Lipids are unique because, they are made from one carbon skeleton unlike the other macro molecules groups which are made from smaller building blocks.
With the exception of steroid hormones, lipids are generally hydrophobic. Also lipids are relative small molecules when compare in size with other macromolecules.
The seasonal movement of animals from one place to another (usually occurs in species with ability to flight and in large amount
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 are called compounds
