You have probably noticed that urine is not always the same. the body is capable of adjusting the volume and the osmolarity of its urine output depending on a number of factors. the kidneys are regulated by hormones such as antidiuretic hormone (adh) and aldosterone. these hormones are secreted in response to changes in the animal's internal water and salt balance. for example, sweating or blood loss can disrupt water and/or salt balance in the body, leading to a hormonal response that returns the system to homeostasis. mechanisms for adjusting blood volume or osmolarity include increasing water and/or sodium reabsorption in the nephrons and collecting ducts. how do the following stimuli affect water and sodium (na+) reabsorption in the kidneys?

The answer is given below

Explanation:

1) Blood Loss :- B. with blood body loses both water and salt. so it will trigger release of vasopressin and aldosterone which will result in the reabsorption of water and salt from the filterate.

2) ADH secretion :- A. vasopressin increase the permeability of DCT for water which diffuses out from it.

3) Aldosterone release:- B. Aldosterone increase membrane permeability to Na+. as the ions move out actively, water diffuse out due to osmotic gradient resulting from ion movement.

4) alcohol consumption:- C. it actually decreases the water uptake. alcohol decrease the level of ADH. this results in less water uptake and excessive urination leading to dehydration.

5) sweating:- A. water loss by sweating decrease the plasma water level. it will stimulate secretion of ADH and increase water uptake in kidneys.

6) dehydration due to less water uptake:- A. same as above.

7) caffeine consumption:- C. caffeine and other xanthines inhibit Na+ reabsoption and increase glomerular filteration.

8) eating salty foods:- A. salty foods increase the blood salt level. to tackle this, ADH is secreted and secretion of aldosterone is inhibited. this increase water uptake and decrease sodium reabsorption.

9) diabetes insipedus:-C. in diabetes, glucose is present in the filterate and final urine. due to presence of glucose in filterate is no more hypotonis to tissue fluid and so not loose water to it. so there is higher loss of water in urine. this leads to excessive urination, due to lesser water reabsorption, and increased thirst, due to high water loss.

10) severe diarrhea:- B. loss of chiefly water and salts in diarrhea will stimulate both ADH and aldosterone to increase their loss in urine to maintain homeostasis.

For POINTS 1 to 7 :once they are excreted from the body, the body will tend to preserve water and salt lost due to diuretics, so it will secrete adh and aldosterone to increase their reabsorption. Here the answer will become "B".

measuring light intensity

light meters can be used to measure light intensity. the meter is held at the soil surface and pointed in the direction of the maximum light intensity, and then the meter is read.

errors can be made when measuring light intensity by accidentally shading the light meter. the reliability of the results can be checked by taking many samples.