How is a fall in blood pressure counteracted by the secretion of aldosterone? What will be an ideal response?
Concepts to Consider: A fall in blood pressure is caused by a decrease in volume of blood
and interstitial fluid. This stimulates the secretion of the enzyme renin by the juxtaglomerular
apparatus, which is a small group of cells located where the renal tubule meets the afferent
and efferent arterioles. Renin converts angiotensinogen, a plasma protein, to angiotensin. An
enzyme from the lungs then converts angiotensin into its active form, angiotensin II, which
stimulates aldosterone secretion. Aldosterone, in turn, stimulates the distal tubules and
collecting ducts to increase sodium reabsorption. This helps restore fluid volume and normal
blood pressure.
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Support for the succession mechanism of tolerance is found in research on plant communities that shows
A. that plants release toxins that prevent other species from establishing. B. succession is random and cannot be predicted by existing species. C. climax communities never form as predicted by Clements. D. succession is determined largely by species that exist in the ground as seeds or old roots. E. competition-tolerant species colonize first.
Multi-cellularity is believed to have evolved multiple times on Earth
Indicate whether the statement is true or false.
Which molecule is released in tissues and diffuses to the target cell?
a. thyroid hormone b. insulin c. adrenalin d. prostaglandins e. growth hormone
All of the following statements are true about the clam's digestion EXCEPT
A. the clam has a single opening for the entry of food and the exit of digestive wastes. B. small food particles are collected on the gills and moved by cilia to the mouth. C. the clam is a filter feeder. D. the clam is a continuous feeder.