A Level H1 Biology Evolution Diversity Quiz

Answer Key - A-Level Biology H1 Quiz: Evolution Diversity

1. Mutation. [1]

2. The evolutionary process by which populations evolve to become distinct species [1] such that they are no longer able to interbreed to produce fertile offspring [1]. [2]

3. Any two from: Fossil record, Comparative anatomy (homologous structures), Molecular evidence (DNA/protein sequences), Biogeography. [2]

4. Homologous structures: Similar anatomy due to common ancestry but may have different functions [1]. Analogous structures: Similar function but different anatomy due to convergent evolution/different ancestry [1]. [2]

5. Environmental change alters the selection pressure [1]. Individuals with alleles that provide a survival advantage in the new environment are more likely to survive and reproduce [1], passing these alleles to the next generation, thus increasing the allele frequency [1]. [3]

6. Mutation creates new alleles/genetic variation [1]. This provides the raw material upon which natural selection acts [1]. Beneficial mutations increase the fitness of the individual, leading to higher reproductive success [1]. [3]

7. Archaea, Bacteria, Eukarya. [3]

8. rRNA is present in all cellular organisms [1]. It evolves very slowly (highly conserved) [1], making it possible to trace relationships over very long evolutionary timescales where morphological changes are too great to be reliable [1]. [3]

9. (a) Brown beetles are better camouflaged against the brown vegetation [1]. They are less likely to be preyed upon by predators compared to green beetles [1]. Brown beetles have a higher survival rate and are more likely to reproduce [1], passing the 'brown' allele to offspring [1]. (b) The proportion of brown beetles will increase / The ratio will shift heavily toward the brown phenotype. [1]

10. A population is split by a physical barrier (e.g., mountain range/river) [1]. The two separated populations face different selection pressures/environments [1]. Over time, genetic divergence occurs through mutation and natural selection [1]. Eventually, reproductive isolation is achieved, and they cannot interbreed even if the barrier is removed [1]. [4]

11. (a) The most recent common ancestor of the lineages branching from that point. [1] (b) They will be connected by a node that is closer to the tips of the tree [1] (shorter path distance between them) [1]. [2]

12. Divergent: Related species evolve different traits due to different environments (e.g., Darwin's finches beaks) [2]. Convergent: Unrelated species evolve similar traits due to similar selection pressures (e.g., wings of bats and insects) [2]. [4]

13. (a) Humans and chimpanzees. [1] (b) Cytochrome c is a highly conserved protein [1]. A smaller number of amino acid differences indicates a more recent common ancestor [1], supporting the idea that humans and chimps diverged more recently than they did from yeast [1]. [3]

14. Speciation occurring within the same geographic area [1]. Mechanism: Polyploidy (common in plants) [1] or strong disruptive selection/sexual selection (behavioral isolation) [1]. This creates a reproductive barrier between groups in the same location [1]. [4]

15. (a) A sharp reduction in the size of a population due to environmental events [1], resulting in a loss of genetic diversity [1]. (b) In small populations, chance events have a larger proportional effect on allele frequencies [1]. A single individual's failure to reproduce can eliminate an allele entirely [1], whereas in large populations, the law of large numbers buffers against such random fluctuations [1]. [3]

16. Binomial nomenclature provides a unique two-part name (Genus species) for each organism [1]. This name reflects the organism's position in the hierarchical classification system [1], specifically identifying its genus and species [1]. [3]

17. Evidence: Shows transitional forms (e.g., Archaeopteryx) [1], demonstrates gradual change in morphology over time [1], and provides a timeline of when certain traits appeared [1]. Limitation: Fossil record is incomplete [1] because not all organisms fossilize well (e.g., soft-bodied) or all fossils are not discovered [1]. [5]

18. Variation exists within a population due to mutation/meiosis [1]. Individuals with traits better suited to the environment have a survival advantage (higher fitness) [1]. These individuals are more likely to survive to reproductive age [1] and pass their advantageous alleles to offspring [1]. Over generations, these traits become more common, resulting in adaptation [1]. [5]

19. Morphological: Based on physical traits [1]; easier to observe in fossils [1]; however, can be misleading due to convergent evolution (analogous structures) [1]. Molecular: Based on DNA/protein sequences [1]; provides more precise, quantitative data and is less prone to convergence [1]; however, requires living tissue or very well-preserved ancient DNA [1]. (Any 5 points/comparisons). [5]

20. The statement is partially true/false [1]. Mutation is random; it occurs without regard to the needs of the organism [1]. However, natural selection is NOT random [1]; it systematically preserves beneficial traits and eliminates harmful ones based on environmental fitness [1]. Therefore, the direction of evolution is driven by non-random selection [1]. [5]