Rat

In 1972, two independent research teams destroyed the suprachiasmatic nucleus in rats and watched their lives dissolve into chaos. Sleep became random. Eating sporadic. Hormone release chaotic. The lesion studies by Moore & Eichler and Stephan & Zucker established that the SCN is necessary for circadian function - without it, temporal organization collapses. Rats were the organism that revealed how biological time is controlled: a tiny cluster of neurons in the hypothalamus orchestrating every rhythm in the body.

But rats also demonstrate why generalists survive extinctions. They're introduced species that have driven hundreds of island bird and endemic species extinct by preying on eggs and chicks. Rats survive environmental disruptions by switching foods, habitats, and behaviors. They're both extinction-resistant and extinction-causing - demonstrating how the same adaptability that makes a species resilient makes it devastating to specialists when environments change.

The strategic insight is uncomfortable: Generalist capabilities create resilience but also competitive brutality. Rats teach that the traits enabling survival during disruption - dietary flexibility, habitat switching, behavioral plasticity - are exactly the traits that let you outcompete specialists when you enter their markets. Generalists don't just survive disruption; they exploit it.