Endurance of life : the implications of genetics for human life / Macfarlane Burnet.

  • Burnet, F. M. (Frank Macfarlane), Sir, 1899-1985.
Date:
1978
Catalogue details

Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Endurance of life : the implications of genetics for human life / Macfarlane Burnet. Source: Wellcome Collection.

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    8 Endurance of Life introduces a chemical poison to disturb the body's regulatory mechanisms will be lethal. Death may be essentially at random, but chance has its own regularities. Whenever bacteria are growing in any natural accumulation of water and nutrients, changes in the proportion of the different bacterial types are constantly taking place. To reduce that situation to a laboratory model, let us think of a fluid containing two nutrients, X and Y. We have at hand a mixed culture of two sorts of bacteria growing in a fluid that contains only X and we transfer a million or two to the X + Y mixture. What happens will depend on whether any of those bacteria can grow at the expense of nutrient Y as well as X. If one of the strains can do this and the other cannot, it will obviously flourish. Both will multiply and both sorts will lose many by death, but the one that can use Y will be at an advantage, and after a time it will probably be found that the population has become composed only of bacteria that can use Y. If there are large enough numbers in the populations concerned, any new option, however minor, will favour the survival of those organisms that can exploit it. Predator and prey As evolution moved into the period of the conventional fossil record, which began with the Cambrian Period 600 million years ago, pré¬ dation had become the major cause of death. From the very begin¬ ning a compact micro-organism was a potential source of nourish¬ ment for any larger type that might evolve means to break it down x +Y 0 o<=> оЛ Fig. 1 : Adaptation in bacteria. In the original culture containing only nutrient X, there are a few of another type which may have arisen by mutation or in some other way. If this minority (shown as white) can, unlike the original (black) form, utilize nutrient Y as well as X, successive transfer of the culture in fluid con¬ taining X and Y will result in rapid replacement of the original (black) population by the new form.