Question

_________ is the second largest phylum in the animal kingdom.

Answer 1

Hint: Animal kingdom consists of around eleven phylum and seven classes. They are broadly divided based on symmetry, body cavity of Coelom, level of organization, circulatory and reproductive system, etc. The crown of the largest kingdom has been given to phylum “Arthropoda”. The second-largest phylum comprises organisms with feather-like gills and an unsegmented body that is covered with a calcareous shell.

Complete answer:
-Mollusca takes the position of second largest phylum in the animal kingdom.
-All around the world, around 85,000 species are known that belong to this phylum.
-Twenty-three per cent of marine life named is categorized under this phylum.
-This phylum comprises organisms which are diverse in various aspects.
-Their habitat, size, behaviour, vary at a whole different level.

Features of Mollusca are-
-Bilaterally symmetrical, organ system organization
-The body is un-segmented and is covered with a calcareous shell.
-Rasping organ for feeding is called Radula
-The organisms are oviparous, development is indirect, and organisms are dioecious.
-Distinct head, presence of visceral hump and a muscular foot.

Examples of this phylum are Pila, Octopus, Sepia, Pinctada, etc.
The answer to the above question is “Mollusca”.

Additional information:
Main features that define this phylum are the presence of Radula (Radula is an organ that helps Mollusca to feed and it is compared to tongue present in mammals); a mantle is present with cavity and is used for breathing and excretion. Also, the structure of their nervous system differs from other phylum bringing diversity in this phylum.

Note: The animal kingdom itself is the biggest kingdom with more than one million species known in the world. The biggest phylum in this kingdom is Phylum- Arthropoda which contains around eighty-four per cent species from around the world. Arthropods are spread all around the world and can be found at every type of habitat, whether it is on land or water. The second most abundant phylum is Mollusca with around 85,000 species present in the world. The third most abundant phylum in the kingdom is Chordata.