Can anyone explain the logic behind why we used exponantial functions to model bacteria growth?

1 Answer
Aug 20, 2016

Imagine that a given strain of bacteria is perfectly predictable: every hour a given bacterium divides into two bacteria. Then, in a given sample, the population of bacteria will double every hour, on the hour. If we look at how this progresses for a starting population pp, we get something like this:

"Hour Population"Hour Population
"0 "p0 p
"1 "2p1 2p
"2 "4p2 4p
"3 "8p3 8p
"4 "16p4 16p
...
"n "2^np

Notice that the population has a geometric growth pattern.

However, actual bacteria do not behave quite so nicely. Within a given population, some may reproduce faster or slower than others. The resulting growth rate tends to be well approximated by an exponential curve, rather than a perfect geometric pattern.

Further reading:

Boundless Biology Textbook

The Biology Project - University of Arizona

Online Textbook of Bacteriology