The evolution of Mycobacterium bovis and the badger culling controversy
The Theory of Evolution
As already mentioned, if a mutation codes for a favourable trait then it is more likely the organism with this mutation will survive and reproduce. As time passes, and genetic material is passed from one generation to the next, there is a build up of favourable traits. This allows an individual organism to become better suited to its habitat. This is the basis of evolution by natural selection.
Natural selection essentially works as thus: ‘selection pressures’ (such as food availability and temperature) mean that not all individuals in a population will survive to reproduce. Some individuals carry advantageous traits that allow them to overcome selection pressures, and so are more likely to survive. Therefore these advantageous traits will be passed onto the next generation of the population.
Lets look at the cheetah for an example. Faster individuals would have more success at catching their prey. These individuals
would be more likely to survive and pass their genetic information to the next generation. Leading to the evolution of the cheetah
as the fastest animal on Earth.
Overall natural selection is a slow and gradual process of change which can lead to the formation of a new species, speciation:
As well as natural selection, two further processes are involved in the evolution of M. bovis. These are population bottlenecks and founder effects:
Population Bottlenecks
A gene pool is the set of all the genes contained within a population. It can be illustrated as a pot of marbles:
Population Bottlenecks
If a populations number suddenly becomes reduced this leads to what is known as a population bottle neck. The reduction in population number leads to a loss of genetic diversity i.e. certain genes may be lost from the population:
Founder Effects
This occurs when a small number of individuals from an existing population move away to start a new colony. This new population will have a reduced genetic diversity compared to the old, original population. This results in a smaller gene pool of the new population:
In both cases this reduced genetic variation can lead to the loss of advantageous traits. This means if environmental changes introduce new selection pressures (such as colder temperatures) then the population will be less able to adapt.