liverwort A green photosynthetic bryophyte belong-
ing to the family Hepaticae (division Hepatophyta). A
small, simple plant that lives in moist, shady areas with
wide, flat leaves that lie close to the ground. Liverworts
reproduce with spores and have one of two forms: thal-
loid liverworts (Marchantiidae) and leafy liverworts
(Jungermanniidae). Liverworts have no roots, but have
thin (one-cell thick) rootlike structures known as rhi-
zoids that serve for attachment and water absorption.
Liverworts comprise two separate generations: the
gametophyte generation and the sporophyte genera-
tion. There are around 6,000 species of liverworts
worldwide, with some 4,000 species belonging to the
Jungermanniales.
lizards Lizards are vertebrates that belong to the
class Reptilia, which contains some 27 families. Lizards
and snakes are scaled reptiles. Lizards were first found
in the Jurassic period about 213 million years ago.
There are about 3,500 species of lizards worldwide liv-
ing in warm tropics and subtropical climates, as well as
in temperate regions, and they can be as large as the
10-foot Kimodo dragon. They have long bodies, typi-
cally with four legs and a tail, have movable eyelids,
and external ear openings. They can lose a tail and
regenerate a new one. Lizards may be the most success-
ful reptiles living today.
locus The specific position or location on a chromo-
some that is occupied by a gene. The plural form is loci.Loewi, Otto(1873–1961) AustrianPhysician, Phar-
macologist Otto Loewi was born on June 3, 1873, in
Frankfurt-am-Main, Germany, to Jacob Loewi, a mer-
chant, and Anna Willstätter. He attended the humanis-
tic gymnasium (grammar school) locally from 1881 to
1890 and entered the Universities of Munich and
Strassburg as a medical student in 1891. In 1896 he
received a doctor’s degree at Strassburg University.
After spending a few months working in the bio-
chemical institute of Franz Hofmeister in Strassburg,
he became an assistant to Carl von Noorden, clinician
at the city hospital in Frankfurt during 1897–98. In
1898 he became an assistant of Professor Hans Horst
Meyer, a renowned pharmacologist at the University of
Marburg-an-der-Lahn and a professor of pharmacolo-
gy in Vienna. In 1905 Loewi became associate profes-
sor at Meyer’s laboratory, and in 1909 he was
appointed to the chair of pharmacology in Graz. In
1940 he moved to the United States and became
research professor at the School of Medicine of New
York University, New York City, where he remained
until his death.
His neurological researches during the period
1921–26 provided the first proof that chemicals were
involved in the transmission of impulses from one
nerve cell to another and from neuron to the responsive
organ. It was for his discovery of the chemical trans-
mission of nerve impulses that he received the Nobel
Prize in physiology or medicine in 1936, jointly with
Sir HenryDALE. Loewi spent his years investigating the
physiology and pharmacology of metabolism, the kid-
neys, the heart, and the nervous system. He became an
American citizen in 1946 and died on December 25,
1961.logistic growth A model developed by Belgian
mathematician Pierre Verhulst (1838) that states that
the growth rate is dependent on population density and
restricted by carrying capacity. Growth is represented
by an S-curve, and the growth rate declines as the pop-
ulation increases. The pattern of growth is a slow start,
an explosive middle growth period, and then a flatten-
ing of the curve as growth slows.208 liverwort
The fringe-toed lizard, which lives in the Palen Dunes of Califor-
nia, is an example of Reptilia as well as an endangered species
and an insectivore.(Courtesy of Tim McCabe)