Human Biology

Fungi & Yeast
Microbial Populations
Staying Clean
Food and disease
Sewage treatment

Explosive Potential!

Say that it takes 20 minutes for a bacterium to replicate. So after 20mins the one cell has become 2, and after another 20 minutes those two have both replicated to 4 and so on.

Within...Population of ...
an hour8
2 hours64
4 hours4096
8 hours16 777 216
16 hours281 474 976 710 656

And within a day there will be 4.72 x 1021 (4 722 366 482 896 650 000 000 000 or 472 million million million) bacteria cells. And assuming the mass of each bacterium is 1 picogram, by the end of 2 days the bacteria would be pver 3 times the mass of the earth

But this unimagineably huge is stunted by our old favourite: limiting factors!

Population graph

This graph shows how the population of yeast or bacteria changes over a period of time.

graph showing microbial population over time period

1. Lag Phase
There are a small number of microbes and this initial growth is slow.

2. Exponential Growth
There is a surplus of resources like food and oxygen so the population booms.

3. Stationary Phase
The rate of cells dying is equal to the rate of new ones being produced.

4. Death Phase
All of the nutrients have been used up; toxic material has built up and so the population plummets with very few new cells and rapid death.