Arthropod

Arthropods are invertebrate animals in the phylum Arthropoda.

Arthropods are invertebrate animals in the phylum Arthropoda, characterized by a segmented body, jointed appendages, and an external skeleton called an exoskeleton, usually made of chitin. They include insects, arachnids, crustaceans, centipedes, and millipedes. Arthropods are ecologically important in Canada, where familiar groups include insects, spiders, crayfish, and other crustaceans in freshwater and marine environments.

Characteristics

Arthropods are defined by a segmented body, paired jointed appendages, and a hard external skeleton. Their exoskeleton must be molted in a process called molting or ecdysis to allow the animal to grow.

Major groups

Commonly recognized arthropod groups include insects, arachnids, crustaceans, and myriapods. Some sources also note extinct groups such as trilobites among arthropods.

Diversity and distribution

Arthropods are among the most diverse animal groups and are found in almost every environment on Earth, including marine, freshwater, terrestrial, and aerial habitats. They include many familiar animals such as spiders, crabs, butterflies, and centipedes.

Etymology

The term arthropod derives from Greek roots referring to 'jointed feet' or 'jointed limbs', reflecting the group's most distinctive anatomical feature.