Question

Cuttlefish belongs to which phylum?
A) Mollusca
B) Echinodermata
C) Pisces
D) Amphibia

Answer 1

Hint: In the hierarchy of classification, Phylum is a taxonomic ranking that comes third after domain and kingdom. Organisms in the same phylum share similar characteristics that distinguish them from organisms in another phylum. Based on specific characteristics of the organism they are further divided into their respective classes.

Complete answer:
The members of the phylum Mollusca have soft-bodies, triploblastic and bilaterally symmetrical and coelomate. The molluscan study is called Malacology. The term Mollusca was coined by Aristotle. Cuttlefish belongs to the phylum Mollusca.

The main characteristics of the phylum Mollusca are
- They are composed of marine and freshwater organisms. They are rarely terrestrial and found in moist soil.
- They exhibit organ system level of organization where the body has the presence of a cavity and it is divided into head, visceral mass, muscular foot and mantle where the head is composed of tentacles and compound eyes and the body is covered by a calcareous cell.
- The digestive system is well-developed and radula is present which helps in feeding and the excretory organs are nephridia.
- Respiration is through the general body surface, gills or pulmonary sac.
- The nervous system consists of a number of paired ganglia and nerves and tentacles, eyes, osphradium, and statocysts act as the sensory organs.

Now let us look at the remaining options:
Echinodermata species are exclusively marine animals with a star-like appearance and are spherical or elongated. Their body is unsegmented where the mouth is present on the ventral side while the anus is on the dorsal side.

Pisces are true, jawed vertebrates that belong to the phylum Chordata. They have specific organs for respiration, excretion and blood circulation. The organisms belonging to this class are cold-blooded i.e., poikilotherms. All the fishes are included in this category.

Amphibians can live both on land and in water and the body is divided into head and trunk. They have a three-chambered heart and mesonephric kidneys are present for excretion. They belong to the phylum Chordata.

Thus the correct answer is option ‘A’.

Note: There are two types of the circulatory system which are namely – open type and closed type. In an open type of circulatory system, the blood is pumped out of the heart. This is found in Mollusca and Arthropods whereas in closed type the blood flows through a progression of vessels that is capillaries, arteries, and veins.