Question

How does a changing climate drive evolution?

Organisms separate and can’t reproduce.

Organisms from other continents move in.

Organisms are forced to live together.

Organisms must adapt or go extinct.

Answer 1

All of the above. Climate change drives evolution through several, often simultaneous, mechanisms:

- Organisms separate and can’t reproduce: Changing climates alter habitats and ranges, creating geographic isolation (allopatric separation). Isolated populations diverge genetically over generations and can form new species. Example: glacial cycles repeatedly split populations and promoted speciation in many northern plants and animals.

- Organisms from other continents move in: Warming and altered currents let species expand into new regions. New immigrants bring different genes, competitors, predators, and pathogens, creating new selective pressures and opportunities for hybridization or adaptive introgression.

- Organisms are forced to live together: Range shifts can produce novel sympatry—previously separated species come into contact, increasing competition, predation, mutualisms, and hybridization. Those new interactions can change which traits are favored.

- Organisms must adapt or go extinct: Changing temperature, precipitation, seasonality, and habitat structure impose new selection pressures. Populations that evolve suitable traits (or shift behavior/phenology) persist; those that cannot often decline or disappear.

Additional points: the outcome depends on the rate of climate change, population size, genetic variation, and life history. Rapid change may exceed species’ capacity to adapt, increasing extinctions, while slower change or high genetic diversity can promote evolutionary responses.