Although there are great many species of animals, they are distinguished by a single common characteristic: their appendages or limbs, which are called extremities. Animals are categorized as having only one set of limbs, although some may have several. Multicellular animals are eukaryotic, a division of the animal Kingdom. With few exceptions, all animals breathe air, can move, reproduce sexually, and eat food. Humans, cats, dogs, bison, dolphins, and whales are a few examples of eukaryotic animals.
In many countries of the world, professional careers in animal sciences research and practice are growing rapidly in relevance and importance. For example, with increased globalization and urbanization, animal nutrition has become a more important part of the health care profession in many areas. There are also growing opportunities in veterinary care and research, including those related to development, vaccines, diseases affecting animals, and related animal studies.
Veterinary medicine has developed into a specialized area of medicine dedicated to animal sciences. There are various specialties within this field, including animal husbandry, veterinarian medicine, parasitology, physiology, diagnostic and clinical procedures, pathology, pharmacology, nutrition, veterinary surgery, and others. Veterinary science is the study of animal health and illness, including the management and control of animal diseases, disorders, and illnesses. The animal sciences include animal husbandry, cattle breeding and farming, dairy farming and rearing, fish raising and marine aquariums, wildlife management, pest management, nutritional science, veterinary diagnostics, and veterinary pharmacology. Veterinary professionals in the animal sciences field also provide diagnosis, treatments, and preventive services relevant to animal diseases, infections, physiology, pathology, and vaccination.
The classification of living things on the basis of their arrangement is a very large subject, and includes animals, plants, fungi, microorganisms, protoplasts, etc. The animal Kingdom includes animals such as fishes, amphibians, reptiles, birds, mammals, and birds’ eggs. The Kingdom of Eukaryotes comprises of eukaryotes, protoplasts, bacteria, and other unicellular organisms. The animal Kingdom has also divided into two major subkingdoms: Protista (plant-like cells) and Eutheria (vertebrates). The Cetacea (bird family) includes cactuses, sturgeon, salamanders, snails, their respective fishes, and salamanders, their mollusks.
The nervous system of animals is the component of the animal kingdom that controls the functions of all other parts. Therefore, all of the other animal systems depend on the functions of the nervous system. The major nerves of the animal kingdom are the brain, spinal cord, nerves, muscles, and sensory organs. All the animals have a nervous system, including all the vertebrates such as fishes, amphibians, and reptiles; the fishes of the ocean including whales and dolphins; birds and its feathery bodies; mammals including humans.
The study of animals has been going on since the very beginning of science itself. Descartes, the great French Physician and Engineer, gave the first clear idea of how science can be defined by the observation of nature. He said, “arium est inquisitiveium, etiamus acus.” And, according to him, observation is the best test of the real nature of things.