Question

In which group of arthropoda, the body is divisible into head, thorax, and abdomen?
A. Myriapoda
B. Crustacea
C. Arachnida
D. Insecta

Answer 1

Hint: The subphylum Hexapoda of the phylum Arthropoda includes the insects. The body of these organisms is divided into three main segments called the head, thorax, and abdomen.

Complete answer:
Phylum Arthropoda is a diverse group of animals that exhibit some distinct features. The presence of a segmented body, a hard chitinous exoskeleton, and paired jointed appendages are the characteristic features of the phylum Arthropoda. Segmentation refers to the presence of segments in the body. It allows specific body parts to perform specialized functions. The phylum Arthropoda is divided into subphyla namely Chelicerata, Myriapoda, Hexapoda, and Crustacea.

Myriapoda includes centipedes and millipedes. These organisms have heads and elongated segmented trunks.

Crustaceans have two or three segments in their body. Mostly, their body is divided into cephalothorax and abdomen. Here, cephalothorax is the structure formed by the fusion of head and thorax. Some examples of crustaceans are crabs, lobsters, crayfishes.

Arachnida includes arthropods such as spiders, scorpions, ticks, and mites and is classified under Chelicerata. These arthropods have two main segments in their body: cephalothorax and abdomen.

Class Insecta is classified under the subphylum Hexapoda. It includes bees, ants, grasshoppers, and other insects. Their body has three segments called the head, thorax, and abdomen. Three pairs of appendages are present on the thorax.

Hence, the correct answer is option (D).

Note: Subphylum Hexapoda includes insects that are mainly terrestrial. Insects are considered the most successful animals. Besides the presence of three body segments, other characteristic features of insects are gas exchange through tracheae, indirect development with metamorphosis, and the presence of three pairs of legs on the thorax.