Evolution by Natural Selection Flashcards
All 5 cards in this deck
What are the steps of Darwin's theory of evolution by natural selection?
e.g. mice living on dark soil becoming darker over time
- Variation from mutation: some mice are born darker.
- Selection pressure (predators) — dark mice are camouflaged, so they are more likely to survive and reproduce.
- They pass the allele to their offspring; over many generations more of the population is dark.
What are the steps by which bacteria become resistant to an antibiotic?
e.g. bacteria becoming resistant to colistin
- A random mutation gives some bacteria a gene/allele for resistance.
- The antibiotic acts as a selection pressure (overuse, or the course not finished): non-resistant bacteria are killed, resistant ones survive.
- The resistant bacteria reproduce and pass on the resistance; the process repeats, so resistance spreads.
True or false? Bacteria mutate in order to become resistant when an antibiotic is used.
False. Mutations happen randomly; the antibiotic simply selects the bacteria that are already resistant (they are resistant, not 'immune').
True or false? Using antibiotics to treat a viral infection can contribute to the development of antibiotic resistance.
True. It is inappropriate use that exposes bacteria to the antibiotic, acting as a selection pressure.
Give two examples of selection pressures.
Any two: predation, disease, and competition for resources such as food, water or mates.