CourseCourseQ BankQuestion BankDocsDocuments

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

Different Seasonal Cues Can Create Phenological Mismatch

HL only

Phenological synchrony is disrupted when interacting populations shift seasonal events by different amounts because their cues respond differently to climate change.

Interaction Possible mismatch mechanism
Arctic mouse-ear chickweed (Cerastium arcticum) and migrating reindeer (Rangifer tarandus) Temperature advances spring plant growth, while migration timing also depends on snow and other cues; reindeer may arrive after peak forage quality
Great tit (Parus major) breeding and caterpillar peak biomass Warming shifts caterpillar biomass timing and egg-laying responses over different temperature windows, reducing food overlap when chicks need it most

Reduced overlap can lower energy transfer, growth, fledgling mass or reproductive success even if both populations remain present.

Mismatch is about the timing overlap required for an interaction. Species may partly adjust behaviour or evolve, so the outcome is not automatically permanent.

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.