Question

What is common between a moth, a frog and a mosquito?
A) The body is clearly differentiated into head, thorax and abdomen
B) The life history is carried out in water
C) The skin acts as the main respiratory organ
D) Their larvae feed on a food different from that of the adult

Answer 1

Hint: Moth, frog and mosquitos are the organisms which have their definite lifecycle. The frog lives in the terrestrial as well as aquatic habitat, the moth is the adult. The mosquito is the adult which infects the humans and feed on their blood.

Complete answer:
To answer this question, we must know about the life cycle of the three organisms. The frog, moth and mosquito are the invertebrates which differ widely in morphology and anatomy. Frog belong to the phylum amphibia whereas the moth is in phylum arthropods and the mosquitos are in the phylum Arthropoda. All the three organisms undergo metamorphosis to become an adult. The adult formed is completely different from the intermediate stage. Let us see the characteristic of all the three.

	Frog	Moth	Mosquito
1. Body differentiation-	Body is divided into a head, a short neck and a trunk.	They have the joint bodies divided into head thorax and abdomen.	The body is divided into head thorax and
2. Life history	The life cycle has four stages- egg, tadpole, froglets and frog. The egg and tadpole are aquatic whereas froglets and frogs are terrestrial.	The life cycle of moths involves egg, larva, pupa and adult moth. They are terrestrial or aerial.	The life cycle involves stages of egg, larvae, pupa and adult. The egg, larva and pupa are aquatic and the adult is aerial.
3. Respiratory organ-	The adult breaths through the lungs on land and moist skin in water.	They have trachea and spiracles for respiration.	The mosquitos have trachea for breathing.
4. Larval stage	The larva is the most active stage which continuously feeds to develop into an adult.	The larva is the most active stage which continuously feeds and becomes a cocoon which grows to develop into an adult.	The larva is the most active stage which continuously feeds to develop into an adult.

Therefore from the above explanation the correct answer is option ‘D’.
Note: Metamorphosis is the process of development which an organism develops from egg stage to a complete adult. This involves several stages of cell growth and differentiation. This process is controlled by the hormone thyroxine in the case of frog, humans.