Which evidence suggests that several mass extinctions have occurred during earths history?

Many fossils of organisms that are no longer living have been discovered.

Explanation:

in 550 b.c.e. cyrus the great, the leader of the persians, conquered the medes and united the iranian people under one ruler for the first time. cyrus became the first king of the persian empire and went on to establish one of the largest empires in world.

1. ford: gerald ford´s presidency, from 1974 to 1977, faced high inflation, named it public enemy nº1, and created the win program (whip inflation now).

2. carter: president from 1977 to 1981, carter had controversial poitions over abortion, but yet, he enforce the roe vs wade decision, which had pro-choice content.

3. reagan. for his eloquency and powerful speeches in his mandates, from 1981 to 1989, reagan earned this nickname, “the great communicator” .

4. george h w bush: despite many presidents had important roles in managing and trying to end the cold war, it was in bush sr's mandate that the berlin wall was materially destroyed, and he was visited by gorbachev in the uspresident from 1989 to 1993.

5. clinton: defense of marriage act. clinton signed this controvesial act, which defined marriage and spouses in strict heterosexual perspective, that was later declard unconstitutional by the us supreme court.

6. george w bush: in the begining of his presidency, which lasted until 2009, bush jr faced the greatest terrorist attacks in us and probably the worlds history, in september, 11 of 2001.

7. obama: in attempts to cease a great economical crisis, barack obama signed the controversial recovery act in february 2009, which handled 780-billion dollars.