ARTHROPODA

INTRODUCTION In Greek arthros means joint podos means foot. The phylum arthropoda is the largest phylum in the animal kingdom. These animals have joint legs. They are called the joint-legged animals or the arthropods. The species so far identified in arthropoda represent about 80% of the total animals species. There are more than 875000 species of animals under this phylum.

HABITATS They are triploblastic animals. Members of this phylum are found almost every where.The speciality of these animals is to adjust to all type of environments. They are found in marine, limnetic, terrestrial and aerial habitats of this world. They are also found in deserts and caves. Some are burrowing form also.There are also parasitic forms under this group.

CHARACTERS The body may be elongated or segmented. Each segment of the Body, bears a pair of appendages. These appendages are modified into Jaws, feet or gills. There is a well developed exoskeleton made up of chitinous Plates on the body. The exoskeleton is protective and supporting in function.

BODY STRUCTURES The body is divided into three regions namely head, thorax and abdomen. Muscles found in these animals are complex in their nature and are capable of contraction

EXO SKELETON The body presence of chitinous exoskeleton does not permit free growth of the animal. This exoskeleton is shed at intervals and there is a formation of new layer. This process is called MOULTING or ECDYSIS .

HAEMOCOEL: Coelom is reduced and the body cavity is filled with blood and is called HAEMOCOEL.This is a colourless fluid. DIGESTIVE SYSTEM: Digestive system is complete and the appendages near the mouth parts are modified for cutting, piercing and sucking the food items. Pharynx, oesophagus, crop, gizzard, intestine are helpful in digestion.

RESPIRATORY SYSTEM Respiration in these animals occurs through the body surface, gills, trachea, or by book lungs.

VASCULAR SYSTEM IN ARTHROPODA THE VASCULAR SYSTEM IS OPEN TYPE WITH A DORSAL HEART , ARTERIES AND HAEMOCOEL.

NERVOUS SYSTEM IN ARTHROPODA THE NERVE SYSTEM IS ALMOST LIKE THAT OF ANNELIDESAND CONSISTS OF A NERVE RING, GANGLION AND A NERVE CORDS.

SENSE ORGANS Sense organs consist of well developed eyes gustatory organs and antenna, balancing organs and auditory organs.

Excretory organs: Excretory organs are Malphigian tubules or green glands help in the process of excretion. Reproduction: Reproduction is of sexual type. Sexes are separate.

ECONOMIC IMPORTANCE OF ARTHROPODS Insects help in pollination. Beetles, ants, larvae improve the soil condition by their burrowing activity. Ants and Termites destroy plant waste products and enrich the soil which provides nutrients to the plants. Dung beetle decays animal waste. Some insects help in biological control. Silk moth provides silk which is of great value. Honey Bees provide honey which is a natural antiseptic and also nutritive food, and veewax. Lac insects provides lac used in paints and toys. Arthropods like crab, prawn and lobster are used as food

HARMFUL ARTHROPODS Some insects like termites destroy wood materials like furniture, cloth, books etc. Locusts destroys crops. Mosquitoes and flies spread diseases. Cockroaches destroy food materials and spread diseases.

PICTURES OF ARTHROPODS

BEETLE LADY BIRD CRAYFISH

LOBSTER COCKROACH