[1]The biosphere is the living world, the sum of all living, interacting
organisms.
[2]Symbiosis is a condition in which two organisms or communities of
organisms live together in close association, either on a basis of
mutual benefit or of benefit to one only, with or without harm to
the other.
[3]Ionizing radiation is radiation that can cause damage to biological
tissues.
[4]Isotopes are variant forms of atoms of the same element.
[5]Nuclides is a term used to describe all the forms of all the atoms.
Radionuclides are radioactive nuclides.
[6]An ecosystem is a natural community, taken as a whole, including all
biological and environmental factors.
[7]Ecologists are scientists concerned with the interrelations of
organisms and their environments.
[8]A thermonuclear device is an explosive, such as a hydrogen bomb,
based on a fusion reaction. In other atomic weapons the energy is
derived from nuclear fission.
[9]The living organisms.
[10]Plankton are the floating, minute plants and animals that live in
the sea (and also in fresh water), including diatoms, algae,
protozoans, and crustaceans.
[11]For more on this program, see _Plowshare_, a companion booklet in
this series.
[12]The half-life of a radioactive element is the time required for half
its atoms to lose their radioactivity.
[13]Atmospheric tests of nuclear weapons through 1962 produced a fission
yield equivalent to 191 million tons of TNT and introduced about
10.01 megacuries of strontium-90, for example, as fallout entering
the environment.
[14]Floating one-celled animals.
[15]A picocurie is one trillionth of a curie; a curie is the basic unit
of intensity of radioactivity, approximately equal to that in 1 gram
of radium.
[16]For more about these studies, see _Fallout from Nuclear Weapons
Tests_, a companion booklet in this series.
[17]Information on this research is found in _Radioactive Wastes_, a
companion booklet in this series.
[18]The lake, drained in 1955, makes an interesting natural basin in
which residual radionuclides are used in studies of mineral cycling.
[19]A roentgen is a unit of exposure to radiation, measuring the
alteration of the atoms (ionization) of the radiated tissues. The
rat dosages compare with recommended limits of exposure to man-made
radiation for average individuals in human populations of an amount
that approximates 0.5 roentgen per year.
[20]The area where highest readings were obtained in the survey. These
studies are described in more detail in _Whole Body Counters_, a
companion booklet in this series.