Differences in courtship or other behaviors prevent mating.

1. emigration the movement of people from one place to another 2. immigration a situation in which resources are being used up at a faster rate than they can be replenished 3. migration the leaving of one's homeland to settle in a new place 4. overpopulation the movement of people to a new country 5. sustainable development a situation in which the birth rate is not sufficient to replace the existing population 6. underpopulation the ability to meet current needs without reducing the ability to meet future needs 7. unsustainable development the increase in the population of a city 8. urbanization a situation in which the number of people exceeds the available natural resources in an area

What percentage of light hits earth's surface directly?

This question is only for applicants to scholars for medicine or scholars for dental medicine: what aspects about medicine (or dental medicine) intrigue you? describe how these aspects influence your life. (100-650 words)