Animals are living creatures that can move at will, hunt for food, and reproduce. They can also defend themselves from predators, find a mate, and adapt to their habitat. A variety of animals live in our forests, mountains, oceans, deserts, and other ecosystems around the world. From the great white shark to the tiny Amau frog, the world’s animals are diverse and fascinating.
The scientific study of animals is called zoology. The word animal comes from Latin anima, meaning breath or soul. Originally, the word meant any living creature that breathes, although plants do this too, but they cannot be seen by the naked eye. The word eventually came to mean a particular type of living being, such as a cat or dog.
To be considered an animal, a creature must be multicellular and made up of cells that have their inner membranes bound together. This criterion eliminates bacteria and archaea, single-celled organisms that lack the internal membranes. In addition, an animal must be heterotrophic and able to produce its own energy.
The animal kingdom, which is a subcategory of the eukaryotic kingdom Metazoa, contains over 2.16 million species. There are many different types of animals, but most are multicellular and have a complex body plan with a distinct shape. Many are eukaryotic and have a cell wall, although there are exceptions. Most are also motile and have specialized sensory organs. Animals are usually sex dimorphic, with males and females differing in their appearance, for example, the plumage of birds and scales of fish.
Some animals are domesticated, which means they have been raised by humans for purposes other than food. Examples include domesticated dogs, cats, and sheep. Some are kept as pets or used in scientific research, with the most common being guinea pigs, rabbits, and hamsters. Other animals are kept in facilities such as universities, medical schools, and government labs for use in experiments. Scientists rely on these animals to help them understand biology, test new surgical techniques, and assess the safety of chemicals and medicines.
In 2019 the National Association of Biology Teachers (NABT) reaffirmed its belief that “students should have access to live and formerly living specimens in order to gain a more complete understanding of life science.” Despite this, NABT recognizes that nonanimal alternatives can be effective teaching tools.
Animals are a vital part of our planet. They provide us with meat, dairy, and wool products, and they also serve as companions and working animals. Moreover, they play an important role in our environment by pollinating flowers and dispersing seeds. In the wild, they can be beautiful and majestic or shy and secretive. Some are even capable of fighting off larger and faster predators. These animals—from the mighty grizzly bear to the tiny Amau frog—are all incredible and worth learning about. sabunqq