Other than mountains, what else could cause geographic isolation?

Other than mountains, what else could cause geographic isolation? population to start a new population. genetic drift -change in allele frequency in a small population due to random chance. migration - some organisms move away to start a new population

Explanation:

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the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.