The series of changes that occur after a disturbance in an existing ecosystem is called
a. primary succession
b. secondary succession
c. disturbance succession
d. pioneer succession

Secondary succession (B).

The soviet union beat the us to the first successful launch, with the october 4, 1957, orbiting of sputnik 1, and later beat the us to have the first human in earth orbit, yuri gagarin, on april 12, 1961. the "race" peaked with the july 20, 1969, us landing of the first humans on the moon with apollo 11

C) to ensure each new cell has an exact copy of the dna