Feathers are epidermal growths that form the distinctive outer covering, or plumage, on birds, other extinct species of dinosaurs, pterosaurs. They are considered the most complex integumentary structures found in vertebrates and a premier example of a complex evolutionary novelty, they are among the characteristics. Although feathers cover most of the bird's bodies, they arise only from certain well-defined tracts on the skin, they aid in flight, thermal insulation, waterproofing. In addition, coloration helps in protection. Plumology is the name for the science, associated with the study of feathers. Feathers are among the most complex integumentary appendages found in vertebrates and are formed in tiny follicles in the epidermis, or outer skin layer, that produce keratin proteins; the β-keratins in feathers and claws — and the claws and shells of reptiles — are composed of protein strands hydrogen-bonded into β-pleated sheets, which are further twisted and crosslinked by disulfide bridges into structures tougher than the α-keratins of mammalian hair and hoof.
The exact signals that induce the growth of feathers on the skin are not known, but it has been found that the transcription factor cDermo-1 induces the growth of feathers on skin and scales on the leg. There are two basic types of feather: vaned feathers which cover the exterior of the body, down feathers which are underneath the vaned feathers; the pennaceous feathers are vaned feathers. Called contour feathers, pennaceous feathers arise from tracts and cover the entire body. A third rarer type of feather, the filoplume, is hairlike and are associated with contour feathers and are entirely hidden by them, with one or two filoplumes attached and sprouting from near the same point of the skin as each contour feather, at least on a bird's head and trunk. In some passerines, filoplumes arise exposed beyond the contour feathers on the neck; the remiges, or flight feathers of the wing, rectrices, the flight feathers of the tail are the most important feathers for flight. A typical vaned feather features a main shaft, called the rachis.
Fused to the rachis are a series of branches, or barbs. These barbules have minute hooks called barbicels for cross-attachment. Down feathers are fluffy because they lack barbicels, so the barbules float free of each other, allowing the down to trap air and provide excellent thermal insulation. At the base of the feather, the rachis expands to form the hollow tubular calamus which inserts into a follicle in the skin; the basal part of the calamus is without vanes. This part is embedded within the skin follicle and has an opening at the base and a small opening on the side. Hatchling birds of some species have a special kind of natal down feathers which are pushed out when the normal feathers emerge. Flight feathers are stiffened so as to work against the air in the downstroke but yield in other directions, it has been observed that the orientation pattern of β-keratin fibers in the feathers of flying birds differs from that in flightless birds: the fibers are better aligned along the shaft axis direction towards the tip, the lateral walls of rachis region show structure of crossed fibers.
Feathers insulate birds from water and cold temperatures. They may be plucked to line the nest and provide insulation to the eggs and young; the individual feathers in the wings and tail play important roles in controlling flight. Some species have a crest of feathers on their heads. Although feathers are light, a bird's plumage weighs two or three times more than its skeleton, since many bones are hollow and contain air sacs. Color patterns serve as camouflage against predators for birds in their habitats, serve as camouflage for predators looking for a meal; as with fish, the top and bottom colors may be different, in order to provide camouflage during flight. Striking differences in feather patterns and colors are part of the sexual dimorphism of many bird species and are important in selection of mating pairs. In some cases there are differences in the UV reflectivity of feathers across sexes though no differences in color are noted in the visible range; the wing feathers of male club-winged manakins Machaeropterus deliciosus have special structures that are used to produce sounds by stridulation.
Some birds have a supply of powder down feathers which grow continuously, with small particles breaking off from the ends of the barbules. These particles produce a powder that sifts through the feathers on the bird's body and acts as a waterproofing agent and a feather conditioner. Powder down has evolved independently in several taxa and can be found in down as well as in pennaceous feathers, they may be scattered in plumage as in the pigeons and parrots or in localized patches on the breast, belly, or flanks, as in herons and frogmouths. Herons use their bill to break the powder down feathers and to spread them, while cockatoos may use their head as a powder puff to apply the powder. Waterproofing can be lost by exposure to emulsifying agents due to human pollution. Feathers can become waterlogged, causing the bird to sink, it is very difficult to clean and rescue birds whose feathers have been fouled by oil spills. The feathers of cormorants soak up water and help to reduce buoyancy, thereby allowing the birds to swim submerged.
Bristles are stiff. Rictal bristles are found around bill, they may serve a similar purpose to e
Predation is a biological interaction where one organism, the predator and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation and parasitoidism, it is distinct from scavenging on dead prey, though many predators scavenge. Predators may search for prey or sit and wait for it; when prey is detected, the predator assesses. This may involve pursuit predation, sometimes after stalking the prey. If the attack is successful, the predator kills the prey, removes any inedible parts like the shell or spines, eats it. Predators are adapted and highly specialized for hunting, with acute senses such as vision, hearing, or smell. Many predatory animals, both vertebrate and invertebrate, have sharp claws or jaws to grip and cut up their prey. Other adaptations include aggressive mimicry that improve hunting efficiency. Predation has a powerful selective effect on prey, the prey develop antipredator adaptations such as warning coloration, alarm calls and other signals, mimicry of well-defended species, defensive spines and chemicals.
Sometimes predator and prey find themselves in an evolutionary arms race, a cycle of adaptations and counter-adaptations. Predation has been a major driver of evolution since at least the Cambrian period. At the most basic level, predators eat other organisms. However, the concept of predation is broad, defined differently in different contexts, includes a wide variety of feeding methods. A parasitoid, such as an ichneumon wasp, lays its eggs on its host. Zoologists call this a form of parasitism, though conventionally parasites are thought not to kill their hosts. A predator can be defined to differ from a parasitoid in two ways: it kills its prey immediately. There are other borderline cases. Micropredators are small animals that, like predators, feed on other organisms. However, since they do not kill their hosts, they are now thought of as parasites. Animals that graze on phytoplankton or mats of microbes are predators, as they consume and kill their food organisms. However, when animals eat seeds or eggs, they are consuming entire living organisms, which by definition makes them predators, albeit unconventional ones: for instance, a mouse that eats grass seeds has no adaptations for tracking and subduing prey and its teeth are not adapted to slicing through flesh.
Scavengers, organisms that only eat organisms found dead, are not predators, but many predators such as the jackal and the hyena scavenge when the opportunity arises. Among invertebrates, social wasps are both scavengers of other insects. While examples of predators among mammals and birds are well known, predators can be found in a broad range of taxa, they are common among insects, including mantids, dragonflies and scorpionflies. In some species such as the alderfly, only the larvae are predatory. Spiders are predatory, as well as other terrestrial invertebrates such as scorpions. In marine environments, most cnidarians, ctenophora and flatworms are predatory. Among crustaceans, crabs and barnacles are predators, in turn crustaceans are preyed on by nearly all cephalopods. Seed predation is restricted to mammals and insects and is found in all terrestrial ecosystems. Egg predation includes both specialist egg predators such as some colubrid snakes and generalists such as foxes and badgers that opportunistically take eggs when they find them.
Some plants, like the pitcher plant, the Venus fly trap and the sundew, are carnivorous and consume insects. Some carnivorous fungi catch nematodes using either active traps in the form of constricting rings, or passive traps with adhesive structures. Many species of protozoa and bacteria prey on other microorganisms. Among freshwater and marine zooplankton, whether single-celled or multi-cellular, predatory grazing on phytoplankton and smaller zooplankton is common, found in many species of nanoflagellates, ciliates, rotifers, a diverse range of meroplankton animal larvae, two groups of crustaceans, namely copepods and cladocerans. To feed, a predator must search for and kill its prey; these actions form a foraging cycle. The predator must decide. If it chooses pursuit, its physical capabilities determine the mode of pursuit. Having captured the prey, it may need to expend energy handling it (e.g. killing it, removing any shell or
Reptiles are tetrapod animals in the class Reptilia, comprising today's turtles, snakes, lizards and their extinct relatives. The study of these traditional reptile orders combined with that of modern amphibians, is called herpetology; because some reptiles are more related to birds than they are to other reptiles, the traditional groups of "reptiles" listed above do not together constitute a monophyletic grouping or clade. For this reason, many modern scientists prefer to consider the birds part of Reptilia as well, thereby making Reptilia a monophyletic class, including all living Diapsids; the earliest known proto-reptiles originated around 312 million years ago during the Carboniferous period, having evolved from advanced reptiliomorph tetrapods that became adapted to life on dry land. Some early examples include Casineria. In addition to the living reptiles, there are many diverse groups that are now extinct, in some cases due to mass extinction events. In particular, the Cretaceous–Paleogene extinction event wiped out the pterosaurs, plesiosaurs and sauropods, as well as many species of theropods, including troodontids, dromaeosaurids and abelisaurids, along with many Crocodyliformes, squamates.
Modern non-avian reptiles inhabit all the continents except Antarctica, although some birds are found on the periphery of Antarctica. Several living subgroups are recognized: Testudines, 350 species. Reptiles are tetrapod vertebrates, creatures that either have four limbs or, like snakes, are descended from four-limbed ancestors. Unlike amphibians, reptiles do not have an aquatic larval stage. Most reptiles are oviparous, although several species of squamates are viviparous, as were some extinct aquatic clades – the fetus develops within the mother, contained in a placenta rather than an eggshell; as amniotes, reptile eggs are surrounded by membranes for protection and transport, which adapt them to reproduction on dry land. Many of the viviparous species feed their fetuses through various forms of placenta analogous to those of mammals, with some providing initial care for their hatchlings. Extant reptiles range in size from a tiny gecko, Sphaerodactylus ariasae, which can grow up to 17 mm to the saltwater crocodile, Crocodylus porosus, which can reach 6 m in length and weigh over 1,000 kg.
In the 13th century the category of reptile was recognized in Europe as consisting of a miscellany of egg-laying creatures, including "snakes, various fantastic monsters, assorted amphibians, worms", as recorded by Vincent of Beauvais in his Mirror of Nature. In the 18th century, the reptiles were, from the outset of classification, grouped with the amphibians. Linnaeus, working from species-poor Sweden, where the common adder and grass snake are found hunting in water, included all reptiles and amphibians in class "III – Amphibia" in his Systema Naturæ; the terms "reptile" and "amphibian" were interchangeable, "reptile" being preferred by the French. Josephus Nicolaus Laurenti was the first to formally use the term "Reptilia" for an expanded selection of reptiles and amphibians similar to that of Linnaeus. Today, the two groups are still treated under the same heading as herptiles, it was not until the beginning of the 19th century that it became clear that reptiles and amphibians are, in fact, quite different animals, Pierre André Latreille erected the class Batracia for the latter, dividing the tetrapods into the four familiar classes of reptiles, amphibians and mammals.
The British anatomist Thomas Henry Huxley made Latreille's definition popular and, together with Richard Owen, expanded Reptilia to include the various fossil "antediluvian monsters", including dinosaurs and the mammal-like Dicynodon he helped describe. This was not the only possible classification scheme: In the Hunterian lectures delivered at the Royal College of Surgeons in 1863, Huxley grouped the vertebrates into mammals and ichthyoids, he subsequently proposed the names of Ichthyopsida for the latter two groups. In 1866, Haeckel demonstrated that vertebrates could be divided based on their reproductive strategies, that reptiles and mammals were united by the amniotic egg; the terms "Sauropsida" and "Theropsida" were used again in 1916 by E. S. Goodrich to distinguish between lizards and their relatives on the one hand and mammals and their extinct relatives on the other. Goodrich supported this division by the nature of the hearts and blood vessels in each group, other features, such as the structure of the forebrain.
According to Goodrich, both lineages evolved from an earlier stem group, Protosauria in which he included some animals today considered reptile-like amphibians, as well as early reptiles. In 1956, D. M. S. Watson observed that the first two groups diverged early in reptilian history, so he divided Goodrich's Protosauria between them, he reinterpreted Sauropsida and Theropsida to exclude birds and mammals, respectively. Thus his Sauropsida included Procolophonia, Millerosauria, Squamata, Rhynchocephalia
The opossum is a marsupial of the order Didelphimorphia endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 103 or more species in 19 genera. Opossums originated in South America and entered North America in the Great American Interchange following the connection of the two continents, their unspecialized biology, flexible diet, reproductive habits make them successful colonizers and survivors in diverse locations and conditions. Although the animal is called a possum in North America, which would refer to the Virginia opossum species, it should not be confused with the suborder Phalangeriformes, which are arboreal marsupials in the Eastern Hemisphere called "possums" because of their resemblance to Didelphimorphia; the word "opossum" is borrowed from the Powhatan language and was first recorded between 1607 and 1611 by John Smith and William Strachey. Both men encountered the language at the British settlement of Jamestown, which Smith helped to found and where Strachey served as its first secretary.
Strachey's notes describe the opossum as a "beast in bigness of a pig and in taste alike," while Smith recorded it "hath an head like a swine... tail like a rat... of the bigness of a cat." The Powhatan word derives from a Proto-Algonquian word meaning "white dog or dog-like beast."Following the arrival of Europeans in Australia, the term "possum" was borrowed to describe distantly related Australian marsupials of the suborder Phalangeriformes, which are more related to other Australian marsupials such as kangaroos. "Didelphimorphia" refers to the fact. Didelphimorphs are small to medium-sized marsupials, they tend to be semi-arboreal omnivores. Most members of this taxon have long snouts, a narrow braincase, a prominent sagittal crest; the dental formula is: 188.8.131.52.1.3.4 × 2 = 50 teeth. By mammalian standards, this is an unusually full jaw; the incisors are small, the canines large, the molars are tricuspid. Didelphimorphs have a plantigrade stance and the hind feet have an opposable digit with no claw.
Like some New World monkeys, opossums have prehensile tails. Like that of all marsupials, the fur consists of awn hair only, the females have a pouch; the tail and parts of the feet bear scutes. The stomach is simple, with a small cecum. Like most marsupials, the male opossum has a forked penis bearing twin glandes. Although all living opossums are opportunistic omnivores, different species vary in the amount of meat and vegetation they include in their diet. Members of the Caluromyinae are frugivorous; the yapok is unusual, as it is the only living semi-aquatic marsupial, using its webbed hindlimbs to dive in search of freshwater mollusks and crayfish. The extinct Thylophorops, the largest known opossum at 4–7 kg, was a macropredator. Most opossums are scansorial, well-adapted to life in the trees or on the ground, but members of the Caluromyinae and Glironiinae are arboreal, whereas species of Metachirus, to a lesser degree Didelphis show adaptations for life on the ground; the Metachirus nudicaudatus, found in the upper Amazon basin, consumes fruit seeds, small vertebrate creatures like birds and reptiles and invertebrates like crayfish and snails, but seems to be most insectivorous.
As a marsupial, the female opossum has a reproductive system that includes a bifurcated vagina, a divided uterus and a marsupium, her pouch. The average estrous cycle of the opossum is about 28 days. Opossums do possess a placenta, but it is short-lived, simple in structure, unlike that of placental mammals, not functional; the young are therefore born at a early stage, although the gestation period is similar to that of many other small marsupials, at only 12 to 14 days. Once born, the offspring must find their way into the marsupium to hold on to and nurse from a teat. Baby opossums, like their Australian cousins, are called joeys. Female opossums give birth to large numbers of young, most of which fail to attach to a teat, although as many as thirteen young can attach, therefore survive, depending on species; the young are weaned between 125 days, when they detach from the teat and leave the pouch. The opossum lifespan is unusually short for a mammal of its size only one to two years in the wild and as long as four or more years in captivity.
Senescence is rapid. The species are moderately sexually dimorphic with males being larger, much heavier, having larger canines than females; the largest difference between the opossum and non-marsupial mammals is the bifurcated penis of the male and bifurcated vagina of the female. Opossum spermatozoa exhibit sperm-pairing; this may ensure that flagella movement can be coordinated for maximal motility. Conjugate pairs dissociate into separate spermatozoa before fertilization. Opossums are solitary and nomadic, staying in one area as long as food and water are available; some families will group together in ready-made burrows or under houses. Though they will temporarily occupy abandoned burrows, they do not dig or put much effort into building their own; as nocturnal animals, they favor secure areas. These areas may be below ground or above; when threatened or harmed, they will "play possum", mimicking the app
Rats are various medium-sized, long-tailed rodents. Species of rats are found throughout the order Rodentia, but stereotypical rats are found in the genus Rattus. Other rat genera include Neotoma and Dipodomys. Rats are distinguished from mice by their size; when someone discovers a large muroid rodent, its common name includes the term rat, while if it is smaller, its name includes the term mouse. The common terms rat and mouse are not taxonomically specific. In other words, rat is not a scientific term; the best-known rat species are the brown rat. This group known as the Old World rats or true rats, originated in Asia. Rats are bigger than most Old World mice, which are their relatives, but weigh over 500 grams in the wild; the term rat is used in the names of other small mammals that are not true rats. Examples include the North American pack rats, a number of species loosely called kangaroo rats, others. Rats such as the bandicoot rat are murine rodents related to true rats but are not members of the genus Rattus.
Male rats are called bucks. A group of rats is referred to as a mischief; the common species are opportunistic survivors and live with and near humans. They may cause substantial food losses in developing countries. However, the distributed and problematic commensal species of rats are a minority in this diverse genus. Many species of rats are island endemics, some of which have become endangered due to habitat loss or competition with the brown, black, or Polynesian rat. Wild rodents, including rats, can carry many different zoonotic pathogens, such as Leptospira, Toxoplasma gondii, Campylobacter; the Black Death is traditionally believed to have been caused by the microorganism Yersinia pestis, carried by the tropical rat flea, which preyed on black rats living in European cities during the epidemic outbreaks of the Middle Ages. Another zoonotic disease linked to the rat is foot-and-mouth disease. Rats become sexually reach social maturity at about 5 to 6 months of age; the average lifespan of rats varies by species.
The black and brown rats diverged from other Old World rats in the forests of Asia during the beginning of the Pleistocene. The characteristic long tail of most rodents is a feature, extensively studied in various rat species models, which suggest three primary functions of this structure: thermoregulation, minor proprioception, a nocifensive-mediated degloving response. Rodent tails—particularly in rat models—have been implicated with a thermoregulation function that follows from its anatomical construction; this particular tail morphology is evident across the family Muridae, in contrast to the bushier tails of Sciuridae, the squirrel family. The tail is hairless and thin skinned but vascularized, thus allowing for efficient countercurrent heat exchange with the environment; the high muscular and connective tissue densities of the tail, along with ample muscle attachment sites along its plentiful caudal vertebrae, facilitate specific proprioceptive senses to help orient the rodent in a three-dimensional environment.
Lastly, murids have evolved a unique defense mechanism termed degloving that allows for escape from predation through the loss of the outermost integumentary layer on the tail. However, this mechanism is associated with multiple pathologies that have been the subject of investigation. Multiple studies have explored the thermoregulatory capacity of rodent tails by subjecting test organisms to varying levels of physical activity and quantifying heat conduction via the animals' tails. One study demonstrated a significant disparity in heat dissipation from a rat's tail relative to its abdomen; this observation was attributed to the higher proportion of vascularity in the tail, as well as its higher surface-area-to-volume ratio, which directly relates to heat's ability to dissipate via the skin. These findings were confirmed in a separate study analyzing the relationships of heat storage and mechanical efficiency in rodents that exercise in warm environments. In this study, the tail was a focal point in measuring heat modulation.
On the other hand, the tail's ability to function as a proprioceptive sensor and modulator has been investigated. As aforementioned, the tail demonstrates a high degree of muscularization and subsequent innervation that ostensibly collaborate in orienting the organism; this is accomplished by coordinated flexion and extension of tail muscles to produce slight shifts in the organism's center of mass, etc. which assists it with achieving a state of proprioceptive balance in its environment. Further mechanobiological investigations of the constituent tendons in the tail of the rat have identified multiple factors that influence how the organism navigates its environment with this structure. A particular example is that of a study in which the morphology of these tendons is explicated in detail. Namely, cell viability tests of tendons of the rat's tail demonstrate a higher proportion of living fibroblasts that produce the collagen for these fibers; as in humans, these tendons contain a high density of golgi tendon organs that help the animal assess stretching of muscle in situ and adjust accordingly by relaying the information to higher cortical areas associated with balance and movement.
Mammals are vertebrate animals constituting the class Mammalia, characterized by the presence of mammary glands which in females produce milk for feeding their young, a neocortex, fur or hair, three middle ear bones. These characteristics distinguish them from reptiles and birds, from which they diverged in the late Triassic, 201–227 million years ago. There are around 5,450 species of mammals; the largest orders are the rodents and Soricomorpha. The next three are the Primates, the Cetartiodactyla, the Carnivora. In cladistics, which reflect evolution, mammals are classified as endothermic amniotes, they are the only living Synapsida. The early synapsid mammalian ancestors were sphenacodont pelycosaurs, a group that produced the non-mammalian Dimetrodon. At the end of the Carboniferous period around 300 million years ago, this group diverged from the sauropsid line that led to today's reptiles and birds; the line following the stem group Sphenacodontia split off several diverse groups of non-mammalian synapsids—sometimes referred to as mammal-like reptiles—before giving rise to the proto-mammals in the early Mesozoic era.
The modern mammalian orders arose in the Paleogene and Neogene periods of the Cenozoic era, after the extinction of non-avian dinosaurs, have been among the dominant terrestrial animal groups from 66 million years ago to the present. The basic body type is quadruped, most mammals use their four extremities for terrestrial locomotion. Mammals range in size from the 30–40 mm bumblebee bat to the 30-meter blue whale—the largest animal on the planet. Maximum lifespan varies from two years for the shrew to 211 years for the bowhead whale. All modern mammals give birth to live young, except the five species of monotremes, which are egg-laying mammals; the most species-rich group of mammals, the cohort called placentals, have a placenta, which enables the feeding of the fetus during gestation. Most mammals are intelligent, with some possessing large brains, self-awareness, tool use. Mammals can communicate and vocalize in several different ways, including the production of ultrasound, scent-marking, alarm signals and echolocation.
Mammals can organize themselves into fission-fusion societies and hierarchies—but can be solitary and territorial. Most mammals are polygynous. Domestication of many types of mammals by humans played a major role in the Neolithic revolution, resulted in farming replacing hunting and gathering as the primary source of food for humans; this led to a major restructuring of human societies from nomadic to sedentary, with more co-operation among larger and larger groups, the development of the first civilizations. Domesticated mammals provided, continue to provide, power for transport and agriculture, as well as food and leather. Mammals are hunted and raced for sport, are used as model organisms in science. Mammals have been depicted in art since Palaeolithic times, appear in literature, film and religion. Decline in numbers and extinction of many mammals is driven by human poaching and habitat destruction deforestation. Mammal classification has been through several iterations since Carl Linnaeus defined the class.
No classification system is universally accepted. George Gaylord Simpson's "Principles of Classification and a Classification of Mammals" provides systematics of mammal origins and relationships that were universally taught until the end of the 20th century. Since Simpson's classification, the paleontological record has been recalibrated, the intervening years have seen much debate and progress concerning the theoretical underpinnings of systematization itself through the new concept of cladistics. Though field work made Simpson's classification outdated, it remains the closest thing to an official classification of mammals. Most mammals, including the six most species-rich orders, belong to the placental group; the three largest orders in numbers of species are Rodentia: mice, porcupines, beavers and other gnawing mammals. The next three biggest orders, depending on the biological classification scheme used, are the Primates including the apes and lemurs. According to Mammal Species of the World, 5,416 species were identified in 2006.
These were grouped into 153 families and 29 orders. In 2008, the International Union for Conservation of Nature completed a five-year Global Mammal Assessment for its IUCN Red List, which counted 5,488 species. According to a research published in the Journal of Mammalogy in 2018, the number of recognized mammal species is 6,495 species included 96 extinct; the word "mammal" is modern, from the scientific name Mammalia coined by Carl Linnaeus in 1758, derived from the Latin mamma. In an influential 1988 paper, Timothy Rowe defined Mammalia phylogenetically as the crown group of mammals, the clade consisting of the most recent common ancestor of living monotremes and therian m
The lion is a species in the family Felidae. The lion is sexually dimorphic. Male lions have a prominent mane, the most recognisable feature of the species. A lion pride consists of related females and cubs. Groups of female lions hunt together, preying on large ungulates; the species is an keystone predator, although they scavenge when opportunities occur. Some lions have been known to hunt humans, although the species does not; the lion inhabits grasslands and savannas but is absent in dense forests. It is more diurnal than other big cats, but when persecuted it adapts to being active at night and at twilight. In the Pleistocene, the lion ranged throughout Eurasia and North America but today it has been reduced to fragmented populations in Sub-Saharan Africa and one critically endangered population in western India, it has been listed as Vulnerable on the IUCN Red List since 1996 because populations in African countries have declined by about 43% since the early 1990s. Lion populations are untenable outside designated protected areas.
Although the cause of the decline is not understood, habitat loss and conflicts with humans are the greatest causes for concern. One of the most recognised animal symbols in human culture, the lion has been extensively depicted in sculptures and paintings, on national flags, in contemporary films and literature. Lions have been kept in menageries since the time of the Roman Empire and have been a key species sought for exhibition in zoological gardens across the world since the late 18th century. Cultural depictions of lions were prominent in the Upper Paleolithic period; the lion's name, similar in many Romance languages, is derived from Latin: leo and Ancient Greek: λέων. The word lavi may be related. Felis leo was the scientific name used by Carl Linnaeus in 1758, who described the lion in his work Systema Naturae; the genus name Panthera was coined by German naturalist Lorenz Oken in 1816. Between the mid-18th and mid-20th centuries, 26 lion specimens were described and proposed as subspecies, of which 11 were recognised as valid in 2005.
They were distinguished on the basis of appearance and colour of mane. Because these characteristics show much variation between individuals, most of these forms were not true subspecies because they were based upon museum material with "striking, but abnormal" morphological characteristics. Based on the morphology of 58 lion skulls in three European museums, the subspecies krugeri, nubica and senegalensis were assessed distinct but bleyenberghi overlapped with senegalensis and krugeri; the Asiatic lion persica was the most distinctive and the Cape lion had characteristics allying it more with persica than the other sub-Saharan lions. The lion's closest relatives are the other species of the genus Panthera. Results of phylogenetic studies published in 2006 and 2009 indicate that the jaguar and the lion belong to one sister group that diverged about 2.06 million years ago. Results of studies published in 2010 and 2011 indicate that the leopard and the lion belong to the same sister group, which diverged between 1.95 and 3.10 million years ago.
Hybridisation between lion and snow leopard ancestors, may have continued until about 2.1 million years ago. In the 19th and 20th centuries, several lion type specimens were described and proposed as subspecies, with about a dozen recognised as valid taxa until 2017. Between 2008 and 2016, IUCN Red List assessors used only two subspecific names: P. l. leo for African lion populations and P. l. persica for the Asiatic lion population. In 2017, the Cat Classification Task Force of the Cat Specialist Group revised lion taxonomy, recognises two subspecies based on results of several phylogeographic studies on lion evolution, namely: P. l. leo − the nominate lion subspecies includes the Asiatic lion, the regionally extinct Barbary lion, lion populations in West and northern parts of Central Africa. Synonyms include P. l. persica, P. l. senegalensis, P. l. kamptzi, P. l. azandica. Some authors referred to it as'Northern lion' and'northern subspecies'. P. l. melanochaita − includes the extinct Cape lion and lion populations in East and Southern African regions.
Synonyms include P. l. somaliensis, P. l. massaica, P. l. sabakiensis, P. l. bleyenberghi, P. l. roosevelti, P. l. nyanzae, P. l. hollisteri, P. l. krugeri, P. l. vernayi, P. l. webbiensis. It has been referred to as'southern subspecies'. Early phylogenetic research was focused on East and Southern African lions, showed they can be divided in two main clades. Lions in eastern Kenya are genetically much closer to lions in Southern Africa than to lions in Aberdare National Park in western Kenya. In a subsequent study and bone samples of 32 lion specimens in museums were used. Results indicated lions form