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D4.3.10 (HL)—Disruption of phenological synchrony

Phenological synchrony is disrupted when climate change shifts interacting species at different rates, separating consumers from seasonal resources and partners.

Syllabus
First assessment 2025
Objective
D4.3.10
Level
HL

Phenological Mismatch Breaks Timing between Partners

HL only

Phenological mismatch occurs when interacting species shift seasonal timing by different amounts, reducing overlap in a resource or life-cycle window.

If plants flower earlier but pollinators do not, or prey peak before predators arrive, energy transfer and reproduction can fall. The mechanism is timing, not simply warming.

Compare both event dates and the overlap needed for the interaction.; separate driver, mechanism, response and timescale

Earlier plankton blooms can occur before a fish larva hatches, leaving less food during its critical growth window. This gives a concrete prediction from the stated climate condition.

Mismatch can be partial or temporary; species may adjust behaviour, migrate or adapt. Interpret the result within the stated evidence and scenario limits.

HL Timing and Selection

HL only

HL D4.3 adds timing and evolution. Phenology tracks when seasonal events happen; warming can desynchronize interacting species, shorten insect development, add generations, and change selection pressures so phenotype frequencies shift.

  • timing of flowering, migration, breeding, nesting or insect emergence
  • interacting species shift timing by different amounts
  • warmer temperatures can add generations and attack periods
  • milder winters alter selection and phenotype frequencies

HL Phenology and Climate Selection

HL only

HL climate questions require reasoning from timing to ecological or evolutionary consequence. The answer starts with a seasonal event or life-cycle stage, explains how warming shifts timing or selection pressure, and states the effect on interaction success, number of generations, attack periods, survival, or phenotype frequency.

  • Define phenology and identify the seasonal event being shifted.
  • Explain timing mismatch or faster development using named examples such as plant-reindeer, great tit-caterpillar, or spruce bark beetles.
  • Link climate-altered selection pressure to phenotype frequency change using the tawny owl example.

Concept essentials

  • Synchrony depends on timing overlap between interacting species or life-cycle events.
  • Climate change can shift different species at different rates.
  • Timing mismatch can reduce feeding, pollination, breeding success, and survival.
ConceptIB Biology HL