Ideas of the Enlightenment
The ideas that blossomed during the
1500s and 1600s influenced many
thinkers during the 1700s—the time of
the Enlightenment. Some of the most
famous Enlightenment thinkers were
Denis Diderot, John Locke, Jean-
Jacques Rousseau, Adam Smith, and
Voltaire.
These thinkers, called philosophers,
wrote many books, including a
35-volume encyclopedia. Some wrote
books questioning religion. They
objected to the church having power
over everyone. The philosophers criticized
the monarchs’ laws. They also
questioned the idea that God had given
the monarchs their power.
Enlightenment thinkers applied science
and reason to society’s problems. They
believed that all people were created
equal. They also saw education as something
that divided people. If education
were available to all, they reasoned, then
everyone would have a fair chance in
life.
Results
Enlightenment ideas were popular and
spread quickly. The Roman Catholic
church and the monarchs tried to censor,
or ban, the books and other works
of the philosophers. The rulers were
right to be alarmed. The Enlightenment
led many people to think about their
government and to think that they
should change the government. They
wanted to take power away from the
kings and queens and give it to the ordinary
people. This led to the American
and French revolutions, when the monarchs
lost their power.
#More to explore
American Revolution • French
Revolution • Philosophy • Renaissance
• Science
Environment
All the physical surroundings on Earth
are called the environment. The environment
includes everything living and
everything nonliving.
The nonliving part of the environment
has three main parts: the atmosphere,
the hydrosphere, and the lithosphere.
The atmosphere is the air—the layer of
nitrogen, oxygen, and other gases that
surrounds Earth. All the oceans and
Children who pick up litter are helping to
protect the environment.
BRITANNICA STUDENT ENCYCLOPEDIA Environment 143
other bodies of water on Earth make up
the hydrosphere. The lithosphere consists
of the rocks and soil on the surface
of Earth. People, animals, plants, and all
other living things rely on the nonliving
parts of the environment to survive. The
part of the environment where life happens
is called the biosphere.
The biosphere is made up of many ecosystems.
These are communities of living
things and the nonliving things that
they rely on.
Changes in the environment therefore
affect living things. Some changes are
natural. They include weather conditions;
the wearing away, or erosion, of
rocks and soil; and natural disasters such
as earthquakes.
People make changes in the environment,
too. Many of these changes are
harmful to living things. Around the
world, human activities have destroyed
animals’ habitats and polluted the air
and water. In addition, people’s use of
oil, coal, and natural gas may have led to
global warming. This is a rise in the
temperature of Earth’s surface.
Today many people are working to protect
the environment. These people try
to conserve, or save, natural resources.
They also try to recycle, or reuse, products
to avoid waste and pollution.
#More to explore
Conservation • Earth • Ecosystem
• GlobalWarming • Habitat • Pollution
• Recycling
Enzyme
Enzymes are important substances made
by the cells of plants and animals. They
are catalysts, or substances that control
how quickly chemical reactions occur.
These reactions are the processes that
keep all plants and animals functioning.
Enzymes help the body perform such
tasks as digestion and growing new cells.
Enzymes travel both inside and outside
cells. However, each enzyme is very particular
about where it will work and
what it will do. An enzyme usually does
just one task. Also, an enzyme acts on
only one type of substance, called the
substrate. The substrate fits into only
one place on an enzyme, the way a key
fits into a keyhole.
The many different types of enzyme
have many different tasks. Enzymes usually
speed up a process that otherwise
would be much slower. Some enzymes
work in the digestive system of animals
to break down food. In plants, enzymes
are used in photosynthesis. Photosynthe-
A woman
named Rachel
Carson wrote
about pollution
in a book
called Silent
Spring in
1962. It
helped start
the modern
effort to protect
the environment.
Yeast has enzymes that make dough rise.
144 Enzyme BRITANNICA STUDENT ENCYCLOPEDIA
sis is the process by which plants get
their food from sunlight. Other enzymes
move parts from one molecule to
another or help a cell burn fuel.
Enzymes are especially important for
controlling the speed at which things
happen in a cell. For example, the body
breaks down sugars for energy. Enzymes
make sure this happens slowly so that
too much energy is not created too
quickly.
People also use enzymes in industry and
medicine. Enzymes help to heal cuts and
to diagnose certain diseases. They are
also an important part of the process
called fermentation. This helps turn
milk to cheese and juice to wine, and it
makes bread rise before it is baked.
#More to explore
Cell • Fermentation
Eoraptor
Eoraptor may be one of the earliest dinosaurs
