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:

the reason the two sea urchins don't compete with each other for food, resources, etc. is because the urchins have adapted to the environment but they have also adapted to each other. this is most likely because the genes of the sea urchins.