1.  Pine trees that are too tall or too short do not do as well as pine trees that are average in height. The short trees do not get as much light as tall or average trees. The tall trees are more likely to break off in storms. Tell how this is an example of stabilizing selection. Be sure to define stabilizing selection in your answer.
Your response must be at least 75 words in length.

2.  There is a moth in England called the peppered moth. Before Britain’s industrial revolution, these moths were usually salt and pepper colored. Because of their coloring, they blended in well with the tree trunks on which they tended to rest. The coloring helped them hide from the birds that ate them. During the British industrial revolution, industry expelled a lot of soot from the burning of coal into the environment. This soot darkened the tree trunks, and it was noted that black-colored moths were becoming predominant. The idea is that with soot in the environment, black-colored moths fared better than light-colored moths. There is some debate as to whether this is actually the case or not, but for the sake of this question, let’s assume it is.
In your own words, explain the concepts from the four observations discussed in 12.2 using the moth as an example. In other words, how does the moth illustrate the first observation, the second observation, etc.?
Your response must be at least 200 words in length.

3. Explain how homology is different from convergent evolution and give examples. Briefly define homologyand convergent evolution in your explanation.
Your response must be at least 200 words in length. 

4.  Your organization recently purchased a large, metal shearing machine. You have been asked to identify the hazards of operating this equipment and make recommendations of ways to control the hazards. Determine at least one control strategy from each level of the hierarchy of controls (elimination, substitution, engineering, administrative, personal protective equipment). Select the control or combination of controls that you feel would be most effective. Explain the reasoning for your choices.

Your response must be at least 300 words in length.

BIO 1100, Non-Majors Biology 1

Course Learning Outcomes for Unit IV

Upon completion of this unit, students should be able to:

1. Define the basic concepts of biological sciences.
1.1 Define terms used when discussing evolution.
1.2 Recall the classification of organisms.

2. Apply the scientific method.

2.1 Apply the scientific method to Darwin’s formulation of the theory of common descent with
modification.

5. Interpret Darwin’s theory of evolution to include natural selection and common descent.

5.1 Discuss common descent and the evidence that supports it.
5.2 Discuss natural selection and the patterns of selection.

Course/Unit
Learning Outcomes

Learning Activity

1.1

Unit Lesson
Chapter 11
Chapter 12
Chapter 14
Unit IV Assessment

1.2
Unit Lesson
Chapter 14
Unit IV Assessment

2.1
Unit Lesson
Chapter 11
Unit IV Assessment

5.1
Unit Lesson
Chapter 11
Unit IV Assessment

5.2
Unit Lesson
Chapter 12
Unit IV Assessment

Required Unit Resources

Chapter 11: Where Did We Come From?

Chapter 12: An Evolving Enemy

Chapter 14: The Greatest Species on Earth?

Unit Lesson

This unit includes materials concerning evolutionary theories, natural selection, and the diversity of life from
Chapters 11, 12, and 14. In Chapter 11, “Where Did We Come From?” the authors explain what evolution
means and the various theories of evolution. In addition, a detailed explanation of Charles Darwin’s theory of

UNIT IV STUDY GUIDE

Evolution

BIO 1100, Non-Majors Biology 2

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evolution is described, including the scientific evidence supporting Darwin’s theory. Linnaean classification is
also explained in this chapter.

Many people report that they do not believe in evolution. It is not the intent of this course to change anyone’s
mind about what he or she believes. This is a biology course, not a theology course. No matter what you
believe, we do expect students to come away from the course with an understanding of the basic concepts of
Darwin’s theory.

Let’s start by understanding what a scientist means when the word theory gets used. Going back to the
scientific method, one begins with an observation. For example, Darwin observed on the Galapagos
Islands that tortoises were different from island to island. This is step one of the scientific method (Belk &
Maier, 2019).

Step two is making a hypothesis. It took some time for
Darwin to come up with a hypothesis, but eventually he
hypothesized common descent with modification. That is,
Darwin thought that all the tortoises on the different
islands descended from a single species that originally
came from the South American mainland. Common
descent is the theory that all living organisms on earth are
descended from the same ancestor.

Step three of the scientific method is to make a
prediction based on the hypothesis. For example, Darwin
predicted that all the different tortoises would have
common characteristics but would also be different
depending on the environment on the island on which
each tortoise lived. How these differences came to be is
explained by natural selection, but we will stick to
common descent for now.

Step four of the scientific method is to test the prediction. The textbook discusses evidence that supports the
prediction on pages 229–230.

Consider why a suspect is innocent until proven guilty in criminal investigations. The reason for this is
because people cannot prove themselves innocent. Even an alibi could be fabricated. For example, during
the Salem witch trials, some people would accuse others of witchcraft. The only proof supporting the
accusation was the testimony of the “victim” of the witchcraft. Since one obviously cannot prove that one is
not a witch, many people were convicted and hanged (Brooks, 2011). Now, you may ask, what does this have
to do with biology? Well, just as innocence cannot be absolutely proved, theories such as the theory of
evolution cannot be absolutely proved, either. Einstein, in referring to his theory of relativity, pointed out that
while many observations support it, a single observation could disprove it. There may always be something
else Einstein or Darwin did not think of to explain the observations. That is why scientists call these ideas
theories, even though the scientific evidence is overwhelming.

Common descent—how closely related is human
evolution to the evolution of other species?
(Pietras, 2017)

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Darwin and the theory of evolution do not address
how life began. But once life began, it immediately
began to evolve. Organisms must evolve because
their environment changes; if the organisms do not
also change, they will die out. Just think, every
organism on the planet has DNA that directs its life.
From the tiniest germ to the largest whales, all living
beings have DNA. What a remarkable molecule! This
fact supports the hypothesis that all living beings have
a common ancestor.

Speaking of common ancestors, humans did not
descend from the great apes. You may have heard
that humans and chimpanzees both derive from a
common ancestor that lived about 7 million years ago
(Belk & Maier, 2019). That common ancestor has not yet
been found. People sometimes ask, “If humans
descended from a common ancestor, why are there
great apes? Why did we not supplant them?” The
answer, of course, is that the various offsprings of the
common ancestor moved into different environments
and evolved differently.

Think back to the Galapagos tortoises. Some offsprings
lived in the forest, while others lived in the savannah.
The demands placed on each type of offspring by the
different environment resulted in different species over
time. This is not to say that one species is superior to
another—evolution does not strive for superior
organisms. Darwin never uttered the well-known phrase

“survival of the fittest.” Evolution involves survival of those who are best suited to the environment in which
they find themselves.

So, what do species do when the environment changes? Those with traits suited to the new environment do
well, while those whose traits do not suit will die out. That is what natural selection is all about. Individuals are
naturally selected to survive and reproduce, or they are not. Be aware that individuals cannot adapt or evolve;
it is only the population that adapts and evolves, and such evolution occurs over time, not immediately.

For most organisms, the male species is the most colorful, can jump the highest, fly the fastest, and so on.
The male’s energy is focused on traits that ensure that the fittest female will mate with him. This is known as
sexual selection; mating is usually not random.

Let’s apply that to a particular scenario. Think about a fish that lives in a pond with predators. Guppies vary in
color, just as different traits vary in humans. Some male guppies are very colorful, which attracts a female. If
there are no predators in an area, its chances of reproducing are better if the guppy is colorful. However,
being colorful also attracts predators. If there are predators in a pond, a guppy’s chances of survival are better
if it is not colorful; if it can blend in with its surroundings, a predator will not be able to see it and eat it. Based
on that information, if guppies live in a pond with predators, would you expect most of the male guppies to be
colorful or to be able to blend in with their surroundings?

Evolution and natural selection ensure survival of organisms such as fish and humans; however, these
factors also influence diseases that are caused by bacteria, viruses, fungi, and protists. Chapter 12, “An
Evolving Enemy,” describes the evolutionary processes of diseases by natural selection. The textbook
chapter presents materials by using the example of Tuberculosis to explain the importance of understanding
the theory of natural selection and the danger of the evolutionary changes that occur within infectious
diseases. Are we overusing antibiotics? Are we forcing the evolution of a superbug? Does the human body
become immune to antibiotics?

Statue of Charles Darwin created by Sir Joseph Boehm and
unveiled in London’s Natural History Museum in 1885
(Patche99z, 2009)

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Mutations are one way the genetics of a population changes. Depending on the circumstances, most
mutations are harmful, some are neutral, and rarely, some are helpful. Do not forget that while mutations are
a part of evolution for a population’s gene pool, natural selection also changes genes over time.

All humans belong to a species called Homo sapiens. What determines a species? A biological species
includes organisms that interbreed naturally and produce offspring that are reproductively viable. Why do
different species fail to mate? There are various reasons that keep organisms belonging to one species from
attempting to mate with those belonging to another species. These are referred to as pre-fertilization
isolation mechanisms. In other words, these isolation measures keep reproduction between species from
naturally occurring. Sometimes fertilization occurs; however, offspring are not produced. These are referred
to as post-fertilization mechanisms. Fertilization can occur between members of two different species;
however, the hybrid offspring is generally not able to reproduce. An example of this would be mules, which
are a cross between a horse and a donkey (Belk & Maier, 2019). Both mechanisms prevent gene flow
between different species. For specific information about the various types of isolating mechanisms, see page
264 in the course textbook.

Even though genes do not flow
from species to species,
diversity is vast. Scientists
have described over 1.3
million different species (Belk &
Maier, 2019). How can
scientists keep up with so
many different species? They
do this by classifying
organisms into groups. This
type of classification is
called taxonomy.

The groups have changed
some over time due to
increased knowledge.
Currently, most scientists group
all living organisms into one of
three domains: Eukarya,
Bacteria, and Archae. Eukarya
are further divided into four
different kingdoms: Plantae,
Animalia, Fungi, and Protista.

Each kingdom is then divided
into phyla, classes, orders,
families, genus, and finally,
species. The levels start out
being very broad or general
and result in the specific
organisms: genus and species.
Where do we fit in?

A billion years is 1,000,000,000 years—a very long time. Scientists think the universe began almost 14 billion
years ago (Crew, 2018).

Consider that the great pyramids of Egypt, which seem to have been around for such a long time, were built
only about 4,000 years ago.

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The Earth formed about 4.5 billion years ago, and after a billion years,
life might have made its first appearance (Belk & Maier, 2019).
Therefore, prokaryotic cells, such as bacteria and archaea, began the
journey of life on this planet around 3.5 billion years ago. Five
hundred million years later, cyanobacteria developed photosynthesis.
These remarkable organisms can live on water, CO2, and sunlight.
Photosynthesis has been on earth 3 billion years.

Not much happened after the development of photosynthesis for a
billion years, and then the first eukaryotic life forms appeared. It took a
billion years for prokaryotic cells to evolve into eukaryotic cells. About
1.5 billion years ago, eukaryotic cells assimilated mitochondria (Crew,
2018). It is thought that single-celled organisms developed
sophisticated metabolisms and that eukaryotes took the tiny
organisms into their cells as organelles.

From this point, things started to move much faster. A billion years
ago, the eukaryotic populations became much greater. Five hundred
million years ago, multi-celled organisms appeared, and the Cambrian
explosion of life occurred (Royal Ontario Museum, 2011). The
Cambrian explosion was an important evolutionary event, as many
new life forms came into existence at that time.

About 700 million years ago, life began to appear on land, and air-
breathing animals arrived (University of California Museum of
Paleontology, n.d-b.). Around 300 million years ago, the Permian extinction began. By the time it ended 251
million years ago, it had wiped out 90% of all marine species and 70% of the land animals in existence at the
time (National Geographic, 2017). While the cause is debated, it might have happened because of planet-
wide cooling and the occurrence of glaciation. Nevertheless, life and evolution continued, and about 225
million years ago, the first dinosaurs and mammals appeared. The first birds did not evolve until about 150
million years ago University of California Museum of Paleontology, n.d.-a).

Then, 65 million years ago, another disaster occurred—the Cretaceous extinction event that wiped out 75% of
the species and gave rise to the first primates. Grass evolved about 35 million years ago (Kellogg, 2001), and
great apes appeared about 25 million years ago (Gorillas-World, 2014). The last common ancestor of humans
and chimpanzees did not appear until about 6-7 million years ago. The first Homo species arrived 2 million
years ago, and finally, modern Homo sapiens arrived about 0.2 million years ago (Pontzer, 2014)—a
comparatively short time when considering all the evolution that preceded their arrival. What a journey!

As you read chapters 11, 12, and 14, appreciate the great diversity of life and how much work it took for
species to get to where they are today.

References

At09kg. (2016). Photosynthesis en [Image]. Retrieved from

https://commons.wikimedia.org/wiki/File:Photosynthesis_en.svg

Belk, C., & Maier, V. B. (2019). Biology: Science for life with physiology (6th ed.). New York, NY: Pearson

Brooks, R. (2011, August 18). History of the Salem witch trials. Retrieved from

http://historyofmassachusetts.org/the-salem-witch-trials/

Crew, B. (2018). This timeline shows the entire history of the universe, and where it’s headed. Retrieved from

https://www.sciencealert.com/timeline-shows-the-entire-history-of-the-universe-and-how-it-ends

Gorillas-World. (2014). Gorilla evolution. Retrieved from https://www.gorillas-world.com/gorilla-evolution/

Photosynthesis—the process of using
sunlight to synthesize foods from carbon
dioxide and water—has been occurring
on earth for around 3 billion years.
(At09kg, 2016)

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Kellogg, E. A. (2001). Evolutionary history of the grasses. Retrieved from
http://www.plantphysiol.org/content/125/3/1198

National Geographic. (2017). Permian Period. Retrieved from

https://www.nationalgeographic.com/science/prehistoric-world/permian/

Patche99z. (2009). Charles Darwin statue 5661r [Photograph]. Retrieved from

https://commons.wikimedia.org/wiki/File:Charles_Darwin_statue_5661r

Pietras, D. (2017). ConEvoEyes2jpg [Photograph]. Retrieved from

https://commons.wikimedia.org/wiki/File:ConEvoEyes2jpg

Pontzer, H. (2012). Overview of hominin evolution. Retrieved from

https://www.nature.com/scitable/knowledge/library/overview-of-hominin-evolution-89010983

Royal Ontario Museum (2011). The Cambrian Explosion. Retrieved from https://burgess-

shale.rom.on.ca/en/science/origin/04-cambrian-explosion.php#top-haut

University of California Museum of Paleontology. (n.d.-a). The origin of birds. Retrieved from

https://evolution.berkeley.edu/evolibrary/article/evograms_06

University of California Museum of Paleontology. (n.d.-b). The Proterozoic Eon. Retrieved from

http://www.ucmp.berkeley.edu/precambrian/proterozoic.php