Charles Darwin

WHAT'S THAT BIG
RED POUCH?

●The Frigate bird of the Galápagos
Islands. This bird can be found throughout
the tropical Atlantic down to the Galápagos
Islands and Ecuador, but not in Europe or
South America, so Darwin may never have
come across one until he landed on the
Galápagos. Such a unique creature was
bound to make a naturalist such as Darwin
wonder why. Why do they look the way
they do? What's that big red pouch? What
are the advantages?

DARWIN’S THEORY

The Englishman Charles Darwin is one of the most famous scientists who
ever lived. His place in the history of science is well deserved. Darwin’s
theory of evolution represents a giant leap in human understanding. It
explains and unifies all of biology.

●Darwin’s theory of evolution actually contains two major ideas:

1. One idea is that evolution occurs. In other words, organisms change

over time. Life on Earth has changed as descendants diverged from
common ancestors in the past.

2. The other idea is that evolution occurs by natural selection. Natural

selection is the process that results in living things with beneficial
traits producing more offspring than others. This results in changes in
the traits of living things over time.

DARWIN’S THEORY

●In Darwin’s day, most people believed that all species were

created at the same time and remained unchanged thereafter.

They also believed that Earth was only about 6,000 years old.

Therefore, Darwin’s ideas revolutionized biology. How did Darwin

come up with these important ideas? It all started when he went

on a voyage.

THE VOYAGE OF THE BEAGLE

●In 1831, when Darwin was
just 22 years old, he set
sail on a scientific
expedition on a ship called
the HMS Beagle. He was
the naturalist on the
voyage. As a naturalist, it
was his job to observe and
collect specimens of plants,
animals, rocks, and fossils
wherever the expedition
went ashore. The route the
ship took and the stops
they made are shown in the
image.

THE VOYAGE OF THE BEAGLE

●Darwin was fascinated by
nature, so he loved his job on
the Beagle. He spent more than
3 years of the 5-year trip
exploring nature on distant
continents and islands. While
he was away, a former teacher
published Darwin’s accounts of
his observations. By the time
Darwin finally returned to
England, he had become
famous as a naturalist.

DARWIN’S OBSERVATIONS

During the long voyage, Darwin made many observations that helped him form his
theory of evolution. For example:

●He visited tropical rainforests and other new habitats where he saw many plants
and animals he had never seen before. This impressed him with the great diversity
of life.

●He experienced an earthquake that lifted the ocean floor 2.7 meters (9 feet) above
sea level. He also found rocks containing fossil sea shells in mountains high above
sea level. These observations suggested that continents and oceans had changed
dramatically over time and continue to change in dramatic ways.

●He visited rock ledges that had clearly once been beaches that had gradually built
up over time. This suggested that slow, steady processes also change Earth’s
surface.

●He dug up fossils of gigantic extinct mammals, such as the ground sloth. This was
hard evidence that organisms looked very different in the past. It suggested that
living things—like Earth’s surface—change over time.

THE
GALÁPAGOS ISLANDS

● Darwin’s most important observations were made on the

Galápagos Islands. This is a group of 16 small volcanic
islands 966 kilometers (600 miles) off the west coast of
Ecuador, South America.

THE GALÁPAGOS
ISLANDS

●Individual Galápagos islands differ from one another in
important ways. Some are rocky and dry. Others have better
soil and more rainfall. Darwin noticed that the plants and
animals on the different islands also differed. For example,
the giant tortoises on one island had saddle-shaped shells,
while those on another island had dome-shaped shells.
People who lived on the islands could even tell the island a
turtle came from by its shell. This started Darwin thinking
about the origin of species. He wondered how each island
came to have its own type of tortoise.