Population growth affects world development. When talking about development, we usually refer to the economic development of a city, country, or even the whole world. Before the industrial revolution, the world's population stood at around 1 billion, not more. After the rapid economic change, the population growth is described as an 'explosion'. But it doesn't even compare to the growth of consumption of resources, especially fossil fuels. This chart describes the ecological footprint up until 2008 and two scenarios that could happen. One scenario being that we continue on as we currently are and the ecological footprint would drastically increase until we need resources equivalent to 3 earths! This means only 1/3 of the population will have enough water, enough food and less than that will have proper sanitation/hospitalization. This is an enormous jump from today's conditions, because today 6/7 of the population meets their basic, consumer needs. The other scenario is a rapid reduction where we will only require the resources of one earth. How will that happen? By more usage of renewable resources and less wastage of the resources we consume on a daily basis. There would also be more enforcement of birth-control and that would reduce population growth too.
This is just a look into the future. Focusing on the present, it isn't that we do not have enough food and resources for all the population, because we do. It's the way we use them, and the way we produce them that makes it unable to feed everyone. There is a lot of consumption and wastage done by the developed countries, being the top 20%. Even though there is only 20% of the population living in developed countries, those people consume 80% of the resources of the world! The spread of resources is too uneven. It isn't fair and it means that if people don't share out the resources properly and evenly, the rich will get richer and the poor will get poorer.