Explain 4 types of population structures?

1. Expansive population structure: This type of population structure is characterized by a high proportion of young individuals and a low proportion of elderly individuals. This can be seen in countries with high birth rates and high levels of fertility. The population pyramid for an expansive population structure will have a wide base and a narrow top, indicating a large number of children and a smaller number of elderly individuals.

2. Stationary population structure: In a stationary population structure, the number of individuals in each age group remains relatively stable over time. This type of population structure is often seen in countries with low birth rates and low levels of fertility, as well as high life expectancy. The population pyramid for a stationary population structure will have roughly equal numbers of individuals in each age group, with a slight tapering towards the top.

3. Constrictive population structure: A constrictive population structure is characterized by a low proportion of young individuals and a high proportion of elderly individuals. This can be seen in countries with low birth rates and low levels of fertility, as well as high life expectancy. The population pyramid for a constrictive population structure will have a narrow base and a wide top, indicating a small number of children and a larger number of elderly individuals.

4. Pyramid-shaped population structure: This type of population structure is characterized by a broad base representing a high proportion of young individuals, tapering towards the top with a decreasing proportion of elderly individuals. This type of population structure is often seen in developing countries with high birth rates and high levels of fertility. The population pyramid for a pyramid-shaped population structure will have a wide base and gradually taper towards the top.

1. Stable Population Structure:

- Equal proportions of individuals in all age groups
- Birth and death rates are balanced
- Little or no population growth
- Pyramid-shaped age distribution with a wide base and narrow top

2. Expanding Population Structure:

- High birth rate and low death rate
- More individuals in younger age groups
- Exponential population growth
- Bell-shaped age distribution with a wider base and narrower top

3. Contracting Population Structure:

- Low birth rate and high death rate
- Fewer individuals in younger age groups
- Population decline
- Reverse pyramid-shaped age distribution with a narrow base and wider top

4. Stationary Population Structure:

- Birth and death rates are approximately equal, but may fluctuate
- Zero population growth
- Age distribution is relatively constant over time
- Rectangular-shaped age distribution with similar proportions of individuals in all age groups