#3: Evolution
Activity
Name: __________________________ Section: _______________ Score: _____
Task 1: Read these passages from the text and answer the questions that follow.
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.
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 South America.
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.
Questions
1. What was Darwin’s role on the Beagle?
2. What was significant about the new habitats Darwin visited?
3. What was significant about the rocks Darwin found in the mountains?
4. What was significant about the fossils Darwin found?
5. What did Darwin notice about life on the Galápagos Islands?
Task 2: Match the vocabulary word with the proper definition.
Definitions
_____ 1. change in species over time
_____ 2. one of the first scientists to propose that species change over time
_____ 3. ship on which Darwin served as naturalist
_____ 4. his theory of evolution unifies all of biology
_____ 5. the process by which evolution occurs
_____ 6. argued that human populations grow faster than the resources they depend on
_____ 7. small volcanic islands where Darwin made many important observations
_____ 8. selecting for plants and animals with useful traits
_____ 9. argued that gradual geological processes have gradually shaped Earth’s surface
_____ 10. states that traits an organism develops during its own life time can be passed on to
offspring
_____ 11. developed a theory of evolution at the same time as Darwin
_____ 12. an organism’s relative ability to survive and produce fertile offspring
Terms
a. artificial selection
b. Darwin
c. evolution
d. fitness
e. Galápagos Islands
f. HMS Beagle
g. inheritance of acquired characteristics
h. Lamarck
i. Lyell
j. Malthus
k. natural selection
l. Wallace
Task 3: Read these passages from the text and answer the questions that
follow.
Evidence from Biogeography
Biogeography is the study of how and why plants and animals live where they do. It provides more
evidence for evolution. Let’s consider the camel family as an example.
Biogeography of Camels: An Example
Today, the camel family includes different types of camels. All of today’s camels are descended
from the same camel ancestors. These ancestors lived in North America about a million years ago.
Early North American camels migrated to other places. Some went to East Asia. They crossed a
land bridge during the last ice age. A few of them made it all the way to Africa. Others went to South
America. They crossed the Isthmus of Panama. Once camels reached these different places, they
evolved independently. They evolved adaptations that suited them for the particular environment
where they lived. Through natural selection, descendants of the original camel ancestors evolved
the diversity they have today.
Island Biogeography
The biogeography of islands yields some of the best evidence for evolution. Consider the birds
called finches that Darwin studied on the Galápagos Islands. All of the finches probably descended
from one bird that arrived on the islands from South America. Until the first bird arrived, there had
never been birds on the islands. The first bird was a seed eater. It evolved into many finch species.
Each species was adapted for a different type of food. This is an example of adaptive radiation.
This is the process by which a single species evolves into many new species to fill available niches.
Eyewitness to Evolution
In the 1970s, biologists Peter and Rosemary Grant went to the Galápagos Islands. They wanted to
re-study Darwin’s finches. They spent more than 30 years on the project. Their efforts paid off. They
were able to observe evolution by natural selection actually taking place. While the Grants were on
the Galápagos, a drought occurred. As a result, fewer seeds were available for finches to eat. Birds
with smaller beaks could crack open and eat only the smaller seeds. Birds with bigger beaks could
crack and eat seeds of all sizes. As a result, many of the small-beaked birds died in the drought.
Birds with bigger beaks survived and reproduced. Within 2 years, the average beak size in the finch
population increased. Evolution by natural selection had occurred.
Questions
1. What is biogeography and what does it provide?
2. Where do all camels come from?
3. Why did camels evolve?
4. What is adaptative radiation? Give an example.
5. What did the Grants study? What did they observe?
