What are free dna nucleotides needed for in pcr?

Free nucleotides are required in the PCR for the elongation for the new DNA strand during replication by the polymerase. Remember that during DNA replication, a primer is recruited at the initiation site then DNA polymerase enzyme elongates the primer by adding nucleotides (dNTPs) at the 3’ end of the primer and catalyzing a phosphodiester bond.    

an adaptation is a change or process by which an organism takes to be better suited for its environment. for example; migration is a behavioral adaptation, this is needed because birds are not built to last extremely cold climates. there are different adaptations because there are different species needing to adjust to different things, bears don't migrate; they hibernate.