Question

Which of the following animals has no skeleton?
A. Sponge
B. Butterfly
C. Jellyfish
D. Starfish

Answer 1

Hint:
The framework of bones and cartilage forms the skeletal system. This system is responsible for the locomotory movement. The two components of the skeletal system:- bone and cartilage are the connective tissue. Bone is the hard one because of the calcium matrix whereas cartilage is pliable due to the chondroitin salts. In the human body, 206 bones and a few cartilages are present.

Complete answer:
Sponges are multicellular pore-bearing animals that belong to the phylum Porifera. Sponges do not possess true tissue and organ systems are asymmetrical in nature. The internal skeleton of sponges is made up of spicules or spongin. These spicules are generally calcium carbonate or silicon fragments which makes them flexible.
Butterflies are protected by the external skeleton. The tissues of butterflies are protected by a hard shell called an exoskeleton. The exoskeleton is made up of a bone-like structure called chitin. The thickness of chitin varies depending on the organ it protects.
Jellyfish do not possess any true skeleton but have mesogloea. This mesogloea can form hardened plates like cartilage that hinge together. These plates get attached to the muscles and provide support to the animal and function as a skeleton.
Starfish belong to the phylum Echinodermata and possess an endoskeleton made up of calcium carbonate.
Thus, the correct answer is jellyfish

Option ‘C’ is correct

Note:
Jellyfish have around 200 species and are marine invertebrates. They are the oldest multicellular animals on earth. They do not have a brain but have some basic set of nerves at the base of their tentacle that can detect touch, temperature, etc and some jellyfish have teeth.