字幕列表 影片播放 列印英文字幕 Please examine the world map of wealth and poverty. What are some examples of relatively wealthy nations across our globe? On the other hand, where are poorest nations located? Now that you have established the pattern of wealth and poverty on our planet, take a look at population growth rates. By comparing the two maps, identify the relationship between population growth and wealth. Is there a relationship? Growth rates are usually higher in poorer nations due to a variety of factors. The most significant of which is that many of the poorer nations rely on agriculture for survival. Agrarian, or agricultural based, societies need more laborers to work the fields and therefore families typically have more children. On the other hand, wealthier societies typically have lower birth rates since children aren't necessary for basic survival. There are many more people in the developing world, but the level of impact per person is relatively low. However, in the developed world, population growth is low, but due to their relative wealth, each person's affect on the environment is much more substantial. As this illustration demonstrates, there is a major difference in how developing and developed countries affect our environment. As you can see, developing and developed nations both put a strain on our environment's ability to sustain life, just in different ways. The actual number of people on our planet is also a major concern. Take a look at how population has grown over time: Notice that after the Agricultural Revolution, population began to increase. It took almost 10,000 years for the population to reach one billion, then only 130 years to double to two billion, but it took only 45 years to double again to four billion. So at today's doubling rate, it will only take 54 years for us to once again double the world's population. -- that would be 13 billion people on our planet. Now let's think: Can we sustain that number? Are we doing a great job of sustaining the 6.5 billion we have today? We will discuss this further in class where I'll introduce the Malthusian theory. A population pyramid, or an age structure diagram, is a chart that describes population by age and gender. These diagrams usually describe the population of a nation; however, this one combines all Less Developed Countries on the left and the More Developed Countries on the right. Please note the different structure of the diagrams. First, let's examine the diagram for the Lesser Developed Countries. Notice there are far more people in their adolescent years than in their elderly years. Why do you think this might be the case? Think about the factors that lead to birth and death rates within the Less Developed Countries. Now examine the diagram for the More Developed Countries and ask the same questions.