How are geologic maps best used by those in construction business

Which statement accurately describes the rock layers? layer 8 is older than layer 1. layer 3 is younger than layer 6. layer 4 and layer 10 are the same relative age. layer 2 and layer 9 are the same relative age.

The gene that causes sickle-cell disease is present in a higher percentage of residents of sub-saharan africa than among those of african descent living in the united states. even though this gene causes sickle-cell disease, it also provides some protection from malaria, a serious disease that is widespread in sub-saharan africa but absent in the united states. discuss an evolutionary process that could account for the different percentages of the sickle-cell gene among residents of the two regions.

Why is it important to reduce the number of chromosomes in half when forming gametes for sexual reproduction?