How did scientists form the geologic time scale?

answer:

scientists use the geologic time scale to illustrate the order in which events on earth have happened. the geologic time scale was developed after scientists observed changes in the fossils going from oldest to youngest sedimentary rocks. the geologic time scale is divided into eons, eras, periods, and epochs.

explanation:

1) gene flow

- it is described as the transfer of genes from one population to another population so that frequency of gene is increased.

-a zebra migrates to join a different herd of zebras.

2) natural selection

- a mechanism of evolutionary change in which individuals with advantageous traits survive and reproduce whereas the others ( those that can not adapt) eliminate from the population.

-competition for sunlight leads to taller trees.

3) mutation

- permanent change in the nucleotide sequence of dna ( genetic material) that could have harmful or useful consequences.

-the dna of a snake changes to make its venom stronger.

4) genetic drift - it is a random phenomenon ( that occurs by chance such as fire) that results in change in the gene frequency in a small population.    

-a grassfire randomly sweeps through a population of buffalo and kills most of the animals.

explanation:

as resources become scarce because of population growth, the growth decreases after few years due to lack of resources and food.