Answer:
Nucleotide arrangement
Step-by-step explanation:
There are obvious differences between humans, oak trees and frogs, but at the molecular level- the cells of all eukaryotes including plants and animals contains DNA in the same shape (double-helical).
All DNA molecule consists of two long polynucleotide chains composed of four types of nucleotide subunits (A, G, C, T). Each of these chains is known as DNA strand. The difference between species lies in the arrangement of the nucleotide bases in the DNA of respective organisms.
The sequence of nucleotides determines which proteins will be synthesized. The way the nucleotides (Adenine, Guanine, Cytosine and Thymine) are arranged determines the information they encode, this information ultimately determines whether the organism will produce scales(frogs), leaves (oak plant) or legs (humans).