Check out this pug chasing his human brother.
Pets as defined by Encylopedia Britannica are animals kept by human beings as a source of companionship and pleasure. While a pet is generally kept for the pleasure that it can give to its owner, often, especially with horses, dogs, and cats, as well as with some other domesticated animals, this pleasure appears to be mutual. Thus, pet keeping can be described as a symbiotic relationship, one that benefits both animals and human beings. As the keeping of pets has been practiced from prehistoric times to the present and as pets are found in nearly every culture and society, pet keeping apparently satisfies a deep, universal human need. The history of pets is intertwined with the process of animal domestication, and it is likely that the dog, as the first domesticated species, was also the first pet. Perhaps the initial steps toward domestication were taken largely through the widespread human practice of making pets of captured young wild animals. Eventually, a working relationship developed between the dogs and their human captors. The dog was swifter, had stronger jaws, and was better at tracking prey; therefore, it could be of great use in hunting and guarding duties. From human beings, on the other hand, the dogs were assured of a constant supply of food as well as warmth from the fire. There is indirect evidence that the dog may have been domesticated and kept as a pet since Paleolithic times, as can be surmised from the paintings and carvings that archaeologists have found in ancient campsites and tombs. In Mesopotamia, dogs that look remarkably like the present-day mastiff were shown participating in a lion hunt. Domestic pets were often depicted in the scenes of family life in ancient Egypt; hunting dogs of the greyhound or saluki type accompany their master to the chase, and lap dogs frequently sit under the chair of their master or mistress. Animals are living things. Like plants, animals need food and water to live. Unlike plants, which make their own food, animals feed themselves by eating plants or other animals. Animals can also sense what goes on around them. Their bodies allow them to move in reaction to their surroundings. They use their senses and movement to find food, mates, and safety.
Millions of different kinds of animals live on Earth. Animals are found throughout the world, from the freezing polar zones to the hottest deserts. They live on land and in the water. They come in a huge variety of shapes and sizes.
Scientists divide animals into two main groups. Animals that have a backbone are called vertebrates. Animals that do not have a backbone are called invertebrates. About 95 percent of all animals are invertebrates.