Emergence in The Biological Hierarchy

The Continuing Creation we see all around us is all about the repeated emergence of complexity in Nature, culture, and technology.

In philosophy, systems theory, and science, emergence occurs when a complex entity has properties or behaviors that its parts do not have on their own. These properties or behaviors emerge only when the parts interact within the wider whole. “The whole is greater than the sum of its parts.”

Emergence plays a central role in theories of integrative levels and of complex systems. For instance, the phenomenon of life as studied in biology is an emergent property of chemistry.

Biology students learn that Nature has a “Hierarchy of Life” that runs from small systems to much larger things. In total, there are thirteen levels in the biological hierarchy. In each of levels 2 through 11, greater complexity emerges – complexity that did not exist at the lower level. In level 4, life itself emerges.

1. The atom – for example, hydrogen and oxygen. (technically, levels 1, 2, and 3 are pre-biology.)
2. The molecule – e.g., when hydrogen and oxygen atoms bond together to make water – H2O. Water has characteristics that are very different from both H and O. For example, at room temperature and pressure, H&O are gases whereas H2O is a liquid. The bonding of H and O is emergent, as is the increased stability of the molecule. The simplest biological molecules are called monomers.
3. At the next level up, simple molecules (“monomers”) string together to make long chains called macromolecules. In biology, there are 4 kinds of macromolecules: carbohydrates, lipids, proteins, and nucleic acids.
4. Next, some macromolecules can become organelles, or even single-celled living things such as a bacterium, when the macromolecules are enclosed within a plasma membrane or a cell wall. The boundary gives each organelle or cell a separate identity – an inside and an outside. Separation, identity, and often motility are the emergent qualities. Life is emergent.  Death is also emergent.
5. Different types of cells work together to form distinct tissues – like muscle tissue or brain tissue. Specialization and Cooperation are emergent.
6. Different Tissues cooperate to form an organ, such as the heart. The heart involves muscle tissue, connective tissue, and epithelial tissue. The heart also has nerve tissue so that it can pace out its “beat.”  Finally, the heart pumps the tissue called blood. Coordination is emergent.
7. Going up another level, the heart is part of the circulatory system including the heart, arteries, and veins. Cooperation between tissues is emergent.
8. An organism. Such as a buffalo or trout. Speciation is emergent.
9. A population – a herd of buffalo or a school of trout. Mating and birthing are emergent.
10. A community – two or more species interact. Behaviors like predation, migration, and symbiosis are emergent.
11. Ecosystem – includes abiotic (non-living) elements like elevation and humidity.  Adaptation to the ecosystem (finding a niche) is emergent.
12. Biome – ecosystems that have similar characteristics, such as jungle, desert, forest, or tidal reef.
13. Biosphere – The sum of all biomes, all places on a planet where we find life, from the deep ocean to the high atmosphere.

Note: Several presentations on this subject — The Hierarchy of Life — can be viewed on YouTube.