Question

Animals of this phylum have a characteristic feature of presence of notochord, a dorsal hollow nerve cord and paired pharyngeal gill slits.
Within this phylum, there is an advanced group called vertebrates, which include fish, amphibians, reptiles, birds and mammals.
A. Chordata
B. Arthropoda
C. Mollusca
D. Porifera

Answer 1

Hint: Vertebrates are also called Craniata, They have backbones. They have a muscle system that mainly consists of a central nervous system, partly enclosed within the backbone.

Complete Answer:
Option A: Chordata - belongs to the Animal Kingdom and includes all vertebrates, and several invertebrates. They possess a bilaterally symmetrical body; and possess the following characteristics :-
1. Dorsal Nerve Cord - a bundle of nerves which runs along the “back” and evenly divides into the spinal cord and the brain.
2. Notochord - a longitudinal, cartilaginous rod that runs between the nerve cord and the digestive tract.
3. Pharyngeal Slits - the openings (on the lateral sides of the pharynx) which allow the entry of water through the mouth, without the water entering into the digestive system.
4. Post anal Tail - an extension of the body to the anus. In chordates, this tail is made up of skeletal muscles, which help in locomotion (of fish-like species).
Thus, this is the Correct option.

Option B: Arthropoda - “Arthropod” = “jointed legs”. This phylum includes invertebrates with jointed legs and an exoskeleton. Thus, this option is incorrect.

Option C: Mollusca - These organisms have soft-bodies, are triploblastic, bilaterally symmetrical and coelomate. They are sluggish in nature, with thin fleshy envelopes, which cover their visceral organs. Thus, this option is incorrect.

Option D: Porifera - “Porifera” mainly means - the pore-bearing species. They appear spongy, and are thus called “sponges”. This option is also incorrect.

Thus, the correct option is A) Chordata.

Note: The study of Mollusca is called Malacology. “Mollusca” is derived from the term given by Aristotle to cuttlefish. Mollusca - means soft. Porifera are the first and lowest multicellular organisms of the Animal Kingdom. Their pores are known as Ostia.