Question

Select the phylum that has jointed appendages:
i) Flatworm
ii) Roundworm
iii) Arthropod
iv) Cnidaria

Answer 1

A jointed appendage is defined as a growth from an organism's body that has joints. The jointed appendages include legs, wings, antenna and mouth parts. These jointed appendages are used by an organism for locomotion, sensing, feeding, etc. The animals with jointed appendages have a segmented body and a hard exoskeleton made of chitin.

Complete answer:
i) Flatworm: The flatworms belong to the phylum of Platyhelminthes. They are flat, unsegmented, soft bodied invertebrates. They do not possess any circulatory and respiratory organs. They intake oxygen and nutrients through a simple diffusion process. They do not possess any joint appendages.
This option is incorrect.
ii) Roundworm: Roundworms belong to the phylum Nematoda. They inhabit a broad range of environments. They are very small and only about $0.1$ to $2.5$mm long. Most roundworms are parasitic in nature. They have a tubular digestive system with openings at both ends. They do not possess any jointed appendages.
This option is incorrect.
iii) Arthropod: Arthropods belong to the phylum Arthropoda. They are invertebrate animals with a segmented body, hard exoskeleton and paired jointed appendages. The jointed appendages are used for moving, chewing food, sensing the environment and flying.
This option is correct.
iv) Cnidaria: Phylum Cnidaria contains over eleven thousand species of aquatic animals found both in freshwater and marine water environments. The specialized feature of Cnidaria is the cnidocytes, which are a type of cells used for capturing their prey. They exist as swimming medusae or sessile polyps. They do not have jointed appendages.
This option is incorrect.

Hence the Correct answer is option iii) Arthropod.

Note:
Arthropoda is the largest phylum in the animal kingdom. About $84$ percent of all species of animals in this world are members of the phylum Arthropoda. Arthropods show a great variety of adaptations and so can be found in every habitat. It includes a variety of animals such as lobsters, crabs, spiders, butterflies, insects, centipedes, millipedes etc. Their exoskeleton is mostly made up of chitin.