Question

Find the odd one:-
A. Sea cucumber
B. Sea urchin
C. Sea lily
D. Sea fan

Answer 1

Hint: These all animals have specific phylum and class in their classification which suggest some similarities in the same species and others are different in terms of structure. One of the phylum includes all sea stars, cucumbers and crinoids.

Complete answer:
Classification of every option
-Sea cucumber :-
Scientific name is holothuroidea
These are marine animals with leathery skin and they have long body and branched gonads. They have an endoskeleton just below the skin.
Kingdom – Animalia
Phylum- Echinodermata

-Sea urchin:-
Scientific name is echinoidea
They are water animals having spines and globular animals are round having hard shells outside which consist of spines. They are closely related sea cucumbers.
Kingdom – Animalia
Phylum – Echinodermata

-Sea lily:-
Scientific name is crinoidea
They are marine animals characterized by having mouths located on the upper surface Surrounded by feeding arms and linked by a U shaped gut.
Kingdom – Animalia
Phylum – Echinodermata

-Sea fan:-
Scientific name is Alcyonacea which is a soft coral and does not have a hard Endoskeleton. They are fan-like bushy erect branches like in the Deep Ocean all Over the world. Their internal skeleton consists of a flexible horny scleroprotein Called gorgonian. The polyps spread their tentacles to form a catching net.
Kingdom- Animalia
Phylum- cnidaria
Hence the Echinodermata do not form nets with any kind of tentacles and make colonies like sea fans rather than individual structures.
So the answer is option (D)

Note: All the animals are from Echinodermata phylum except the sea fan which is from Cnidaria phylum. Echinodermata mostly have hard endoskeleton whereas the sea fan is a soft coral.