms.
Primitive: In an evolutionary sense, 'primitive' refers to a character that is present in a lineage's common ancestor; primitive characters may be lost in some, or even all, members of a lineage over evolutionary time, or may be retained. Primitive characters are useful for tracing evolutionary relationships; for example, possessing four limbs is the primitive state in all tetrapods, including snakes, whales and others with two or fewer limbs.
Prosimian: Any primate belonging to the lineage ancestral to monkeys, collectively grouped into the suborder Strepsirrhini. Living prosimians occur in Africa and Asia, and include lemurs (confined to Madagascar and the Comoros), bushbabies (a large complex of species resembling mouse lemurs, and found in much of mainland Africa) and Asian lorises. The eight species of tarsier are also often regarded as prosimians, though are usually placed in a suborder of their own.
Snout-vent length: In reptiles, the most common measurement of body size, taken from the tip of the snout to the cloacal opening (vent), taken as being the length of the body excluding the tail. Adult amphibians are usually measured to the tip of the final bone of the spine, known as the urostyle, and the term snout-urostyle length (SUL) is often used; tadpoles are measured using snout-vent length.
Synapsid: One of the two major amniote lineages that diverged during the Carboniferous period (360-300 million years ago), the other being the diapsids. Synapsids are ultimately ancestral to the mammals, which first appeared in the late Triassic.
Tetrapod: Any vertebrate with four limbs or four-limbed ancestors, including living amphibians, reptiles, mammals and birds together with extinct vertebrate groups that share a common ancestor with them. The term tetrapod broadly corresponds with 'terrestrial vertebrate', and the two can be used interchangeably. However, the former is more precise as it encompasses a variety of taxa that have become adapted to a fully-aquatic lifestyle, such as whales and the extinct plesiosaurs.