<em><u>DNA are important molecules that carry hereditary information in all organisms. The nucleotide sequences or the genes are subject to change as a result of mutations.</u></em>
<em><u>Mutations are spontaneous random changes that occur in the genetic make up of an organisms or the DNA sequences of an organism.</u></em>
<em><u>When mutations occur they can cause insertion of new DNA segments, substitution of DNA sequences with new ones, and also deletion of some sequences of DNA.</u></em>
<em><u>Substitutions, deletions and insertion mutations are types of mutations that affect cells at gene level. </u></em>
Sunlight would be an answer because you are talking about the lower depths of the ocean meaning the bottom of the ocean, and the farther away you get from the surface the less sunlight