phylum arthropoda

Phylum Arthropoda

Phylum Arthropoda

This is the largest of kingdom animalia. About ¾ of all known animals are arthropods

Characteristics of phylum arthropoda

They are triploblastic coelomates
They are mathematically segment
They are bilaterally symmetrical
The coelom is much reduced, and the main body cavity is called a haemocoel in it, blood moves freely over the tissues through a series of spaces (i.e. they have open blood circulation).
Their Central nervous system consists of a pairs pre-oral ganglion connected by nerves called commissures to a central nerve cord
Their excretory system consists of coelomoducts instead of (nephridia as in annelids). The coelomoducts are tubes which open to the outside of the organism at the base of appendages.
Arthropods posses Malpighian tubules which open to the mid and hind gut for excretion.
Each segment bears a pair of jointed appendages (arthros = Jointed) (poda = legs) this serves purposes like locomotion feelings and sensation.
There is a dorsal heart and their circulation, and the body is differentiated into a head thorax and abdomen
Many larva forms exist within the phylum; there is indirect development or metamorphosis
They have a chitinous exoskeleton.

Importance of exoskeleton to arthropods

It offers structural support
It prevents water loss since it is impermeable to water
It provides a system of levers for the muscle attachment
It is modified for the development of sensory structures like antennae
It is modified to provide flexibility at the joints
It undergoes ecdysis (moulting) for increase in the arthropods seize
It is modified for gaseous exchange e.g. the trachea system in insects or book lungs in arachnids.