Statement I: Even a slow growing animal like elephant could reach enormous numbers in the absence of checks.

Statement II: The birth rate and death rate are required to calculate intrinsic rate of natural increase.

A slow growing animal like elephant could reach enormous numbers in the absence of checks. 

If in a population of size N, the birth rates (not total number but per capita births) are represented as b and death rates (again, per capita death rates) as d, then the increase or decrease in N during a unit time period t (dN/dt) will be 

dN/dt = (b – d) × N 

Let (b–d) = r, then 

dN/dt = rN 

The r in this equation is called the ‘intrinsic rate of natural increase’. 

So to calculate r (intrinsic rate of natural increase), b (birth rates) and d (death rates) are required.