Question

Why is excretion necessary? Name the common excretory substances in our body. [3 MARKS]

Answer 1

Necessity: 1 Mark
Excretory substances: 2 Marks

There are a number of chemical substances which are regularly formed in our body or which are absorbed through the food that must be got rid of. These products, if allowed to accumulate within the body, prove toxic and eventually result in the death of an organism. Excretion is necessary to remove such harmful unwanted (nitrogenous) waste products from the body. In this way, excretion plays an important role in maintaining the homeostatic (steady) condition of the body.

The common excretory substances in our body are:
1. Excess water
2. Excess salts including common salt and some water soluble vitamins.
3. Nitrogenous metabolic wastes, which include urea, uric acid, ammonia etc. Of these, urea is highly poisonous.
4. Bile pigments.