A Level H1 Biology Evolution Diversity Quiz

A-Level Biology H1 Quiz - Evolution Diversity

ANSWER KEY

Section A: Multiple Choice

(1 mark each, total 5 marks)

Section B: Short Answer

6. Evolution is the change in heritable characteristics of a population over successive generations [1], driven by processes such as natural selection, mutation, and genetic drift [1]. (Accept: “descent with modification”.)

7.

• Variation exists in a bacterial population; some bacteria carry genes that confer resistance to the antibiotic. [1]
• When exposed to the antibiotic, susceptible bacteria die while resistant ones survive and reproduce, passing the resistance alleles to offspring. Over generations, the frequency of resistant alleles increases – evolution by natural selection. [1]

8. Any two of: geographical isolation, temporal isolation, behavioural isolation, mechanical isolation, gametic isolation, hybrid inviability, hybrid sterility. (2 separate mechanisms, 1 mark each.)

9. A binomial name is the two-part Latin scientific name of a species, consisting of the genus name (capitalised) and the species epithet (lowercase), e.g., Homo sapiens. [1 for definition, 1 for correct example italicised/underlined.]

10. Archaeal cell walls lack peptidoglycan [1]; many contain pseudopeptidoglycan or other polymers. Bacterial cell walls contain peptidoglycan (murein) [1]. (Or: Archaeal membrane lipids have ether-linked isoprenoid chains; Bacteria have ester-linked fatty acids – 2 marks for any clear difference.)

(Total 10 marks)

Section C: Structured Questions

11.
(a) Homologous structures. [1]
(b) The forelimbs have a similar basic bone arrangement (pentadactyl limb) [1], indicating they were inherited from a common ancestor. [1] Over time, different selection pressures in different environments led to modifications of the limb for different functions (e.g., flying, swimming). This divergence from a common ancestral form is evidence for divergent evolution. [1]

12.
(a) The node/most recent common ancestor that connects only P and Q. (Accept “the common ancestor of P and Q” or “node X” if labelled. Must not be the ancestor of all four.) [1]
(b) A phylogenetic tree shows ancestry and descent relationships [1]; each branching point (node) represents a common ancestor [1]; the pattern of branching indicates the order in which lineages diverged, allowing inference of evolutionary history and relative times of divergence. [1]

13.

• Variation existed in the population: some plants genetically tall, some short. [1]
• Ground-dwelling herbivores exerted a selection pressure, eating short plants more heavily. [1]
• Tall plants were more likely to survive and reproduce, passing on the alleles for tallness to their offspring. [1]
• Over many generations, the frequency of tall-stem alleles increased in the population – evolution by natural selection. [1]

14.

• Homologous structures have a similar underlying anatomy and embryonic origin, indicating common ancestry, but may serve different functions (e.g., pentadactyl limb of mammals). [1.5]
• Analogous structures perform a similar function but have different anatomical origins and do not derive from a common ancestor; they arise via convergent evolution (e.g., wing of a bird and wing of a butterfly). [1.5]
• Two clear named examples with correct categorisation = 1 mark. (e.g., human arm and whale flipper are homologous; eye of octopus and eye of human are analogous – accept any correct pair.) [1]

15.
(a) Chimpanzee (98.8% similarity). [1]
(b) DNA sequences are inherited from ancestors [1]; the greater the similarity in sequence, the more recently two species shared a common ancestor [1]; the pattern of decreasing sequence similarity from chimpanzee → gorilla → orangutan → gibbon mirrors the pattern of evolutionary divergence predicted by descent with modification. This molecular evidence corroborates the evolutionary relationships inferred from other lines of evidence (fossils, morphology). [1]

(Total 20 marks)

Section D: Extended Response

16. Description of allopatric speciation (5 marks):

• A physical/geographical barrier (e.g., mountain range, river, sea) separates a population into two or more isolated groups. [1]
• Each group experiences different selection pressures in its environment. [1]
• Natural selection acts on heritable variation, leading to different adaptations over time. [1]
• Accumulated genetic differences eventually result in reproductive isolation – even if the groups come back into contact they cannot interbreed and produce fertile offspring. [1]
• Named example clearly linked to the above, e.g., Darwin’s finches on Galápagos Islands separated by ocean, or squirrels separated by the Grand Canyon. [1]
  (5 marks maximum)

17. Discussion of pesticide resistance (5 marks):

• Pre-existing genetic variation in the insect population means some individuals naturally carry alleles that confer resistance to a pesticide (e.g., via detoxifying enzymes or altered target site). [1]
• Application of the pesticide acts as a strong selection pressure: susceptible insects die, resistant insects survive. [1]
• Resistant survivors reproduce, passing on resistance alleles to the next generation; the frequency of these alleles increases. [1]
• With repeated pesticide use, the population becomes predominantly resistant – a clear example of directional natural selection. [1]
• The process can occur rapidly in large populations with short generation times, demonstrating how human-induced selection pressures drive evolutionary change. [1]
  (5 marks maximum)

18. (5 marks)

• The three-domain system classifies life into Bacteria, Archaea, and Eukarya based primarily on differences in ribosomal RNA sequences [1]. Domain Archaea includes prokaryotes often found in extreme environments; Bacteria includes typical prokaryotes; Eukarya contains all eukaryotes (protists, fungi, plants, animals). [1]
• The older five-kingdom system (Monera, Protista, Fungi, Plantae, Animalia) grouped all prokaryotes together as Monera and did not recognise the deep genetic divide between Bacteria and Archaea. [1]
• Molecular (rRNA and protein sequences) and biochemical evidence (cell wall composition, membrane lipids, transcription machinery) shows that Archaea are more closely related to Eukarya than to Bacteria [1].
• Thus, the three-domain system better reflects true evolutionary relationships and common ancestry. [1]
  (5 marks maximum; accept any 5 valid, well-explained points)

19. Comparative embryology evidence (5 marks):

• Named vertebrate group: e.g., all vertebrate embryos (fish, amphibians, reptiles, birds, mammals) exhibit pharyngeal pouches/arches and a post-anal tail at early stages. [1]
• These structures are homologous, suggesting inheritance from a common vertebrate ancestor. [1]
• In different groups, these structures develop into different adult forms (e.g., gill slits in fish, parts of the ear and throat in mammals) – an example of divergent evolution. [1]
• The similarity of early embryos indicates shared developmental genes (e.g., Hox genes) and a conserved body plan [1].
• Such shared embryonic features cannot be easily explained by adaptation to similar environments; they provide strong evidence for descent with modification from a common ancestor. [1]
  (5 marks maximum)

20. Adaptive radiation in finches (5 marks):

• Adaptive radiation is the rapid diversification of a single ancestral species into many species, each adapted to exploit different ecological niches. [1]
• On the newly formed island, many unoccupied niches were available (different food sources: seeds, insects, nectar). [1]
• The original finch population showed genetic variation in beak size/shape. [1]
• Different food sources imposed different selection pressures; finches with beak traits best suited to a particular food survived and reproduced. [1]
• Over many generations, these selection pressures led to reproductive isolation and the evolution of several distinct species, each with a beak morphology adapted to its specific niche – classic adaptive radiation. [1]
  (5 marks maximum)

(Total 25 marks)

Grand Total: 60 marks