Substitutions, additions, or deletions of one or more nucleotides in the dna molecule are called
a. genetic variations
c. recombinant dna
b. gene mutations
d. dna fragmentation

I believe that the best answer for this question is "gene mutations." Gene mutations can either take place through nucleotide substitutions, which occur when the the sequence of nucleotides are altered. Frameshift mutations can also occur. They involve the insertion or deletion of a DNA molecule's bases. Hope this helps.

An ecosystem is in a certain area and includes living and non living plus there is weather conditions and a biome is a large amount of area with similar climate.so ecosystem is based on weather and biome is based on the average climate