Which of the following is a population?

all the animals in a prairie ecosystem.
all the mesquite trees in a desert ecosystem.
all the living organisms in a river ecosystem.
the tree where a squirrel lives in a forest ecosystem.

An enzymatic hydrolysis of fructose-1-p, fructose-1-p(aq) + h2o(l) - fructose (aq) + pi (aq) was allowed to proceed to equilibrium at 25°c. the original concentration of fructose-1-p was 0.2 m, but when the system had reached equilibrium, the concentration of fructose-1-p was only 6.52 x 10^-5 m. calculate the equilibrium constant for this reaction and the free energy of hydrolysis of fructose-1-p.