Ateacher taps on a hardboiled egg until cracks appear on the surface. she gently presses the egg between her fingers and thumb. the students observe some changes in the egg shell, a few of which are presented in the table. what is the teacher trying to model?

a) weathering of rocks
b) retreating glaciers
c) formation of volcanoes
d) tectonic plate movements

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