What Are Living Animals?

A single-celled Girlwithanswers organism that makes its own food, moves, responds to stimuli, and reproduces is called a living thing. In contrast, a chair or car is not alive because it does not produce its own energy, move without external help, or reproduce.

Most living things are too big to be formed by a single cell and, as such, they must be made of many cells that live and work together. Some of the simplest multicellular organisms are algae. Algae form a chain in the water, and the bottom of each alga — called a holdfast—holds to rocks or wood to keep it from drifting away.

“Living Animals: Conservation, Habitats, and Awareness

Animals are part of the kingdom of multicellular eukaryotes and, like plants, lack chlorophyll. They have different types of tissues in their bodies, and most can move. Animals can be divided into two major groups: invertebrates and vertebrates. The invertebrates, including insects, sea stars (starfish) and worms, lack a backbone and have body tissues supported by hard outer structures, such as exoskeletons. The vertebrates include fish, amphibians, such as frogs and salamanders; reptiles, such as snakes and lizards; birds; and mammals, including dogs, cats, horses, monkeys, humans, and other primates.

Some animals live very long lives. A 190-year-old Seychelles giant tortoise was the longest-living land animal when it died in 2008. A bowhead whale, which often lives as a lone animal, can also live very long. It is thought that the long lifespans of these creatures may be related to their social behaviors. Social animals tend to be less susceptible to predation and starvation than solitary ones. They also take more time to reach reproductive age and invest more in nurturing young, which may provide survival benefits for their offspring.