When we talk of animals, we speak of vertebrates that are alive; animals that are warm-blooded and have limbs with joints. All animals, with the exception of fishes, have evolved from animals that were land animals. In fact, it is a common mistake to think of animals only as creatures of the land. Animals have been in existence since the beginning of the earth. They are animals, as well as plants, which have roots, stems, and leaves; and animals that have evolved from plants.
The majority of animals are multicellular, meaning they are eukaryotic, which is a living organism with a nervous system. With few exceptions, animals breathe oxygen; produce proteins, digest food, secrete waste products, and secrete hormones. All animals have teeth for chewing, eyelids for protecting the eyes, ears for receiving and sending sounds, and claws for grasping and removing prey. In fact, most animals use more than one kind of organ for the purpose of living and moving about.
All animals have guts and stomachs where food is digested and absorbed and intestines where waste products are eliminated. Digestive tracts include lips, gums, esophagus, and throat. Bacteria in the gut break down proteins, fats, carbohydrates, and sugars and produce enzymes, vitamins, and hormones. Animals therefore obtain nutrients from the foods they eat and through their diets excrete waste products from the excretion systems.
All animals breathe air by means of lungs. Through respiration animals breathe air into their lungs and out of their mouth. The heart pumps blood through the body and animals thus obtain oxygen from the air and release carbon dioxide to breathe air.
All animals have trunks where they store their bones, teeth, fur, and so forth. The incisors are used to make cuts and the teeth are used to bite into hard objects. Flexor digesters are muscles in animals’ backs that enable them to extend their bodies and walk on two feet. Tracheas are long tubes that are responsible for bringing food and water into and out of the animals’ bodies. Lastly, all animals have skin that protects their organs, as well as preventing moisture and cold from entering or leaving the body.
Knowing the answers to the above questions will give a person insight into the various animals and plants we see and interact with on a day to day basis. An understanding of the ways animals live and function will broaden a person’s appreciation for all living things. In addition, this new knowledge will inspire people to look deeper into the lives of animals and learn more about the animals they come into contact with on a daily basis.