Phylum Arthropoda ("Joint leg")
Description
Phylum Arthropoda is by far the largest phylum, with about 70 to 85% of animals belonging to it. Their legs are jointed, which is one of their most defining traits. They perform ecdysis, or "molting". They have exoskeletons that are made of chitin. Most arthropods are bilaterally symmetrical, and are coelomates. Their bodies are divided into segments; Their segmentation consists of the head, thorax (body) and abdomen (posterior). Some Arthropods have a cephalothorax, which is when the head and the thorax are combined. Some have mandibles for feeding, which are the sideways pinchers in front of the mouth or head That can bite, grab, and put food into the mouth. For respiration, aquatic arthropods have gills, insects have tracheal tubes and spiders have book lungs. They have open circulatory systems, and have Malpighian tubules for excretion. Their nervous system is very well developed. They see through compound eyes, which are well evolved. They have tympanums for hearing. Their muscles are attached to their exoskeleton, allowing for a lever-like system for movement. They have very strong chemoreception, which is the sense of pheromones given off by things. They can use this to get around, sensing the pheromones that other organisms give off. Their reproduction is sexual with mostly separate sexes.