Explain how increasing global temperatures can alter the geographical distribution of terrestrial species and describe the potential ecological consequences of these changes.

IB DP Biology Higher Level (2023 syllabus) — D4.3 Climate change · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

1. Species have specific temperature tolerance ranges for their metabolic processes and survival.
2. As temperatures exceed these tolerance limits, species may shift their geographical range towards cooler regions.
3. These range shifts can lead to new competitive or predatory interactions with existing species in the new habitat.
4. Ultimately, this can disrupt food webs, alter community structures, and lead to reduced biodiversity or local extinctions.

Examiner tips

  • Use the word ‘explain’ to show cause and effect; link temperature to tolerance, shift, interaction, and ecosystem impact.
  • Include the sequence: tolerance → shift → new interactions → ecosystem change.
  • Use precise terms: ‘metabolic processes’, ‘geographical range’, ‘food webs’, ‘biodiversity’.

Common mistakes

  • Focusing only on species migration without mentioning temperature tolerance limits.
  • Using vague phrases like ‘change’ instead of specific ecological consequences such as altered food webs or local extinctions.

Mark scheme (4 marks)

  1. Species have specific temperature tolerance ranges for their metabolic processes and survival.
  2. As temperatures exceed these tolerance limits, species may shift their geographical range towards cooler regions.
  3. These range shifts can lead to new competitive or predatory interactions with existing species in the new habitat.
  4. Ultimately, this can disrupt food webs, alter community structures, and lead to reduced biodiversity or local extinctions.

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