How does antibiotic resistance of bacteria demonstrate various principles of evolution?
Good question! I would ask u to go through this link before reading the answer below.
Accepted evolutionary theory is based on few facts which could be applicable to bacteria as well, for example:
1. there are genetic variations present in a gene pool of population
2. variations are omnipotent; generally such preadaptive characters are already present in some organisms which derive benefit in a new/changed environment
In some bacteria resistance against specific antibiotics could be naturally present and such variations would help those organisms to survive an onslaught of specific antibiotic chemicals. Thus resistant bacteria will exhibit:
3. survival of the fittest; in this case fittest are the resistant bacteria
Bacterial organisms without any resistance to antibiotic would fail to reproduce in an environment loaded with antibiotic chemicals but resistant bacteria of the population will successfully multiply, that too in faster rate because of less number of competing bacteria present in the environment. Thus:
4. the 'fittest' shows differential reproduction, hence favorable variations increase in frequency in the genepool
In this case 'selection' is not absolutely natural, but due to application of antibiotic by human.
5. Selection of organisms with favourable variation in each generation with time changes the genepool and the population is said to have evolved with time
I could enlist five points which elaborate the basic concepts of evolution in light of antibiotic resistance as seen in bacteria.