Childbirth in mammals is an example of endocrine-controlled negative feedback, because the production of oxytocin during childbirth results in additional oxytocin being synthesized by the posterior pituitary gland. A. True B. False

B. False

Explanation:

Child-birth in mammals is not an example of endocrine-controlled negative feedback, because the production of oxytocin during childbirth doesn't result in additional oxytocin being synthesized by the posterior pituitary gland.

Oxytocin is the enzyme which is necessary at the time of birth in order to contract the walls of the uterus and expel the baby out of the body. Oxytocin levels rise at the onset of labour,causing regular contractions of womb and abdominal muscles. Oxytocin induced contractions become stronger and more frequent without the influence of progesterone and estrogen, which at high levels prevent labour.

False

Explanation:

Negative feedback mechanisms act like a thermostat in the

home. As the temperature rises (deviation from the ideal normal

value), the thermostat detects the change and triggers the air-

conditioning to turn on and cool the house. Once the

temperature reaches its thermostat setting (ideal normal value),

the air conditioning turns off. <_o3a_p>

In negative feedback, the response will reverse or cause the

opposite effect of the original stimulus. Negative feedback can

be explained with the process of insulin production and

release. After a meal the blood sugar level will be elevated due

to the absorption of sugars from the digestive tract. This

triggers the release of insulin from pancreas. Insulin converts

sugar into cells and hence the blood sugar level drops. This

low blood sugar level will result in the cessation of insulin

release. This insulin response is a negative feedback. Most

endocrine glands are under the control of negative feedback

mechanisms <_o3a_p>

Positive feedback mechanisms are rare. It amplifies changes

rather than reversing them. The release of oxytocin from the

posterior pituitary gland during labor is an example of positive

feedback mechanism. Oxytocin stimulates the muscle

contractions that push the baby through the birth canal. The

release of oxytocin result in stronger or augmented contractions

during labor. The contractions intensify and increase until the

baby is outside the birth canal. When the stimulus to the

pressure receptors ends, oxytocin production stops and labor

contractions cease.

Positive feedback mechanisms control self-perpetuating events

that can be out of control and do not require continuous

adjustment. In positive feedback mechanisms, the original

stimulus is promoted rather than negated. Positive feedback

increases the deviation from an ideal normal value.

Explanation:

The bottleneck effect is an extreme example of genetic drift that happens when the size of a population is severely reduced. Events like natural disasters (earthquakes, floods, fires) can decimate a population, killing most indviduals and leaving behind a small, random assortment of survivors.