Insects (Encyclopedia of Science)
Insects are invertebrates in the class Insecta, which contains 28 living orders. The animals that make up this class have a number of distinctive features. Their adult bodies are typically divided into three parts, known as the head, thorax, and abdomen. In addition, they have three pairs of segmented legs attached to the thorax and one pair of antennae. Members of the subclass Pterygota have two pairs of wings as adults. By contrast, some relatively primitive members of the subclass Apterygota are wingless.
Taxonomists (scientists who classify organisms) have recognized more than one million species of insects, more than any other group of organisms. In addition, scientists believe that tens of millions of species of insects remain undiscovered. Currently, scientists estimate that as many as 30 million species of insects inhabit Earth; most of these are thought to be beetles. In fact, all of the insect orders are poorly known. Most of the undiscovered species of insects occur in tropical rain forests, especially in the upper parts of the forest known as the canopy.
Globally, the insects exploit a remarkable diversity of habitats. They are ecologically important as herbivores (plant-eaters), predators (meateaters who hunt their prey), parasites (who feed on living organisms), and scavengers (who feed on dead organisms). As a result of these attributes,...
(The entire section is 940 words.)
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