Doubling time

Generation time is the time period in which the number of individuals in a population of organisms doubled.

Determination of generation time

The increase in the number of individuals is in the exponential phase by the equation

Described. N being the number of individuals at the time t, the initial N0 number of individuals, and k is the rate of growth ( propagation constant ). Thus, for a doubling of the number of individuals of the equation

For determining the growth rate of the logarithm of the number of individuals is plotted against time. For the exponential growth phase results in a straight line whose slope is the growth constant.


In bacteria, the generation time can be very different depending on growth conditions and depending on the bacterial strain. The generation time during the exponential phase of bacterial growth on the shortest. The adjacent table shows examples of generation times in bacteria under optimal conditions.

The generation time of the respective bacterial culture is influenced mainly by external factors such as temperature, localization of culture ( culture medium ), pH, surface area and air composition. For industrially producing bacterial cultures are grown in a bioreactor under optimal growth conditions, and thus shorten the generation time.

Invasion Biology

Similar exponential growth processes are also observed in higher organisms that live in an ecosystem with no natural enemies, such as because they have been introduced by man. Examples are the cane toad in Australia, the water hyacinth on Lake Victoria and several in New Zealand, Tasmania, and elsewhere exposed by European settlers domestic species. In Europe, there is the phenomenon: prominent invaders are the glandular Balsam, known as the giant hogweed Giant Hogweed and the Chinese mitten crab.