Question

In the following graph which of the expressions of the exponential growth equation should be increased in order for curve 1 to become more like curve 2?

• A.
  N
• B.
  d
• C.
  b
• D.
  (b-d)

Answer 1

The correct option is B

d
In exponential growth, a population's per capita (per individual) growth rate stays the same regardless of population size, making the population grow faster and faster as it gets larger.

When resources are unlimited, populations exhibit exponential growth, resulting in a J-shaped curve. Exponential growth is represented by the equation dN/dt=rN or dN/dt = (b-d) N, which is the population growth rate, where b is the average per-capita birth rate (NOT the number of births), d is the average per-capita death rate (NOT the number of deaths), and N is the population size.

In this equation, dN/dt is the growth rate of the population in a given instant, N is population size, t is time, and r is the per capita rate of increase –that is, how quickly the population grows per individual already in the population.

When per capita births exceed per capita deaths b > d, the population is increasing and r is positive; when deaths exceed births b < d, r is negative and the population is decreasing. So in order for the curve 1 to become more like curve 2, there should be increase in death rate. So option "b" is the correct answer.