Taking into account the information from previous chapters, we found that 3,800 million years ago there were few unicellular organisms that for 700 million years enriched the seas and the atmosphere with oxygen.

Simultaneously they produced organic carbon compounds that it was an energy reserve to be subsequently used by other beings.

Based on these facts we can discuss the options on the type of beings capable of doing both.

1) The oldest free cell, known and exists today in the form of organulle capable of producing O2 and carbon compounds is the chloroplast.

2) The oldest free cell, known and exists today as organulle, capable of oxidizing carbon compounds chloroplast and produce energy is the mitochondria.

Comparing chloroplasts and mitochondria characteristics, as free cells, and including in the box archaea as current oldest free cell (mitochondria and chloroplasts ceased to be to become organulles of eukaryotes) we can see remarkable similarities:

This information and the Table N º 1 allow us to understand that the first free cell capable of self-nourishment was a chloroplast or chloroplast primitive form. Its functions are made by the activity of a circular DNA containing 150 genes with a bidirectional replication system favored by the circular shape (see Table 3).

The rbcS, and rbcL RBCM genes are involved in the processing of messenger RNA synthesizing RuBisCO enzyme that allows the production of organic carbon compounds from CO2 and solar energy.

Likewise the same information and table No. 1 allow us to understand that the second free cell with the ability to consume organic compounds was mitochondria or an early form of mitochondria.

Its DNA also circular like a smaller version of chloroplast DNA to make exclusively the function of recover the energy stored in the molecules of organic carbon and return the CO2 to the atmosphere.

Mitochondrial DNA contains only 37 genes, with a one way replication system, (see Table 2), of which 22 encode transfer RNA, 2 to produce encoding ribosomal RNA (fraction S and L) and 13 encode 13 proteins involved in oxidative phosphorylation. Between its genes are important CO (cytochrome oxidase I, II, III).

From these two original free cells, or adjacent, archaea may have evolved. These living organisms still exist as free cells containing an oversized circular DNA comprising gene 1,500 to 2400 and could be an evolution of the basic model of the chloroplast.

That would make the chloroplast circular DNA in the basic instrument for the beginning of life on Earth and the chloroplast as the first free cell from which evolved the archaea, the bacteria and plant eukaryotes.

It would be proof that animal eukaryotic cells descend from the premitochondrias and plant eukaryotic cells precloroplasts. Consequently eukaryotic animals would depend on eukaryotic plant as premitochondrias depended on its  commencement of precloroplasts.