Question

Which of the following is an example of homeostasis?

	a.	In hot and dry temperatures, plants will eventually wilt as the amount of water lowers in their cells.
	b.	Water moves down its concentration gradient.
	c.	When the concentration of glucose in the blood is low, glycogen is broken down into glucose.
	d.	A human's body temperature increases while running.
	e.	Uterine contractions trigger the release of a hormone that then triggers stronger uterine contractions.

Answer 1

Option 3 is correct.

Homeostasis is a process to maintain optimal, stable and equilibriated conditions of survival in the body of an organism. Important factors like body temperature, blood fluid balance, ionic balance and sugar levels are generally kept within the pre-set limits by various homeostasis mechanism in the body of a plant or an animal. It is a kind of coping mechanism to prevent the organism from any kind of adverse condition that might happen due to imbalance of certain levels. Option 3 correctly justifies the homeostasis mechanism. It says that when concentration of glucose in the blood is low glycogen is broken down into glucose. As the blood glucose level goes down in the body, the liver has stores glycogen which is then as a response is broken down to increase and bring back the blood sugar levels to its optimum or normal in the body.

Option a,  which says that in hot and dry temperatures plants will eventually wilt as the amount of water lowers in their cells. This is not any kind of homeostasis mechanism as had there been loss of water by the plant, a homeostasis mechanism would have insured to increase its level by blocking off or decreasing the rate of transpiration.

Option b, says that water moves down its concentration gradient, just describes the normal process of osmosis which takes place.

Option d which says a human body temperature increases while running is also a natural physiological process which takes place. Homeostasis mechanism in this case would try to bring back the body temperature to normal by the mechanism of sweating etc.

Option e,  which says that uterine contractions trigger the the release of hormone that then triggers stronger uterine contractions is just a type of positive feedback mechanism which takes place at the time of parturition for childbirth.

So, the correct answer is option C.