What other traits are highly variable like human skin color ?

the supermassive black hole is in the middle of the galaxy.

succession returns a disturbed

ecosystem to a more stable state. this is also classified into two (2) types:

primary succession and secondary succession. the primary succession arises when

a new land is transformed and a bare rock has been exposed providing an environment

that can be occupied for the first time. while, secondary succession occurs

when a previously occupied environment was disturbed that kills much of all its

community

explanation:

the cost of mining is extremely low compared to the money earned from mining, creating income to improve the environment.