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The aardvark (Orycteropus afer) is a medium-sized, burrowing, nocturnal mammal native to Africa.
The aardwolf (Proteles cristata) is a small, insectivorous mammal, native to East and Southern Africa.
Abalone (or; via Spanish abulón, from Rumsen aulón) is a common name for any of a group of small to very large sea snails, marine gastropod molluscs in the family Haliotidae.
The abdomen (less formally called the belly, stomach, tummy or midriff) constitutes the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates.
The abomasum, also known as the maw, rennet-bag, or reed tripe, is the fourth and final stomach compartment in ruminants.
In biology, adipose tissue, body fat, or simply fat is a loose connective tissue composed mostly of adipocytes.
Aestivation or æstivation (from aestas, summer, but also spelled estivation in American English) is a state of animal dormancy, similar to hibernation, characterized by inactivity and a lowered metabolic rate, that is entered in response to high temperatures and arid conditions.
African elephants are elephants of the genus Loxodonta.
The Afroinsectiphilia (African insectivores) is a clade that has been proposed based on the results of recent molecular phylogenetic studies.
The order Afrosoricida (a Latin-Greek compound name which means "looking like African shrews") contains the golden moles of southern Africa and the tenrecs of Madagascar and Africa.
Afrotheria is a clade of mammals, the living members of which belong to groups that are either currently living in Africa or of African origin: golden moles, elephant shrews (also known as sengis), tenrecs, aardvarks, hyraxes, elephants, sea cows, and several extinct clades.
Agricultural machinery is machinery used in farming or other agriculture.
Agriculture is the cultivation of land and breeding of animals and plants to provide food, fiber, medicinal plants and other products to sustain and enhance life.
In animal communication, an alarm signal is an antipredator adaptation in the form of signals emitted by social animals in response to danger.
Albrecht Dürer (21 May 1471 – 6 April 1528)Müller, Peter O. (1993) Substantiv-Derivation in Den Schriften Albrecht Dürers, Walter de Gruyter.
Algae (singular alga) is an informal term for a large, diverse group of photosynthetic organisms that are not necessarily closely related, and is thus polyphyletic.
Allen's rule is an ecogeographical rule formulated by Joel Asaph Allen in 1877, broadly stating that animals adapted to cold climates have shorter limbs and body appendages than animals adapted to warm climates.
Allometry is the study of the relationship of body size to shape, anatomy, physiology and finally behaviour, first outlined by Otto Snell in 1892, by D'Arcy Thompson in 1917 in On Growth and Form and by Julian Huxley in 1932.
Allotheria (meaning "other beasts", from the Greek αλλός, –other and θήριον, –wild animal) is an extinct branch of successful Mesozoic mammals.
The Alpaca (Vicugna pacos) is a species of South American camelid, similar to, and often confused with the llama.
Altungulata or Pantomesaxonia (sensu and later authors) is an invalid clade (mirorder) of ungulate mammals comprising the perissodactyls, hyracoids, and tethytheres (sirenians, proboscideans, and related extinct taxa.) The name "Pantomesaxonia" was originally introduced by, a German zoologist and racial theorist.
The Amazon rainforest (Portuguese: Floresta Amazônica or Amazônia; Selva Amazónica, Amazonía or usually Amazonia; Forêt amazonienne; Amazoneregenwoud), also known in English as Amazonia or the Amazon Jungle, is a moist broadleaf forest in the Amazon biome that covers most of the Amazon basin of South America.
Ambondro mahabo is a mammal from the middle Jurassic (about 167 million years ago) of Madagascar.
The American black bear (Ursus americanus) is a medium-sized bear native to North America.
The American Museum of Natural History (abbreviated as AMNH), located on the Upper West Side of Manhattan, New York City, is one of the largest museums in the world.
Ameridelphia is traditionally a superorder that includes all marsupials living in the Americas except for the Monito del monte (Dromiciops).
Ammonia is a compound of nitrogen and hydrogen with the formula NH3.
Amniotes (from Greek ἀμνίον amnion, "membrane surrounding the fetus", earlier "bowl in which the blood of sacrificed animals was caught", from ἀμνός amnos, "lamb") are a clade of tetrapod vertebrates comprising the reptiles, birds, and mammals.
Amphilestes is a genus of extinct eutriconodont mammal from the Middle Jurassic of the United Kingdom.
Amphitherium is an extinct genus of stem cladotherian mammal that lived during the Middle Jurassic.
The Ancient Greek language includes the forms of Greek used in ancient Greece and the ancient world from around the 9th century BC to the 6th century AD.
Animal cognition describes the mental capacities of non-human animals and the study of those capacities.
Echolocation, also called bio sonar, is the biological sonar used by several kinds of animals.
Animal rights is the idea in which some, or all, non-human animals are entitled to the possession of their own lives and that their most basic interests—such as the need to avoid suffering—should be afforded the same consideration as similar interests of human beings.
Animal testing, also known as animal experimentation, animal research and in vivo testing, is the use of non-human animals in experiments that seek to control the variables that affect the behavior or biological system under study.
Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera.
Anti-predator adaptations are mechanisms developed through evolution that assist prey organisms in their constant struggle against predators.
Apes (Hominoidea) are a branch of Old World tailless anthropoid primates native to Africa and Southeast Asia.
Aposematism (from Greek ἀπό apo away, σῆμα sema sign) is a term coined by Edward Bagnall PoultonPoulton, 1890.
Aquatic and semiaquatic mammals are a diverse group of mammals that dwell partly or entirely in bodies of water.
Arboreal locomotion is the locomotion of animals in trees.
Archicebus is a genus of fossil primates that lived in the early Eocene forests (~55 million years ago) of what is now Jingzhou in the Hubei Province in central China, discovered in 2003.
The Archonta are a group of mammals, considered a superorder in some classifications, which consists of the following orders.
Archosaurs are a group of diapsid amniotes whose living representatives consist of birds and crocodilians.
The Arctic fox (Vulpes lagopus), also known as the white fox, polar fox, or snow fox, is a small fox native to the Arctic regions of the Northern Hemisphere and common throughout the Arctic tundra biome.
The Arctic ground squirrel (Spermophilus parryii or Urocitellus parryii) is a species of ground squirrel native to the Arctic.
The arrector pili muscles are small muscles attached to hair follicles in mammals.
Art is a diverse range of human activities in creating visual, auditory or performing artifacts (artworks), expressing the author's imaginative, conceptual idea, or technical skill, intended to be appreciated for their beauty or emotional power.
The articular bone is part of the lower jaw of most vertebrates, including most jawed fish, amphibians, birds and various kinds of reptiles, as well as Stem-mammal.
Asioryctitheria ("asian digging beasts") is an extinct order of early eutherians.
The Atlantic Ocean is the second largest of the world's oceans with a total area of about.
Atlantogenata is a proposed clade of mammals containing the cohorts or superorders Afrotheria and Xenarthra.
The atrium is the upper chamber in which blood enters the heart.
The aurochs (or; pl. aurochs, or rarely aurochsen, aurochses), also known as urus or ure (Bos primigenius), is an extinct species of large wild cattle that inhabited Europe, Asia, and North Africa.
Australidelphia is the superorder that contains roughly three-quarters of all marsupials, including all those native to Australasia and a single species from South America (all other American marsupials are members of the Ameridelphia).
The Australosphenida are a proposed infraclass of mammals within subclass Yinotheria.
Awn hairs are the intermediate hairs in a mammal's coat.
Bacteria (common noun bacteria, singular bacterium) is a type of biological cell.
The baculum (also penis bone, penile bone, or os penis, or os priapi) is a bone found in the penis of many placental mammals.
Baleen whales (systematic name Mysticeti), known earlier as whalebone whales, form a parvorder of the infraorder Cetacea (whales, dolphins and porpoises).
In phylogenetics, basal is the direction of the base (or root) of a rooted phylogenetic tree or cladogram.
Bats are mammals of the order Chiroptera; with their forelimbs adapted as wings, they are the only mammals naturally capable of true and sustained flight.
Bears are carnivoran mammals of the family Ursidae.
The beaver (genus Castor) is a large, primarily nocturnal, semiaquatic rodent.
Bees are flying insects closely related to wasps and ants, known for their role in pollination and, in the case of the best-known bee species, the European honey bee, for producing honey and beeswax.
A bellows or pair of bellows is a device constructed to furnish a strong blast of air.
The Bengal tiger (Panthera tigris tigris) is the most numerous tiger subspecies in Asia, and was estimated at fewer than 2,500 individuals by 2011.
The informal term "big cat" is typically used to refer to any of the five living members of the genus Panthera, namely tiger, lion, jaguar, leopard and snow leopard.
Bile or gall is a dark green to yellowish brown fluid, produced by the liver of most vertebrates, that aids the digestion of lipids in the small intestine.
Bilirubin is a yellow compound that occurs in the normal catabolic pathway that breaks down heme in vertebrates.
A biome is a community of plants and animals that have common characteristics for the environment they exist in.
Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs or legs.
Birds, also known as Aves, are a group of endothermic vertebrates, characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight skeleton.
The black and rufous elephant shrew, (Rhynchocyon petersi) the black and rufous sengi, or the Zanj elephant shrew is one of the 17 species of elephant shrew found only in Africa.
A blood cell, also called a haematopoietic cell, hemocyte, or hematocyte, is a cell produced through hematopoiesis and found mainly in the blood.
Blubber is a thick layer of vascularized adipose tissue under the skin of all cetaceans, pinnipeds and sirenians.
The blue whale (Balaenoptera musculus) is a marine mammal belonging to the baleen whale parvorder, Mysticeti.
In digestion, a bolus (from Latin bolus, "ball") is a ball-like mixture of food and saliva that forms in the mouth during the process of chewing (which is largely an adaptation for plant-eating mammals).
Boreoeutheria (synonymous with Boreotheria) (Greek: βόρειο "north" + ευ "good" + θεριό "beast") is a clade (magnorder) of placental mammals that is composed of the sister taxa Laurasiatheria (most hoofed mammals, most pawed carnivores, and several other groups) and Euarchontoglires (Supraprimates).
The bowhead whale (Balaena mysticetus) is a species of the family Balaenidae, in suborder Mysticeti, and genus Balaena, which once included the right whale.
Brachiation (from "brachium", Latin for "arm"), or arm swinging, is a form of arboreal locomotion in which primates swing from tree limb to tree limb using only their arms.
The size of the brain is a frequent topic of study within the fields of anatomy and evolution.
Brain-to-body mass ratio, also known as the brain-to-body weight ratio, is the ratio of brain mass to body mass, which is hypothesized to be a rough estimate of the intelligence of an animal, although fairly inaccurate in many cases.
Breeding back is a form of artificial selection by the deliberate selective breeding of domestic animals, in an attempt to achieve an animal breed with a phenotype that resembles a wildtype ancestor, usually one that is extinct in its wild form.
A bronchus, is a passage of airway in the respiratory system that conducts air into the lungs.
The Callitrichidae (also called Arctopitheci or Hapalidae) are a family of New World monkeys, including marmosets, tamarins and lion tamarins.
Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see (crypsis), or by disguising them as something else (mimesis).
Canis is a genus of the Canidae containing multiple extant species, such as wolves, coyotes, jackals, dingoes, and dogs.
The canter and gallop are variations on the fastest gait that can be performed by a horse or other equine.
The Cape golden mole (Chrysochloris asiatica) is a small, insectivorous mammal of the family Chrysochloridae, the golden moles.
The capybara (Hydrochoerus hydrochaeris) is a mammal native to South America.
A carbohydrate is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water); in other words, with the empirical formula (where m may be different from n).
The Carboniferous is a geologic period and system that spans 60 million years from the end of the Devonian Period million years ago (Mya), to the beginning of the Permian Period, Mya.
Carl Linnaeus (23 May 1707 – 10 January 1778), also known after his ennoblement as Carl von LinnéBlunt (2004), p. 171.
Carnassials are paired upper and lower teeth (either molars or premolars and molars) modified in such a way as to allow enlarged and often self-sharpening edges to pass by each other in a shearing manner.
Carnivora (from Latin carō (stem carn-) "flesh" and vorāre "to devour") is a diverse scrotiferan order that includes over 280 species of placental mammals.
A carnivore, meaning "meat eater" (Latin, caro, genitive carnis, meaning "meat" or "flesh" and vorare meaning "to devour"), is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging.
Carrier's constraint is the observation that air-breathing vertebrates which have two lungs and flex their bodies sideways during locomotion find it very difficult to move and breathe at the same time, because the sideways flexing expands one lung and compresses the other, shunting stale air from lung to lung instead of expelling it completely to make room for fresh air.
Castorocauda is a genus of small, semi-aquatic mammal relatives living in the Jurassic period, around 164 million years ago, found in lakebed sediments of the Daohugou Beds of Inner Mongolia.
The domestic cat (Felis silvestris catus or Felis catus) is a small, typically furry, carnivorous mammal.
Cattle—colloquially cows—are the most common type of large domesticated ungulates.
Cave paintings, also known as parietal art, are painted drawings on cave walls or ceilings, mainly of prehistoric origin, beginning roughly 40,000 years ago (around 38,000 BCE) in Eurasia.
The cecum or caecum (plural ceca; from the Latin caecus meaning blind) is an intraperitoneal pouch that is considered to be the beginning of the large intestine.
Cellulase is any of several enzymes produced chiefly by fungi, bacteria, and protozoans that catalyze cellulolysis, the decomposition of cellulose and of some related polysaccharides.
Cellulose is an organic compound with the formula, a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units.
The Cenozoic Era meaning "new life", is the current and most recent of the three Phanerozoic geological eras, following the Mesozoic Era and, extending from 66 million years ago to the present day.
The cerebrum is a large part of the brain containing the cerebral cortex (of the two cerebral hemispheres), as well as several subcortical structures, including the hippocampus, basal ganglia, and olfactory bulb.
In vertebrates, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull.
The cervix or cervix uteri (neck of the uterus) is the lower part of the uterus in the human female reproductive system.
Cetacea are a widely distributed and diverse clade of aquatic mammals that today consists of the whales, dolphins, and porpoises.
Cetacean bycatch is the incidental capture of non-target cetacean species such as dolphins, porpoises, and whales by fisheries.
Charles Robert Darwin, (12 February 1809 – 19 April 1882) was an English naturalist, geologist and biologist, best known for his contributions to the science of evolution.
The taxonomical genus Pan (often referred to as chimpanzees or chimps) consists of two extant species: the common chimpanzee and the bonobo.
Cilia (Latin for eyelashes; the singular is cilium) in entomology are fine hairs along the edges of the insect wing.
Cingulata, part of the superorder Xenarthra, is an order of armored New World placental mammals.
A civilization or civilisation (see English spelling differences) is any complex society characterized by urban development, social stratification imposed by a cultural elite, symbolic systems of communication (for example, writing systems), and a perceived separation from and domination over the natural environment.
A clade (from κλάδος, klados, "branch"), also known as monophyletic group, is a group of organisms that consists of a common ancestor and all its lineal descendants, and represents a single "branch" on the "tree of life".
Cladistics (from Greek κλάδος, cládos, i.e., "branch") is an approach to biological classification in which organisms are categorized in groups ("clades") based on the most recent common ancestor.
A cladogram (from Greek clados "branch" and gramma "character") is a diagram used in cladistics to show relations among organisms.
Cladotheria is a group (legion) of mammals that includes the ancestor of Dryolestoidea, Peramuridae and Zatheria (living therians plus all of its ancestors).
In biological classification, class (classis) is a taxonomic rank, as well as a taxonomic unit, a taxon, in that rank.
The clitoris is a female sex organ present in mammals, ostriches and a limited number of other animals.
In animal anatomy, a cloaca (plural cloacae or) is the posterior orifice that serves as the only opening for the digestive, reproductive, and urinary tracts (if present) of many vertebrate animals, opening at the vent.
The cloaca is a structure in the development of the urinary and reproductive organs.
Clothing (also known as clothes and attire) is a collective term for garments, items worn on the body.
The cochlea is the part of the inner ear involved in hearing.
Dicrostonyx is a genus of rodent in the family Cricetidae.
Colugos are arboreal gliding mammals found in Southeast Asia.
The common vampire bat (Desmodus rotundus) is a small, leaf-nosed bat native to the Americas.
Condylarthra is an informal group – previously considered an order – of extinct placental mammals, known primarily from the Paleocene and Eocene epochs.
The Convention on Biological Diversity (CBD), known informally as the Biodiversity Convention, is a multilateral treaty.
Convergent evolution is the independent evolution of similar features in species of different lineages.
A coprolite is fossilized feces.
Coprophagia or coprophagy is the consumption of feces.
Coronary circulation is the circulation of blood in the blood vessels of the heart muscle (myocardium).
The corpus callosum (Latin for "tough body"), also callosal commissure, is a wide commissure, a flat bundle of commissural fibers, about 10 cm long beneath the cerebral cortex in the brains of placental mammals.
In biogeography, a taxon is said to have a cosmopolitan distribution if its range extends across all or most of the world in appropriate habitats.
A courtship display is a set of display behaviors in which an animal attempts to attract a mate and exhibit their desire to copulate.
A cranial nerve nucleus is a collection of neurons (gray matter) in the brain stem that is associated with one or more cranial nerves.
Crawling or Quadrupedal movement is a method of human locomotion that makes use of all four limbs.
Creodonta is an extinct, potentially polyphyletic order of carnivorous mammals that lived from the Paleocene to the Miocene epochs.
The Cretaceous is a geologic period and system that spans 79 million years from the end of the Jurassic Period million years ago (mya) to the beginning of the Paleogene Period mya.
The Cretaceous–Paleogene (K–Pg) extinction event, also known as the Cretaceous–Tertiary (K–T) extinction, was a sudden mass extinction of some three-quarters of the plant and animal species on Earth, approximately 66 million years ago.
Crocodilia (or Crocodylia) is an order of mostly large, predatory, semiaquatic archosaurian reptiles, known as crocodilians.
Crocodylomorpha is a group of archosaurs that includes the crocodilians and their extinct relatives.
In phylogenetics, the crown group of a collection of species consists of the living representatives of the collection together with their ancestors back to their most recent common ancestor as well as all of that ancestor's descendants.
Cud is a portion of food that returns from a ruminant's stomach to the mouth to be chewed for the second time.
A cursorial organism is one that is adapted specifically to run.
The cynodonts ("dog teeth") (clade Cynodontia) are therapsids that first appeared in the Late Permian (approximately 260 Ma).
A dagger, obelisk, or obelus is a typographical symbol usually used to indicate a footnote if an asterisk has already been used.
Dairy products, milk products or lacticinia are a type of food produced from or containing the milk of mammals, primarily cattle, water buffaloes, goats, sheep, camels, and humans.
The Damaraland mole-rat, Damara mole rat, or Damaraland blesmol (Fukomys damarensis) is a burrowing rodent found in southern Africa.
Deer (singular and plural) are the ruminant mammals forming the family Cervidae.
Defaunation is the loss of animals from ecological communities.
Deforestation, clearance, or clearing is the removal of a forest or stand of trees where the land is thereafter converted to a non-forest use.
Dentin (American English) or dentine (British English) (substantia eburnea) is a calcified tissue of the body and, along with enamel, cementum, and pulp, is one of the four major components of teeth.
The dermis or corium is a layer of skin between the epidermis (with which it makes up the cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from stress and strain.
Diastole is the part of the cardiac cycle during which the heart refills with blood after the emptying done during systole (contraction).
Dicynodontia is a taxon of anomodont therapsids or synapsids with beginnings in the mid-Permian, which were dominant in the Late Permian and continued throughout the Triassic, with a few possibly surviving into the Early Cretaceous.
A digitigrade, is an animal that stands or walks on its digits, or toes.
Dimetrodon (or, meaning "two measures of teeth") is an extinct genus of synapsids that lived during the Cisuralian (Early Permian), around 295–272 million years ago (Ma).
Dinosaurs are a diverse group of reptiles of the clade Dinosauria.
Deoxyribonucleic acid (DNA) is a thread-like chain of nucleotides carrying the genetic instructions used in the growth, development, functioning and reproduction of all known living organisms and many viruses.
DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome.
Docodonta is an order of extinct mammaliaforms that lived during the mid- to late-Mesozoic era.
The domestic dog (Canis lupus familiaris when considered a subspecies of the gray wolf or Canis familiaris when considered a distinct species) is a member of the genus Canis (canines), which forms part of the wolf-like canids, and is the most widely abundant terrestrial carnivore.
The domestic pig (Sus scrofa domesticus or only Sus domesticus), often called swine, hog, or simply pig when there is no need to distinguish it from other pigs, is a large, even-toed ungulate.
Domestication is a sustained multi-generational relationship in which one group of organisms assumes a significant degree of influence over the reproduction and care of another group to secure a more predictable supply of resources from that second group.
Dominance hierarchy is a type of social hierarchy that arises when members of a social group interact, often aggressively, to create a ranking system.
The donkey or ass (Equus africanus asinus) is a domesticated member of the horse family, Equidae.
A dorsal fin is a fin located on the back of most marine and freshwater vertebrates such as fishes, cetaceans (whales, dolphins, and porpoises), and the (extinct) ichthyosaur.
In the biological context of organisms' production of gene products, downregulation is the process by which a cell decreases the quantity of a cellular component, such as RNA or protein, in response to an external stimulus.
In fluid dynamics, drag (sometimes called air resistance, a type of friction, or fluid resistance, another type of friction or fluid friction) is a force acting opposite to the relative motion of any object moving with respect to a surrounding fluid.
In the anatomy of humans and various other tetrapods, the eardrum, also called the tympanic membrane or myringa, is a thin, cone-shaped membrane that separates the external ear from the middle ear.
The Early Cretaceous/Middle Cretaceous (geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous.
The Early Jurassic epoch (in chronostratigraphy corresponding to the Lower Jurassic series) is the earliest of three epochs of the Jurassic period.
The eastern grey kangaroo (Macropus giganteus) is a marsupial found in southern and eastern Australia, with a population of several million.
Echidnas, sometimes known as spiny anteaters, belong to the family Tachyglossidae in the monotreme order of egg-laying mammals.
Ecological extinction is defined as "the reduction of a species to such low abundance that, although it is still present in the community, it no longer interacts significantly with other species".
An ectotherm (from the Greek ἐκτός (ektós) "outside" and θερμός (thermós) "hot"), is an organism in which internal physiological sources of heat are of relatively small or quite negligible importance in controlling body temperature.
Educational toys (sometimes called "instructive toys") are objects of play, generally designed for children, which are expected to stimulate learning.
Sir Edwin Henry Landseer RA (7 March 1802 – 1 October 1873) was an English painter and sculptor, well known for his paintings of animals — particularly horses, dogs, and stags.
An egg is the organic vessel containing the zygote in which an animal embryo develops until it can survive on its own; at which point the animal hatches.
Elephants are large mammals of the family Elephantidae and the order Proboscidea.
Elephant shrews, also called jumping shrews or sengis, are small insectivorous mammals native to Africa, belonging to the family Macroscelididae, in the order Macroscelidea. Their traditional common English name "elephant shrew" comes from a fancied resemblance between their long noses and the trunk of an elephant, and their superficial similarity with shrews (family Soricidae) in the order Eulipotyphla.
An embryo is an early stage of development of a multicellular diploid eukaryotic organism.
Empty forest is a term coined by Kent H. Redford's article "The Empty Forest" (1992), which was published in BioScience.
Encephalization quotient (EQ) or encephalization level is a relative brain size measure that is defined as the ratio between actual brain mass and predicted brain mass for an animal of a given size, which may approximate intelligence level or cognition of the species.
An endotherm (from Greek ἔνδον endon "within" and θέρμη thermē "heat") is an organism that maintains its body at a metabolically favorable temperature, largely by the use of heat set free by its internal bodily functions instead of relying almost purely on ambient heat.
The Eocene Epoch, lasting from, is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era.
Eomaia ("dawn mother") is a genus of extinct fossil mammals containing the single species Eomaia scansoria, discovered in rocks that were found in the Yixian Formation, Liaoning Province, China, and dated to the Barremian Age of the Lower Cretaceous about.
Eparctyona is a clade of placental mammals comprising the artiodactyls (even-toed ungulates), cetacea (whales and related), and the extinct condylarths.
The epidermis is the outer layer of the three layers that make up the skin, the inner layers being the dermis and hypodermis.
Epipubic bones are a pair of bones projecting forward from the pelvic bones of modern marsupials and most non-placental fossil mammals: multituberculates, monotremes, and even basal eutherians (the ancestors of placental mammals).
Epitherians comprise all the placental mammals except the Xenarthra.
An erection (clinically: penile erection or penile tumescence) is a physiological phenomenon in which the penis becomes firm, engorged, and enlarged.
Erythrotherium is an extinct genus of basal mammal from the Lower Jurassic.
The estrous cycle or oestrus cycle (derived from Latin oestrus 'frenzy', originally from Greek οἶστρος oîstros 'gadfly') is the recurring physiological changes that are induced by reproductive hormones in most mammalian therian females.
The Euarchonta are a proposed grandorder of mammals containing four orders: the Scandentia or treeshrews, the Dermoptera or colugos, the extinct Plesiadapiformes, and the Primates.
Euarchontoglires (synonymous with Supraprimates) is a clade and a superorder of mammals, the living members of which belong to one of the five following groups: rodents, lagomorphs, treeshrews, colugos and primates.
Eulipotyphla ("truly fat and blind") is an order of mammals suggested by molecular methods of phylogenetic reconstruction, and includes the laurasiatherian members of the now-invalid polyphyletic order Lipotyphla, but not the afrotherian members (tenrecs and golden moles, now in their own order Afrosoricida).
The Eupelycosauria originally referred to a suborder of 'pelycosaurs' (Reisz 1987), but has been redefined (Laurin and Reisz 1997) to designate a clade of synapsids that includes most pelycosaurs, as well as all therapsids and mammals.
The Eurasian beaver or European beaver (Castor fiber) is a species of beaver which was once widespread in Eurasia.
The eureka effect (also known as the Aha! moment or eureka moment) refers to the common human experience of suddenly understanding a previously incomprehensible problem or concept.
Eusociality (from Greek εὖ eu "good" and social), the highest level of organization of animal sociality, is defined by the following characteristics: cooperative brood care (including care of offspring from other individuals), overlapping generations within a colony of adults, and a division of labor into reproductive and non-reproductive groups.
Eutheria (from Greek εὐ-, eu- "good" or "right" and θηρίον, thēríon "beast" hence "true beasts") is one of two mammalian clades with extant members that diverged in the Early Cretaceous or perhaps the Late Jurassic.
Eutriconodonta is an order of early mammals.
The even-toed ungulates (Artiodactyla) are ungulates (hoofed animals) whose weight is borne equally by the third and fourth toes.
The evolution of biological complexity is one important outcome of the process of evolution.
Exafroplacentalia or Notolegia is a clade of placental mammals proposed in 2001 on the basis of molecular research.
The excretory system is a passive biological system that removes excess, unnecessary materials from the body fluids of an organism, so as to help maintain internal chemical homeostasis and prevent damage to the body.
Exhalation (or expiration) is the flow of the breath out of an organism.
An extinct in the wild (EW) species is one which has been categorized by the International Union for Conservation of Nature as only known by living members kept in captivity or as a naturalized population outside its historic range due to massive habitat loss.
In biology, extinction is the termination of an organism or of a group of organisms (taxon), normally a species.
The facial nerve is the seventh cranial nerve, or simply cranial nerve VII.
In biological classification, family (familia, plural familiae) is one of the eight major taxonomic ranks; it is classified between order and genus.
The fat-tailed dwarf lemur (Cheirogaleus medius), also known as the lesser dwarf lemur, western fat-tailed dwarf lemur, or spiny forest dwarf lemur, is endemic to Madagascar.
Feathers are epidermal growths that form the distinctive outer covering, or plumage, on birds and other, extinct species' of dinosaurs.
Feces (or faeces) are the solid or semisolid remains of the food that could not be digested in the small intestine.
Felis is a genus of small and medium-sized cat species native to most of Africa and south of 60° latitude in Europe and Asia to Indochina.
The Ferae are a clade of mammals, consisting of the orders Carnivora (over 260 species, around the globe) and Pholidota (eight species of pangolins in tropical Africa and Asia).
A fern is a member of a group of vascular plants that reproduce via spores and have neither seeds nor flowers.
Ferungulata or Fereuungulata is a clade of placental mammals that groups together various carnivorans and ungulates.
A fetus is a stage in the prenatal development of viviparous organisms.
In ethology, a fission–fusion society is one in which the size and composition of the social group change as time passes and animals move throughout the environment; animals merge into a group (fusion)—e.g. sleeping in one place—or split (fission)—e.g. foraging in small groups during the day.
Fitness (often denoted w or ω in population genetics models) is the quantitative representation of natural and sexual selection within evolutionary biology.
The Florida panther is an endangered population of the cougar (Puma concolor) that lives in pinelands, hardwood hammocks, and mixed swamp forests of South Florida in the United States.
A number of animals have evolved aerial locomotion, either by powered flight or by gliding.
In zoology, a folivore is a herbivore that specializes in eating leaves.
The Food and Agriculture Organization of the United Nations (FAO; Organisation des Nations unies pour l'alimentation et l'agriculture, Organizzazione delle Nazioni Unite per l'Alimentazione e l'Agricoltura) is a specialized agency of the United Nations that leads international efforts to defeat hunger.
A fossil (from Classical Latin fossilis; literally, "obtained by digging") is any preserved remains, impression, or trace of any once-living thing from a past geological age.
Cape ground squirrel. A fossorial (from Latin fossor, "digger") is an animal adapted to digging and lives primarily, but not solely, underground.
The fox squirrel (Sciurus niger), also known as the eastern fox squirrel or Bryant's fox squirrel, is the largest species of tree squirrel native to North America.
A frugivore is a fruit eater.
Fruitafossor was a termite-eating mammal endemic to North America during the Late Jurassic epoch (around 150 mya).
Fungivory or mycophagy is the process of organisms consuming fungi.
A fungus (plural: fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms.
Fur is the hair covering of non-human mammals, particularly those mammals with extensive body hair that is soft and thick.
Gait is the pattern of movement of the limbs of animals, including humans, during locomotion over a solid substrate.
Human gait refers to locomotion achieved through the movement of human limbs.
Gale is an educational publishing company based in Farmington Hills, Michigan, in the western suburbs of Detroit.
Gambling is the wagering of money or something of value (referred to as "the stakes") on an event with an uncertain outcome with the primary intent of winning money or material goods.
Game or quarry is any animal hunted for sport or for food.
Gas exchange is the physical process by which gases move passively by diffusion across a surface.
The gastrointestinal tract (digestive tract, digestional tract, GI tract, GIT, gut, or alimentary canal) is an organ system within humans and other animals which takes in food, digests it to extract and absorb energy and nutrients, and expels the remaining waste as feces.
A gazelle is any of many antelope species in the genus Gazella or formerly considered to belong to it.
In biology, a gene is a sequence of DNA or RNA that codes for a molecule that has a function.
In population genetics, gene flow (also known as gene migration or allele flow) is the transfer of genetic variation from one population to another.
The gene pool is the set of all genes, or genetic information, in any population, usually of a particular species.
Genetic pollution is a controversial term for uncontrolled gene flow into wild populations.
A genetically modified mouse (Mus musculus) is a mouse that has had its genome altered through the use of genetic engineering techniques.
A genus (genera) is a taxonomic rank used in the biological classification of living and fossil organisms, as well as viruses, in biology.
George Gaylord Simpson (June 16, 1902 – October 6, 1984) was a US paleontologist.
George Stubbs (25 August 1724 – 10 July 1806) was an English painter, best known for his paintings of horses.
Gestation is the carrying of an embryo or fetus inside viviparous animals.
The giant anteater (Myrmecophaga tridactyla), also known as the ant bear, is a large insectivorous mammal native to Central and South America.
The giant armadillo (Priodontes maximus), colloquially tatou, ocarro, tatu-canastra or tatú carreta, is the largest living species of armadillo (although their extinct relatives, the glyptodonts, were much larger).
The giant panda (Ailuropoda melanoleuca, literally "black and white cat-foot";, literally "big bear cat"), also known as panda bear or simply panda, is a bear native to south central China.
Gibbons are apes in the family Hylobatidae.
The giraffe (Giraffa) is a genus of African even-toed ungulate mammals, the tallest living terrestrial animals and the largest ruminants.
Glires (Latin glīrēs, dormice) is a clade (sometimes ranked as a grandorder) consisting of rodents and lagomorphs (rabbits, hares, and pikas).
Gnathostomata are the jawed vertebrates.
Gobiconodonta is an order of extinct mammals known from the Early Jurassic (such as Huasteconodon) to early Late Cretaceous.
Golden moles are small, insectivorous burrowing mammals endemic to Southern Africa, where their Afrikaans names are gouemolle or kruipmolle (singular gouemol or kruipmol).
Pocket gophers, commonly referred to as gophers, are burrowing rodents of the family Geomyidae.
The gray whale (Eschrichtius robustus), also known as the grey whale,Britannica Micro.: v. IV, p. 693.
The gray wolf (Canis lupus), also known as the timber wolf,Paquet, P. & Carbyn, L. W. (2003).
Grazing is a method of feeding in which a herbivore feeds on plants such as grasses, or other multicellular organisms such as algae.
The greater spear-nosed bat (Phyllostomus hastatus) is a bat species of the family Phyllostomidae from South and Central America.
Greyhound racing is an organized, competitive sport in which greyhound dogs are raced around a track.
Gummivores are a hybrid class of omnivores that defines a group of animals whose diet consists primarily of the gums and saps of trees (about 90%) and bugs for protein.
Guns, Germs, and Steel: The Fates of Human Societies (also titled Guns, Germs and Steel: A short history of everybody for the last 13,000 years) is a 1997 transdisciplinary non-fiction book by Jared Diamond, professor of geography and physiology at the University of California, Los Angeles (UCLA).
Gut flora, or gut microbiota, or gastrointestinal microbiota, is the complex community of microorganisms that live in the digestive tracts of humans and other animals, including insects.
Habitat destruction is the process in which natural habitat is rendered unable to support the species present.
Hair is a protein filament that grows from follicles found in the dermis.
A hairball is a small collection of hair or fur formed in the stomach of animals, and uncommonly in humans, that is occasionally vomited up when it becomes too big.
Haldanodon exspectatus is an extinct mammaliaform, specifically a docodont.
The hammer-headed bat (Hypsignathus monstrosus), also known as the big-lipped bat, is a megabat widely distributed in equatorial Africa.
Haramiyavia was a genus of synapsid in the Haramiyida clade that existed about 200 million years ago in the Norian/Rhaetian period of the Triassic.
Haramiyidans are a long lived lineage of mammaliaform cynodonts.
The hard palate is a thin horizontal bony plate of the skull, located in the roof of the mouth.
A harem is an animal group consisting of one or two males, a number of females, and their offspring.
Harry Frederick Harlow (October 31, 1905 – December 6, 1981) was an American psychologist best known for his maternal-separation, dependency needs, and social isolation experiments on rhesus monkeys, which manifested the importance of caregiving and companionship to social and cognitive development.
The haustra (singular haustrum) of the colon are the small pouches caused by sacculation (sac formation), which give the colon its segmented appearance.
The heart is a muscular organ in most animals, which pumps blood through the blood vessels of the circulatory system.
Heck cattle are a hardy breed of domestic cattle.
A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage, for the main component of its diet.
Herbivores are dependent on plants for food, and have coevolved mechanisms to obtain this food despite the evolution of a diverse arsenal of plant defenses against herbivory.
Heterosis, hybrid vigor, or outbreeding enhancement, is the improved or increased function of any biological quality in a hybrid offspring.
Hibernation is a state of inactivity and metabolic depression in endotherms.
A hierarchy (from the Greek hierarchia, "rule of a high priest", from hierarkhes, "leader of sacred rites") is an arrangement of items (objects, names, values, categories, etc.) in which the items are represented as being "above", "below", or "at the same level as" one another A hierarchy can link entities either directly or indirectly, and either vertically or diagonally.
The common hippopotamus (Hippopotamus amphibius), or hippo, is a large, mostly herbivorous, semiaquatic mammal native to sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae, the other being the pygmy hippopotamus (Choeropsis liberiensis or Hexaprotodon liberiensis).
The Holocene extinction, otherwise referred to as the Sixth extinction or Anthropocene extinction, is the ongoing extinction event of species during the present Holocene epoch, mainly as a result of human activity.
Holotheria are a diverse group of mammals that are descendants of the last common ancestor of Kuehneotherium and Theria (the group that includes marsupials and placental mammals).
The honey badger (Mellivora capensis), also known as the ratel, is the only species in the mustelid subfamily Mellivorinae and its only genus Mellivora.
The horse (Equus ferus caballus) is one of two extant subspecies of ''Equus ferus''.
Horse gaits are the various ways in which a horse can move, either naturally or as a result of specialized training by humans.
Horse racing is an equestrian performance sport, typically involving two or more horses ridden by jockeys (or sometimes driven without riders) over a set distance for competition.
Humans (taxonomically Homo sapiens) are the only extant members of the subtribe Hominina.
The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion (the tongue, salivary glands, pancreas, liver, and gallbladder).
The humpback whale (Megaptera novaeangliae) is a species of baleen whale.
A hunter-gatherer is a human living in a society in which most or all food is obtained by foraging (collecting wild plants and pursuing wild animals), in contrast to agricultural societies, which rely mainly on domesticated species.
Hunting is the practice of killing or trapping animals, or pursuing or tracking them with the intent of doing so.
In biology, a hybrid, or crossbreed, is the result of combining the qualities of two organisms of different breeds, varieties, species or genera through sexual reproduction.
A hybrid zone exists where the ranges of two interbreeding species or diverged intraspecific lineages meet and cross-fertilize.
Hyenas or hyaenas (from Greek ὕαινα hýaina) are any feliform carnivoran mammals of the family Hyaenidae.
A hypercarnivore is an animal which has a diet that is more than 70% meat, with the balance consisting of non-animal foods such as fungi, fruits or other plant material.
A hypocarnivore is an animal that consumes less than 30% meat for its diet, the majority of which consists of non-vertebrate foods that may include fungi, fruits, and other plant material.
The hypoglossal nerve is the twelfth cranial nerve, and innervates all the extrinsic and intrinsic muscles of the tongue, except for the palatoglossus which is innervated by the vagus nerve.
Hyraxes (from the Greek ὕραξ, hýrax, "shrewmouse"), also called dassies, are small, thickset, herbivorous mammals in the order Hyracoidea.
Incertae sedis (Latin for "of uncertain placement") is a term used for a taxonomic group where its broader relationships are unknown or undefined.
Incisors (from Latin incidere, "to cut") are the front teeth present in most mammals.
The anvil or incus is a bone in the middle ear.
Infrasound, sometimes referred to as low-frequency sound, is sound that is lower in frequency than 20 Hz or cycles per second, the "normal" limit of human hearing.
An infratemporal fenestra, also called the lateral temporal fenestra is an opening in the skull behind the orbit in some animals.
Insects or Insecta (from Latin insectum) are hexapod invertebrates and the largest group within the arthropod phylum.
The order Insectivora (from Latin insectum "insect" and vorare "to eat") is a now-abandoned biological grouping within the class of mammals.
robber fly eating a hoverfly An insectivore is a carnivorous plant or animal that eats insects.
Intelligence has been defined in many different ways to include the capacity for logic, understanding, self-awareness, learning, emotional knowledge, reasoning, planning, creativity, and problem solving.
The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natural resources.
Introgression, also known as introgressive hybridization, in genetics is the movement of a gene (gene flow) from one species into the gene pool of another by the repeated backcrossing of an interspecific hybrid with one of its parent species.
The IUCN Red List of Threatened Species (also known as the IUCN Red List or Red Data List), founded in 1964, has evolved to become the world's most comprehensive inventory of the global conservation status of biological species.
The ivory trade is the commercial, often illegal trade in the ivory tusks of the hippopotamus, walrus, narwhal, mammoth, and most commonly, African and Asian elephants.
The Japanese macaque (Macaca fuscata), also known as the snow monkey, is a terrestrial Old World monkey species that is native to Japan.
Jared Mason Diamond (born September 10, 1937) is an American ecologist, geographer, biologist, anthropologist and author best known for his popular science books The Third Chimpanzee (1991); Guns, Germs, and Steel (1997, awarded a Pulitzer Prize); Collapse (2005); and The World Until Yesterday (2012).
The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food.
The Journal of Mammalogy is the flagship publication of the American Society of Mammalogists.
Juramaia is an extinct genus of very basal eutherian mammal from the Late Jurassic (Oxfordian stage) deposits of western Liaoning, China; it is a small shrew-like mammal of body length approximately 70–100 mm.
The Jurassic (from Jura Mountains) was a geologic period and system that spanned 56 million years from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period Mya.
Kangaroo rats, small rodents of genus Dipodomys, are native to western North America.
Kitti's hog-nosed bat (Craseonycteris thonglongyai), also known as the bumblebee bat, is a vulnerable species of bat and the only extant member of the family Craseonycteridae.
A knockout mouse or knock-out mouse is a genetically modified mouse (Mus musculus) in which researchers have inactivated, or "knocked out", an existing gene by replacing it or disrupting it with an artificial piece of DNA.
Knuckle-walking is a form of quadrupedal walking in which the forelimbs hold the fingers in a partially flexed posture that allows body weight to press down on the ground through the knuckles.
Ku80 is a protein that, in humans, is encoded by the XRCC5 gene.
Kuehneotheria is a group of basal mammals that were once classified in the now paraphyletic Symmetrodonta.
The labia majora (singular: labium majus) are two prominent longitudinal cutaneous folds that extend downward and backward from the mons pubis to the perineum.
The labia minora, Latin for smaller lips, singular: labium minus "smaller lip", also known as the inner labia, inner lips, vaginal lips or nymphae, are two flaps of skin on either side of the human vaginal opening in the vulva, situated between the labia majora (the Latin for larger lips; also called outer labia, or outer lips).
Lactation describes the secretion of milk from the mammary glands and the period of time that a mother lactates to feed her young.
The lagomorphs are the members of the taxonomic order Lagomorpha, of which there are two living families: the Leporidae (hares and rabbits) and the Ochotonidae (pikas).
In fluid dynamics, laminar flow (or streamline flow) occurs when a fluid flows in parallel layers, with no disruption between the layers.
Lascaux (Grotte de Lascaux, "Lascaux Cave") is the setting of a complex of caves near the village of Montignac, in the department of Dordogne in southwestern France.
The Late Triassic is the third and final of three epochs of the Triassic Period in the geologic timescale.
Latin (Latin: lingua latīna) is a classical language belonging to the Italic branch of the Indo-European languages.
Laurasiatheria is a clade of placental mammals that originated on the northern supercontinent of Laurasia 99 million years ago.
Learning is the process of acquiring new or modifying existing knowledge, behaviors, skills, values, or preferences.
Leather is a durable and flexible material created by tanning animal rawhides, mostly cattle hide.
A lek, from the Swedish word for "play", is an aggregation of male animals gathered to engage in competitive displays, lekking, to entice visiting females which are surveying prospective partners for copulation.
Lemurs are a clade of strepsirrhine primates endemic to the island of Madagascar.
Leptictida (leptos iktis "small/slender weasel") is a possibly invalid extinct order of placental mammals.
Liaoning is a province of China, located in the northeast of the country.
The lion (Panthera leo) is a species in the cat family (Felidae).
In biology and biochemistry, a lipid is a biomolecule that is soluble in nonpolar solvents.
Lipotyphla is a formerly used invalid order of mammals, including the members of the order Eulipotyphla (i.e. the solenodons, family Solenodontidae; hedgehogs and gymnures, family Erinaceidae; desmans, moles, and shrew-like moles, family Talpidae; and true shrews, family Soricidae) as well as two other families of the former order Insectivora, Chrysochloridae (golden moles) and Tenrecidae (tenrecs).
There are currently 1258 genera, 156 families, 28 orders, and around 5937 recognized living species of mammal.
This is a list of notable mammalogists, in alphabetical order by surname.
Although the mammals are well studied in comparison to other animal groups, a number of new species are still being discovered.
The class Mammalia (mammals) is divided into two subclasses based on reproductive techniques: egg-laying mammals (yinotherians or monotremes - see also Australosphenida), and mammals which give live birth (therians).
List of placental mammals contains the placental mammals.
This is an incomplete list of prehistoric mammals.
Recently extinct mammals are any mammal that went extinct since the year 1500 C. E., as defined by the International Union for Conservation of Nature (IUCN).
This is a list of tetrapods that are semiaquatic; that is, while being at least partly terrestrial, they spend part of their life cycle or a significant fraction of their time in water as part of their normal behavior, and/or obtain a significant fraction of their food from an aquatic habitat.
According to the International Union for Conservation of Nature (IUCN), 65 mammal species in the United States are threatened or nearly threatened with extinction.
Version 2014.2 of the IUCN Red List of Threatened Species identified 4574 Critically Endangered species, subspecies and varieties, stocks and subpopulations.
This is a collection of lists of mammal species by estimated global population, divided by orders.
The following are the regional mammal lists by continent.
Live Science is a science news website run by Purch, which it purchased from Imaginova in 2009.
The liver, an organ only found in vertebrates, detoxifies various metabolites, synthesizes proteins, and produces biochemicals necessary for digestion.
Livestock are domesticated animals raised in an agricultural setting to produce labor and commodities such as meat, eggs, milk, fur, leather, and wool.
The Living Planet Index (LPI) is an indicator of the state of global biological diversity, based on trends in vertebrate populations of species from around the world.
Lizards are a widespread group of squamate reptiles, with over 6,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains.
Local extinction or extirpation is the condition of a species (or other taxon) that ceases to exist in the chosen geographic area of study, though it still exists elsewhere.
In the kidney, the loop of Henle (or Henle's loop, Henle loop, nephron loop or its Latin counterpart ansa nephroni) is the portion of a nephron that leads from the proximal convoluted tubule to the distal convoluted tubule.
In acoustics, loudness is the subjective perception of sound pressure.
The lungs are the primary organs of the respiratory system in humans and many other animals including a few fish and some snails.
The Maastrichtian is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem.
Machairodontinae is an extinct subfamily of carnivoran mammals of the family Felidae (true cats).
Malcolm Carnegie McKenna (1930–2008) was an American paleontologist and author on the subject.
The malleus or hammer is a hammer-shaped small bone or ossicle of the middle ear which connects with the incus and is attached to the inner surface of the eardrum.
Mammalia is a class of animal within the Phylum Chordata.
Mammal Species of the World: A Taxonomic and Geographic Reference is a standard reference work in mammology giving descriptions and bibliographic data for the known species of mammals.
Mammaliaformes ("mammal-shaped") is a clade that contains the crown group mammals and their closest extinct relatives; the group radiated from earlier probainognathian cynodonts.
Mammals have played a crucial role in creating and sustaining human culture.
A mammary gland is an exocrine gland in mammals that produces milk to feed young offspring.
A mammoth is any species of the extinct genus Mammuthus, proboscideans commonly equipped with long, curved tusks and, in northern species, a covering of long hair.
Manatees (family Trichechidae, genus Trichechus) are large, fully aquatic, mostly herbivorous marine mammals sometimes known as sea cows. There are three accepted living species of Trichechidae, representing three of the four living species in the order Sirenia: the Amazonian manatee (Trichechus inunguis), the West Indian manatee (Trichechus manatus), and the West African manatee (Trichechus senegalensis).
The mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human face.
Marine mammals are aquatic mammals that rely on the ocean and other marine ecosystems for their existence.
The marmosets,, also known as zaris, are twenty-two New World monkey species of the genera Callithrix, Cebuella, Callibella and Mico.
Marsupials are any members of the mammalian infraclass Marsupialia.
Marsupial moles (Notoryctidae) are specialized marsupial mammals, known from two species distributed in the Australian interior.
The maxilla (plural: maxillae) in animals is the upper jawbone formed from the fusion of two maxillary bones.
In human dentistry, the maxillary canine is the tooth located laterally (away from the midline of the face) from both maxillary lateral incisors of the mouth but mesial (toward the midline of the face) from both maxillary first premolars.
Meat is animal flesh that is eaten as food.
Megaconus is an extinct genus of mammaliaforms from the Middle Jurassic Tiaojishan Formation of Inner Mongolia, China.
In terrestrial zoology, megafauna (from Greek μέγας megas "large" and New Latin fauna "animal life") are large or giant animals.
Megazostrodon is an extinct Mammaliaform that is widely accepted as being one of the first mammals and which appeared in the fossil record approximately 200 million years ago.
The melon is a mass of adipose tissue found in the forehead of all toothed whales.
Meridiungulata is an extinct clade with the rank of cohort or superorder, containing the South American ungulates Pyrotheria (possibly including Xenungulata), Astrapotheria, Notoungulata and Litopterna.
Merkel cells, also known as Merkel-Ranvier cells or tactile epithelial cells, are oval-shaped mechanoreceptors essential for light touch sensation and found in the skin of vertebrates.
A mesocarnivore is an animal whose diet consists of 30–70% meat with the balance consisting of non-vertebrate foods which may include fungi, fruits, and other plant material.
The Mesozoic Era is an interval of geological time from about.
Metabolic wastes or excretes are substances left over from metabolic processes (such as cellular respiration) which cannot be used by the organism (they are surplus or toxic), and must therefore be excreted.
Metabolism (from μεταβολή metabolē, "change") is the set of life-sustaining chemical transformations within the cells of organisms.
Metacognition is "cognition about cognition", "thinking about thinking", "knowing about knowing", becoming "aware of one's awareness" and higher-order thinking skills.
Metatheria is a mammalian clade that includes all mammals more closely related to marsupials than to placentals.
The microbats constitute the suborder Microchiroptera within the order Chiroptera (bats).
A microorganism, or microbe, is a microscopic organism, which may exist in its single-celled form or in a colony of cells. The possible existence of unseen microbial life was suspected from ancient times, such as in Jain scriptures from 6th century BC India and the 1st century BC book On Agriculture by Marcus Terentius Varro. Microbiology, the scientific study of microorganisms, began with their observation under the microscope in the 1670s by Antonie van Leeuwenhoek. In the 1850s, Louis Pasteur found that microorganisms caused food spoilage, debunking the theory of spontaneous generation. In the 1880s Robert Koch discovered that microorganisms caused the diseases tuberculosis, cholera and anthrax. Microorganisms include all unicellular organisms and so are extremely diverse. Of the three domains of life identified by Carl Woese, all of the Archaea and Bacteria are microorganisms. These were previously grouped together in the two domain system as Prokaryotes, the other being the eukaryotes. The third domain Eukaryota includes all multicellular organisms and many unicellular protists and protozoans. Some protists are related to animals and some to green plants. Many of the multicellular organisms are microscopic, namely micro-animals, some fungi and some algae, but these are not discussed here. They live in almost every habitat from the poles to the equator, deserts, geysers, rocks and the deep sea. Some are adapted to extremes such as very hot or very cold conditions, others to high pressure and a few such as Deinococcus radiodurans to high radiation environments. Microorganisms also make up the microbiota found in and on all multicellular organisms. A December 2017 report stated that 3.45 billion year old Australian rocks once contained microorganisms, the earliest direct evidence of life on Earth. Microbes are important in human culture and health in many ways, serving to ferment foods, treat sewage, produce fuel, enzymes and other bioactive compounds. They are essential tools in biology as model organisms and have been put to use in biological warfare and bioterrorism. They are a vital component of fertile soils. In the human body microorganisms make up the human microbiota including the essential gut flora. They are the pathogens responsible for many infectious diseases and as such are the target of hygiene measures.
The midbrain or mesencephalon (from Greek mesos 'middle', and enkephalos 'brain') is a portion of the central nervous system associated with vision, hearing, motor control, sleep/wake, arousal (alertness), and temperature regulation.
The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the inner ear.
The Middle Jurassic is the second epoch of the Jurassic Period.
Milk is a white liquid produced by the mammary glands of mammals.
A mineral is a naturally occurring chemical compound, usually of crystalline form and not produced by life processes.
The Miocene is the first geological epoch of the Neogene Period and extends from about (Ma).
The mirror stage (stade du miroir) is a concept in the psychoanalytic theory of Jacques Lacan.
The mirror test, sometimes called the mark test, mirror self-recognition test (MSR), red spot technique or rouge test is a behavioural technique developed in 1970 by psychologist Gordon Gallup Jr. as an attempt to determine whether a non-human animal possesses the ability of visual self-recognition.
Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, adenosine triphosphate (ATP).
A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms.
Moles are small mammals adapted to a subterranean lifestyle (i.e., fossorial).
Molecular genetics is the field of biology that studies the structure and function of genes at a molecular level and thus employs methods of both molecular biology and genetics.
The monito del monte (Spanish for "little monkey of the mountain") or colocolo opossum, Dromiciops gliroides, also called chumaihuén in Mapudungun, is a diminutive marsupial native only to southwestern South America (Argentina and Chile).
Monkeys are non-hominoid simians, generally possessing tails and consisting of about 260 known living species.
Monogamous pairing in animals refers to the natural history of mating systems in which species pair bond to raise offspring.
Monotremes are one of the three main groups of living mammals, along with placentals (Eutheria) and marsupials (Metatheria).
Morganucodonta ("Glamorgan teeth") is an extinct order of basal mammaliaformes, the precursors to crown-group mammals (Mammalia).
Morphology is a branch of biology dealing with the study of the form and structure of organisms and their specific structural features.
Mosses are small flowerless plants that typically grow in dense green clumps or mats, often in damp or shady locations.
In biology and genealogy, the most recent common ancestor (MRCA, also last common ancestor (LCA), or concestor) of any set of organisms is the most recent individual from which all the organisms are directly descended.
The motor cortex is the region of the cerebral cortex involved in the planning, control, and execution of voluntary movements.
A motor neuron (or motoneuron) is a neuron whose cell body is located in the motor cortex, brainstem or the spinal cord, and whose axon (fiber) projects to the spinal cord or outside of the spinal cord to directly or indirectly control effector organs, mainly muscles and glands.
In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer layer or covering), either at specific times of the year, or at specific points in its life cycle.
A mouse (Mus), plural mice, is a small rodent characteristically having a pointed snout, small rounded ears, a body-length scaly tail and a high breeding rate.
Multituberculata (commonly known as multituberculates, named for the multiple tubercles of their teeth) is an extinct taxon of rodent-like allotherian mammals that existed for approximately 166 million years, the longest fossil history of any mammal lineage.
The Muridae, or murids, are the largest family of rodents and of mammals, containing over 700 species found naturally throughout Eurasia, Africa, and Australia.
Muscle contraction is the activation of tension-generating sites within muscle fibers.
A muscle fascicle is a bundle of skeletal muscle fibers surrounded by perimysium, a type of connective tissue.
The muskox (Ovibos moschatus), also spelled musk ox and musk-ox (in ᐅᒥᖕᒪᒃ, umingmak), is an Arctic hoofed mammal of the family Bovidae, noted for its thick coat and for the strong odor emitted during the seasonal rut by males, from which its name derives.
The naked mole-rat (Heterocephalus glaber), also known as the sand puppy, is a burrowing rodent native to parts of East Africa.
In phonetics, nasalization (or nasalisation) is the production of a sound while the velum is lowered, so that some air escapes through the nose during the production of the sound by the mouth.
In zoology, a nectarivore is an animal which derives its energy and nutrient requirements from a diet consisting mainly or exclusively of the sugar-rich nectar produced by flowering plants.
The neocortex, also called the neopallium and isocortex, is the part of the mammalian brain involved in higher-order brain functions such as sensory perception, cognition, generation of motor commands, spatial reasoning and language.
The Neogene (informally Upper Tertiary or Late Tertiary) is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago (Mya) to the beginning of the present Quaternary Period Mya.
The Neolithic Revolution, Neolithic Demographic Transition, Agricultural Revolution, or First Agricultural Revolution, was the wide-scale transition of many human cultures during the Neolithic period from a lifestyle of hunting and gathering to one of agriculture and settlement, making an increasingly larger population possible.
The City of New York, often called New York City (NYC) or simply New York, is the most populous city in the United States.
The nipple is a raised region of tissue on the surface of the breast from which milk leaves the breast through the lactiferous ducts.
The nocturnal bottleneck hypothesis is a hypothesis to explain several mammal traits.
Non-governmental organizations, nongovernmental organizations, or nongovernment organizations, commonly referred to as NGOs, are usually non-profit and sometimes international organizations independent of governments and international governmental organizations (though often funded by governments) that are active in humanitarian, educational, health care, public policy, social, human rights, environmental, and other areas to effect changes according to their objectives.
The northern elephant seal (Mirounga angustirostris) is one of two species of elephant seal (the other is the southern elephant seal).
The northern white-cheeked gibbon (Nomascus leucogenys) is a species of gibbon native to South East Asia.
Nuclear DNA, or nuclear deoxyribonucleic acid (nDNA), is the DNA contained within the nucleus of a eukaryotic organism.
Observational learning is learning that occurs through observing the behavior of others.
The occipital condyles are undersurface protuberances of the occipital bone in vertebrates, which function in articulation with the superior facets of the atlas vertebra.
Occlusion, in a dental context, means simply the contact between teeth.
Oceanic dolphins or Delphinidae are a widely distributed family of dolphins that live in the sea.
Members of the order Perissodactyla, also known as odd-toed ungulates, are mammals characterized by an odd number of toes and by hindgut fermentation with somewhat simple stomachs.
The omasum, also known as the bible, the fardel, the manyplies and the psalterium, is the third compartment of the stomach in ruminants.
Omnivore is a consumption classification for animals that have the capability to obtain chemical energy and nutrients from materials originating from plant and animal origin.
In biological classification, the order (ordo) is.
Orycteropodidae is a family of afrotherian mammals.
The ossicles (also called auditory ossicles) are three bones in either middle ear that are among the smallest bones in the human body.
Otters are carnivorous mammals in the subfamily Lutrinae.
In vertebrates, other than mammals, the passageway from the ovaries to the outside of the body is known as the oviduct.
A pack animal or beast of burden is an individual or type of working animal used by humans as means of transporting materials by attaching them so their weight bears on the animal's back, in contrast to draft animals which pull loads but do not carry them.
Paenungulata is a clade that groups three extant mammal orders: Proboscidea (including elephants), Sirenia (sea cows, including dugongs and manatees), and Hyracoidea (hyraxes).
In biology, a pair bond is the strong affinity that develops in some species between a pair consisting of a male and female, or in some cases as a same-sex pairing, potentially leading to producing offspring and/or a lifelong bond.
Palaeogeography (or paleogeography) is the study of historical geography, generally physical landscapes.
The Paleocene or Palaeocene, the "old recent", is a geological epoch that lasted from about.
The Paleogene (also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period million years ago (Mya) to the beginning of the Neogene Period Mya.
The Paleolithic or Palaeolithic is a period in human prehistory distinguished by the original development of stone tools that covers c. 95% of human technological prehistory.
Paleontology or palaeontology is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene Epoch (roughly 11,700 years before present).
Pangolins or scaly anteaters are mammals of the order Pholidota (from the Greek word φολῐ́ς, "horny scale").
Parental care is a behavioural and evolutionary strategy adopted by some animals, making a parental investment into the evolutionary fitness of their offspring.
Pastoralism is the branch of agriculture concerned with the raising of livestock.
The Père David's deer (Elaphurus davidianus), also known as the milu or elaphure, is a species of deer that are mostly found in captivity.
A peccary (also javelina or skunk pig) is a medium-sized hoofed mammal of the family Tayassuidae (New World pigs) in the suborder Suina along with the Old World pigs, Suidae.
Pecking order or peck order is the colloquial term for the hierarchical system of social organization.
The pelycosaurs (from Greek πέλυξ pelyx 'wooden bowl' or 'axe' and σαῦρος sauros 'lizard') are an informal grouping (previously considered an order) composed of basal or primitive Late Paleozoic synapsids, sometimes erroneously referred to as "mammal-like reptiles".
Penguins (order Sphenisciformes, family Spheniscidae) are a group of aquatic, flightless birds.
Almost all mammal penises have foreskins or prepuce, although in non-human cases the foreskin is usually a sheath (sometimes called the preputial sheath or penile sheath) into which the whole penis is retracted.
A penis (plural penises or penes) is the primary sexual organ that male animals use to inseminate sexually receptive mates (usually females and hermaphrodites) during copulation.
The Pennsylvanian (also known as Upper Carboniferous or Late Carboniferous) is, in the ICS geologic timescale, the younger of two subperiods (or upper of two subsystems) of the Carboniferous Period.
The periaqueductal gray (PAG, also known as the central gray) is the primary control center for descending pain modulation.
The Permian is a geologic period and system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic period 251.902 Mya.
The Permian–Triassic (P–Tr or P–T) extinction event, colloquially known as the Great Dying, the End-Permian Extinction or the Great Permian Extinction, occurred about 252 Ma (million years) ago, forming the boundary between the Permian and Triassic geologic periods, as well as the Paleozoic and Mesozoic eras.
A pet or companion animal is an animal kept primarily for a person's company, protection, or entertainment rather than as a working animal, livestock, or laboratory animal.
Phalangeriformes is a suborder of any of about 70 small- to medium-sized arboreal marsupial species native to Australia, New Guinea, and Sulawesi (and introduced to New Zealand and China).
Pharmacovigilance (PV or PhV), also known as drug safety, is the pharmacological science relating to the collection, detection, assessment, monitoring, and prevention of adverse effects with pharmaceutical products.
A phenotype is the composite of an organism's observable characteristics or traits, such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior (such as a bird's nest).
The term phonation has slightly different meanings depending on the subfield of phonetics.
In biology, phylogenetics (Greek: φυλή, φῦλον – phylé, phylon.
A pig is any of the animals in the genus Sus, within the even-toed ungulate family Suidae.
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The order Pilosa is a group of placental mammals, extant today only in the Americas.
Pinnipeds, commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic marine mammals.
Pitch is a perceptual property of sounds that allows their ordering on a frequency-related scale, or more commonly, pitch is the quality that makes it possible to judge sounds as "higher" and "lower" in the sense associated with musical melodies.
The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, thermo-regulation, waste elimination, and gas exchange via the mother's blood supply; to fight against internal infection; and to produce hormones which support pregnancy.
Placentalia ("Placentals") is one of the three extant subdivisions of the class of animals Mammalia; the other two are Monotremata and Marsupialia.
The plains zebra (Equus quagga, formerly Equus burchellii), also known as the common zebra or Burchell's zebra, or locally as the "quagga" (not to be confused with the extinct subspecies), is the most common and geographically widespread species of zebra.
Human skeleton, showing plantigrade habit In terrestrial animals, plantigrade locomotion means walking with the toes and metatarsals flat on the ground.
The platypus (Ornithorhynchus anatinus), sometimes referred to as the duck-billed platypus, is a semiaquatic egg-laying mammal endemic to eastern Australia, including Tasmania.
Poaching has been defined as the illegal hunting or capturing of wild animals, usually associated with land use rights.
A poikilotherm is an animal whose internal temperature varies considerably.
The polar bear (Ursus maritimus) is a hypercarnivorous bear whose native range lies largely within the Arctic Circle, encompassing the Arctic Ocean, its surrounding seas and surrounding land masses.
Poly (ADP-ribose) polymerase (PARP) is a family of proteins involved in a number of cellular processes such as DNA repair, genomic stability, and programmed cell death.
In behavioral ecology, polyandry is a class of mating system where one female mates with several males in a breeding season.
Polygyny (from Neo-Greek πολυγυνία from πολύ- poly- "many", and γυνή gyne "woman" or "wife") is a mating system in which one male lives and mates with multiple females, but each female only mates with a single male.
Polyphagia or hyperphagia is excessive hunger or increased appetite.
A polyphenic trait is a trait for which multiple, discrete phenotypes can arise from a single genotype as a result of differing environmental conditions.
Porcupines are rodents with a coat of sharp spines, or quills, that protect against predators.
The pouch is a distinguishing feature of female marsupials (and rarely in the males as in the water opossumNogueira, José Carlos, et al. "" Journal of mammalogy 85.5 (2004): 834-841. and the extinct thylacine); the name marsupial is derived from the Latin marsupium, meaning "pouch".
Prairie dogs (genus Cynomys) are herbivorous burrowing rodents native to the grasslands of North America.
In mammals, pregnancy is the period of reproduction during which a female carries one or more live offspring from implantation in the uterus through gestation.
A prehensile tail is the tail of an animal that has adapted to be able to grasp or hold objects.
Prehistoric mammals are groups of mammals that became extinct before humans developed writing.
The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth.
Preptotheria is a superorder of placental mammals proposed by McKenna & Bell in their classification of mammals.
A primate is a mammal of the order Primates (Latin: "prime, first rank").
The probainognathians are members of one of the two major clades of the infraorder Eucynodontia, the other being Cynognathians.
The Proboscidea (from the Greek προβοσκίς and the Latin proboscis) are a taxonomic order of afrotherian mammals containing one living family, Elephantidae, and several extinct families.
Proceedings of the National Academy of Sciences of the United States of America (PNAS) is the official scientific journal of the National Academy of Sciences, published since 1915.
Proteins are large biomolecules, or macromolecules, consisting of one or more long chains of amino acid residues.
Prototheria (from Greek πρώτος, prōtos, first, + θήρ, thēr, wild animal) is the subclass to which the order Monotremata belongs.
Protozoa (also protozoan, plural protozoans) is an informal term for single-celled eukaryotes, either free-living or parasitic, which feed on organic matter such as other microorganisms or organic tissues and debris.
Protungulatum donnae is the type species for the Protungulatum genus, an extinct early form of eutherian mammal.
Pterosaurs (from the Greek πτερόσαυρος,, meaning "winged lizard") were flying reptiles of the extinct clade or order Pterosauria.
A pulmonary alveolus (plural: alveoli, from Latin alveolus, "little cavity") is a hollow cavity found in the lung parenchyma, and is the basic unit of ventilation.
The pulmonary veins are the veins that transfer oxygenated blood from the lungs to the heart.
Purebreds, also called purebreeds, are cultivated varieties or cultivars of an animal species, achieved through the process of selective breeding.
A purr is a tonal fluttering sound made by some species of felids, and two species of genets.
The quadrate bone is part of a skull in most tetrapods, including amphibians, sauropsids (reptiles, birds), and early synapsids.
Quadrupedalism or pronograde posture is a form of terrestrial locomotion in animals using four limbs or legs.
The quagga (Equus quagga quagga) is an extinct subspecies of plains zebra that lived in South Africa until the 19th century.
The Quagga Project is an attempt by a group in South Africa to use selective breeding to achieve a breeding lineage of plains zebra (Equus quagga) which optically resemble the extinct quagga (Equus quagga quagga).
The Quaternary period saw the extinctions of numerous predominantly megafaunal species, which resulted in a collapse in faunal density and diversity, and the extinction of key ecological strata across the globe.
In ecology, r/K selection theory relates to the selection of combinations of traits in an organism that trade off between quantity and quality of offspring.
Rabbits are small mammals in the family Leporidae of the order Lagomorpha (along with the hare and the pika).
Rats are various medium-sized, long-tailed rodents in the superfamily Muroidea.
The recurrent laryngeal nerve (RLN) is a branch of the vagus nerve (cranial nerve X) that supplies all the intrinsic muscles of the larynx, with the exception of the cricothyroid muscles.
The red deer (Cervus elaphus) is one of the largest deer species.
The red wolf (Canis lupus rufus or Canis rufus) also known as the Florida black wolf or Mississippi Valley wolf,Glover, A. (1942),, American Committee for International Wild Life Protection, pp.
The reindeer (Rangifer tarandus), also known as the caribou in North America, is a species of deer with circumpolar distribution, native to Arctic, sub-Arctic, tundra, boreal and mountainous regions of northern Europe, Siberia and North America.
The renal cortex is the outer portion of the kidney between the renal capsule and the renal medulla.
The renal medulla is the innermost part of the kidney.
The renal pelvis or pelvis of the kidney is the basin-like or funnel-like dilated proximal part of the ureter in the kidney.
Renal pyramids (or malpighian pyramids or Malpighi's pyramids named after Marcello Malpighi, a seventeenth-century anatomist) are cone-shaped tissues of the kidney.
The reniculate kidney is a multilobed kidney found in marine and aquatic mammals such as pinnipeds (seals, sea lions and walruses) and cetaceans (dolphins and whales) but absent in terrestrial mammals except bears.
Reptiles are tetrapod animals in the class Reptilia, comprising today's turtles, crocodilians, snakes, amphisbaenians, lizards, tuatara, and their extinct relatives.
Reptiliomorpha is a clade containing the amniotes and those tetrapods that share a more recent common ancestor with amniotes than with living amphibians (lissamphibians).
The reticulum is the first chamber in the alimentary canal of a ruminant animal.
Retrotransposons (also called transposons via RNA intermediates) are genetic elements that can amplify themselves in a genome and are ubiquitous components of the DNA of many eukaryotic organisms.
Retrotransposon markers are retrotransposons that are used as cladistic markers.
The rhesus macaque (Macaca mulatta) is one of the best-known species of Old World monkeys.
A rhinoceros, commonly abbreviated to rhino, is one of any five extant species of odd-toed ungulates in the family Rhinocerotidae, as well as any of the numerous extinct species.
The rib cage is an arrangement of bones in the thorax of most vertebrates.
Right whales or black whales are three species of large baleen whales of the genus Eubalaena: the North Atlantic right whale (E. glacialis), the North Pacific right whale (E. japonica) and the Southern right whale (E. australis).
A roar is a type of animal vocalization consisting of both a low fundamental frequency (pitch) and low formant frequency.
Rodents (from Latin rodere, "to gnaw") are mammals of the order Rodentia, which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws.
The rumen, also known as a paunch, forms the larger part of the reticulorumen, which is the first chamber in the alimentary canal of ruminant animals.
Ruminants are mammals that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microbial actions.
Running is a method of terrestrial locomotion allowing humans and other animals to move rapidly on foot.
Sauropsida ("lizard faces") is a group of amniotes that includes all existing birds and other reptiles as well as their fossil ancestors and other extinct relatives.
Science, also widely referred to as Science Magazine, is the peer-reviewed academic journal of the American Association for the Advancement of Science (AAAS) and one of the world's top academic journals.
Science Advances is a peer-reviewed multidisciplinary open-access scientific journal established in early 2015.
Scientific American (informally abbreviated SciAm) is an American popular science magazine.
A scream, shout, yell, shriek, hoot, holler, vociferation, outcry, bellow, or raising one's voice is a loud vocalization in which air is passed through the vocal folds with greater force than is used in regular or close-distance vocalisation.
Scrotifera is a clade of placental mammals that comprises the following orders and their common ancestors: Chiroptera, Carnivora, Pholidota, Perissodactyla and Cetartiodactyla, with the latter including the traditional orders Artiodactyla and Cetacea.
The scrotum is an anatomical male reproductive structure that consists of a suspended dual-chambered sack of skin and smooth muscle that is present in most terrestrial male mammals and located under the penis.
Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines.
A seed is an embryonic plant enclosed in a protective outer covering.
Seed predation, often referred to as granivory, is a type of plant-animal interaction in which granivores (seed predators) feed on the seeds of plants as a main or exclusive food source,Hulme, P.E. and Benkman, C.W. (2002) "Granivory", pp.
Selective breeding (also called artificial selection) is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics) by choosing which typically animal or plant males and females will sexually reproduce and have offspring together.
Self-awareness is the capacity for introspection and the ability to recognize oneself as an individual separate from the environment and other individuals.
In genetics and biochemistry, sequencing means to determine the primary structure (sometimes falsely called primary sequence) of an unbranched biopolymer.
In biology, setae (singular seta; from the Latin word for "bristle") are any of a number of different bristle- or hair-like structures on living organisms.
An allosome (also referred to as a sex chromosome, heterotypical chromosome, heterochromosome, or idiochromosome) is a chromosome that differs from an ordinary autosome in form, size, and behavior.
A sex-determination system is a biological system that determines the development of sexual characteristics in an organism.
Sexual dimorphism is the condition where the two sexes of the same species exhibit different characteristics beyond the differences in their sexual organs.
Sexual selection is a mode of natural selection where members of one biological sex choose mates of the other sex to mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex (intrasexual selection).
Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite.
Domestic sheep (Ovis aries) are quadrupedal, ruminant mammal typically kept as livestock.
A shoe is an item of footwear intended to protect and comfort the human foot while the wearer is doing various activities.
A shrew (family Soricidae) is a small mole-like mammal classified in the order Eulipotyphla.
The family Caenolestidae contains the seven surviving species of shrew opossum: small, shrew-like marsupials that are confined to the Andes mountains of South America.
The Siberian tiger (Panthera tigris tigris), also called Amur tiger, is a tiger population inhabiting mainly the Sikhote Alin mountain region in southwest Primorye Province in the Russian Far East.
Within evolutionary biology, signalling theory is a body of theoretical work examining communication between individuals, both within species and across species.
Silicon dioxide, also known as silica (from the Latin silex), is an oxide of silicon with the chemical formula, most commonly found in nature as quartz and in various living organisms.
The silky anteater, or pygmy anteater (Cyclopes didactylus), is a species of anteaters from Central and South America, the only living genus in the family Cyclopedidae.
Sinoconodon rigneyi (Chinese spike tooth) is an ancient mammaliamorph or early mammal (depending on systematic approach) that appears in the fossil record of China in the Sinemurian stage of the Early Jurassic period, about 193 million years ago.
Sinodelphys is an extinct mammal from the Early Cretaceous.
The Sirenia, commonly referred to as sea cows or sirenians, are an order of fully aquatic, herbivorous mammals that inhabit swamps, rivers, estuaries, marine wetlands, and coastal marine waters.
Skin is the soft outer tissue covering vertebrates.
The skull is a bony structure that forms the head in vertebrates.
Skunks are North and South American mammals in the family Mephitidae.
Sloths are arboreal mammals noted for slowness of movement and for spending most of their lives hanging upside down in the trees of the tropical rainforests of South America and Central America.
Snakes are elongated, legless, carnivorous reptiles of the suborder Serpentes.
The snowshoe hare (Lepus americanus), also called the varying hare, or snowshoe rabbit, is a species of hare found in North America.
The social environment, social context, sociocultural context or milieu refers to the immediate physical and social setting in which people live or in which something happens or develops.
Solenodons (meaning "slotted-tooth") are venomous, nocturnal, burrowing, insectivorous mammals belonging to the family Solenodontidae.
Soricomorpha ("shrew-form") is a taxon within the class of mammals.
The southern pig-tailed macaque (Macaca nemestrina), also known as the Sundaland pigtail macaque and Sunda pig-tailed macaque, is a medium-sized macaque that lives in southern Thailand, Malaysia, and Indonesia. It is known locally as the beruk.
Spalacotheriidae is a family of extinct mammals belonging to the group Symmetrodonta.
Speciation is the evolutionary process by which populations evolve to become distinct species.
In biology, a species is the basic unit of classification and a taxonomic rank, as well as a unit of biodiversity, but it has proven difficult to find a satisfactory definition.
Species affected by poaching refers both to the effects of illegal hunting and fishing or capturing of wild animals on certain species, and, in a recent usage, the illegal harvesting of wild plant species.
Specific gravity is the ratio of the density of a substance to the density of a reference substance; equivalently, it is the ratio of the mass of a substance to the mass of a reference substance for the same given volume.
The sperm whale (Physeter macrocephalus) or cachalot is the largest of the toothed whales and the largest toothed predator.
Sphenacodontia is a stem-based clade of derived synapsids.
Spider monkeys are New World monkeys belonging to the genus Ateles, part of the subfamily Atelinae, family Atelidae.
In a zoological context, spines are hard, needle-like anatomical structures found in both vertebrate and invertebrate species.The spines of most spiny mammals are modified hairs, with a spongy center covered in a thick, hard layer of keratin and a sharp, sometimes barbed tip.
The spongy urethra (cavernous portion of urethra, penile urethra) is the longest part of the male urethra, and is contained in the corpus spongiosum of the penis.
The spotted hyena (Crocuta crocuta), also known as the laughing hyena, is a species of hyena, currently classed as the sole member of the genus Crocuta, native to Sub-Saharan Africa.
The squamosal is a bone of the head of higher vertebrates.
Squirrels are members of the family Sciuridae, a family that includes small or medium-size rodents.
The stapes or stirrup is a bone in the middle ear of humans and other mammals which is involved in the conduction of sound vibrations to the inner ear.
The star-nosed mole (Condylura cristata) is a small mole found in wet low areas in the northern parts of North America.
The stoat (Mustela erminea), also known as the short-tailed weasel or simply the weasel in Ireland where the least weasel does not occur, is a mammal of the genus Mustela of the family Mustelidae native to Eurasia and North America, distinguished from the least weasel by its larger size and longer tail with a prominent black tip.
The stomach (from ancient Greek στόμαχος, stomachos, stoma means mouth) is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates.
Stotting (also called pronking or pronging) is a behavior of quadrupeds, particularly gazelles, in which they spring into the air, lifting all four feet off the ground simultaneously.
The subcutaneous tissue, also called the hypodermis, hypoderm, subcutis, or superficial fascia, is the lowermost layer of the integumentary system in vertebrates.
The sugar glider (Petaurus breviceps) is a small, omnivorous, arboreal, and nocturnal gliding possum belonging to the marsupial infraclass.
The superior laryngeal nerve is a branch of the vagus nerve.
Susan Alberts is a Bass Fellow and professor at Duke University.
Sweat glands, also known as sudoriferous or sudoriparous glands,, are small tubular structures of the skin that produce sweat.
Symbiosis (from Greek συμβίωσις "living together", from σύν "together" and βίωσις "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasitic.
In phylogenetics, a plesiomorphy, symplesiomorphy or symplesiomorphic character is an ancestral character or trait state shared by two or more taxa.
Synapsids (Greek, 'fused arch'), synonymous with theropsids (Greek, 'beast-face'), are a group of animals that includes mammals and every animal more closely related to mammals than to other living amniotes.
Biological systematics is the study of the diversification of living forms, both past and present, and the relationships among living things through time.
Talpa is a genus in the mole family Talpidae.
The tamarins are squirrel-sized New World monkeys from the family Callitrichidae in the genus Saguinus.
A tapir is a large, herbivorous mammal, similar in shape to a pig, with a short, prehensile nose trunk.
The Tasmanian devil (Sarcophilus harrisii) is a carnivorous marsupial of the family Dasyuridae.
Taxonomy is the science of defining and naming groups of biological organisms on the basis of shared characteristics.
Teinolophos trusleri was a prehistoric species of monotreme, or egg-laying mammal.
A tenrec is any species of mammal within the family Tenrecidae, found on Madagascar and in parts of the African mainland.
Termites are eusocial insects that are classified at the taxonomic rank of infraorder Isoptera, or as epifamily Termitoidae within the cockroach order Blattodea.
In ethology, territory is the sociographical area that an animal of a particular species consistently defends against conspecifics (or, occasionally, animals of other species).
The testicle or testis is the male reproductive gland in all animals, including humans.
The superclass Tetrapoda (from Greek: τετρα- "four" and πούς "foot") contains the four-limbed vertebrates known as tetrapods; it includes living and extinct amphibians, reptiles (including dinosaurs, and its subgroup birds) and mammals (including primates, and all hominid subgroups including humans), as well as earlier extinct groups.
The Economist is an English-language weekly magazine-format newspaper owned by the Economist Group and edited at offices in London.
The Guardian is a British daily newspaper.
Therapsida is a group of synapsids that includes mammals and their ancestors.
Theria (Greek: θηρίον, wild beast) is a subclass of mammals amongst the Theriiformes (the sister taxa to Yinotheria).
Theriiformes is a subclass of mammals.
The thoracic cavity (or chest cavity) is the chamber of the body of vertebrates that is protected by the thoracic wall (rib cage and associated skin, muscle, and fascia).
For other uses, see Diaphragm (disambiguation). The thoracic diaphragm, or simply the diaphragm (partition), is a sheet of internal skeletal muscle in humans and other mammals that extends across the bottom of the thoracic cavity.
The three-toed sloths are tree-living mammals from South and Central America.
Thrinaxodon is an extinct genus of cynodonts, most commonly regarded by its species T. liorhinus which lived in what are now South Africa and Antarctica.
Tikitherium is an extinct genus of Mammaliaformes from the Late Triassic.
Tinodon is an extinct genus of Late Jurassic mammal from the Morrison Formation.
Tool use by animals is a phenomenon in which an animal uses any kind of tool in order to achieve a goal such as acquiring food and water, grooming, defense, recreation or construction.
The sea otter, Enhydra lutris, is a member of the Mustelidae that is fully aquatic.
A tooth (plural teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food.
Tooth enamel is one of the four major tissues that make up the tooth in humans and many other animals, including some species of fish.
The toothed whales (systematic name Odontoceti) are a parvorder of cetaceans that includes dolphins, porpoises, and all other whales possessing teeth, such as the beaked whales and sperm whales.
Transport or transportation is the movement of humans, animals and goods from one location to another.
Traversodontidae is a family of herbivorous cynodonts.
Trechnotheria is a group of mammals that includes the therians and some fossil mammals from the Mesozoic Era.
The tree pangolin (Phataginus tricuspis) is one of eight extant species of pangolins ("scaly anteaters"), and is native to equatorial Africa.
The treeshrews (or tree shrews or banxrings) are small Euarchontoglire mammals native to the tropical forests of Southeast Asia.
The Triassic is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.9 million years ago (Mya), to the beginning of the Jurassic Period Mya.
Tritylodontidae ("three-knob teeth", named after the shape of animal's teeth) is an extinct family of small to medium-sized, highly specialized mammal-like cynodonts, bearing several mammalian traits like erect limbs, endothermy and details of the skeleton.
The trot is a two-beat diagonal gait of the horse where the diagonal pairs of legs move forward at the same time with a moment of suspension between each beat.
Trucidocynodon is an extinct, monotypic genus of cynodonts from Upper Triassic of Brazil.
Tupinambis is a lizard genus which belongs to the family Teiidae, and contains eight described species.
The Argentine red tegu, (Tupinambis rufescens), often referred to as simply red tegu, is one of the largest species of the Tupinambis lizards.
Turtles are diapsids of the order Testudines (or Chelonii) characterized by a special bony or cartilaginous shell developed from their ribs and acting as a shield.
Choloepus is a genus of mammals of Central and South America, within the family Megalonychidae consisting of two-toed sloths.
Ukhaatherium is a now extinct species of mammal that lived during the upper Cretaceous about 84 to 72 million years ago in today's East Asia.
Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing.
Ungulates (pronounced) are any members of a diverse group of primarily large mammals that includes odd-toed ungulates such as horses and rhinoceroses, and even-toed ungulates such as cattle, pigs, giraffes, camels, deer, and hippopotami.
Upholstery is the work of providing furniture, especially seats, with padding, springs, webbing, and fabric or leather covers.
The Upper Paleolithic (or Upper Palaeolithic, Late Stone Age) is the third and last subdivision of the Paleolithic or Old Stone Age.
Urea, also known as carbamide, is an organic compound with chemical formula CO(NH2)2.
The urea cycle (also known as the ornithine cycle) is a cycle of biochemical reactions that produces urea ((NH2)2CO) from ammonia (NH3).
In anatomy, the urethra (from Greek οὐρήθρα – ourḗthrā) is a tube that connects the urinary bladder to the urinary meatus for the removal of urine from the body.
Urine is a liquid by-product of metabolism in humans and in many animals.
The uterine horns are the points where the uterus and the fallopian tubes meet.
The uterus (from Latin "uterus", plural uteri) or womb is a major female hormone-responsive secondary sex organ of the reproductive system in humans and most other mammals.
In mammals, the vagina is the elastic, muscular part of the female genital tract.
The vagus nerve, historically cited as the pneumogastric nerve, is the tenth cranial nerve or CN X, and interfaces with parasympathetic control of the heart, lungs, and digestive tract.
A ventricle is one of two large chambers in the heart that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs.
Vertebrates comprise all species of animals within the subphylum Vertebrata (chordates with backbones).
The vervet monkey (Chlorocebus pygerythrus), or simply vervet, is an Old World monkey of the family Cercopithecidae native to Africa.
Vestigiality is the retention during the process of evolution of genetically determined structures or attributes that have lost some or all of their ancestral function in a given species.
The Virginia opossum (Didelphis virginiana), commonly known as the North American opossum, is a marsupial found in North America.
Among animals, viviparity is development of the embryo inside the body of the parent, eventually leading to live birth, as opposed to reproduction by laying eggs that complete their incubation outside the parental body.
The vocal folds, also known commonly as vocal cords or voice reeds, are composed of twin infoldings of mucous membrane stretched horizontally, from back to front, across the larynx.
The vocal tract is the cavity in human beings and in animals where the sound produced at the sound source (larynx in mammals; syrinx in birds) is filtered.
A vole is a small rodent.
Walking (also known as ambulation) is one of the main gaits of locomotion among legged animals.
The water buffalo (Bubalus bubalis) or domestic Asian water buffalo is a large bovid originating in South Asia, Southeast Asia, and China.
A weasel is a mammal of the genus Mustela of the family Mustelidae.
Whales are a widely distributed and diverse group of fully aquatic placental marine mammals.
Whale sounds are used by whales for different kinds of communication.
Whiskers or vibrissae (singular: vibrissa) are a type of mammalian hair that are typically characterised, anatomically, by their large length, large and well-innervated hair follicle, and by having an identifiable representation in the somatosensory cortex of the brain.
The white-tailed deer (Odocoileus virginianus), also known as the whitetail or Virginia deer, is a medium-sized deer native to the United States, Canada, Mexico, Central America, and South America as far south as Peru and Bolivia.
The wild boar (Sus scrofa), also known as the wild swine,Heptner, V. G.; Nasimovich, A. A.; Bannikov, A. G.; Hoffman, R. S. (1988), Volume I, Washington, D.C.: Smithsonian Institution Libraries and National Science Foundation, pp.
Wild type (WT) refers to the phenotype of the typical form of a species as it occurs in nature.
The wild water buffalo (Bubalus arnee), also called Asian buffalo, Asiatic buffalo and wild Asian buffalo, is a large bovine native to the Indian Subcontinent and Southeast Asia.
Wombats are short-legged, muscular quadrupedal marsupials that are native to Australia.
Wool is the textile fiber obtained from sheep and other animals, including cashmere and mohair from goats, qiviut from muskoxen, angora from rabbits, and other types of wool from camelids.
The woolly mammoth (Mammuthus primigenius) is an extinct species of mammoth that lived during the Pleistocene epoch, and was one of the last in a line of mammoth species, beginning with Mammuthus subplanifrons in the early Pliocene.
A working animal is an animal, usually domesticated, that is kept by humans and trained to perform tasks.
The World Wide Fund for Nature (WWF) is an international non-governmental organization founded in 1961, working in the field of the wilderness preservation, and the reduction of human impact on the environment.
The superorder Xenarthra is a group of placental mammals, extant today only in the Americas and represented by anteaters, tree sloths, and armadillos.
Yinotheria is a proposed basal mammalian subclass clade that contains a few fossils of the Mesozoic and the extant monotremes.
Zebras are several species of African equids (horse family) united by their distinctive black and white striped coats.
Zoopharmacognosy is a behaviour in which non-human animals apparently self-medicate by selecting and ingesting or topically applying plants, soils, insects, and psychoactive drugs to prevent or reduce the harmful effects of pathogens and toxins.
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