The domestic dog (Canis lupus familiaris or Canis familiaris) is a domesticated canid which has been selectively bred for millennia for various behaviors, sensory capabilities, and physical attributes.

Although initially thought to have originated as a manmade variant of an extant canid species (variously supposed as being thedhole, golden jackal, or gray wolf), extensive genetic studies undertaken during the 2010s indicate that dogs diverged from an extinct wolf-like canine in Eurasia 40,000 years ago. Being the oldest domesticated animals, their long association with people has allowed dogs to be uniquely attuned to human behavior, as well as thrive on a starch-rich diet which would be inadequate for other canid species.

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 impact on human society has given them the nickname "man's best friend" in the Western world. In some cultures, however, dogs are a source of meat.

The domestic cat^[1][2] (Felis catus or Felis silvestris catus)^[2][4] is a small, typically furry, domesticated, and carnivorous mammal. They are often called house cats when kept as indoor pets or simply cats when there is no need to distinguish them from other felidsand felines.^[6] Cats are often valued by humans for companionship and their ability to hunt vermin.

Cats are similar in anatomy to the other felids, with strong, flexible bodies, quick reflexes, sharp retractable claws, and teeth adapted to killing small prey. Cat senses fit a crepuscular and predatory ecological niche. Cats can hear sounds too faint or too high infrequency for human ears, such as those made by mice and other small animals. They can see in near darkness. Like most other mammals, cats have poorer color vision and a better sense of smell than humans.

Despite being solitary hunters, cats are a social species and cat communication includes the use of a variety of vocalizations (mewing,purring, trilling, hissing, growling, and grunting), as well as cat pheromones and types of cat-specific body language.^[7]

Cats have a high breeding rate. Under controlled breeding, they can be bred and shown as registered pedigree pets, a hobby known as cat fancy. Failure to control the breeding of pet cats by neutering and the abandonment of former household pets has resulted in large numbers of feral cats worldwide, requiring population control.^[8] This has contributed, along with habitat destruction and other factors, to extinction of many bird species. Cats have been known to extirpate a bird species within a specific region and may have contributed to extinction of isolated island populations.^[9] Cats are thought to be primarily, though not solely, responsible for the extinction of 33 species of birds, and the presence of feral and free ranging cats makes some locations unsuitable for attempted species reestablishment in otherwise suitable locations.^[10]

Since cats were venerated in ancient Egypt, they were commonly believed to have been domesticated there,^[11] but there may have been instances of domestication as early as the Neolithic from around 9,500 years ago (7,500 BC).^[12] A genetic study in 2007 concluded that domestic cats are descended from African wildcats (Felis silvestris lybica), having diverged around 8,000 BC in West Asia.^[11][13] Cats are the most popular pet in the world, and are now found in almost every place where humans live.^[14]

There are more than 70 cat breeds around the world. Different associations proclaim different numbers according to their standards. The International Progressive Cat Breeders Alliance (IPCBA) recognizes 73 cat breeds while TICA (The International Cat Association) recognizes 58, CFA (The Cat Fanciers' Association) recognizes 44 and Federation International Feline (FIFE) recognizes 43 cat breeds.^[15]