The question of whether insects and animals are the same thing is a common source of confusion due to the immense diversity present in the biological world. Insects are indeed animals, but the term “animal” encompasses a vast range of life forms. This distinction is clarified by the hierarchical system scientists use to classify all living organisms, which places insects within a specific subset of the broader Animal Kingdom. This article will clarify the biological classification and the unique features that define insects within the animal kingdom.
Defining the Animal Kingdom
Organisms classified into the Animal Kingdom (Animalia) share fundamental biological traits that set them apart from plants, fungi, and other life forms. Animals are multicellular organisms composed of specialized cells. All animals are heterotrophs, meaning they must consume other organisms or organic matter for energy and nutrients, unlike plants which use photosynthesis. Animal cells lack the rigid cell walls found in plants, allowing for greater flexibility. Most animal species also exhibit mobility at some point in their life cycle. These characteristics confirm the insects’ place in the Animal Kingdom.
The Taxonomic Home of Insects
To understand how insects fit into the Animal Kingdom, one must examine the biological classification structure, known as taxonomy. Below the Kingdom Animalia is the Phylum Arthropoda, the largest phylum, which includes insects, crustaceans, spiders, and millipedes. All arthropods share defining characteristics, such as a segmented body, a hard external skeleton (exoskeleton), and jointed appendages. Within this group, insects are placed into the Class Insecta, a specific category that separates them from other arthropods.
Distinctive Features of Insects
The Class Insecta is defined by unique physical attributes that distinguish them from other arthropods, such as arachnids and crustaceans. The body of an adult insect is distinctly divided into three main regions: a head, a thorax, and an abdomen. This three-part segmentation is a primary feature that separates them from arachnids, which typically have only two body sections. The thorax serves as the center of locomotion and always bears three pairs of jointed legs, totaling six legs. Most adult insects also possess one or two pairs of wings attached to the thorax, making them the only invertebrates capable of sustained flight.