A Level H1 Biology Evolution Diversity Quiz

A-Level Biology H1 Quiz - Evolution Diversity (Answer Key)

1. Define the term variation in the context of a population. [2]

• Differences in characteristics/traits [1]
• Between individuals of the same species/population [1].

2. Distinguish between continuous and discontinuous variation, giving one biological example for each. [4]

• Continuous: Shows a range of values with no distinct categories; usually controlled by polygenic inheritance and environment [1]. Example: Height, mass, skin color [1].
• Discontinuous: Falls into distinct categories with no intermediates; usually controlled by single genes (monogenic) and less influenced by environment [1]. Example: Blood group, tongue rolling, sex [1].

3. Explain why genetic variation is essential for the process of natural selection. [3]

• Provides a range of phenotypes/traits in the population [1].
• Ensures that some individuals possess traits better suited to the environment/selection pressure [1].
• Allows these individuals to survive and reproduce, passing on advantageous alleles [1].
  (Note: Without variation, all individuals would be equally affected by selection pressure, preventing evolutionary change.)

4. State two sources of genetic variation in sexually reproducing organisms. [2]

1. Mutation (gene mutation or chromosomal mutation) [1].
2. Sexual reproduction processes: Random fertilization / Crossing over (meiosis) / Independent assortment (meiosis) [1].
   (Accept any two valid sources.)

5. Beetle Scenario:
(a) Selection pressure: Predation by birds [1].
(b) Prediction: The frequency of the brown allele will increase [1]. Brown beetles are better camouflaged, survive predation, and reproduce more successfully, passing the brown allele to offspring [1].

6. Homologous Structures:
(a) Type of evidence: Homologous structures / Comparative anatomy [1].
(b) Explanation:

• The bones have a similar structural arrangement/layout [1].
• But serve different functions (grasping, flying, swimming) [1].
• This suggests they evolved from a common ancestor with this basic limb structure, which was then modified by natural selection for different environments [1].

7. Molecular Evidence:
(a) Most closely related: Chimpanzee [1].
(b) Explanation:

• Closely related species share a more recent common ancestor [1].
• Therefore, there has been less time for mutations to accumulate in their DNA/amino acid sequences [1].
• Fewer differences in sequence indicate closer evolutionary relationship [1].

8. Fossil Evidence:
(a) Term: Transitional fossil / Intermediate fossil [1].
(b) Why incomplete:

• Fossilization is a rare event requiring specific conditions [1].
• Many soft-bodied organisms do not fossilize well / Many fossils have been destroyed by geological activity [1].

9. Comparative Embryology:

• Closely related species show similar stages in early embryonic development [1].
• This suggests they share common genetic instructions inherited from a common ancestor [1].

10. Convergent Evolution:

• Analogous structures arise due to similar selection pressures/environments, not common ancestry [1].
• They have different underlying anatomical structures/embryonic origins despite similar functions [1].

11. Define species. [2]

• A group of organisms [1]
• That can interbreed to produce fertile offspring [1].

12. Outline allopatric speciation. [4]

• A physical/geographic barrier separates a population into two isolated groups [1].
• No gene flow occurs between the groups [1].
• Different selection pressures/mutations act on each group, leading to different allele frequencies [1].
• Over time, reproductive isolation evolves, so they can no longer interbreed even if the barrier is removed [1].

13. Reproductive Isolation:
(a) Type: Behavioral isolation [1].
(b) Explanation:

• Individuals will only mate with those that recognize their specific mating call [1].
• This prevents gene flow between the populations, allowing them to diverge genetically into separate species [1].

14. Taxonomic Ranks Order:
Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species [2].
(1 mark for correct relative order of at least 6 ranks; 2 marks for perfect order.)

15. Three-Domain System:

• Based on molecular evidence (rRNA sequences) which shows fundamental differences between Archaea and Bacteria [1].
• Reflects evolutionary relationships more accurately than morphology alone [1].

16. Peppered Moths:
(a) Increase in dark moths:

• Soot darkened the tree trunks, making light moths more visible to predators [1].
• Dark moths were better camouflaged and had higher survival rates [1].
• Dark moths reproduced more, passing the dark allele to the next generation [1].
  (b) Effect of clean air:
• Tree trunks became lighter (lichen grew back) [1].
• Light moths became better camouflaged, so their population increased while dark moth population decreased [1].

17. Antibiotic Resistance:
(a) Acceleration:

• Bacteria have genetic variation; some possess resistance mutations [1].
• Antibiotics kill non-resistant bacteria, leaving resistant ones to survive (selection pressure) [1].
• Resistant bacteria reproduce rapidly, passing resistance genes to offspring (vertical transmission) or other bacteria (horizontal transmission) [1].
  (b) Strategy:
• Complete the full course of antibiotics / Do not use antibiotics for viral infections / Rotate antibiotics [1].

18. Phylogenetic Tree:
(a) Most closely related: A and B [1].
(b) Nodes represent: Common ancestors [1].

19. Refuting "Individual Evolution":

• Evolution occurs at the population level over generations, not within an individual's lifetime [1].
• Individuals do not change their genetic makeup in response to the environment; they either possess advantageous alleles or they do not [1].
• Natural selection acts on existing variation, selecting individuals that survive to reproduce [1].

20. Role of Geographic Isolation:

• Prevents gene flow between sub-populations [1].
• Allows each sub-population to accumulate different mutations and adapt to local environmental conditions [1].
• Leads to genetic divergence until reproductive isolation is established [1].