WORLD OF ANIMALS. Funny anf Cute Dogs. Nice and Lovely Puppies
The domestic dog (Canis lupus familiaris or Canis familiaris) is a member of genus Canis (canines) that forms part of the wolf-like canids, and is the most widely abundant carnivore. The dog and the extant gray wolf are sister taxa, with modern wolves not closely related to the wolves that were first domesticated. The dog was the first domesticated species and has been selectively bred over millennia for various behaviors, sensory capabilities, and physical attributes.
Their long association with humans has led dogs to be uniquely attuned to human behavior and they are able to thrive on a starch-rich diet that would be inadequate for other canid species. Dogs vary widely in shape, size and colours. Dogs perform many roles for people, such as hunting, herding, pulling loads, protection, assisting police and military, companionship and, more recently, aiding handicapped individuals. This influence on human society has given them the sobriquet “man’s best friend”.
Domestic dogs have been selectively bred for millennia for various behaviors, sensory capabilities, and physical attributes. Modern dog breeds show more variation in size, appearance, and behavior than any other domestic animal. Dogs are predators and scavengers, and like many other predatory mammals, the dog has powerful muscles, fused wrist bones, a cardiovascular system that supports both sprinting and endurance, and teeth for catching and tearing.
Dogs are highly variable in height and weight. The smallest known adult dog was a Yorkshire Terrier, that stood only 6.3 cm (2.5 in) at the shoulder, 9.5 cm (3.7 in) in length along the head-and-body, and weighed only 113 grams (4.0 oz). The largest known dog was an English Mastiff which weighed 155.6 kg (343 lb) and was 250 cm (98 in) from the snout to the tail. The tallest dog is a Great Dane that stands 106.7 cm (42.0 in) at the shoulder.
Despite their close genetic relationship and the ability to inter-breed, there are a number of diagnostic features to distinguish the gray wolves from domestic dogs. Domesticated dogs are clearly distinguishable from wolves by starch gel electrophoresis of red blood cell acid phosphatase. The tympanic bullae are large, convex and almost spherical in gray wolves, while the bullae of dogs are smaller, compressed and slightly crumpled. Compared to equally sized wolves, dogs tend to have 20% smaller skulls and 30% smaller brains. The teeth of gray wolves are also proportionately larger than those of dogs. Compared to wolves, dogs have a more domed forehead. The temporalis muscle that closes the jaws is more robust in wolves. Wolves do not have dewclaws on their back legs, unless there has been admixture with dogs that had them. Dogs lack a functioning pre-caudal gland, and most enter estrus twice yearly, unlike gray wolves which only do so once a year. Dogs require fewer calories to function than wolves. The dog’s limp EARSmay be the result of atrophy of the jaw muscles. The skin of domestic dogs tends to be thicker than that of wolves, with some Inuit tribes favoring the former for use as CLOTHING due to its greater resistance to wear and tear in harsh weather. The paws of a dog are half the size of those of a wolf, and their tails tend to curl upwards, another trait not found in wolves. The dog has developed into hundreds of varied breeds, and shows more behavioral and morphological variation than any other land mammal. For example, height measured to the withers ranges from a 6 inches (150 mm) in the Chihuahua to 3.3 feet (1.0 m) 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; coats can be short or long, coarse-haired to wool-like, straight, curly, or smooth. It is common for most breeds to shed their coat.
The global dog population is estimated at 900 million and rising. Although it is said that the “dog is man’s best friend” regarding 17–24% of dogs in developed countries, in the developing world they are feral, village or community dogs, with pet dogs uncommon. These live their lives as scavengers and have never been owned by humans, with one study showing their most common response when approached by strangers was to run away (52%) or respond with aggression (11%). We know little about these dogs, nor about the dogs that live in developed countries that are feral, stray or are in shelters, yet the great majority of modern research on dog cognition has focused on pet dogs living in human homes.
(Wikipedia)
source