6.16 Evidence for evolution: fossils and resistant bacteria
5 exam questions worth 12 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
0 / 12
Give two ways fossils can form.
Mark scheme
Any two from:
- parts of organisms that have not decayed (conditions for decay absent) (1)
- parts replaced by minerals (1)
- traces such as footprints / burrows (1)
Model answer
When parts of an organism are replaced by minerals as they decay, and as preserved traces such as footprints.
Explain why there are very few fossils of the earliest forms of life.
Mark scheme
- early organisms were soft-bodied (so did not fossilise well) (1)
- traces destroyed by geological activity (1)
Model answer
The earliest organisms were soft-bodied and left few traces, and many of the traces that did form have been destroyed by geological activity.
Explain why some organisms do not decay after they die.
Mark scheme
- one or more conditions for decay is absent (1)
- e.g. no oxygen / too cold / too dry / too acidic (1)
Model answer
Decay needs conditions such as oxygen, warmth and moisture. If one is missing, for example in ice or a peat bog, the organism does not decay.
Explain how antibiotic-resistant strains of bacteria develop, and why this is evidence for evolution.
Mark scheme
- mutation causes resistance in some bacteria (1)
- antibiotic kills non-resistant bacteria; resistant survive (1)
- resistant bacteria reproduce and pass on the allele (1)
- population changes over generations, which is natural selection observed (1)
Model answer
A mutation makes some bacteria resistant. The antibiotic kills the others, but the resistant bacteria survive, reproduce and pass on the resistance allele. The population changes over a few generations, which is natural selection that we can see happening.
Give two ways to reduce the spread of antibiotic-resistant bacteria.
Mark scheme
Any two from:
- do not prescribe antibiotics for viral / non-serious infections (1)
- complete the course (1)
- restrict agricultural use (1)
- hospital hygiene / isolation (1)
Model answer
Do not use antibiotics for viral infections, and always finish the full course.
Found a mistake?