Geography

4. Human migration within a country.
7. The rapid expansion of the geographic extent of cities and towns
9. A natural feature of the earth's surface.
11. the ability to be maintained at a certain rate or level.
12. An increase in the number of people living in towns and cities.
14. The strength and vitality required for sustained physical or mental activity.
15. Relating to, or characteristic of a town or city.

1. capable of being renewed.
2. Seasonal movement of animals from one region to another.
3. The concentration of individuals within a species in a specific geographic locale.
5. The introduction of contaminants into the natural environment that cause adverse change.
6. A city that with a population of over ten million people.
8. All the inhabitants of a particular place.
10. characteristic of the countryside rather than the town.
13. the basic physical and organizational structures and facilities needed for the operation of a society or enterprise