TOPIC 6 The Best Selection

Figure 1.53 Domestic animals have been bred to help us with various tasks. Canada’s Aboriginal
people once relied on dogs to carry loads. Items were packed onto travois, triangular wooden
frames that the dogs would drag. After the horse was reintroduced into North America, people
used horses to pull larger travois.
Do you have a cat or dog at home? Do you own a pet rabbit? Domestic
animals have had a long history of living with people. Cats and dogs
are ideal living companions. They share our houses, eat our food, and
How do wildflowers found sleep in our beds.
around Alberta differ from
There are other domestic animals that are important to us. Do you
cultivated flowers grown
in gardens? Do you think
drink milk or eat cheese or yogurt? Do you eat eggs or meat? Where
cultivated flowers would did these animals come from, and why do they meet our needs so well?
survive unattended in the The distant ancestors of these animals were wild. Our own ancestors
wild? Record your thoughts captured them, and over time, shaped these animals into the ones we
in your Science Log. know today.
In the last Topic you saw how biotechnology can be used to create
animals and plants with favourable traits. People have used breeding,
or artificial selection, for thousands of years, to produce
domestic plants and animals with particular characteristics.
Farmers bred dairy cows that produced the most milk. In
other cases, farmers selected the best beef cattle. Sheep
were bred based on the quality of their wool or meat. By
breeding animals with the most desirable qualities,
farmers were able to manipulate the characteristics of
domestic animals over a number of generations.

Figure 1.54 Distinctive dog breeds, such as this tiny Chihuahua and
enormous Great Dane, have been produced through selective breeding. Health
problems are common in purebred animals. Why do you think this is so?

58 MHR • Biological Diversity

 Find Out
Why Are There So Many
Different Kinds of Dogs?
Archaeological finds prove that dogs have been by the Canadian Kennel Club. There are also
domesticated for more than 14 000 years. countless combinations of these breeds called
There are over 160 breeds of dog recognized mutts, mongrels, or mixed-breeds.

Procedure
The chart above shows that all of today’s 3. Which dogs were bred for protection?
dog breeds came from one ancestral species.
Use the chart to trace how so much variation 4. How would you go about breeding a dog
came about. that would make a good house pet? What
characteristics would you look for?
What Did You Find Out? Analyzing and Interpreting

1. For what purpose was the Tibetan mastiff

bred? What characteristics do you think
the breeders were looking for?

2. Many of these dogs were bred to help in

hunting. Which specific characteristics
were bred for in:
(a) hounds?
(b) terriers?
(c) setters and spaniels?

The Best Selection • MHR 59

 Artificial Selection in Agriculture
Our hunter-gatherer ancestors began planting seeds in order to have a
Have you ever heard of
reliable source of food. Wheat and barley, members of the grass family,
beefalo? Beefalo are a
cross between bison and
were among the first plants that were grown for food. Archaeologists
domestic cattle. Unlike have found samples of these plants in the sites of some of the oldest
domestic cattle, beefalo settlements in the Middle East. Although 80 different plants were
have thick fur, which domesticated during prehistoric times, today only a few make up the
protects them from cold majority of the world’s food supply. Wheat and rice alone provide 40%
temperatures. Another of our food energy.
advantage of beefalo is
The science of plant breeding is an important part of agriculture. By
that the meat is low in fat
and cholesterol. If you choosing individual plants with desirable traits, scientists use selective
could develop a cross- breeding to bring the positive characteristics of two different varieties
breed, what would it be? together. Selective breeding was used to create specific varieties of Canada
Describe this new breed’s Western Red Spring Wheat. Wheat flour from this class of wheat is
characteristics and give it commonly used to make pan bread. Researchers have developed varieties
a name.
that produce high quantities of flour that is high in protein. In contrast,
Canadian Western Amber Durum wheat flour is good for making pasta.
One new variety of this wheat has improved cooking qualities and a pleas-
ant yellow colour. Researchers stationed throughout the country work to
find out what kind of wheat will grow the best in their region. Some wheat
varieties have been bred to mature faster than others or resist colder
temperatures and early frost. Others are resistant to insects and diseases.
By breeding plants that produce good-quality flour with plants adapted to
specific locales, researchers have developed valuable crop plants.
Figure 1.55 Canada is one of the major
suppliers of wheat to the world. We grow
Organism Energy about 20 billion tonnes of wheat each year,
and export about 14 billion tonnes. Most of
(kJ/m2/year)
the wheat grown in Canada is one of two
wheat cereal 3400 different species, but there are also many
rice or rice cereal 5200 other varieties grown for specific uses.
carrots 3400
milk 1800
eggs 840
beef (feedlot) 550
This table lists the average
amount of energy, in kilojoules
(kJ) per square metre of land
per year, in different organisms
that people use for food.
Assume that 800 kJ of each
organism is consumed in one www.mcgrawhill.ca/links/sciencefocus9
meal. Team up with another stu- Conduct research on how Canadian scientists have developed cold-tolerant
dent to calculate the area needed
varieties of wheat, triticale, and rye. Go to the web site above, and click on
to produce 800 kJ of food energy
from wheat and 800 kJ from beef Web Links to find out where to go next. Write a short report on how one
in one year. of the crops mentioned above was developed.

60 MHR • Biological Diversity

 Caspian
TURKEY Tigris Sea

R
Agriculture is only about 10 000 years old. Prior to that time our ances-

.
150 km
Aleppo
tors were mostly hunters and gatherers. Groups of people moved from Eup
Ashur
IRAN
Katna hr
place to place hunting available game and gathering edible plants. Mari

at
SYRIA

es
LEBANON R. Eshnunna
Farming (and the ability to stay in one place) is believed to have originat-
ISRAEL Babylon
ed in an area called the “fertile crescent.” This area included the land IRAQ
Larsa
Erech
between the Tigris and Euphrates rivers, which contained rich soil that JORDAN
Ur
Eridu
was suitable for growing crops. EGYPT KUWAIT
SAUDI ARABIA
Persian
Gulf

Fertile Crescent Babylonia Current Political Boundaries

Find Out
Thoughts on Food
Procedure
Examine the pictures of the different types
of cattle.

beef cattle

Jersey cow

What Did You Find Out? Analyzing and Interpreting 4. Apply What are some ways in which
1. What characteristics do you think were farmers can produce beef cattle with
selected for in each type of cattle? very tender meat?

2. How does the sex of the animal affect Extension

its function? 5. There are many cattle breeds. Choose one
to research on the Internet. Find out what
3. Are all of the differences between the
traits this variety is bred for and what
two kinds of cattle due to selective
makes it different from other breeds.
breeding? What else could account
Design a one-page “Wanted” ad to
for these differences?
describe this breed of cattle.

The Best Selection • MHR 61

 Figure 1.56 This iguana (left) and tortoise (right) are just two of the many unusual species
adapted to life on the Galápagos Islands. Naturalist Charles Darwin was very interested in the
biological diversity he found in this region.

Accounting for Biological Diversity

in When the H.M.S. Beagle set sail to map the coast of South America
ok
in 1831, 22-year-old Charles Darwin was aboard. During the five-year
g
Lo

voyage, which would eventually take the crew around the world, Darwin
d

A
hea
explored and gathered specimens from a wide variety of habitats. The
Discuss with your Galápagos Islands off the west coast of South America were just one
group how you could stop on a long voyage, but these islands would be permanently linked
monitor and record to Darwin and his theory. When the Beagle returned to England,
the plant life in an area Darwin tried to make sense of his observations. In 1859 he published
before making a deci-
his most influential book, Origin of Species by Means of Natural Selection.
sion about burning a
forested area.

Charles Darwin was born into a family of doctors in 1809 in Shrewsbury, England. He
was educated in his home town before being sent to university to become a doctor
like his father and grandfather. However, Darwin was a terrible student and preferred
to spend his time exploring the surrounding woods. He particularly disliked medical
school, which he eventually quit. Convinced that Darwin would never be a success,
his father sent him to study theology at Cambridge in the hope that Darwin would
become a church minister. Darwin did graduate, but later signed on as “gentleman
naturalist” of the H.M.S. Beagle — against his father’s wishes.

62 MHR • Biological Diversity

 S K I L L C H E C K

Initiating and Planning

Performing and Recording

1-J
Analyzing and Interpreting

Communication and Teamwork

Diversity in the Galápagos

Think About It
The chart below was taken from Darwin’s Journal
During the Voyage of the H.M.S. “Beagle” Round the
World. The table was composed of data gathered by
Darwin and other naturalists. At the time, Darwin
had no explanation of the results.
The Plants of the Galápagos Islands
Number of Plant Species
Name of Island A B C D
James Island 71 33 38 30
Albemarle Island 46 18 26 22
Chatham Island 32 16 16 12
Charles Island 68 39 29 21

A  Total number of plant species found on this island

B  Number of plant species found in other parts of the world
C  Number of plant species found only on the
Galápagos Archipelago
D  Number of plant species found only on this island

A cactus finch feeds from a cactus plant.

Analyze
1. Draw a bar graph to illustrate the data from the chart above.
The data for each island should be represented using four
bars (A–D). For tips on drawing bar graphs
turn to SkillFocus 10.
2. Is it likely that plants found growing on the Galápagos could
also be found growing where you live? Explain your thinking.
How might the data above be used to support your answer?

3. Darwin found these results “striking,” and pointed out www.mcgrawhill.ca/links/

that most of the islands were within sight of each sciencefocus9
other, in the same climate, and formed from the Which species are unique to the Galápagos?
same rock. Which is the most “striking” column What threats from human activities do these species
in the above chart? Explain your reasoning. face? To answer these questions, go to the web site
above, and click on Web Links to find out where to go
4. Can you offer an explanation for the data? next. Create a poster to illustrate what you have
learned about one species unique to the
Extend Your Skills Galápagos. You may use a computer to
5. Make a hypothesis about the more “striking” create your poster.
data. Devise a way of testing your hypothesis.

The Best Selection • MHR 63

 The Theory of Natural Selection
Darwin was hesitant to When Darwin tried to explain the diversity
publish The Origin of of life in the Galápagos, he began to
Species by Means of
think about artificial selection. He
Natural Selection. He
knew that the book would
spoke with farmers and breeders
generate controversy about breeding cattle, horses, and
because it attempted to other domestic animals. Darwin
explain how the process of himself raised fancy pigeons and
evolution occurred. Many knew that artificial selection could
people in England and the
produce great diversity, even within
rest of the world felt that
this theory disagreed with
a species. Darwin developed a theory
their religious beliefs. of natural selection to explain Figure 1.57 Pigeon fanciers have developed
how a process closely related to diverse breeds of pigeons. Some of the
artificial selection occurred in pigeons have been bred for racing. Other
varieties come in various forms and colours.
nature. Around the same time,
biologist Alfred Wallace had also
Illustrate the evolution made similar conclusions. The Galápagos finches provided a good
of an organism of your illustration of how the fittest, or best-adapted, organisms for a specific
choice using models, environment survived.
posters, or video The theory of natural selection can be summed up in four statements:
presentation. Organize
1. All organisms produce more offspring than can possibly survive.
your ideas by making
notes in your Science Log. 2. There is incredible variation within each species.
3. Some of these variations increase the chances of an organism
surviving to reproduce.
4. Over time, variations that are passed on lead to changes in the
genetic characteristics of a species.

Figure 1.57 Over millions of years, natural selection has produced a horse that looks very
different from its ancestors. Horse breeders have made further changes using artificial selection.

64 MHR • Biological Diversity

Can you spot the peppered moth? Birds Suppose a group of
are more likely to prey on the moths children that attend
that are easier to see. Light-coloured a local day care have
peppered moths are hard to detect on become ill with ear
tree trunks covered with white lichen. infections. All of the
In mid nineteenth-century England, children are treated
soot from industrial pollution covered with the antibiotic
the trees. The once rare, dark-coloured methicillin. After a few
moths became predominant. When air days, all of the children,
became cleaner in the 1970s, the light- except one, are well.
coloured moth became common once The following week,
again. People were able to influence most of the children are
natural selection by causing changes sick again. This time,
in the environment. none of the children
get better after taking
methicillin. Why?
How is this situation
TOPIC 6 Review an “unnatural example
of natural selection”?

1. Which animal would you guess is the ancestor of the domestic pig?
Explain your answer. (Hint: see the photo below.)

2. How do artificial and natural selection contribute to biological diversity?

3. Why does artificial selection produce changes in organisms faster than

natural selection?

4. Game farms in Canada raise animals such as deer and elk. Explain how
elk bred on game farms are the result of both natural and artificial selection.

5. Purebred animals are sometimes very unhealthy. For example, Great

Danes often have weak hearts and Dalmations commonly become deaf.

(a) Would you expect to see similar health problems in wild animals?
Explain your answer.
(b) What are the advantages and
disadvantages to owning a
purebred animal compared
to a mixed breed?

The Best Selection • MHR 65