A genetic change will be maintained in a population if the change?

1.The oldest living primates are____?
2.It is not possible for one speciesto evolve into two new species without____?
3.A _____ factor is something that keeps the size of a population down
4.Fourteen beavers live in a pond with an area of 2 square kilometers. What is the population density of the beavers?
5.Darwin explained the similiarity of structures among living organisms by the concept of______?
6.A genetic change will be maintained in a population if the change____