As the proteins present in our body break, they produce toxic ammonia. This ammonia will be converted to urea, in all mammals. The urea produced can be eliminated from the body when it is dissolved in water present in the urine. In a similar way, in birds and reptiles, the ammonia produced will be converted as uric acid. This solid substance will be excreted when it dissolves with little amount of water.
The amount of water required to excrete 1 gram of urea is twenty to thirty times more than that is required to eliminate 1 gram of uric acid. This indicates that mammals require more amount of water, than birds and reptiles do. Thus, water is the deciding factor for species richness of mammals, birds, and reptiles.
For mammals to be more in number there should be good amount of water in their surroundings. But, birds and reptiles can survive well even when there is very little amount of water. For example, lizards can live long even without water. They have the ability to absorb moisture from the solid food they eat.
In order to test our hypothesis, let us examine the area in which there is very less amount of water. If we count the numbers of each species surviving in that area, then we can observe the numbers of mammals to be very less, than birds and reptiles. This shows the importance of water for the survival of mammals. Unless the toxic ammonia is converted to urea, no mammal can survive on the land.
Thus, the species richness is related to the amount of water required for the conversion of toxic ammonia into urea and uric acid.
1) Ureter is a channel or tube that connects the kidney to the urinary bladder. These carry the urine filtered from the kidneys to the urinary bladder to get expelled from the body.
Hence, 1 matches with (c) 'carries urine from kidney to bladder'.
2) Bowman's capsule is the part of nephron from where the nephron starts. It collects the fluid from the glomerular capillaries.
Hence, 2 matches with (a) 'start of nephron'.
3) Urethra is the tube that carries the urine from the urinary bladder to the body surface so that it can be expelled from the body.
Hence, 3 matches with (b) 'delivers urine to body surface'.
4) Collecting duct connects the nephron to ureter. It receives the aldosterone secreted by the adrenal gland which stimulates the sodium-potassium pump.
Hence, 4 matches with (e) 'target of aldosterone'.
5) Pituitary gland is one of the major gland of the body. It plays role in excretory system by releasing ADH.
Hence, 5 matches with (d) 'secretes ADH'.
The thirst behaviour is initiated and controlled by a negative feedback loop between kidney and brain.
It involves a thirst centre located in the hypothalamus along with the pituitary gland which secretes the ADH and osmoreceptors located in the brain.
Thus, thirst centre of the hypothalamus is not exclusively involved in initiating and controlling the thirst behaviours.
Hence, it is false that thirst centre in hypothalamus is exclusively involved in initiating and controlling thirst behaviour.