In a neutral atom, the number of protons are equal to the number of:
A. ions
B. electrons
C. the atomic mass
D. neutrons
Answer: B
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Over long periods of time, many cave-dwelling organisms have lost their eyes. Tapeworms have lost their digestive systems. Whales have lost their hind limbs. How can natural selection account for these losses?
A) Natural selection cannot account for losses, but accounts only for new structures and functions. B) Natural selection accounts for these losses by the principle of use and disuse. C) Under particular circumstances that persisted for long periods, each of these structures presented greater costs than benefits. D) The ancestors of these organisms experienced harmful mutations that forced them to lose these structures.
Which of the following is the most direct source of energy for cotransport?
-the movement of one of the transported substances up its concentration gradient -the movement of one of the transported substances down its concentration gradient -ATP hydrolysis -ATP formation cotransport requires no energy
Permanently swollen veins, common in the legs and feet, are known as ________
Fill in the blank(s) with correct word
Which of the following statements regarding the Watson–Crick model of DNA is false?
A) It is the most common biological form of DNA. B) The two DNA strands form a left-handed helix. C) The two DNA strands are antiparallel. D) The bases are "stacked" in the center of the molecule. E) The backbone consists of alternating sugars and phosphates.