In a marsh community, aquatic plankton contain 0.04 ppm of DDT, small fish contain 0.30 ppm of DDT, larger fish contain 1.5 ppm of DDT, and cormorants (fish-eating birds) contain 24 ppm of DDT. This is an example of
A. the carbon cycle.
B. succession.
C. nutrient cycling.
D. biomagnification.
D. biomagnification.
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Which of the following are not transported in phloem?
A. sugars B. amino acids C. hormones D. large starch molecules E. RNA
You are having lunch with an elderly friend when suddenly he begins to experience chest pain and tightness. He reaches into his pocket, gets out one of his nitroglycerin tablets and quickly takes it. After the episode passes, your friend asks you how the nitroglycerin helps his angina. You explain that nitroglycerin gets converted by cells to nitric oxide (NO) causing the smooth muscle cells of
the blood vessel to relax and increase blood flow to the heart. He pushes you for a more detailed explanation, so you explain further that: A. NO activates guanylyl cyclase, which catalyzes the synthesis of cGMP, which acts as an intracellular messenger in a pathway leading to smooth muscle relaxation. B. NO activates a protein kinase which catalyzes the synthesis of cGMP, which acts as an intracellular messenger in a pathway leading to smooth muscle relaxation. C. NO inhibits guanylyl cyclase, which allows the build up of cGMP, which acts as an intracellular messenger in a pathway leading to smooth muscle relaxation. D. NO activates cGMP, which catalyzes the synthesis of guanylyl cyclase, which acts as an intracellular messenger in a pathway leading to smooth muscle relaxation.
________________ decreases the reabsorption of sodium ions.
A. Anti-diuretic hormone (ADH) B. Aldosterone C. Atrial natriuretic hormone D. Angiotensin II
Which of the following statements regarding the lymphatic system is FALSE?
A) Lymph fluid is similar to blood plasma. B) The lymphatic vessels contract to move lymphatic fluid. C) The lymphatic vessels have valves to control the direction of fluid flow. D) The lymphatic system begins with highly permeable capillaries. E) Fluid flows through lymph nodes on its way to the bloodstream.