1. ‘S’ – Shaped Growth or Sigmoid growth curve:

It is also called a sigmoid curve.

**It has 3 phases:**

1. Early or Lag phase: There is little or no growth.

2. Middle or Log or Exponential phase: There is fast growth in the population.

3. Stationary or Zero or Plateau phase:

- The population growth is zero.
- Mortality and natality are equal.
- The population becomes equal to the environmental carrying capacity.

In S (sigmoid) form, the population increases slowly at first, then more rapidly but it soon slows down gradually as the environment resistance increases.

**Factors affecting Population Growth:**

- The population of any country is effected by 4 factors
- Natality
- Mortality
- Migration
- Age Distribution

- More natality in any country and less mortality increases population and the vice versa. Similarly, if human Immigration is more than migration, the population will increase and vice versa.