Arthropoda

Arthropoda is the animal phylum of segmented invertebrates with jointed appendages and a chitin-based external skeleton that molts as they grow.

Exoskeleton: A rigid external covering that supports and protects an animal’s body. Arthropods’ cuticular exoskeleton provides support but must be shed for growth.
Open circulatory system: A circulatory system in which fluid leaves vessels and bathes organs in body cavities. Most arthropods circulate hemolymph through body spaces rather than a closed vessel network.
Pollination: The transfer of pollen from an anther to a receptive stigma, enabling seed plant reproduction. Bees and other arthropods pollinate many crops and wild plants.
Insect: A hexapod arthropod with a body divided into head, thorax, and abdomen. Insects are the most species-rich and familiar arthropod lineage.
Cambrian explosion: A geologically brief interval beginning about 539 million years ago when animal diversity and fossil visibility rose sharply. Arthropod fossils are prominent in the early diversification of animal life.
Ecdysis: The shedding of an old external covering to permit growth or change in form. Arthropods grow by periodically shedding and replacing their exoskeleton.
Hemolymph: The circulating fluid of animals with open circulatory systems, carrying nutrients and immune cells. Hemolymph moves through the arthropod body cavity and supports transport and defense.
Biological pest control: The use of living organisms to suppress populations of agricultural or other pests. Predatory and parasitic arthropods can control crop pests.
Arachnid: A chelicerate arthropod, including spiders, scorpions, mites, and ticks. Arachnids form a major lineage distinct from insects and crustaceans.
Burgess Shale: A Middle Cambrian fossil deposit in British Columbia renowned for exceptionally preserved animals. Its fossils reveal early arthropod diversity and unusual extinct forms.

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