Natural selection Flashcards
What does the theory of evolution state?
Life began as simple organisms from which more complex organisms evolved
This contrasts with the idea that organisms simply appeared.
Who developed the theory of evolution by natural selection?
Charles Darwin
Darwin’s theory is often summarized as ‘survival of the fittest’.
What are the three main observations that led to Darwin’s conclusions?
- Organisms over-produce offspring
- Population sizes remain relatively stable
- There is variation between individuals
These observations highlight the competition for resources.
What conclusion did Darwin draw from the observation of variation in individuals?
Some variation must help an individual to survive and reproduce
This suggests that organisms best suited to their environment are more likely to survive.
What causes variation in a population according to the theory of evolution?
Mutation
Mutation is described as a rare and random event.
Fill in the blank: Organisms with the beneficial allele for _______ survive and reproduce.
[describe the beneficial feature]
The beneficial feature varies depending on environmental pressures.
What happens over many generations to the proportion of the population with the beneficial allele?
It increases
This occurs as those with the beneficial allele survive and reproduce.
What is a mutation in bacteria during replication?
A spontaneous and random change in the DNA
This mutation can provide bacteria with an advantage.
How can bacteria gain antibiotic resistance?
By mutating to be less affected or unable to be killed by antibiotics
This gives them a huge advantage in a treated host.
What is the consequence of antibiotic-resistant bacteria surviving in a host?
They live longer and reproduce, passing on the resistance
This occurs by passing down the beneficial allele.
Why is the rapid reproduction of bacteria a concern?
Antibiotic resistance spreads quickly through the population
This can lead to dangerous infections that are difficult to treat.
What are superbugs?
Bacteria that have become resistant to several antibiotics
An example of a superbug is MRSA.
