OCR GCSE Biology A (Gateway)
OCR GCSE Biology A B5.2 Natural Selection and Evolution Exam Questions
Free OCR GCSE Biology A exam questions for B5.2 Natural Selection and Evolution, with a mark scheme for every pack. Covers variation, evolution by natural selection, Darwin and Wallace, evidence for evolution, antibiotic resistance, speciation and classification systems.
B5.2 Natural Selection and Evolution exam questions
1 question pack of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About OCR GCSE Biology A B5.2 Natural Selection and Evolution
B5.2 explains how species change over time through natural selection and how living things are classified. On the OCR Gateway Biology A course it completes Topic B5 Genes, inheritance and selection, assessed in Paper 2 (Foundation) or Paper 4 (Higher). It builds on variation and mutation from B5.1 and links to antibiotics and disease in B6.3. Examiners often ask for a step-by-step explanation of natural selection, the evidence for evolution such as fossils and antibiotic resistance, how scientific ideas about evolution developed, and how classification changed from Linnaeus to the three-domain system.
What you need to know
- Natural selection Individuals in a population show variation caused by mutations. Those with alleles that give an advantage are more likely to survive and reproduce, passing on these alleles, so over many generations the allele frequency changes.
- Evolution and speciation Evolution is the gradual change in the inherited characteristics of a population over time. A new species forms when populations become so different that they can no longer interbreed to produce fertile offspring.
- Darwin and Wallace Charles Darwin and Alfred Russel Wallace independently developed the theory of evolution by natural selection. Darwin published On the Origin of Species in 1859; the theory was slowly accepted as evidence built up and genetics explained inheritance.
- Evidence for evolution Fossils show how organisms changed over long periods, though the record is incomplete. Antibiotic resistance in bacteria shows natural selection happening quickly, because bacteria reproduce rapidly.
- Classification Linnaeus grouped organisms into kingdom, phylum, class, order, family, genus and species, and introduced the binomial naming system (genus and species). Developments in microscopy and DNA analysis led to Woese's three-domain system: Archaea, Bacteria and Eukaryota.
- Antibiotic resistance A random mutation can make a bacterium resistant; when antibiotics are used, non-resistant bacteria die and resistant ones survive and reproduce. Overuse and not finishing courses increase the spread of resistant strains such as MRSA.
Common mistakes in B5.2 Natural Selection and Evolution
- Saying organisms change or mutate 'in order to' survive. Mutations are random; the environment selects individuals that already have advantageous alleles.
- Writing that antibiotics cause bacteria to become resistant. Resistance arises by random mutation; antibiotics kill non-resistant bacteria so resistant ones survive.
- Describing evolution as an individual changing during its life. Evolution happens to populations over many generations.
- Forgetting the role of reproduction. Survivors must reproduce and pass on their alleles for the population to change.
- Writing binomial names incorrectly. The genus starts with a capital letter, the species with a lower case letter, for example Homo sapiens.
Try three B5.2 Natural Selection and Evolution exam-style questions
1. Explain how a population of bacteria can become resistant to an antibiotic. (4 marks)
Show the mark scheme answer
A random mutation produces a resistant bacterium; when the antibiotic is used, non-resistant bacteria are killed; resistant bacteria survive and reproduce; the resistance allele is passed on so the proportion of resistant bacteria increases.
2. Give two reasons why the fossil record is incomplete. (2 marks)
Show the mark scheme answer
Soft-bodied organisms rarely fossilise; fossilisation needs rare conditions; many fossils have been destroyed by geological activity; many fossils have not yet been found. Any two.
3. Name the three domains in the three-domain classification system and state what evidence led to it. (2 marks)
Show the mark scheme answer
Archaea, Bacteria and Eukaryota; evidence from chemical analysis of DNA or RNA (improved molecular techniques).
B5.2 Natural Selection and Evolution FAQs
What does OCR GCSE Biology A B5.2 cover?
It covers variation, natural selection and evolution, the work of Darwin and Wallace, evidence for evolution including fossils and antibiotic resistance, and classification systems.
Which paper is B5.2 examined in?
As part of Topic B5, it is assessed in Paper 2 (Foundation) or Paper 4 (Higher).
How should I write a natural selection answer for B5.2?
Use the sequence variation, mutation, selection pressure, survival of the best adapted, reproduction, alleles passed on, and change in the population over many generations.
