entropy: A measure of disorder; according to the second law of
thermodynamics, in any closed system (including the Universe as a whole)
the total level of entropy must slowly increase as energy is distributed more
and more evenly and is therefore less and less capable of performing work.
eukaryotes: Cells more complex than prokaryotes, in which there are distinct
“organelles” (such as mitochondria), and in which the genetic material is
protected within the nucleus; many single-celled organisms are eukaryotic,
and so are all multi-celled organisms; Lynn Margulis has shown that the ¿ rst
eukaryotes probably arose through a symbiotic merging of prokaryotic cells.
evolution: Change over time; applied most frequently to the evolution
of living organisms according to the principles of natural selection, ¿ rst
discovered by Charles Darwin in the 19th century; does not necessarily
mean change in the direction of a “higher,” more “advanced,” or more
“progressive” state.
exchange networks: The networks through which humans exchange
information, goods, styles, and even diseases.
extensi¿ cation: An ugly word coined speci¿ cally for this course; it describes
processes of innovation and growth that lead to more extensive settlement
without leading to increase in the size of individual human communities;
extensi¿ cation was the characteristic form of growth in the Paleolithic era;
the opposite of intensi¿ cation.
extinctions: There have been several episodes in the Earth’s history in
which large numbers of species have suddenly become extinct; we are living
through such an episode now, and its main cause appears to be increasing
human consumption of resources and habitats.
feedback loops (negative): Causal chains in which some factors reduce the
impact of other causal factors, potentially leading to stability or equilibrium;
a thermostat in a heating system is an example of negative feedback.
feedback loops (positive): Causal chains in which each factor magni¿ es
the impact of other factors; can lead to accelerating or runaway change, as