Chapter 1, Problem 1Q

Summary Introduction

To analyze:

The results of the investigation showing the relationship between gradual and sudden environmental changes on the extinction, evolution, and adaptation of the populations.

Given:

Overuse of drugs has been associated with the significant increase in drug-resistance. In the given experiment, the researchers use a serial transfer for propagating 1,255 population of Escherichia coli in gradually increasing antibiotic (rifampicin) concentration environment.

Figure A shows the increasing rifampicin concentrations which are increased suddenly, gradually and moderately.

In the figure B the results of the experiments depicting the percentage of population surviving the antibiotic conditions are shown.

Introduction:

Extinction of the organisms is by the fact of sudden changes which occur in ecosystem. Sudden changes do not allow the organism to adapt and acclimatize to the environmental conditions. Gradual changes allow the organism to get accustomed to the changes and allow it to adapt accordingly.

Explanation of Solution

The experiment involved the exposure of antibiotic to the bacteria, by two ways one gradual other sudden. Survival population after treatment with different antibiotic concentrations at different rates differed greatly.

It is very much clear from survival population numbers in the graph that a sudden increase leads to the death because of such sudden increase in antibiotic concentration.

In the case of gradual increase the bacteria survived eventually end up becoming antibiotic resistant because of the fact that the gradual increase allowed the bacteria to save and protect itself by acquiring plasmids, point mutations, and genetic recombination.

The less time in sudden increase in antibiotics made the bacterium incapable of genetic exchange and hence the bacterial population decreased in numbers considerably.

The above experiment can explain the adaptation in case of multidrug resistant (MDR) and extensively drug resistant (XDR) species of Mycobacterium tuberculosis as well as sudden extinction of dinosaurs.

Conclusion

Therefore, it can be concluded that the extinction and loss of organisms is due to sudden change in environmental factors whereas acclimatization is the result of gradual changes in the environmental conditions.