How long can it take for an Aquatic Ecosystem to develop into a terrestrial ecosystem?

Who developed the theory of plate tectonics?

Mexico city is an example of how humans alter their environment because it was a. one of the world’s largest cities b. built on drained and filled lake beds c. built after conquest by the spanish d. once the capital of the aztec empire

What term describes the government positions that officials who passed the civil service exam became a part of?