How did plants and animals adapt to past natural variability?
* A: Plants and animal species responded to historical climate variability through changes in genetic diversity (evolution) and shifts in geographic range (migration). Genetic diversity is affected as a result of climate-driven changes in natural selection, gene flow and breeding patterns, genetic drift (that is, random effects resulting from changes in population size, isolation, and fragmentation), and changes in mutation rates. Evolutionary change in the past commonly increased adaptation in species, but in other situations resulted in decreased adaptation such as loss of fitness, population extirpation (loss of a population but not entire species), and species extinction. Plants and animal species also responded to past climate change by migrating to favorable environments. For animals, this happens through individuals moving to new locations for breeding and home ranges. For plants, geographic shifts (migration) usually take place through seed and pollen transport. Mortality and p
