Answer:
In MDCs (More-Developed countries), the age structure is much more rectangular-shaped if you were to represent it in a population pyramid, as there is about an even number of people in each age group. The US is an example of one country that displays this. In LDCs (Less-dev. countries), however, the age structure contains much more people who are younger; if you were to draw the age structure for one of these countries, it would look like a triangle. This is due to a couple reasons: first off, there is likely not a solid health care system, education is likely not, so to speak, top-notch, religion likely has a much greater influence on the people, leading to lots of births and a very high TFR (total fertility rate). Second, numerous people cannot reach old age due to, again, the reasons above.
