- (Topic 3)
Although technically their members were hunter-gatherers, many early Native California communities exhibited traits more typically associated with well-developed agrarian societies and. therefore, are often presented in the ethnographic literature as _____ .
Correct Answer:CE
- (Topic 2)
A car service charges S5 for the first mile of a trip and S2 for each additional mile or part thereof. If the car service charges SI01 for an //-mile trip, where // is an integer, what is the value of n ?
Correct Answer:B
- (Topic 3)
Scientists have long debated the exact timing of the lunar cataclysm, a period approximately 4 billion years ago when Earth and the Moon were pummeled with asteroids. A clue to this puzzle may come from spherules, millimeter-sized droplets of molten rock formed after au asteroid collides explosively with a planet. Upon impact, the asteroid vaporizes both itself and the target rock, producing a vapor plume that condenses into spherules. These form a layer preserved in rock, whose age can be estimated using radiometric dating. Scientists know of fourteen of these spherule layers scattered across Earth, but none dates to the theorized lunar cataclysm time period. Four layers, however, are from between 3.47 and 3.24 billion years ago. indicating perhaps a slow decline in collisions.
The primary purpose of the passage is to
Correct Answer:D
- (Topic 3)
Recent research has questioned the long-standing view of pearly mussels as exclusively suspension feeders (animals that strain suspended particles from water) that subsist on phytoplankton (mostly algae). Early studies of mussel feeding were based on analyses of gut contents, a method that has three weaknesses. First, material in mucus-bound gut contents is difficult to identify and quantify. Second, material found in the gut may pass undigested out of the mussel, not contributing to its nutrition. Finally, examination of gut contents offers limited insight into the mechanisms and behaviors by which mussels acquire food. Modem studies suggest that pearly mussels feed on more than just algae and may use other means than suspension feeding. Pedal feeding (sweeping up edible material with a muscular structure called the foot) has been observed in juvenile pearly mussels.
Besides the phytoplankton pearly mussels capture from the water column, their guts also contain small animals, protozoans, and detritus (nonliving particulate organic material). Recent studies show that mussels can capture and assimilate bacteria as well, a potentially important source of food in many fresh waters. Another potential source of food for mussels is dissolved organic matter. Early studies showing that pearly mussels could take up simple organic compounds were largely discounted because such labile (unstable) compounds are rarely abundant in nature. Nevertheless, recent work on other bivalves suggests that dissolved organic matter may be a significant source of nutrition.
Of this complex mix of materials that pearly mussels acquire, what is actually required and assimilated? Stable-isotope analyses of mussels taken from nature and of captive-reared mussels are beginning to offer some insight into this question. Nichols and Garling showed that pearly mussels in a small river were omnivorous, subsisting mainly on particles less than 2S micrometers in diameter, including algae, detritus, and bacteria. Bacterially derived carbon was apparently the primary source of soft-tissue carbon. However, bacteria alone cannot support mussel growth, because they lack the necessary long-chain fatty acids and sterols and are deficient in some amino acids. Bacteria may supplement other food resources, provide growth factors, or be the primary food In habitats such as headwater streams, where phytoplankton is scarce. Juvenile mussels have been most successfully reared m the laboratory on diets containing algae high in polyunsaturated fatty acids. Thus, it appears that the pearly mussel diet in nature may consist of algae, bacteria, detritus, and small animals and that at least some algae and bacteria may be required as a source of essential biochemicals.
Which of the following can be inferred about the "recent research?
Correct Answer:C
- (Topic 2)
A continuous random variable R has a mean of 77 and a standard deviation of 8. What is the value of R that is 2.5 standard deviations above the mean?
Correct Answer:E