Question

An animal class with the largest number of animals is
A. Mammalia
B. Insecta
C. Reptilia
D. Pisces

Answer 1

Hint: The subphylum Hexapoda has a class that includes more than one million species. This class includes terrestrial as well as aquatic organisms and they possess wings for the flight. It is the largest taxa of all the animals and plants.

Complete answer:
The phylum Arthropoda has the largest number of organisms having jointed legs. Arthropoda includes insects, arachnids and crustaceans. They have a chitinous exoskeleton, three-pair of jointed legs, and one pair of antennae on their heads. It is a diverse group of the organism and their body is differentiated into three parts; head, thorax and the abdomen. They have two pairs of wings and three pairs of legs. They have specialized mouthparts, nervous systems, and digestive systems. The class of insects is also known as Hexapoda. Some common examples of class Insecta are bedbugs, houseflies, aphids, mosquitoes, fleas, and beetles. They dominate the present-day fauna. Insects have spiracles and a tracheal system for the process of respiration. Mostly sexual reproduction is found in insects. Many insects are ecologically beneficial as they can be used as biological pesticides, while some are harmful.
Hence, the correct answer is option B.

Note: The number of species that belong to class Insecta ranges from six to ten million. They are ubiquitous, they are usually solitary but some are social and live in large colonies. Communication can occur through sense pheromones or sounds that attract mates. Their gut is divided into foregut, midgut, and hindgut.