Unit 3: Biodiversity, Conservation and Change
Topic 3.2: Natural Selection, Variation and Speciation Questions
Practice 17 exam-style questions for IB ESS Topic 3.2. Review the question stems below, then unlock the full Question Bank to access markschemes, model answers, and AI grading.
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State what is meant by 'genetic variation' within a population.
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Outline two conditions necessary for natural selection to occur.
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State what is meant by 'speciation'.
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Identify one factor that could cause reproductive isolation between two populations.
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Two groups of the same bird species become separated when a new volcanic lava field forms a barrier between them. Over time, the two sides have different food types. Outline the process that could lead to the formation of a new species.
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Table 1 shows survival of two colour forms of a moth in a forest before and after trees become darker due to pollution.
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Explain how evolution and speciation can increase biodiversity and why this may increase ecosystem resilience.
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Outline how natural selection operates within a population.
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A few mainland birds reach an island with no large predators. After many generations, the island birds are larger and spend more time feeding on the ground. Outline how this could eventually lead to speciation.
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Two populations of the same frog species become separated when a highway is built through their wetland. After many years, they breed at different times of year. Explain why this increases the chance of speciation.
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A small group of insects is blown by a storm onto a nearby island. The island has darker tree bark than the mainland. After many generations, most island insects are darker than mainland insects. Explain why.
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A farmer uses the same pesticide for many years. At first, most pests die. Later, the pesticide becomes less effective. Suggest how evolution could explain this change.
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A population of fish lives in a lake. Over 30 years, water temperatures rise and oxygen levels fall during summer. Explain two possible outcomes for the fish population.
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A long drought reduces the number of flowering plants in a grassland. A specialist bee that feeds only on one flower species declines rapidly. Suggest one reason why this bee population is at risk of extinction if the drought continues.
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A cold winter becomes the new normal in a region. Some lizards are slightly darker in colour than others. Explain how natural selection could change the lizard population over many generations.
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Explain how long-term environmental change can influence biodiversity and the evolution of species.
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