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Module 7 Population Distribution and Its%u00a0Consequences 115over a large area, which made the spread of the disease more difficult. In addition, the increasingly dense population distribution is contributing to the severity of losses from natural disasters such as floods and earthquakes because more people now live in hurricane- and earthquake-prone areas, such as the coastal areas of the United States.In this Module, we examined population distribution at different geographic scales, from global to local. We identified the four major population clusters and the sparsely populated areas on Earth. Unevenness is a key characteristic of population distribution regardless of the scale of analysis. This distribution pattern is shaped by a number of physical, social, and cultural factors. Population tends to be the most dense where the terrain is level, the climate is mild and humid, the soil is fertile, mineral resources are abundant, and the sea is accessible. Population tends to thin out with excessive elevation, aridity, coldness, ruggedness of terrain, and distance from the coast. The distribution and density of population have social, economic, political, and environmental implications.consider desirable. More and more people are living in cities worldwide because cities, particularly big cities, offer many amenities that people enjoy even though air quality may be worse, housing usually costs more, and traffic congestion is common. Fortunately, urban planning and technology may help to reduce or even eliminate some negative aspects of city life. For example, air quality in London has improved significantly over time while its population has grown.Disease and Natural DisastersPopulation distribution and density may affect people%u2019s health and vulnerability to natural disasters. Infectious diseases may spread faster in densely populated areas. For example, malaria is a major killer in tropical African countries such as Gambia. Malaria is caused by five types of parasite, which spread through mosquito bites. One contributing factor is that more and more people in African countries now live in crowded cities and towns so more people may get infected. In the past, many people lived in rural villages dispersed Module 7 Review7-1 How is population distributed around the%u00a0world?%u2022 Population distribution is highly uneven at global, regional, national, and local scales.%u2022 There are four major population clusters in the world, but much of Earth%u2019s surface is sparsely populated.%u2022 Population size and land area by country vary greatly. The top 10 countries in terms of population will change because their populations are growing at different rates.7-2 What factors influence population distribution?%u2022 A number of physical, cultural, and economic factors have shaped the population distribution patterns on Earth.%u2022 The key factors that affect population distribution patterns may depend on the scale of analysis.7 -3 What are the three methods for calculating population density?%u2022 Arithmetic or crude population density refers to the average number of people per unit area of land.%u2022 Physiological density is the ratio of population to arable land (i.e., land suitable for agriculture). It is a good indicator of the pressure that the population exerts on the land resource and agriculture.%u2022 Agricultural density is the average number of farmers per unit area of arable land. It reflects the labor intensiveness of agriculture.7-4 What are the consequences of population distribution and density?%u2022 Population distribution and density can affect economic development, political power distribution, the environment, and human health and vulnerability to natural disasters.Preparing for the AP%u00ae Exam%u00a9 Bedford, Freeman & Worth Publishers. For review purposes only. Do not distribute.