Kennel Clubs maintain breed standards, record pedigrees, and issue the rules for conformation dog shows and trials and accreditation of judges. They often serve as registries, which are lists of adult purebred dogs and lists of litters of puppies born to purebred parents. A kennel club manages all these aspects of the dog breeds it claims to represent, either directly or through its member bodies.

• Crocodilia (crocodiles, gharials, caimans and alligators): 23 species
• Sphenodontia (tuataras from New Zealand): 2 species
• Squamata (lizards, snakes and amphisbaenids (“worm-lizards”)): approximately 7,900 species
• Testudines (turtles and tortoises): approximately 300 species

Modern reptiles inhabit every continent except for Antarctica, although their main distribution comprises the tropics and subtropics. Though all cellular metabolism produces some heat, most modern species of reptiles do not generate enough to maintain a constant body temperature and are thus referred to as “cold-blooded” or ectothermic (the Leatherback Sea Turtle might be an exception, see also gigantothermy). Instead, they rely on gathering and losing heat from the environment to regulate their internal temperature, e.g, by moving between sun and shade, or by preferential circulation . moving warmed blood into the body core, while pushing cool blood to the periphery.

In their natural habitats, most species are adept at this, and can usually maintain core body temperatures within a fairly narrow range. Reptiles are thick-skinned; unlike amphibians, they do not need to absorb water. While this lack of adequate internal heating imposes costs relative to temperature regulation through behavior, it also provides a large benefit by allowing reptiles to survive on much less food than comparably-sized mammals and birds, who burn much of their food for warmth. While warm-blooded animals move faster in general, an attacking lizard, snake or crocodile moves very quickly.

Horses have long been among the most economically important domesticated animals; however their importance has declined with the introduction of mechanization. The horse is a prominent figure in the ideals of religion, mythology, and art and plays an important role in transportation, agriculture, and warfare. Horses also serve as a source of food, fuel, and clothing.

Most breeds of horses are able to perform work such as carrying humans on their backs or be harnessed to pull objects such as carts or plows. However, horse breeds were developed to allow horses to be specialized for certain tasks; lighter horses for racing or riding, heavier horses for farming and other tasks requiring pulling power. Some horses, such as the miniature horse, can be kept as pets. In some societies, horses are a source of food, both meat and milk; in others it is taboo to consume them. In industrialized countries, horses are predominantly kept for leisure and sporting pursuits, while in other parts of the world they are used as working animals.

Because horses and humans have lived and worked together for thousands of years, an extensive specialized vocabulary has arisen to describe virtually every horse behavioral and anatomical characteristic with a high degree of precision.

The dog has developed into hundreds of varied breeds. Height measured to the withers ranges from a few inches in the Chihuahua to a few feet in the Irish Wolfhound; color varies from white through grays (usually called blue) to black, and browns from light (tan) to dark (“red” or “chocolate”) in a wide variation of patterns; and, coats can be very short to several centimeters long, from coarse hair to something akin to wool, straight or curly, or smooth.

Similarly as with its teeth, a cat’s digestive tract has become specialized over time to suit its diet, having shortened in length to only those segments of intestine best able to break down proteins and fats from animal flesh. The evolved trait severely limits the cat’s ability to properly digest, metabolize, and absorb plant-derived or synthesized nutrients, as well as certain fatty acids. For example, cats cannot convert the pro-vitamin A abundant in plants, to make vitamin A. Also, a number of required nutrients are not sufficiently available in plant matter to begin with; one critical absence is taurine, a key amino sulfonic acid for eye health. Taurine deficiency can cause a condition called macular degeneration wherein the cat’s retina slowly degenerates, eventually causing irreversible blindness.

Due to the above, most felines eat fairly little if any plantstuffs. Yet it is nevertheless quite common for a cat to occasionally supplement its carnivorous diet with small amounts of grass, leaves, shrubs, houseplants, or other plant matter anyway. One theory suggests this behaviour is to facilitate regurgitation if their digestion is upset; another is that it perhaps introduces fibre or trace minerals to the diet. In this context, caution is recommended for cat owners because some houseplants are harmful to cats. The leaves of the Easter Lily can cause permanent and life-threatening kidney damage to cats. Philodendron are also poisonous to cats. Cat Fancy has a full list of plants harmful to cats.

As an exception to the general rule, certain domesticated cats are known to like vegetables. This happenstance may inspire some vegetarian or vegan pet owners to encourage or even impose their own dietary preferences upon their cats, often using commercially-available cat foods supplemented with chemically-synthesized taurine and other added nutrients to address nutritional shortfalls. However, it remains arguable as to whether or not such a vegetarian diet can in fact meet a cat’s dietary requirements.

Additionally, cats have been known to develop a fondness for prepared human foods, normally such entrees which are rich in proteins or fats. However, a diet consisting only of human food (even if high quality meat) is unlikely to contain the balanced nutrition required by the cat. Cats normally are good self-regulators of diet; however, unlimited access to food, or excessive human-food ‘treats’, will often lead to the cat becoming obese, particularly if it is older or more sedentary. This may lead to several health complications, such as diabetes, especially in neutered males. Such health conditions can be prevented through diet and exercise (playing), especially for cats living exclusively indoors.

Cats can be fussy eaters (which may be due in some way to the aforementioned mutation which caused their species to lose sugar-tasting ability). Unlike most mammals, cats can voluntarily starve themselves indefinitely despite being presented with palatable food, even a food which they had previously readily consumed. This can happen when the vomeronasal or Jacobson’s organ becomes accustomed to a specific food, or if the cats are spoiled by their owners, in which case the cat will reject any food that does not fit the pattern it is expecting. It is also known for cats to merely become bored with their given food and decide to stop eating until they are tempted into eating again. Although it is extremely rare for a cat to deliberately starve itself to the point of injury, the sudden loss of weight can cause a fatal condition called hepatic lipidosis, a liver dysfunction which causes pathological loss of appetite and reinforces the starvation, which can lead to death within as little as 48 hours.

Some cats have a fondness for catnip, which is sensed by their olfactory systems. While they generally do not consume it, they will often roll in it, paw at it, and occasionally chew on it. The effect is usually relatively short, lasting for only a few minutes. After two hours or less, susceptible cats gain interest again. Several other species of plants (such as mint) cause this effect, to a lesser degree.

Cats can also develop pica. Pica is a condition in which animals chew or eat unusual things such as fabric, plastic or wool. In cats, this is mostly harmless as they do not digest most of it, but can be fatal or require surgical removal if a large amount of foreign material is ingested (for example, an entire sock). It tends to occur more often in Burmese, Oriental, Siamese and breeds with these in their ancestry.

Modern birds are characterised by feathers, a beak with no teeth, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a lightweight but strong skeleton. All birds have forelimbs modified as wings and most can fly, though the ratites and several others, particularly endemic island species, have lost the ability to fly. Birds also have unique digestive and respiratory systems that are highly adapted for flight.

Many species of bird undertake long distance annual migrations, and many more perform shorter irregular movements. Birds are social and communicate using visual signals and through calls and song, and participate in social behaviours including cooperative hunting, cooperative breeding, flocking and mobbing of predators. The vast majority of bird species are socially monogamous, usually one breeding season at a time, sometimes for years, and rarely for life. Other species have breeding systems that are polygynous (“many females”) or, rarely, polyandrous (“many males”). Among some monogamous species, extra-pair copulations are common. Eggs are usually laid in a nest and incubated and most birds have an extended period of parental care after hatching.

Birds are economically important to humans: many are important sources of food, acquired either through hunting or farming, and they provide other products. Some species, particularly songbirds and parrots, are popular as pets. Birds figure prominently in all aspects of human culture from religion to poetry and popular music. About 120.130 species have become extinct as a result of human activity since 1600, and hundreds more before this. Currently around 1,200 species of birds are threatened with extinction by human activities and efforts are underway to protect them.