Question

Which of the following has the least number of body segments?
A. Lobster
B. Grasshopper
C. Earthworm
D. Flatworm

Answer 1

Hint: Body segment is a characteristic feature of Arthropods. Arthropoda is a phylum of invertebrates that show the presence of an exoskeleton, paired jointed appendages, and segmented body. Many of the insects, myriapods, arachnids, and crustaceans belong to the phylum Arthropoda.

Complete answer: Lobsters are marine crustaceans in which 14 segments of the body are fused together to form the cephalothorax is called somite. Somites are located on the different areas of the lobster usually on either side of the body or on the underside of the lobster body. Each somite bears a pair of appendages. Grasshopper is an insect. The body of insects has three major parts called head, abdomen, and thorax. 5 to 7 segments are fused together to form the head of the grasshopper. The head consists of eyes, mouthparts, and antennae. The thorax is made up of three segments called the pro-thorax, mesothorax, and the meta-thorax. Appendages are attached to the thorax and are used for locomotion. Each segment of the thorax consists of one pair of legs. Wings are present in mesothorax and meta-thorax only. The upper portion of the prothorax is called the pronotum. The abdomen of the insect consists of 11 or fewer segments. The earthworm is an annelid that is made up of 100-150 segments. Each segment of the earthworm has a pair of nephridia which is used for excretion and filtration. The body of the flatworm is unsegmented and bilateral. The body is made up of three layers called ectoderm, mesoderm, and endoderm.
So, option D is the correct answer.

Note: The division of an animal or plant body into a series of repetitive segments is called segmentation of the body. The segmented body is a characteristic feature of Arthropoda, Chordata, and Annelida. Segmentation of the body plan allows the development and free movement of certain parts of the body.