compare the population pyramids of an under developed a developing and a developed country(answer in brief because this is long answer questions and I need help right now)
Answers
Population profiles in developed countries tend to look more like population columns than pyramids, whereas the profiles of developing countries tend to look more like pyramids.
In developed countries, family sizes tend to be much smaller due to birth control and the sheer expense of raising and educating a large family. Also more people don't have children at all, either through deliberate choice or circumstance. Marriage and having children is just one option among many. There are also more options for elderly care, with less likelihood that children will look after their elderly parents. In many developed countries such as Japan, Italy and Germany, the age profile is such that there are not enough children being born to support the existing population, and so it's likely that the population will decline in the coming decades.
In developing countries, having larger families may be more of a guarantee of support or care in later life. There may be traditional reasons for marrying and having children and there may be fewer career options in some cases. Birth control might be less widely available or even circumscribed. That said, family sizes have been dropping worldwide. Previously, one of the main reasons for having lots of children was the likelihood that many children would die before they reached maturity. With more access to vaccines, antibiotics, clean water and better medical care, this is less of a concern nowadays- but there are still areas of the world where this remains a problem.