Question

Write the features of arthropods.

Answer 1

They are the largest phylum in the animal kingdom. Arthropods are a very diverse group of animals. They are the largest group of animals on the planet, containing 5 million distinct species.

Complete answer: The following are some of the characteristics of arthropods:
1. They have a segmented body containing three segments. These include the head, a thorax, and abdominal segments.
2. Each segment has a pair of appendages. They are used for feeding, sensory perception, defense, and locomotion. In addition to the pairs of legs, antennas, and mouthparts (labium and mandible) are considered as modified appendages.
3. Their nervous system consists of ganglions for each segment.
4. They have a hard exoskeleton made of chitin (also present in certain bacteria).
They provide physical protection and resistance against dry climates.
Arthropods shed this outer covering in order to grow. This process is called molting.
5. It has an open circulatory system with hemolymph that is a blood-like fluid.
An open circulatory system doesn’t contain vessel bound blood, the blood is free-flowing and enters a series of sinuses. Hemolymph is involved in oxygen distribution.
6. It has a complete digestive system with a mouth and an anus.
7. Terrestrial arthropods have an internal surface that helps in the exchange of gasses.
They have a tracheal system that consists of air sacs that lead into the body from pores present in the exoskeleton.

Note: Aquatic arthropods use pairs of gills to exchange gases. These gills have a larger surface area when compared to fishes.
Other modes of respiration include book lungs, gills modified for breathing air, they are seen in species like the coconut crab.