How come we can see water but never air

I believe refraction plays a big part on why we can distinguish water from air. As light hits the water, it's bent to a different angle because it's slowed down. If you've ever held a pole in the water, you'll see a break in the line where it meets the water. That's the effect of refraction.

Explanation:

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).

nucleic acid molecules are incredibly complex, containing the code that guarantees the four different nucleotide units comprise dna, the nucleic acid of interest to the genealogist. and one of four nitrogen-containing molecules called nucleotides