Question: How do things evolve?

Reka Nagy answered on 9 Nov 2016:

Things evolve gradually, using changes in their DNA called mutations, through a process called natural selection – what you may have heard of as ‘survival of the fittest’. Contrary to what you may think, this does not think that whoever does the most exercise survives best – it simply means that those most fit to meet the challenges of their environment survive.

Here is a great video showing evolution in action:

What this shows is bacteria evolving – compared to humans, bacteria copy themselves really fast, every 20 minutes or so depending on the bacterium, which is why they are great for these kinds of experiments.

The massive dish in the video contains no antibiotic on the sides, and more and more antibiotic towards the middle.

You see bacteria start off growing fast in a favourable environment, where no antibiotic is present. But then they hit a barrier of antibiotics, which kills most of them. This is where you see the growth seem to pause. Some, however, have acquired DNA mutations that enable them to become resistant to these antibiotics – these are the ones that are capable of growing further. Once the mutation has been acquired, any descendants of that bacterium will be able to happily grow even in the presence of a low amount of antibiotic.

New mutations are needed to overcome increasingly high concentrations of antibiotic – this is why you see colonies of bacteria ‘branching’ out from certain places on the massive dish in the video – these are the ones that managed to evolve to become the fittest!