Give Jeason: si System is accepted by all nations in the world.
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it's very practical, because it's on base 10, so conversion between stuff like meters to kilometer is always just a multiplication with 10 to some power

like 1 km = 1000m (10³m)

or 1 m = 10^-3km = 0.001km

same reason for other SI units.

except time, that's base 60, or 12, or 24. that's more complicated, but there isn't any real competition

they each offer a fresh glut of resources to the organisms that can arrive and exploit them. as individuals and new species continue to appear, they actively and passively alter the environment. competition for shared resources increases, local abiotic and biotic conditions shift, and the relative abundances of species change accordingly. the process is called ecological succession, and it is one of the earliest and most well-known concepts in ecology.