O Level Biology Evolution Diversity Quiz

O-Level Biology Quiz - Evolution Diversity (Answer Key)

Section A: Fundamental Concepts

1. Variation: The differences in characteristics/traits between individuals of the same species. [1]
2. Continuous vs Discontinuous: Continuous variation shows a range of phenotypes with no clear-cut categories (e.g., height) [1], whereas discontinuous variation has distinct categories with no intermediates (e.g., blood group) [1]. [2]
3. Sources of Variation: (Any two) Random mutation [1]; Crossing over during meiosis [1]; Independent assortment of chromosomes [1]; Random fertilisation of gametes [1]. [2]
4. Mutation: A spontaneous, random change in the DNA sequence of a gene or the structure/number of chromosomes. [1]
5. Somatic Cell Mutation: Somatic cells are not gametes [1]; therefore, the mutation is not passed to the zygote during fertilisation [1]. [2]
6. Natural Selection: The process where individuals with characteristics best suited to their environment [1] are more likely to survive and reproduce, passing those traits to the next generation [1]. [2]
7. Survival of the Fittest: "Fitness" refers to the ability to survive and reproduce in a specific environment [1]. Those with the highest fitness leave the most offspring [1]. [2]
8. Selective Pressure: (Any one) Predation [1]; Availability of food/water [1]; Climate/Temperature [1]; Disease [1]. [1]

Section B: Mechanisms of Evolution

9. (a) Mutations change the nucleotide sequence of a gene [1], which can lead to a change in the amino acid sequence of a protein, resulting in a different phenotype/trait [1]. [2] (b) If the environment changes, some individuals may possess a variation that allows them to survive the new conditions [1]. Without variation, the entire population might be susceptible and go extinct [1]. [2]
10. Moth Evolution:
    • Variation exists in moth colour (light and dark) [1].
    • Sooty trunks provide better camouflage for dark moths / light moths are more visible to predators [1].
    • Dark moths are more likely to survive and reproduce [1].
    • They pass the allele for dark colour to their offspring, increasing the frequency of the trait in the population [1]. [4]
11. Artificial Selection: Humans choose individuals with desired traits to breed [1]. Unlike natural selection, where the environment determines survival [1], in artificial selection, humans determine which traits are "advantageous" [1]. [3]
12. Antibiotic Resistance:
    • Random mutation occurs in some bacteria, giving them the ability to produce a resistance enzyme [1].
    • When penicillin is used, non-resistant bacteria are killed [1].
    • Resistant bacteria survive and multiply rapidly via binary fission [1].
    • The resistance gene is passed to offspring (and potentially other bacteria via plasmids) [1]. [4]
13. (a) Species: A group of organisms that can interbreed to produce fertile offspring. [1] (b) Speciation: Population is split by a physical barrier [1]. Different selective pressures act on the two groups, leading to different adaptations/mutations [1]. Over time, they become genetically different enough that they can no longer interbreed [1]. [3]
14. Competition & Selection: Resources (food, mates, space) are limited, leading to competition [1]. Only those with the most advantageous traits win the competition and survive [1]. This ensures that only the "fittest" alleles are passed on [1]. [3]
15. Gradual Process: Mutations occur randomly and infrequently [1]. It takes many generations for a beneficial trait to increase in frequency across a whole population [1]. [2]

Section C: Synthesis and Application

16. Gene vs Chromosome Mutation: Gene mutations affect a single protein/trait (e.g., sickle cell) [1], often having a specific effect [1]. Chromosome number mutations (e.g., Down Syndrome) affect hundreds of genes simultaneously [1], usually resulting in more severe systemic developmental issues [1]. [4]
17. (a) Insecticide Resistance:
    • Variation existed in the pest population; some were naturally resistant due to mutation [1].
    • Insecticide acted as a selective pressure, killing susceptible pests [1].
    • Resistant pests survived and reproduced [1].
    • The frequency of the resistance allele increased in the population [1]. [4] (b) Management: Crop rotation to break the pest life cycle [1]; using biological control (natural predators) [1]. [2]
18. Meiosis & Evolution: Meiosis produces haploid gametes [1]. Through crossing over and independent assortment, it creates genetically unique combinations of alleles [1]. This increases the variation in offspring [1], providing a wider range of phenotypes for natural selection to act upon [1]. [4]
19. Adaptation & Fitness: An adaptation is a structural, behavioral, or physiological feature that improves survival [1]. The more adapted an organism is to its specific environment, the higher its fitness [1], meaning it is more likely to reach reproductive age and leave offspring [1]. [3]
20. Biodiversity Concern: Loss of species reduces the genetic pool available for future evolution [1]. It disrupts food webs and ecosystem stability (e.g., loss of pollinators) [1]. This makes ecosystems less resilient to further environmental changes [1], potentially leading to a collapse of services humans rely on (e.g., oxygen, food) [1]. [4]