Question

Incorrect information about a frog (Rana tigrina ) :
(a) 10 pairs of cranial nerves and 10 pairs of spinal nerves
(b) 4000 uriniferous tubules in the body
(c) 2 lymph hearts in the body
(d) Breeding season is from July to September

Answer 1

Hint: Frogs, in general, are found in or near freshwater and in very damp places on land. They belong to the class Amphibia of phylum Chordata and kingdom Animalia.

Complete answer:
Incorrect information about a frog (Rana tigrina ) is ’10 pairs of cranial nerves and 10 pairs of spinal nerves’. An adult frog normally has 10 pairs of spinal nerves and 10 pairs of cranial nerves but in the case of R. tigrina, the 10^th pair of the spinal nerves are either reduced or absent. Therefore, there are only 9 pairs of spinal nerves present in R. tigrina.
Additional information:
Excretory system
- R. tigrina has a well developed excretory system which helps in eliminating the nitrogenous wastes from the body. They are ureotelic organisms predominantly excreting urea.
- The excretory system consists of:
1. A pair of kidneys- Two mesonephric kidneys are present. Each one is a compact mass of about 2000 highly twisted microscopic uriniferous tubules of nephrons.
2. Ureters
3. Urinary bladder
4. Cloaca
Lymphatic system
Lymph flows through the lymphatic system. The lymph is different from the blood. It is without any RBC’s and contains few proteins. Lymph is continuously produced from the filtering of blood through capillaries into intercellular spaces. The frog has two pairs of lymph hearts that pump lymph.
Croaking
- The characteristic noise or sound made by frogs is known as croaking. It is commonly heard during the breeding season during rains. The breeding season of R. tigrina is from July to September.
So, the correct answer is ’10 pairs of cranial nerves and 10 pairs of spinal nerves’.

Note: Frog is useful to mankind because it eats up insects that are harmful to the crops. Thus, it saves expenditure on insecticides. They eat mosquitoes that act as vectors for disease- causing parasites to man.