It was observed that the tadpoles are not growing into adult frogs in a village pond. A scientist who was asked to find the reason for this concluded that the pond water did not contain a sufficient amount of a mineral P which could make a hormone Q. The hormone Q can cause a phenomenon R in tadpoles so that they become adult frogs.

(a) What are (i) P (ii) Q, and (iii) R?

(b) Name one human disease which can also be caused due to the deficiency of P in the food and water.

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Solution

(a) 1. Iodine 2. Thyroxine 3. Metamorphosis
(b) Iodine is needed continuously by the thyroid gland to make the thyroxine hormone. If people do not have enough iodine in their diet, they will get goiter disease caused by a lack of thyroxine. So, people are advised to use iodized salt in cooking food.

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Name the hormone which is required for the metamorphosis of larvae (tadpoles) into adult frogs.

The gland A is attached to the wind pipe in the human body. The gland A makes and secretes a hormone B which controls the metabolism of carbohydrates, fats and proteins in the body. The non-metal element C is necessary for the formation of hormone B. The deficiency of C in the diet can cause a deficiency of hormone B in the body leading to a disease D in which the neck of a person appears to be swollen. People are advised to use salt E in cooking food so as to avoid disease D.

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(d) Name (i) disease D, and (ii) salt E.

Q. Milo found some tadpoles in a pond and caught a few in a bottle. He grew those in a small glass water tank and supplied them with proper tadpole food. Despite all these efforts, the tadpoles never grew into adults. Which of the following can be a possible reason?

Q. After the rain, tadpoles were found swimming in a pond but not the frogs. This is due to:

What will happen if the water in which tadpoles are growing does not contain sufficient iodine?

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