and heaviest organ. It lies mostly under
the bottom five ribs on the right side of
the body. It is made up of two rounded
parts, or lobes. The right lobe is much
larger than the left lobe.
Jobs of the Liver
Blood brings many substances to the
liver for processing. The liver takes poisons
and other harmful substances from
the blood. It then breaks them down
into safer forms. It breaks down wornout
red blood cells, too.
The William J. Clinton Presidential Library is
in Little Rock, Arkansas.
166 Little Rock BRITANNICA STUDENT ENCYCLOPEDIA
The liver also takes useful substances
from the blood and stores them. These
substances include sugars, vitamins,
minerals such as iron, and amino acids.
(Amino acids are the building blocks of
proteins, which make up the body’s
cells.) The liver releases these stored
materials when the body needs them.
In addition, the liver makes substances
needed by the body. The liver makes
proteins that help to clot blood. It makes
certain enzymes, which break down food
into fuel for the body. It also makes a
yellow-green fluid called bile. Bile flows
through ducts, or tubes, from the liver
into a sac called the gallbladder. From
the gallbladder, bile flows into the small
intestine. There it helps to digest fats.
Liver Problems
Several different viruses and drugs can
cause a liver disease called hepatitis.
Drinking too much alcohol can scar the
liver. This condition is called cirrhosis.
These and other problems with the liver
can cause jaundice, which is a yellowing
of the skin and eyeballs. The yellow
color comes from a buildup of bile substances
in the blood. Doctors can sometimes
transplant a new liver into a
patient whose liver has failed.
#More to explore
Blood • Digestive System • Hepatitis
Living Thing
Animals, plants, fungi, algae, protozoans,
and bacteria are living things. Living
things are also called organisms.
Scientists can tell living things and nonliving
things apart because living things
behave in ways that nonliving things do
not. Scientists have discovered about 1.5
million different kinds of living things
on Earth.
The liver is a large organ, or body part,
located next to the stomach.
Scientists think that there are more than
14 million different species, or kinds, of
living things on Earth. However, only about
1.5 million have been discovered. Most of
these species are animals.
BRITANNICA STUDENT ENCYCLOPEDIA Living Thing 167
What Living Things Do
The most obvious clue to whether something
is living is its ability to move. All
living things can move, using their own
energy. Even though plants stay in one
spot, they move their leaves to get sunlight.
Living things are also sensitive. This
means that they are able to feel. The
simplest life forms can feel only when
something touches them, or they have
only a sense of hot and cold.
Living things take in certain chemicals
and release other chemicals.Humans and
other animals breathe in oxygen and
breathe out carbon dioxide. Green plants
take in carbon dioxide through their
leaves and release oxygen into the air.
All living things need the nutrients and
energy that food gives. Green plants
make their own food with the help of
sunlight. Animals eat plants and other
animals to get energy.
Living things reproduce. This means
that they create a new generation of life.
People and animals have babies. Plants
make seeds or spores that grow into new
plants. Even the most basic life form, a
single cell, reproduces. It does so by
dividing into two new cells.
Living things grow. When many cells in
a plant or an animal divide, the plant or
Scientists divide living things into five main groups: protists, monerans, fungi, plants, and
animals. These groups are called kingdoms.
168 Living Thing BRITANNICA STUDENT ENCYCLOPEDIA
animal becomes larger. Living things
also grow by making new parts—for
example, branches or teeth.
Finally, living things get rid of waste.
When an animal or plant takes in nutrients,
there is always a part that is not
needed. This part is excreted, or released
from the system.
Groups of Living Things
Scientists divide living things into
groups. This process is called classification.
The most basic groups are called
kingdoms. There are five kingdoms of
living things.
The first kingdom is called Monera.
Monerans are single-celled organisms.
They are too simple to be called plants
or animals. They are so small that it
takes the power of a microscope to see
them. Bacteria, or germs, are monerans.
The second kingdom is called Protista.
Most of these organisms are also single
cells. Algae and protozoans are in this
kingdom.
The third kingdom is Fungi. Most fungi
have many cells arranged in threadlike
groups. Mushrooms are fungi, and so are
yeasts and molds.
The fourth kingdom is Plantae. Plants
are also made of many cells. Most plants
are green or have parts that are green.
The fifth and largest kingdom is Animalia.
Like fungi and plants, animals have
many cells. Unlike other living things,
animals move around easily and quickly
react to their surroundings.
#More to explore
Algae • Animal • Bacteria • Fungus
• Plant • Protozoan
Lizard
