Arthropods are animals with a hard external skeleton like a suit of armour. The skeleton is jointed to allow movement. Arthropods have evolved in a different way to vertebrates and even their blood is chemically different and so it is not red. They do not have a brain and spinal cord like vertebrates. Instead, they have a nerve cord running along the underside of their body, and small thicknings of this nerve cord instead of a brain. Arthropods have efficient eyes, but these work in a different way from those of vertebrates. Arthropods such as spiders may have many eyes.
Fact file
The most important groups of arthropods are the following: (1) insects; (2) crustaceans (including this red-banded sea shrimp); (3) arachnids; (4) chilopods or centipedes; and (5) diplo-pods or millipedes.
resources: Tell me what (Chancellor Press)
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