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By Root 1219 0

state of development. All insects are in arrested development when they hibernate (in part because low temperature, if not also freezing, retards or stops biochemical processes unless special mechanisms are invoked to circumvent the cold), but they are not strictly in diapause unless they do not respond with resumed development as soon as they experience warming. Many (but by no means all) moths arrest their development in the pupal stage during late summer and fall when it is still warm, and then hibernate as diapausing pupae. Others, depending on the species, hibernate in the egg, larval, or adult stage. Special adaptations are required for arresting development and combine with other traits for withstanding the cold during overwintering. Diapause also occurs in the absence of hibernation. For example, some adult insects enter reproductive diapause in the summer when they migrate or search for host plants.

The muddle in terminology of what hibernation means can be avoided if hibernation is defined not in terms of body temperature or some other specific physiological or behavioral phenomenon characteristic of a given species, but in terms of its adaptive function. In most animals hibernation and/or aestivation are seasonal periods of adaptive torpor that allow the animal to survive regularly occurring famine. Cold, heat, and aridity are factors that exacerbate the seasonal famine that hibernation has addressed through the evolution of various adaptations.

Even more confusion of terminology could be avoided by realizing that making ever more precise or restrictive definitions does not generate greater precision in the understanding of any animal. Animals are dynamic. Each animal’s choices fit in somewhere in a long continuum of almost anything that can be measured or imagined. Different terms may apply in any one animal in varying degree, depending on circumstances, but ultimately the species, and often the individual, fashion their own solutions to fit the situation or the occasion. We gain understanding not so much by lumping and defining, but by differentiating the specifics from the generalized features. The latter have a tendency to become enshrined as rules or laws that are ultimately statistically derived descriptive artifacts. But animals don’t follow rules or easily allow us to pigeonhole them into convenient intellectual boxes. A “rule” is nothing more than a consistency of response that we have deduced animals exhibit because it serves their interests. Rules are the sum of decisions made by individuals. They are a result. The chaos, and the art, of nature remains.

01

FIRE AND ICE

Microscopic life evolved some 3.5 billion years ago in the Precambrian period during the first and longest chapter of life that covers about 90 percent of geological time. No one knows exactly what the earth was like when microbial life began, but we do know that at some time the earth was a hot and hellish place with an atmosphere that lacked oxygen. Early microbes, probably blue-green algae or bacterialike organisms, invented photosynthesis to harness sunlight as a source of energy. They took carbon dioxide out of the air as their food, and they generated oxygen as a waste product that further transformed the atmosphere and hence the climate. They developed DNA for storing information, invented sex, which produced variation for natural selection, and evolution took off on its unending and largely unpredictable course.

Molecular fingerprinting suggests that every life-form on earth today originated from the same bacterialike ancestor. That ancestor eventually led to the three main surviving branches of life, the archaea, bacteria, and the eukaryotes (the organisms made of cells with a nucleus that include algae, plants, fungi, and animals).

Remnants of the first ancient pre-oxygen-using life may still exist little-changed today. They are thought to be sulphur-consuming bacteria now living only in the few remaining places where the ancient and to us hellish conditions still remain. These habitats include hot springs and