How big is Biology?

Nature's Envelope
The green area is Nature’s Envelope. It encompasses all biological processes, Nature’s envelope is a simple depiction of the scope and scale of the life sciences.

If we treat Biology as interacting activities rather than as an array of objects, we can plot them on a grid that shows the sizes of participating components, and how long each activity endures. The axes use logarithmic scales. The result includes subatomic, molecular, cellular activities as well as those of tissues, organisms, populations, species, and ecosystems.

The briefest event and the one involving the smallest agents is the capture of energy from a photon as it passes through a chlorophyll molecule at the speed of light. By a simple calculation based on the speed of a photon (about 300,000 km /second) and the 20 nm or so width of a chlorophyll molecule, the capture of the energy must be completed within 10-17 seconds.  The size of the photon is treated as 10-15 m. Thereafter, with various changes in shape and other properties of the photoreceptive molecule, the energy is transferred to other compounds to continue the metabolic steps of the photosynthetic process.  At the other extreme of biological processes is the most enduring: that of evolution from the first living organisms to the millions of species that now cover the globe, populate the oceans, in some cases grow within rocks, and their effect on the composition of the atmosphere.  Organisms began to appear about 4 billion years ago, and their influence affects Earth and at least 100 km of the surrounding atmosphere. The largest participant in a biological activities has a diameter of about 13,000 kms – it is the biosphere.

Between those extremes is a marvellous array of processes, from the movements of molecules within cells, fluxes of ions and other compounds across membranes, the growth of molecules, cells, tissues, organisms and populations, movements of individuals and of communities which include great migrations of birds and marine mammals, or the spread of invasive species and of the agents of disease.  The blink of an eye in this context is not particularly quick, nor is the explosion of a dead whale caused by the production of gases by the microbial communities within the body. Each process is plotted to one or more decadal blocks. Together they form a broadly S-shaped space. The margins are inexact, largely because of the variations between and within organisms that reflect genetic differences and differing circumstances – such as more or less food, parasitism, and predation.  The curve has been referred to as ‘Nature’s Envelope’.  It was first described in the Pensoft journal, Research Ideas and Outcomes, and the article can be accessed here.

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