Although not actually producing living cells this model offers a hypothesis on how cells could have evolved. This stage of chemical evolution of life is the most tenuous, least well understood. Experiments have shown that if some of the enclosed compounds were RNA and various other polymers such as nucleotides, then reactions are triggered that initiate a crude form of doubling, or replication. In terms of energy-acquisition. Autotrophs use light or chemical energy outside of the cell or group of cells to stimulate production of chemicals inside the cell.
Prokaryotes have an area roughly similar to a nucleus known as the nucleoid.
Eukaryotes - the step from prokaryotes to eukaryotes is an interesting and not fully understood phenomenon. Both have been found in very old fossils. As they grew in number during primitive Earth the food source became depleted and some type of competition ensued. Hence, the most efficient cells survived and reproduced. Heterotrophs now include all fungi, some algae, most bacteria, all animals.