18.3 Selection

Natural selection described in 5 Cambridge steps: (a) genetic variation in populations, (b) overproduction of offspring, (c) struggle for survival including competition for resources, (d) better-adapted individuals reproduce more, (e) alleles passed to next generation. Selective breeding (artificial selection) described in 3 steps: (a) select desirable individuals, (b) cross them, (c) select offspring with desired feature — repeated over many generations to improve crops and domesticated animals. HL extension: adaptation defined as the PROCESS by which populations become more suited to environment; antibiotic resistance in MRSA as a real-time example of natural selection; differences between natural and artificial selection (selecting agent: environment vs human; trait value: survival vs human-desired; timescale).