Biology: 3b Interitance (Natural Selection and Antibiotics Resistance)

What theory did charles darwin propose?

theory of evolution by natural selection

What are the four stages of natural selection?

1. Each species reproduces and the offspring show variation. 

2. There is a lot of competition between these offspring (for food, space, mates etc). 

3. The ones with the best adaptations for their environment survive, the others die (survival of the fittest).

4. These survivors pass on their beneficial alleles to their offspring. 

What is ‘survival of the fittest’?

Individuals with characteristics that are advantageous in their environment have a higher chance of survival

How do advantageous mutations become more common?

Increase individuals survival and they are more likely to reproduce → more likely to pass on their advantageous alleles and so advantageous characteristics become more common in the population.

What is speciation?

When two populations of the same species get separated and evolve differently due to natural selection, changing so much that they eventually become two separate species.

What are superbugs?

bacteria evolved to become resistant to antibiotics

What happens to cause antibiotic resistance?

• a random mutation can give rise to a new bacterial allele that codes for antibiotic resistance

• when the bacterial population is exposed to an antibiotic any individuals without the resistance allele die, while those with the resistance allele survive

• the surviving bacteria are more likely to reproduce, passing on their resistance alleles to their offspring

What does antibiotic resistance lead to?

antibiotic resistant strain of bacteria as antibiotic resistance allele increases.

Why is antibiotic resistance an issue?

too many antibiotics have been prescribed for illness’ caused by viruses which antibiotics have no effect on.

makes bacterial infections more difficult to control