Biological organisation

The biological organisation of life is a fundamental premise for numerous areas of scientific research, particularly in the medical sciences.

Without this necessary degree of organisation, it would be much more difficult—and likely impossible—to apply the study of the effects of various physical and chemical phenomena to diseases and physiology (body function).

For example, a molecule can be viewed as a grouping of elements, and an atom can be further divided into subatomic particles (these levels are outside the scope of biological organisation).

Each level can also be broken down into its own hierarchy, and specific types of these biological objects can have their own hierarchical scheme.

[6] Biological organisation is thought to have emerged in the early RNA world when RNA chains began to express the basic conditions necessary for natural selection to operate as conceived by Darwin(heritability, variation of type, and competition for limited resources).

Fitness of an RNA replicator (its per capita rate of increase) would likely have been a function of adaptive capacities that were intrinsic (in the sense that they were determined by the nucleotide sequence) and the availability of resources.

[7][8] These capacities would have been determined initially by the folded configurations of the RNA replicators (see "Ribozyme") that, in turn, would be encoded in their individual nucleotide sequences.

Empirically, a large proportion of the (complex) biological systems we observe in nature exhibit hierarchical structure.

System hierarchies analysis performed in the 1950s,[9][10] laid the empirical foundations for a field that would be, from the 1980s, hierarchical ecology.

A population of bees shimmers in response to a predator.
The simplest unit in this hierarchy is the atom, like oxygen. Two or more atoms is a molecule, like a dioxide. Many small molecules may combine in a chemical reaction to make up a macromolecule, such as a phospholipid. Multiple macromolecules form a cell, like a club cell. A group of cells functioning together as a tissue, for example, Epithelial tissue. Different tissues make up an organ, like a lung. Organs work together to form an organ system, such as the Respiratory System. All of the organ systems make a living organism, like a lion. A group of the same organism living together in an area is a population, such as a pride of lions. Two or more populations interacting with each other form a community, for example, lion and zebra populations interacting with each other. Communities interacting not only with each other but also with the physical environment encompass an ecosystem, such as the Savanna ecosystem. All of the ecosystems make up the biosphere, the area of life on Earth.