Evolution and Antibiotic Resistance | 9-1 GCSE Science Biology | OCR, AQA, Edexcel

Показать описание

They key points covered in this video include:
1. Current thoughts on the theory of evolution
2. The emergence of antibiotic resistant bacteria
3. The emergence of other resistant organisms
4. The emergence of resistance explained in terms of natural selection
5. Problems caused by the spread of antibiotic resistance
6. How can the spread of antibiotic resistance be reduced?

Current Thoughts on the Theory of Evolution

The theory of evolution by natural selection is now widely accepted because there are several lines of evidence in support of it. A perfect example is the emergence of antibiotic resistance - this is evolution that occurs over a much shorter time period.

The Emergence of Antibiotic Resistant Bacteria

Bacteria can evolve rapidly because they reproduce at a fast rate. This means that random mutations are likely to occur at a fast rate too. Bacteria may develop a random mutation which, instead of killing it, leads to change in its phenotype - for example, it may be less affected by an antibiotic.

The Emergence of Other Resistant Organisms

Bacteria are not the only living organisms that can develop resistance to a substance. For instance, random mutations in rats can make it resistant to rat poison.

The Emergence of Resistance Explained in Terms of Natural Selection

Drugs such as antibiotics or rat poison act as selection pressures which favour the survival of resistant organisms. For example, when treating bacterial diseases, bacteria less affected by antibiotics are more likely to survive and reproduce many times - this will lead to antibiotic-resistant strains forming.

Problems Caused by the Spread of Antibiotic Resistance

The problem with new resistant strains of bacteria is that organisms will not have encountered it before, and so they won't be immune to it. It is also difficult to find an effective treatment. This makes it easier for the resistant strain to spread between individuals, so the population size of the resistant strain increases even more. Examples include MRSA and multidrug-resistant tuberculosis.

How Can the Spread of Antibiotic Resistance be Reduced?

There are several ways the growth of antibiotic resistant bacterial populations can be reduced. This includes: Avoiding the use of antibiotics for treating non-serious or viral infections. Patients should finish the course of antibiotics so no bacteria (particularly those least affected by antibiotics) are left to divide and mutate. The use of antibiotics in agriculture should be limited. Unfortunately, the development of new antibiotics is too costly and slow to keep up with the emergence of new resistant strains of bacteria.

Summary
1. The emergence of antibiotic-resistant organisms is an example of evolution that occurs in a short time period due to rapid reproduction rates
2. Resistance itself is caused by random mutations, but it is selected for by drugs which act as selection pressures
3. Bacteria are not the only organisms that can develop resistance to a particular substance - for example rats may gain resistance to poison
4. Antibiotic resistance is a problem because patients are not immune to new strains of bacteria and effective treatments are difficult, if not impossible, to find
5. Avoiding the unnecessary use of antibiotics in medicine and agriculture and completing a course of antibiotics may reduce the rate of development of antibiotic-resistant strains