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The term “arthropod” means “jointed legs”.

The term “arthropod” means “jointed legs”. The phylum included invertebrates with an exoskeleton and jointed legs, hence named, arthropoda.

The important characteristics of arthropoda include:

They possess an exoskeleton.

They have jointed appendages.

Their body is segmented.

They are bilaterally symmetrical.

They possess an open circulatory system.

Spiders, centipedes, mites, crabs, ticks, lobsters, scorpions, shrimp, are some of the animals found in phylum arthropoda.

It is believed that the arthropods evolved from the same root as the annelids. The three lineages of arthropods are believed to have evolved independently from a common ancestor.

The early arthropods evolved adaptations such as tracheae for breathing. They also developed exoskeleton that prevents the skin of the animals from drying and provides support in case of buoyant water.

According to fossil records, the first arthropods are believed to have evolved 545 million years ago. Scorpions, centipedes and millipedes were the first arthropods to have adapted to dry land.

Phylum arthropoda includes 80% species of animals. These species evolved certain adaptive features over the years to survive the changing climatic conditions and form the largest phylum in the animal kingdom.

The coconut crab, Birgus latro, is the largest arthropod on land. It is also a crustacean.

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.

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 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.

The classification of phylum arthropoda are as follows:

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.

The subphylum Crustacea is divided into six classes-

The body is elongated with numerous segments.

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

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.

The subphylum Myriapoda is divided into the following classes:

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

The thorax is divided into three segments.

They have three pair of appendages.

They respire through gills and trachea.

Malpighian tubules are the excretory organ.

Development is indirect, and the larval stage is present.

The subphylum Hexapoda is divided into two classes:

The body is differentiated into cephalothorax and abdomen.

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.

The subphylum Chelicerata is divided into the following classes:

These are small-sized, terrestrial arthropods.

Excretion occurs through nephridia.

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.

The subphylum had only one class- Trilobita

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