How long ago did invertebrates become common on earth?

Invertebrates appeared on Earth around 570 million years ago.

520 Million years ago

c it says nothing about connecting those 2 seas.

affirmative action refers to the policies that take gender, race, or ethnicity into account in order to promote equal opportunity.

employers subject to title vii are prohibited from taking race or sex into account in any employment decisions. aa is a penalty for having any job group substantially statistically "underutilized" in any race or either sex. the employer must take steps to eliminate the underutilization, then stop, ending its aa efforts