Question

explain Arthropoda .​

Answer 1

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An arthropod is an invertebrate animal having an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Euarthropoda, which includes insects, arachnids, myriapods, and crustaceans.

Answer 2

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Arthropoda:-

Arthropoda is the largest phylum with about nine lakh species. They may be aquatic, terrestrial or even parasitic. They have jointed appendages and a chitinous exoskeleton.

This phylum includes several large classes and contains the class Insecta which itself represents a major portion of the animal species in the world. They possess the ability to survive in every habitat.

Arthropoda Characteristics

The arthropoda characteristics are mentioned below:

• The body is triploblastic, segmented, and bilaterally symmetrical.

• They exhibit organ system level of organization.

• The body is divided into head, thorax, and abdomen.

• Their body has jointed appendages which help in locomotion.

• The coelomic cavity is filled with blood.

• They have an open circulatory system.

• The head bears a pair of compound eyes.

• The exoskeleton is made of chitin.

• The terrestrial Arthropods excrete through Malpighian tubules while the aquatic ones excrete through green glands or coaxal glands.

• They are unisexual and fertilization is either external or internal.

• They have a well-developed digestive system.

• They respire through the general body surface or trachea.

• They contain sensory organs like hairs, antennae, simple and compound eyes, auditory organs, and statocysts.

Classification of Phylum Arthropoda

The classification of phylum arthropoda are as follows:

Crustacea:-

• They are aquatic, terrestrial, or parasitic.

• The head is fused with the thorax region known as the cephalothorax.

• Respiration occurs through gills or general body surface.

• The body is covered by a single large carapace.

• They possess two pairs of antennae and five pairs of appendages.

• They excrete through green glands or antennal glands.

• They have a pair of compound eyes and gonopores.

• Development is indirect. Larval stage is present.

• Eg., Daphnia, Palaemon

The subphylum Crustacea is divided into six classes-

• Branchiopoda

• Remipedia

• Chephlocarida

• Maxillopoda

• Ostracoda

• Malacostraca

• Myriapoda
• These are mostly terrestrial.

• The body is elongated with numerous segments.

• The head is provided with antennae, two pairs of jaws, and a pair of simple eyes.

• They contain numerous legs.

• The upper lip of the mouth contains epistome and labrum, and the lower lip contains a pair of maxillae.

• A pair of mandibles is present inside the mouth.

• They respire by trachea and excretion occurs by Malpighian tubules.

• Eg., Julus, Scolopendra

The subphylum Myriapoda is divided into the following classes:

• Chilopoda
• Diplopoda

• Pauropoda

• Symphyla

• Hexapoda
• They are mostly terrestrial.

• The body is differentiated into head, thorax, and abdomen.

• Head bears a pre-segmental acron.

• The thorax is divided into three segments.

• The abdomen has 7-11 segments.

• They have three pair of appendages.

• It has a pair of compound eyes

• They respire through gills and trachea.

• Malpighian tubules are the excretory organ.

• Development is indirect, and the larval stage is present.

• Eg., Tabernus, Mosquitoes, Ants.

The subphylum Hexapoda is divided into two classes:

• Insecta

• Entognatha

• Chelicerata
• They are mostly found on land.

• The body is differentiated into cephalothorax and abdomen.

• Antennae are absent.

• The abdomen is divided into 13 segments.

• It has four pairs of interior appendages.

• They respire through trachea or gills.

• The Malpighian tubules help in excretion.

• Eg., Aramea, Limulus

The subphylum Chelicerata is divided into the following classes:

• Arachnida

• Merostomata

• Pycnogonida

• Onychophora
• These are small-sized, terrestrial arthropods.

• The body is divided into segments.

• Excretion occurs through nephridia.

• They respire through the trachea.

• Eg., Paripatus

Trilobitomorpha

• These are primitive arthropods and are extinct.

• They were found in abundance during the Paleozoic era.

• The body was divided into three lobes- one median and two lateral lobes.

• Head bore a pair of compound eyes and a pair of antennae.

• There was no structural differentiation of the body parts.

• The body was divided into head, thorax and pygidium.

• Appendages are biramous.

The subphylum had only one class-

• Trilobita

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