Question

Non-cleidoic eggs occur in
A. Birds
B. Fish
C. Reptiles
D. Platypus

Answer 1

Hint: Non-cleidoic eggs are not protected by a hard shell. In all oviparous animals which lay eggs in water, these eggs are seen.

Complete Answer:
The egg is the zygote-containing organic reservoir in which an embryo grows until it is able to live on its own, at which time the animal hatches. An egg comes from egg cell fertilisation. Eggs are laid by most arthropods, vertebrates (except for live-bearing mammals), and mollusks, though some do not, such as scorpions.

Now, let us find the solution from the options-
- Cleidoic eggs are eggs of reptiles and birds separated by albumen membranes and shells from the environment. The calcareous shell found around the bird’s eggs is porous and causes $O_2$ and $CO_2$ to be diffused. It is an egg of terrestrial animals because it is made up of hard $CaCO_3$. Therefore, reptiles and birds are incorrect options.
- Non-cleidoic eggs are deposited in water, not covered by shells and without enough dietary content for the embryo to fully mature. A non-cleidoic egg usually hatches into a larva. This type of eggs is found in fish.
- The Platypus is an eastern Australian semi-aquatic egg-laying animal. Therefore, platypus is an incorrect option.

Thus, the correct answer is option (B) Fish.

Note: Cleidoic eggs and non-cleidoic eggs are divided on the basis of shell. Cleidoic eggs have an outermost shell that is thick and hard. This hard shell is gas-permeable. The egg membranes of the non-cleidoic egg are so delicate and as they lack the hard protective coating that helps them from drying out, these eggs must be placed in water.