Layers

The Earth is covered by atmosphere.
Some of the gases might have belonged to the original ‘cloud’ which had given birth to the solar system. Others have originated from the Earth itself. And still others are a ‘consequence’ of ‘life’. Oxygen, for instance. And some of the CO2.

The land crust has rocky cliffs and fertile plains.
While the rocky cliffs are a consequence of geology, the fertile topsoil is the consequence of the elements having eroded the cliffs, the debris being transported by flowing water, plant life taking hold and slowly transforming some of the minerals into organic matter, animals eating some of the plants and transforming them into feces, micro-organisms digesting/recycling those feces together with the dead plants and animal carcasses… And so on.

Primitive life forms, Bacteria and Archea, “are organisms whose cells lack a membrane-bound nucleus, mitochondria and other membrane-bound organelles…. All the intracellular water-soluble components (proteins, DNA and metabolites) are located together in the same volume enclosed by the cell membrane, rather than in separate cellular compartments.“

More ‘sophisticated’ life forms are organisms which have “a nucleus and organelles bounded by internal phospholipid membrane systems. In contrast to bacteria and archaea, eukaryotes may be multicellular. Animals, plants, fungi…. “
So, in this case, living cells have internal divisions, each surrounded by ‘secondary’ membranes. Furthermore, this type of organisms may consist of more than one cell. Many of them – including us, humans, actually comprise many layers of cells. Skin, muscle, bones, ‘internal’ organs, brain… Each of them carefully constructed using building blocks taken, with the help of the digestive system, from the environment.

Making a parallel between a humble unicellular organism, let’s say an amoeba, and a proud ape we’ll notice that the role played by the amoeba’s membrane is fulfilled by a host of the ape’s organs. Skin, lungs, digestive system and kidneys are the first to jump up for attention. On a closer examination – amoeba’s membrane keeps the organism together and acts as a locomotion device besides performing the respiratory, digestive and excretory tasks, the ape’s bones and muscles start to beg for attention

But what about the brain? What role does it play? What is it? An ‘internal organ’ or just another descendant of the membrane?
I’ll let you make that call.
I’ll only mention that the brain ingests information, digests it and then ‘excretes’ decisions. Which coalesce into ‘fate’/’destiny’, are remembered as ‘history’ and eventually end up as ‘tradition’.