Insects are often a source of curiosity regarding their classification, particularly whether they are considered animals. Understanding the biological definitions of animals and the specific traits of insects clarifies this. This article explains the scientific basis for including insects within the animal kingdom.
The Defining Traits of Animals
Animals belong to the Kingdom Animalia, a broad group characterized by several distinct features. They are multicellular organisms, meaning their bodies are composed of many cells working together. Animals are also heterotrophic, obtaining nutrition by consuming other organisms, rather than producing their own food like plants.
Animal cells, unlike plant cells, lack rigid cell walls, allowing for greater flexibility and movement. Most animals exhibit some form of mobility during at least one stage of their life cycle, enabling them to move independently. Furthermore, animals typically reproduce sexually, involving the fusion of specialized reproductive cells. Many animals also possess specialized tissues and organs, organized into complex body systems.
Insects: A Look at Their Animal Characteristics
Insects fulfill these biological criteria. They are multicellular, with complex bodies organized into tissues and organs. Insects are heterotrophic, feeding on a wide range of organic matter, from plants and decaying material to other insects.
Their cells do not have cell walls, aligning with a fundamental characteristic of animal cells. Insects are highly mobile, using their six jointed legs for walking and often wings for flight. Like most animals, insects reproduce sexually, typically laying eggs. Their bodies are also highly specialized, featuring distinct head, thorax, and abdomen regions, along with specialized appendages like antennae, compound eyes, and mouthparts.
Classifying Insects Within the Animal Kingdom
Insects are animals, their place within the Animal Kingdom well-defined by biological classification. Within this kingdom, insects are part of the Phylum Arthropoda, the largest phylum in the animal kingdom, encompassing over 80% of all known animal species.
Arthropods are characterized by features such as an exoskeleton, a hard external covering made of chitin, segmented bodies, and jointed appendages. Insects specifically belong to the Class Insecta within the Phylum Arthropoda. This class is distinguished by adults typically having a body divided into three parts—head, thorax, and abdomen—three pairs of legs attached to the thorax, and usually one or two pairs of wings. Insects are a diverse group of animals found in nearly all environments.