It helps classify animals according to their needs.
Hope this helps!
-Payshence xoxo
Every cell of the organism has the same DNA sequence and same genes. However, not all genes are expressed in every single cell at the same time. Only those genes necessary for a specialised function of a specialised cell are expressed in the specialised cell. For example, skin cells have some different proteins than nerve cells. Genes responsible for those "skin proteins" are activated in skin cells and are turned off in nerve cells.
Answer:
I'd say it's The discovery that all protists come from one common ancestor.
Explanation:
Based on some quick research, The current attempts of classification focus on grouping protists into between three and ten kingdoms, based on species’ common evolutionary ancestors.