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O Level Biology Evolution Diversity Quiz

Free O Level Biology Evolution Diversity quiz, Gemma31B Exam version, with questions, answers, and O Level-style practice for Singapore students.

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O Level Biology From Real Exams Generated by Gemma 4 31B Updated 2026-09-16

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Questions

O-Level Biology Quiz - Evolution Diversity

Name: ____________________ Class: ____________________ Date: ____________________ Score: / 45

Duration: 60 minutes
Total Marks: 45
Instructions: Answer all questions. Write your answers in the spaces provided.

Section A: Short Answer Questions (1-8)

Focus: Fundamental Concepts of Variation and Selection

Define the term variation. [1]
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State the difference between continuous variation and discontinuous variation. [2]
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Give one example of a characteristic that shows continuous variation in humans. [1]
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Explain why mutations are the primary source of new alleles in a population. [2]
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Define natural selection. [2]
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What is meant by the term selective pressure? [1]
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State two factors that can act as selective forces in a wild environment. [2]
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Distinguish between a genotype and a phenotype. [2]
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Section B: Structured Response (9-15)

Focus: Mechanisms of Evolution and Adaptation

A population of beetles exists in two colours: light green and dark green. They live in a forest where the foliage is primarily dark green. (a) Which phenotype is more likely to survive? [1] ___________________________________________________________________________ (b) Explain how this leads to evolution over several generations. [3] ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________
Explain the role of competition in the process of natural selection. [3]
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Describe how the use of antibiotics can lead to the evolution of antibiotic-resistant bacteria. [4]
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Compare the process of natural selection with artificial selection (selective breeding). [3]
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A species of bird has a variety of beak shapes. During a drought, only large, hard seeds remain available. (a) Describe the expected change in the average beak size of the population over time. [1] ___________________________________________________________________________ (b) Explain the biological reasoning behind this change. [3] ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________
Explain why a population with high genetic diversity is more likely to survive a sudden environmental change than a population with low genetic diversity. [3]
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State the relationship between natural selection and evolution. [2]
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Section C: Extended Response (16-20)

Focus: Synthesis and Application

Using the example of the Peppered Moth, describe how a change in the environment can shift the frequency of phenotypes in a population. [5]
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Explain how the process of differential survival contributes to the change in the genetic makeup of a population. [4]
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Discuss the impact of "bottleneck effect" (a drastic reduction in population size) on the evolutionary potential of a species. [4]
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Describe how a specific adaptation (structural or behavioural) allows an organism to survive in a desert environment. [4]
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Explain why evolution is described as a "gradual change in inheritable characteristics" rather than a sudden transformation of an individual. [4]
___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________

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Answers

O-Level Biology Quiz Answers - Evolution Diversity

Variation: The differences in characteristics between individuals of the same species. [1]
Difference: Continuous variation shows a range of phenotypes with no distinct categories (e.g., height), whereas discontinuous variation has distinct, separate categories (e.g., blood group). [2]
Example: Height, skin colour, mass. (Any one) [1]
Mutations: They are random changes in the DNA sequence/nucleotide sequence, which can create new alleles that did not previously exist in the gene pool. [2]
Natural Selection: The process where organisms with favourable traits are more likely to survive and reproduce, passing these traits to the next generation. [2]
Selective Pressure: An external factor (e.g., predator, climate, disease) that affects the survival and reproduction of individuals in a population. [1]
Factors: Predators, food availability, temperature, competition for mates. (Any two) [2]
Genotype vs Phenotype: Genotype is the genetic makeup/alleles of an organism; Phenotype is the observable physical characteristic resulting from the genotype and environment. [2]
(a) Dark green beetles. [1] (b) Dark green beetles are better camouflaged $\rightarrow$ less likely to be eaten by predators $\rightarrow$ higher survival rate $\rightarrow$ more likely to reproduce and pass the "dark green" allele to offspring $\rightarrow$ frequency of dark green phenotype increases over generations. [3]
Competition: Resources (food, space, mates) are limited $\rightarrow$ only those with the most advantageous traits can successfully compete $\rightarrow$ these individuals survive and reproduce, while others perish. [3]
Antibiotic Resistance: Variation exists in bacteria (some have mutations for resistance) $\rightarrow$ Antibiotics act as a selective pressure $\rightarrow$ Non-resistant bacteria are killed; resistant bacteria survive $\rightarrow$ Resistant bacteria multiply and pass the resistance gene to offspring. [4]
Comparison: Natural selection is driven by environmental pressures for survival; artificial selection is driven by humans choosing desired traits for breeding. [3]
(a) Average beak size will increase. [1] (b) Birds with larger/stronger beaks can crack the hard seeds $\rightarrow$ they obtain more energy/survive $\rightarrow$ they reproduce more successfully $\rightarrow$ offspring inherit the large-beak trait. [3]
Genetic Diversity: Higher diversity means a greater variety of alleles $\rightarrow$ higher probability that some individuals possess a trait that allows them to survive a new environmental stressor $\rightarrow$ prevents total extinction of the population. [3]
Relationship: Natural selection is the mechanism that drives evolution; evolution is the result (the gradual change in characteristics over time). [2]
Peppered Moth: Originally light-coloured moths were camouflaged on lichen-covered trees $\rightarrow$ Industrial Revolution caused soot to cover trees $\rightarrow$ Light moths became visible to predators; dark moths became camouflaged $\rightarrow$ Dark moths survived and reproduced more $\rightarrow$ Population shifted from predominantly light to predominantly dark. [5]
Differential Survival: Individuals with unfavourable traits die before reproducing $\rightarrow$ Individuals with favourable traits survive $\rightarrow$ Only favourable alleles are passed to the next generation $\rightarrow$ The allele frequency of the population changes. [4]
Bottleneck Effect: Drastic reduction in population $\rightarrow$ loss of many alleles/genetic diversity $\rightarrow$ reduced ability to adapt to future environmental changes $\rightarrow$ increased risk of extinction. [4]
Desert Adaptation: (Example: Camel) Long eyelashes to keep out sand / Humps to store fat for energy and water / Concentrated urine to reduce water loss. (Explain how it aids survival). [4]
Gradual Change: Individuals cannot change their own genes during their lifetime $\rightarrow$ Evolution occurs across generations $\rightarrow$ It is the change in the proportion of phenotypes in a population $\rightarrow$ Requires multiple cycles of selection and reproduction. [4]