Question

Ritu learned that excretion removes harmful metabolic wastes, i.e. nitrogenous wastes from the body. Different processes are employed in varied organisms depending on body’s organisation. 

Read the passage and answer the following questions. 

(i) Why can’t diffusion be carried out as excretory process in multicellular organisms? 

(ii) Aquatic animals usually excrete ammonia as excretory waste. Give reason. 

(iii) List the values observed in Ritu.

Answer 1

(i) The multi-cellular organisms have a very complex body organization. They possess many different organ-systems to perform the basic life processes, such as respiration, excretion, etc. Also, the cells and tissues of these organisms are not in direct contact with the environment. Moreover, diffusion is quite a slow process. So, excretion cannot be performed through diffusion. 

(ii) Ammonia is a toxic nitrogenous waste and is highly soluble in water. The removal of ammonia requires a large amount of water. Aquatic animals are ammonotelic as they need not conserve water. The conversion of ammonia into less toxic metabolite (urea, uric acid) is highly energy intensive. Therefore, aquatic animals prefer not to expend energy in conversion of ammonia. 

(iii) Ritu possesses a number of values. She seems to be attentive, vigilant, observant and zealous. She has a curiosity for learning.