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Biology · Class 12
Individuals vary, some variation is heritable, more offspring are produced than survive, and carriers of advantageous variants leave more descendants.
PracticeSpeciation occurs when populations become reproductively isolated and diverge. Geographic isolation often starts the process, but isolation can also arise without a barrier.
PracticeLight, water, temperature, soil and chemicals are abiotic factors; competitors, predators, prey, parasites and mutualists are biotic factors.
PracticeAn adaptation is a heritable feature shaped by selection for a function. Fitness means relative reproductive contribution in a particular environment, not physical strength.
PracticeAdaptive immunity uses specific lymphocyte receptors, clonal expansion and memory. B cells produce antibodies; T cells coordinate responses or kill infected cells.