riverbank. They also may live in mounds
of mud and plants in shallow water. A
female muskrat can give birth to several
litters during a year. A litter consists of 1
to 11 young. The babies are born blind,
but after a month they can care for
themselves. A muskrat usually lives for
about three years in the wild.
The muskrat is hunted for its fur. In
some areas people eat muskrats. The
animal can become a pest when it digs
into dams and other structures.
#More to explore
Beaver
Mustard
Mustard is a spice made from the seeds
of certain plants. There are two main
types of mustard plant. One is called
white, or yellow, mustard. The other is
called brown, or Indian, mustard.
A mustard plant has a soft green stem
and produces bright yellow flowers. The
plant reaches its full height of 5 to 6.5
feet (1.5 to 2 meters) as its flowers fade.
Green pods then appear on its branches.
These pods hold the seeds.
Mustard seeds are tiny and almost
round. They can be light or dark yellow.
The seeds have no odor when whole.
But when they are ground up and mixed
with water, a chemical reaction takes
place. This produces mustard oil, which
has a smell and taste.
Muskrats look like a cross between a rat
and a beaver. They live in water, where
they build homes of mud and plants that
rise above the water’s surface.
Mustard plants produce bright yellow
flowers.
BRITANNICA STUDENT ENCYCLOPEDIA Mustard 219
Mustard is used to flavor foods such as
meat and salad dressings. Most people
buy mustard as a paste. The paste
includes vinegar and other ingredients
along with crushed mustard seeds. In
some places people cook and eat the
leaves of mustard plants.
Mustard also has been used in medicine.
Doctors once used mustard to treat
chest colds and other illnesses. They also
gave a drink made of mustard seeds and
warm water to people who had been
poisoned. The drink forced the person
to vomit out the poison.
#More to explore
Spice
Mutation
A mutation is a mistake or a change in a
living thing’s DNA. DNA, or deoxyribonucleic
acid, is a chain of chemical
units found in each cell of a living thing.
DNA makes up the parts of a cell called
genes. The chemical units of DNA are
arranged in a particular sequence, or
order in the genes. This sequence forms
a kind of code, called a genetic code,
that tells cells what to do. If the chain
gets out of order, breaks, or changes in
some other way, a mutation has
occurred.
Some mutations may happen when the
DNA is made. Other mutations are the
result of damage to the DNA. This damage
can be caused by too much exposure
to harmful energy, such as X-rays, or to
certain chemicals.
Most mutations are harmless. Often a
stronger than normal gene can prevent a
mutated gene from causing a problem.
However, some mutations are very serious.
Some can cause a cell to divide
incorrectly. This can lead to a type of
disease called cancer. Some mutations
can be passed from a parent to its offspring,
or young. This may cause the
young to be born with a defect or a disease.
For example, a particular mutation
that comes from both parents causes a
blood disease called sickle-cell anemia.
But sometimes a mutation leads to a
helpful change. For example, a mutation
could cause an animal to have a hair
color that blended in with its surroundings.
This animal would be more likely
to survive, and it would pass the hair
color down to its young. Scientists think
that such mutations lead to the evolution,
or formation, of different living
things.
#More to explore
DNA • Evolution • Genetics
As a result of a mutation, a starfish grew
only four legs instead of five.
220 Mutation BRITANNICA STUDENT ENCYCLOPEDIA
Myanmar
Myanmar is a country in Southeast Asia.
In 1989 the government changed the
country’s name from Burma to Myanmar.
The capital was Yangon until 2005.
In that year the government began moving
some offices north to a site near the
town of Pyinmana.
Geography
Myanmar shares borders with Bangladesh,
India, China, Laos, and Thailand.
The Indian Ocean lies to the west.
The land is mostly mountainous.
Plants and Animals
Evergreen rain forests grow in the wettest
regions. Teaks and other trees that
lose their leaves grow in areas with less
rainfall. Many birds, snakes, and monkeys
live in the rain forests. Myanmar’s
tigers and elephants are endangered.
People
The Burman people make up most of
the population. The Shan, Karen, and
other peoples form smaller groups.
Burmese is the main language.Most of
the people practice Buddhism. Almost
three quarters of the population lives in
rural areas.
Economy
Most of Myanmar’s workers are farmers.
The main crops are rice, sugarcane,
beans, peanuts, corn, and cotton. Cattle,
pigs, and buffalo are the main livestock.
Myanmar has deposits of copper, lead,
tin, jade, and gems. It also has reserves
of oil and natural gas. Factories make
clothing, cement, and fertilizers.
History
From the 800s to the 1200s the Burmans
ruled a powerful Buddhist kingdom.
In the mid-1700s a Burman king
unified Myanmar’s peoples. Great Britain
took control in 1885. The British
called the land Burma. Burma gained
independence in 1948.
..More to explore
Asia • Yangon
