Which is not a reason for the lack of a fossil record from the precambrian time? (45 points)

a.) like the rocks of the phanerozoic eon, precambrian rocks contain many visible signs of complex life forms

b.) precambrian rock has been eroded or metamorphosed over billions of years, and very little of it remains at the surface

c.) multi-celled organisms evolved in the oceans during the latest years of the precambrian time

d.) the single-celled organisms that existed during that time did not leave easily identifiable fossils

If you have a difficult time knowing where your hand is without looking at it you may be having a problem with your what ?

Which two factors contributed to creating a global culture? the creation of the united nations improvement in telecommunications health issues such as the ebola virus increased opportunities for global travel

To answer this question, researchers studied populations of the dusky salamander (desmognathus ochrophaeus) living on different mountain ranges in the southern appalachian mountains. the researchers tested the reproductive isolation of pairs of salamander populations by leaving one male and one female together and later checking the females for the presence of sperm. four mating combinations were tested for each pair of populations (a and b)—two within the same population (female a with male a and female b with male b) and two between populations (female a with male b and female b with male a). the proportion of successful matings for each mating combination was measured. for example, when all the matings of a particular combination were successful, the researchers gave it a value of 1; when none of the matings were successful, they gave it a value of 0. then the researchers calculated an index of reproductive isolation that ranged from 0 (no isolation) to 2 (full isolation). the reproductive isolation value for two populations is the sum of the proportion of successful matings of each type within populations (aa + bb) minus the sum of the proportion of successful matings of each type between populations (ab + ba). the table provides data for the geographic distances and reproductive isolation values for 27 pairs of dusky salamander populations.