Frozen water (ice) has less density than liquid water.
how does this property of water affect life on earth?
a. ice floats on the surface, sustaining life at the bottom of lakes and oceans.
b. ice floats on the surface, animals migrate over lakes and bays.
c. ice floats on the surface, maintaining sub–zero temperatures at the bottom of lakes and oceans.

Assume that you are interested in separating short (200-400 bp) dna molecules from a pool of longer molecules in the 10,000-20,000 nucleotide range. you have two recipes for making your polyacrylamide gels: one recipe uses 1.5 percent agarose and would be considered a “hard gel,” while the other uses 0.5 percent agarose and would be considered a loose gel. which gel should you use to separate the short (200-400 bp) dna molecules from a pool of longer molecules in the 10,000-20,000 nucleotide range?