Plants, which as sessile organisms are intimately tied to their environment, have evolved many ways to deal with changing local conditions. One coping mechanism is the circadian oscillator or clock, which produces self-sustained rhythms with an approximately 24-h period. It is often suggested that the clock provides an adaptive advantage by allowing organisms to anticipate regular changes in the environment and temporally separate incompatible metabolic events.

Between 1970 and 1989, half of Africa’s elephants (Loxodonta africana), perhaps 700,000 individuals, were killed, mostly to supply the international ivory trade. This catastrophic decline prompted the Conference of the Parties (CoP) to the Convention on the International Trade in Endangered Species of Wild Flora and Fauna (CITES) to list African elephants on Appendix I of the convention, banning the international ivory trade.

Early analysis of the development of visual cortex by Hubel and Wiesel focused on binocular interactions and showed that both anatomy and physiology of ocular dominance is plastic and shaped in a visually-driven, activity-dependent process [1]. In a similar vein, the development of circuits in the somatosensory cortex (S1) was studied. It was recognized early on that precise topographic (barrel) representation of the whisker pattern in cortical input layer 4 [2] is imposed by peripheral inputs and has an early and brief critical period, after which it can no longer be changed [3].

Animals must balance food intake with energy expenditure to maintain optimal health. In choosing what and how much to eat, animals integrate external cues like tastes and smells with internal motivational states like hunger and satiety. Powerful homeostatic mechanisms tie these motivational states to the sensing of nutrient and energy status. Because fat is the primary long-term energy storage molecule, these homeostatic sensors monitor fat levels—triggering increased feeding when they fall and decreased feeding when they rise.