Question

Two common characters found in centipede, cockroach and crab are
A) Jointed legs and chitinous exoskeleton
B) Green glands and tracheae
C) Book lungs and antennae
D) Compound eyes and anal cerci

Answer 1

Cockroach, centipede and crab belongs to the phylum arthropoda which is known as the largest phylum of Animalia. It constitutes the largest population among all the fauna in the ecosystem i.e. about 70% which means in each 10 animals, seven are belonging to the phylum arthropoda.

Complete answer:
Over two thirds of all the named species present on earth are arthropods. It is the phylum having organ-system level of body organization. They are generally bilaterally symmetrical, triploblastic, segmented and coelomate animals. The segmented body of arthropods is covered by a chitinous exoskeleton. They have jointed appendages thus they are called arthropods (arthro= joint ; poda=appendages).

Additional information: The body is divided into 3 segments that are head, thorax and abdomen. Respiratory organs like gills, book gills, book lungs or tracheal system are present in them that help in respiration. Circulatory system is of an open type in which the blood is pumped out of the heart and the cells and tissues are directly bathed in it.
Sensory organs are also found in them. It includes antennae, eyes (compound or simple), statocysts or balancing organs that are responsible for performing different functions.
Excretion takes place through malpighian tubules in all arthropods. They are generally dioecious and show sexual dimorphism. Fertilization is generally internal and is mostly oviparous. Development can be direct or indirect.

Hence the correct option is ‘ A’ i.e. jointed legs and chitinous exoskeleton.

Note: Members of this phylum have different importance. Some members of them are having economic importance like Apis(honey bee for beeswax and honey), Bombyx (silkworm used for production of silk on large scale), Laccifer( lac insect used for production of lac ). Some act as a vector of various diseases and cause disease transmission. It includes Anopheles, Culex & Aedes responsible for the transmission of dengue, chikungunya and malaria.