The Aztecs were famous for developing which agricultural achievement? Astronomy • a complex Irrigation system that made inhospitable land able to cultivate plant life

• the slash-and-burn technique that allowed ash to create rich soll for next year's crops

• a series of plows that would first cut through the soil then turn up the earth

• the idea of crop rotation so that soils did not become over-used and unfertile

The concept of keystone species is controversial among ecologists because most organisms are highly interdependent. if each of the trophic levels is dependant on all others how can we say one is most important

How does upwelling affect coastal fisheries? upwelling damages nutrient supplies at coastal fisheries as the warm, nutrient-rich surface water is replaced by nutrient-poor, cold water. upwelling damages nutrient supplies at coastal fisheries as the cold, nutrient-rich surface water is replaced by nutrient-poor, warm water. upwelling improves the nutrient supply at coastal fisheries as the warm, nutrient-rich surface water replaces the nutrient-poor, cold water. upwelling improves the nutrient supply at coastal fisheries as cold, nutrient-rich water replaces the warm, nutrient-poor surface water.

Mineral rich water heated by newly found oceanic crust escapes through cracks in the ocean floor called