Question

Insects and Houseflies have bodies that are differentiated into head, thorax, and abdomen. They have joint legs but no vertical column. In which phylum would you classify these animals?
a. Annelida
b. Birds
c. Arthropoda
d. Mollusca

Answer 1

Hint: Invertebrates are animals that are without backbone and during their lifetime neither possess nor develop a vertebral column. Apart from the subphylum Vertebrata, all the animals are included. Some examples of invertebrates include arthropods, mollusks, annelids, and cnidarians.

Complete answer:
An arthropod is a phylum that includes all invertebrates (lacking the vertebral column). Animals in this kingdom have an exoskeleton (external skeleton), a segmented body, and jointed appendages. Arthropoda is triploblastic and has a true coelom. The animals possess bilateral symmetry. Its body is divided into three parts. These three parts are -head, thorax, and abdomen. Birds belong to the phylum Chordata and class Aves. Birds are warm-blooded animals.

Their forelimbs are modified into wings. For walking, hopping, perching, grasping, wading, and swimming, their hind limbs are adapted. There are epidermal scales on their legs. The endoskeleton is bony with long hollow bones. These hollow bones are filled with air cavities known as pneumatic bones. The beak is the modification of lower and upper jaws.

Phylum Annelida, the Annelids are found in aquatic as well as terrestrial environments. These are bilaterally symmetrical invertebrate organisms. They have a segmented body that is a distinguishable feature, from any other organism. The Annelids are coelomate and triploblastic. They exhibit organ level organization. Their body is segmented. They respire through their body surface.

In phylum Mollusca, animals have soft-bodies, triploblastic, and bilaterally symmetrical, and coelomate. They are mostly found in marine and freshwater. They exhibit an organ system level of organization. The body of the Molluscs is divided into head, visceral mass, muscular foot, and mantle. The head comprises tentacles and compound eyes. The body is covered by a calcareous shell.

Hence, the correct answer is option (C).

Note: Invertebrates lack a bony skeleton. Arthropoda is the phylum belonging to the animal kingdom. They possess a segmented body, have an exoskeleton and jointed appendages. The body of the arthropods is differentiated into the head, thorax, and abdomen. The body of the Molluscs is divided into head, visceral mass, muscular foot, and mantle. Annelids have a segmented body that is a distinguishable feature, from any other organism.