Evolution by Natural Selection Flashcards
All 6 cards in this deck
What is evolution?
The change of inherited characteristics (in a species) over time through natural selection.
What are the key steps of natural selection?
e.g. a population of beetles on dark bark
- Variation: some beetles are darker due to a mutation.
- Competition and survival: the best adapted (dark) beetles survive and reproduce.
- Inheritance: they pass the advantageous allele to offspring, so over generations most beetles are dark.
True or false? Individual organisms change their own characteristics during their lifetime so they can survive better.
False. Variation already exists from mutation; natural selection acts on the individuals that are already best adapted.
How does a population of bacteria become resistant to an antibiotic?
e.g. bacteria treated with Colistin
- Some bacteria have a mutation / gene for resistance.
- The antibiotic kills the non-resistant bacteria; the resistant bacteria survive.
- The resistant bacteria reproduce and pass on the beneficial allele, so eventually all the bacteria are resistant.
True or false? Bacteria become immune to an antibiotic after being exposed to it.
False. They become resistant, not immune — resistance comes from a mutation some bacteria already have.
Why is antibiotic resistance in bacteria strong evidence for Darwin's theory?
Bacteria reproduce very quickly, so natural selection (evolution) can be observed over a short timescale.