Omnivore in the context of Kea

A hunter-gatherer or forager is a human living in a community, or according to an ancestrally derived lifestyle, in which most or all food is obtained by foraging, that is, by gathering food from local naturally occurring sources or by hunting game. This is a common practice among most vertebrates that are omnivores. Hunter-gatherer groups, usually a few dozen people, were and are nomadic or semi-nomadic. Hunter-gatherer societies are contrasted with more sedentary agricultural societies, which rely mainly on cultivating crops and raising domesticated animals for food production.

Hunting and gathering emerged with Homo erectus about 1.8 million years ago and was humanity's original and most enduring successful competitive adaptation in the natural world, occupying at least 90 percent of human (pre)history. Following the invention of agriculture, hunter-gatherers who did not change were displaced or conquered by farming or pastoralist groups in most parts of the world. In Western Eurasia, farming and metallurgical societies gradually replaced hunter-gatherers, but dense forests remained their last refuge until Bronze and Iron Age societies fully overcame them.

The black rat (Rattus rattus), also known as the roof rat, ship rat, or house rat, is a common long-tailed rodent of the stereotypical rat genus Rattus, in the subfamily Murinae. It likely originated in the Indian subcontinent, but is now found worldwide.

The black rat is black to light brown in colour with a lighter underside. It is a generalist omnivore and a serious pest to farmers because it feeds on a wide range of agricultural crops. It is sometimes kept as a pet. In parts of India, it is considered sacred and respected in the Karni Mata Temple in Deshnoke.

Food is any substance consumed by an organism for nutritional support. Food is usually of plant, animal, or fungal origin and contains essential nutrients such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is ingested by an organism and assimilated by the organism's cells to provide energy, maintain life, or support growth. Different species of animals have different feeding behaviours that satisfy the needs of their metabolisms and have evolved to fill specific ecological niches within specific geographical contexts.

Omnivorous humans are highly adaptable and have adapted to obtaining food in many different ecosystems. Humans generally use cooking to prepare food for consumption. The majority of the food energy required is supplied by the industrial food industry, which produces food through intensive agriculture and distributes it through complex food processing and food distribution systems. This system of conventional agriculture relies heavily on fossil fuels, which means that the food and agricultural systems are one of the major contributors to climate change, accounting for as much as 37% of total greenhouse gas emissions.

Theropoda (/θɪəˈrɒpədə/; from ancient Greek θηρίο- ποδός [θηρίον, (therion) "wild beast"; πούς, ποδός (pous, podos) "foot"]) is one of the three major clades of dinosaur, alongside Ornithischia and Sauropodomorpha. Theropods, both extant and extinct, are characterized by hollow bones and three toes and claws on each limb. They are generally classed as a group of saurischian dinosaurs, placing them closer to sauropodomorphs than to ornithischians. They were ancestrally carnivorous, although a number of theropod groups evolved to become herbivores and omnivores. Members of the subgroup Coelurosauria were most likely all covered with feathers, and it is possible that they were also present in other theropods. In the Jurassic, birds evolved from small specialized coelurosaurian theropods, and are currently represented by about 11,000 living species, making theropods the only group of dinosaurs alive today.

Theropods first appeared during the Carnian age of the Late Triassic period 231.4 million years ago (Ma) and included the majority of large terrestrial carnivores from the Early Jurassic until the end of the Cretaceous, about 66 Ma, including the largest terrestrial carnivorous animals ever, such as Tyrannosaurus and Giganotosaurus, though non-avian theropods exhibited considerable size diversity, with some non-avian theropods like scansoriopterygids being no bigger than small birds.

Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the host) and parasitoidism (which always does, eventually). It is distinct from scavenging on dead prey, though many predators also scavenge; it overlaps with herbivory, as seed predators and destructive frugivores are predators.

Predation behaviour varies significantly depending on the organism. Many predators, especially carnivores, have evolved distinct hunting strategies. Pursuit predation involves the active search for and pursuit of prey, whilst ambush predators instead wait for prey to present an opportunity for capture, and often use stealth or aggressive mimicry. Other predators are opportunistic or omnivorous and only practice predation occasionally.

Crabs are decapod crustaceans, either the Brachyura (the "true crabs") or various groups within the closely related Anomura, characterised by having a heavily armoured shell, their tail segments concealed under the body, the ability to run sideways, and the habit of hiding in rocky crevices. They do not form a single natural group or clade, but have convergently evolved multiple times from the ancestral decapod body plan through the process of carcinisation. As a group they are thus polyphyletic.

Crabs vary in size from the pea crab, a few millimeters wide, to the Japanese spider crab, with a leg span up to 4 m (13 ft). Many crabs are free-living marine omnivores; others are specialist herbivores or carnivores, while some are parasitic. A substantial number of species are adapted to freshwater or other non-marine habitats.

Paranthropus is a genus of extinct hominin which contains two widely accepted species: P. robustus and P. boisei. However, the validity of Paranthropus is contested, and it is sometimes considered to be synonymous with Australopithecus. They are also referred to as the robust australopithecines. They lived between approximately 2.9 and at least 1 million years ago (mya) from the end of the Pliocene to the Middle Pleistocene.

Paranthropus is characterised by robust skulls, with a prominent gorilla-like sagittal crest along the midline—which suggest strong chewing muscles—and broad, herbivorous teeth used for grinding. However, they likely preferred soft food over tough and hard food. Typically, Paranthropus species were generalist feeders, but while P. robustus was likely an omnivore, P. boisei seems to have been herbivorous, possibly preferring abundant bulbotubers. Paranthropoids were bipeds. Despite their robust heads, they had comparatively small bodies. Average weight and height are estimated to be 40 kg (88 lb) at 132 cm (4 ft) for P. robustus males, 50 kg (110 lb) at 137 cm (4 ft 6 in) for P. boisei males, 32 kg (71 lb) at 110 cm (3 ft 7 in) for P. robustus females, and 34 kg (75 lb) at 124 cm (4 ft 1 in) for P. boisei females.

Vitamin A is a fat-soluble vitamin that is an essential nutrient. The term "vitamin A" encompasses a group of chemically related organic compounds that includes retinol, retinyl esters, and several provitamin (precursor) carotenoids, most notably β-carotene (beta-carotene). Vitamin A has multiple functions: growth during embryo development, maintaining the immune system, and healthy vision. For aiding vision specifically, it combines with the protein opsin to form rhodopsin, the light-absorbing molecule necessary for both low-light (scotopic vision) and color vision.

Vitamin A occurs as two principal forms in foods: A) retinoids, found in animal-sourced foods, either as retinol or bound to a fatty acid to become a retinyl ester, and B) the carotenoids α-carotene (alpha-carotene), β-carotene, γ-carotene (gamma-carotene), and the xanthophyll beta-cryptoxanthin (all of which contain β-ionone rings) that function as provitamin A in herbivore and omnivore animals which possess the enzymes that cleave and convert provitamin carotenoids to retinol. Some carnivore species lack this enzyme. The other carotenoids do not have retinoid activity.

Turtles (order Testudines) are reptiles characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked turtles), which differ in the way the head retracts. There are 360 living and recently extinct species of turtles, including land-dwelling tortoises and freshwater terrapins. They are found on most continents, some islands and, in the case of sea turtles, much of the ocean. Like other amniotes (reptiles, birds, and mammals) they breathe air and do not lay eggs underwater, although many species live in or around water.

Turtle shells are made mostly of bone; the upper part is the domed carapace, while the underside is the flatter plastron or belly-plate. Its outer surface is covered in scales made of keratin, the material of hair, horns, and claws. The carapace bones develop from ribs that grow sideways and develop into broad flat plates that join up to cover the body. Turtles are ectotherms or "cold-blooded", meaning that their internal temperature varies with their direct environment. They are generally opportunistic omnivores and mainly feed on plants and animals with limited movement. Many turtles migrate short distances seasonally. Sea turtles are the only reptiles that migrate long distances to lay their eggs on a favored beach.

Human food is food which is fit for human consumption, and which humans willingly eat. Food is a basic necessity of life, and humans typically seek food out as an instinctual response to hunger; however, not all things that are edible constitute as human food.

Humans eat various substances for energy, enjoyment and nutritional support. These are usually of plant, animal, or fungal origin, and contain essential nutrients, such as carbohydrates, fats, proteins, vitamins, and minerals. Humans are highly adaptable omnivores, and have adapted to obtain food in many different ecosystems. Historically, humans secured food through two main methods: hunting and gathering and agriculture. As agricultural technologies improved, humans settled into agriculture lifestyles with diets shaped by the agriculture opportunities in their region of the world. Geographic and cultural differences have led to the creation of numerous cuisines and culinary arts, including a wide array of ingredients, herbs, spices, techniques, and dishes. As cultures have mixed through forces like international trade and globalization, ingredients have become more widely available beyond their geographic and cultural origins, creating a cosmopolitan exchange of different food traditions and practices.

A tooth (pl.: teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tearing food, for defensive purposes, to intimidate other animals often including their own, or to carry prey or their young. The roots of teeth are covered by gums. Teeth are not made of bone, but rather of multiple tissues of varying density and hardness that originate from the outermost embryonic germ layer, the ectoderm.

The general structure of teeth is similar across the vertebrates, although there is considerable variation in their form and position. The teeth of mammals have deep roots, and this pattern is also found in some fish, and in crocodilians. In most teleost fish, however, the teeth are attached to the outer surface of the bone, while in lizards they are attached to the inner surface of the jaw by one side. In cartilaginous fish, such as sharks, the teeth are attached by tough ligaments to the hoops of cartilage that form the jaw.

The pig (Sus domesticus), also called swine (pl.: swine) or hog, is an omnivorous, domesticated, even-toed, hoofed mammal. It is named the domestic pig when distinguishing it from other members of the genus Sus. Some authorities consider it a subspecies of Sus scrofa (the wild boar or Eurasian boar); other authorities consider it a distinct species. Pigs were domesticated in the Neolithic, both in China and in the Near East (around the Tigris Basin). When domesticated pigs arrived in Europe, they extensively interbred with wild boar but retained their domesticated features.

Pigs are farmed primarily for meat, called pork. The animal's skin or hide is used for leather. China is the world's largest pork producer, followed by the European Union and then the United States. Around 1.5 billion pigs are raised each year, producing some 120 million tonnes of meat, often cured as bacon. Some are kept as pets.

Eating (also known as consuming) is the ingestion of food. In biology, this is typically done to provide a heterotrophic organism with energy and nutrients and to allow for growth. Animals and other heterotrophs must eat in order to survive – carnivores eat other animals, herbivores eat plants, omnivores consume a mixture of both plant and animal matter, and detritivores eat detritus. Fungi digest organic matter outside their bodies as opposed to animals that digest their food inside their bodies.

For humans, eating is more complex, but is typically an activity of daily living. Physicians and dieticians consider a healthful diet essential for maintaining peak physical condition. Some individuals may limit their amount of nutritional intake. This may be a result of a lifestyle choice: as part of a diet or as religious fasting. Limited consumption may be due to hunger or famine. Overconsumption of calories may lead to obesity and the reasons behind it are myriad, however, its prevalence has led some to declare an "obesity epidemic".