What kind of bonds hold the two strands of the DNA molecule together?
a. glycosidic
b. phosphodiester
c. hydrogen
d. tetravalent
c. hydrogen
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You have two beakers. One contains pure water, the other contains pure methanol (wood alcohol). The covalent bonds of methanol molecules are nonpolar, so there are no hydrogen bonds among methanol molecules
You pour crystals of table salt (NaCl) into each beaker. Predict what will happen. A) Equal amounts of NaCl crystals will dissolve in both water and methanol. B) NaCl crystals will not dissolve in either water or methanol. C) NaCl crystals will dissolve readily in water but will not dissolve in methanol. D) NaCl crystals will dissolve readily in methanol but will not dissolve in water. E) When the first crystals of NaCl are added to water or to methanol, they will not dissolve; but as more crystals are added, the crystals will begin to dissolve faster and faster.
Which of the following are important biotic factors that can affect the structure and organization of biological communities?
A) precipitation, wind B) nutrient availability, soil pH C) predation, competition D) temperature, water E) light intensity, seasonality
Why is the velocity of blood flow lowest in capillaries?
a. Capillaries are far from the heart, and blood flow starts to slow as it moves away from the heart. b. The systemic capillaries are supplied by the left ventricle, which has a lower cardiac output than the right ventricle. c. The total surface area of capillaries is larger than the total surface area of the arterioles. d. The capillary walls are not thin enough to allow oxygen to exchange with the cells. e. The diastolic blood pressure is too low to deliver blood to capillaries at a high flow rate.
Which of the following statements about soil is false?
A. the O and A horizon has the greatest physical, chemical, and biological activity B. the A horizon is the topsoil C. the B horizon is the subsoil D. the R horizon is bedrock or parent material E. none of the above are false