A biologist studied the population of rats in a barn. He found that the average natality was $250$, average mortality $240$, immigration $20$ and emigration $30$. The net increase in population is

The physiological capacity to produce offsprings is called

When does the growth rate of a population following the logistic model equal zero? The logistic model is given as $dN/dt = rN(1-N/K)$