Problem: Annelids with blood vessels use metanephridia to remove soluble waste products, while those without use protonephridia. Both of these systems use a two-stage filtration process, in which fluid and waste products are first extracted and these are filtered again to re-absorb any re-usable materials while dumping toxic and spent materials as urine. The difference is that protonephridia combine both filtration stages in the same organ, while metanephridia perform only the second filtration and rely on other mechanisms for the first – in annelids special filter cells in the walls of the blood vessels let fluids and other small molecules pass into the coelomic fluid, where it circulates to the metanephridia. In annelids the points at which fluid enters the protonephridia or metanephridia are on the forward side of a septum while the second-stage filter and the nephridiopore (exit opening in the body wall) are in the following segment. As a result, the hindmost segment (before the growth zone and pygidium) has no structure that extracts its wastes, as there is no following segment to filter and discharge them, while the first segment contains an extraction structure that passes wastes to the second, but does not contain the structures that re-filter and discharge urine.
What annelid system combines both filtration states in one organ?
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Answer: protonephridia


Problem: Waitz defined anthropology as "the science of the nature of man". By nature he meant matter animated by "the Divine breath"; i.e., he was an animist. Following Broca's lead, Waitz points out that anthropology is a new field, which would gather material from other fields, but would differ from them in the use of comparative anatomy, physiology, and psychology to differentiate man from "the animals nearest to him". He stresses that the data of comparison must be empirical, gathered by experimentation. The history of civilization as well as ethnology are to be brought into the comparison. It is to be presumed fundamentally that the species, man, is a unity, and that "the same laws of thought are applicable to all men".
How did Broca define nature?
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Answer: unanswerable


Problem: UN aerial reconnaissance had difficulty sighting PVA units in daytime, because their march and bivouac discipline minimized aerial detection. The PVA marched "dark-to-dark" (19:00–03:00), and aerial camouflage (concealing soldiers, pack animals, and equipment) was deployed by 05:30. Meanwhile, daylight advance parties scouted for the next bivouac site. During daylight activity or marching, soldiers were to remain motionless if an aircraft appeared, until it flew away; PVA officers were under order to shoot security violators. Such battlefield discipline allowed a three-division army to march the 286 miles (460 km) from An-tung, Manchuria, to the combat zone in some 19 days. Another division night-marched a circuitous mountain route, averaging 18 miles (29 km) daily for 18 days.
When would PVA forces march to minimize the chances of being seen?
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Answer:
19:00–03:00