Natural Zone: A part of a geographical belt with uniform climatic conditions, vegetation, and animal world. Natural zones change each other systematically from the equator to the poles and from the oceans to the interiors of continents, primarily due to differences in heat and moisture. On land, natural zones extend latitudinally (west-east) and change each other longitudinally (north-south).
Soil: The uppermost, loose surface layer of the Earth's crust, which has fertility.