Question

Why do earthworms come out of their burrows when it rains heavily?
(A) Earthworm floats along with flooded water
(B) Earthworm breathes in the oxygen from the porous soil with the help of its moist skin
(C) Soil pores are filled with water when it rains
(D) Both B and C

Answer 1

Hint: When there is heavy rain, the soil is filled up from the water, and the air is not able to pass from the soil which is filled up from the water and in turn leads to difficulty for various organisms.

Complete solution:
All the terrestrial animals are usually found to breathe oxygen from the air with the help of the lungs. An earthworm breathes the oxygen by absorbing it through the moist skin. It likes damp soil, but if the rain is very heavy, mostly in the rainy season, the oxygen in the water-logged soil may run out.
-The scientific name of an earthworm is Lumbricina that belongs to the phylum Annelida of the order Opisthopora. The earthworms are most commonly found in soils that are rich in organic matter.
-Earthworms are invertebrate therefore they lack a skeleton but usually maintain their structure with the help of a coelom chamber which is filled with fluid and acts as a hydrostatic skeleton.
-Specialised respiratory organs are not present in the earthworm. That's why they take Oxygen and give out carbon dioxide directly through their skin.
-Diffusion of oxygen takes through the earthworm's body surfaces and there is a network of
capillaries present just under the body surfaces through which oxygen diffuses inside their body.
-Usually, the air dissolves on the mucous of the earthworm's skin. Therefore they need to
stay moist to breathe and they feel suffocation if the worms are dry out. Oxygen moves into the worm’s circulatory system as fresh air is taken in through their skin. Pumping of the oxygenated blood to the head area of the worm is taken by the heart of the worm.
-Earthworms have Central and peripheral nervous systems.

So, the correct answer is ‘Both B and C’

Note:
-A thin layer of cuticle present on the skin of the earthworm that helps in keeping the skin of the earthworm moist and slimy.
-The exchange of gases that are taking Oxygen and giving out carbon dioxide takes place by the moist skin of earthworms.
-Earthworms will feel suffocation if their body becomes dry because of the inhibition of the exchange of gases.