They unzip the double helix into single strands during replication. The unzipping occurs at regions called origins where replication is initiated. The protein breaks the hydrogen bonds (using energy from ATP) between the complimentary bases of the strands hence forming a replication fork.
I believe the correct answer is upwelling. Lets say we have producers such as plankton. well upwelling currents bring dead matter from the ocean floor up to the surface, creating plankton.
