Question

Explain the equation:

N_{t + 1} = N_t + [(B + I) − (D + E)]

On the basis of the flow chart given below.

Answer 1

1. The equation N_{t + 1} = N_t + [(B + I) − (D + E)] explains how population density changes over time.
2. Here, N_t is the current population density, and N_{t + 1} is the population density in the next time unit.
3. The terms inside the bracket represent net changes: (B) is natality (births), (I) is immigration (individuals entering), (D) is mortality (deaths), and (E) is emigration (individuals leaving).
4. The population density will increase if the sum of births and immigration (B + I) is greater than that of deaths and emigration (D + E); otherwise, it will decrease.
5. This equation models the flow chart where natality and immigration positively influence population density, while mortality and emigration decrease it.
6. Hence, population change depends on the balance of these four factors, showing how populations grow or shrink based on births, deaths, and movement of individuals in and out of the population area.