What is the ancestral group in this phylogenetic tree

the electromagnetic energy from the sun arrives in the form of visible and invisible light.

during the process of dna replication, brdu can replace thymidine and incorporate into the newly synthesized dna, cell proliferation thus can be reflected in the extent of brdu incorporation.

all matter is made up of atoms

in any element all atoms are the same

elements in a compound are always in a constant ratio: apex