Question

The main features of arthropods. How can arthropods be described according to examples of representative species, basic morphology, type of symmetry, germ layers and coelom, digestive system, respiratory system, circulatory system, excretory system, nervous system and types of reproduction?

Answer 1

Main feature of Arthropoda:-

1. Term Arthropod was coined by Von Seibold.Animal in this kingdom have joint legs.
2. Different part of body is head,thorax and abdomen.
3. There are open blood vascular system
4. Respiratory system have different components they are trachea,gills or booklungs.
5. Component of Excretory system are malpighian tubules,green gland or coxal glands.
6. Sexual dimorphism
7. Striated muscle

Example: Cockroach

Morphology and symmetry:Body is covered with exoskeleton called sclerites.Dorsal sclerite is known as tergum and ventral sclerite is known as sternum.Body wall is made up of three layer cuticle,epidermis and basement membrane.Body divide into head,thorax and abdomen.

Germ layer and coelom:It has true coelom.All the visceral organ filled with blood,hence body cavity is haemocoel.

Digestive system:Alimentary canal consist of three part foregut or stomodaeum,midgut or mesenteron and hindgut or proctodaeum.Food is received into cebarium or preoral cavity.At the junction of foregut and mid gut a finger like structure is present called as hepatic Caecae.

Respiratory system :Respiration is carried out by tracheae and spiracles.There are ten pair of spiracles or stigmata.Each spiracles open into atrium.Trachea tubes are branched and there ends called tracheoles.

Circulatory system:Open type, blood always contact with tissues.Heart is long and contractile.It is a thirteen chambered structure.

Excretory system:There are present of malpighian tubules.They are present in 6group of 15 each.The main excretory product is Uric acid.

Nervous system:It consist of a nerve ring and double ventral nerve cord.Nerve ring having pair of supra oesophageal ganglia,sub oesophageal ganglia and a pair of circum oesophageal connectives.

Reproductive system:It is a unisexual animal.4th and 5th abdominals segment contains a pair of trilobed testes.Ejaculatory duct open through male gonopore.In female ovaries present in 4th,5th and 6th segments.Each ovary is made up of eight ovarioles.