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Ecosystems of the Body
HASPI Medical Biology Lab 10
Background/Introduction
Biodiversity
Ecosystems have carrying capacities, which are limits to the
numbers of organisms and populations they can support.
These limits result from such factors as the availability of living
and nonliving resources and from such challenges as
predation, competition, and disease. Organisms would
have the capacity to produce populations of great size
were it not for the fact that environments and resources
are finite. This fundamental tension affects the abundance
(number of individuals) of species in any given ecosystem.
The amount of variation in living organisms is called biodiversity.
It encompasses species, genetic, and ecosystem variation in a
specific location or biome.
www.cspeirs.blogspot.com
A complex set of interactions within an ecosystem can keep its numbers and types of
organisms relatively constant over long periods of time under stable conditions. If a modest
biological or physical disturbance to an ecosystem occurs, it may return to its more or less
original status (i.e. the ecosystem is resilient), as opposed to becoming a very different
ecosystem. Extreme fluctuations in conditions or the size of any population, however, can
challenge the functioning of ecosystems in terms of resources and habitat availability.
Factors That Affect Biodiversity
Biodiversity in an area is different depending on the type of biome. For example, tropical
biomes near the equator tend to have very high biodiversity. Within the body, biodiversity of
microorganisms is highest in the intestinal tract. Throughout the Earth, biodiversity tends to
accumulate in small areas called hot spots. The map below identifies those hot spots, and
how much of the original habitat is remaining.
http://www.takepart.com/article/2010/05/21/infographic-international-biodiversity
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Normal ecosystem interactions, such as competition and predation, can affect the amount
of biodiversity in an area. Natural disasters such as wild fires, floods, or volcanic eruptions
can also impact biodiversity. In a healthy ecosystem, there would be a healthy rise and fall
of species and organisms. Unfortunately, human activity has a large impact on biodiversity
worldwide. Human activities that affect biodiversity include:
 Introduction of invasive species – a new species in an environment can change the
dynamics of an ecosystem
 Habitat loss or alteration – an ecosystem is changed to accommodate human
habitats or industrialization
 Overexploitation – humans harvest resources faster than the resources can be
produced
 Pest control – overuse of pesticides, herbicides, and overhunting of species that
threaten humans
 Pollution – human activities can produce pollution to air, water, and soil
 Climate change – while climate change is a natural occurrence, human activity is
increasing the rate of climate change; climate change results in new ecosystems
These human activities have already altered biodiversity, particularly in areas of high
urbanization. The following graph depicts specific activities and how they impact species,
and therefore biodiversity.
http://www.biodiversitybc.org/assets/Taking~Natures~Pulse/figure-36.png
Ecosystems of the Body
As discussed in Lab 09, there is an entire microscopic world living in and on the human
body. There are even separate ecosystems depending on the location. For example, the
microorganisms that live in the intestines are very different than the microorganisms that live
on the skin, or in the mouth. The large majority of these microorganisms are bacteria that live
peacefully in symbiosis with their human host. There is greater biodiversity in the human
microbiome than any other biome on the entire planet.
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Normal Flora of the Skin & Mouth
The skin is our body’s first line of defense against pathogens. The surface of the skin is
covered with millions of bacteria and other one-celled organisms. Certain bacteria like to
live on certain parts of the body. For example, the bacterial species that live under the arms
are similar among most people on Earth.
Many disorders that affect the skin have been linked to an improper balance of normal flora.
[Flora are all forms of plant life including fungus and bacteria.] Some of these skin disorders
include eczema, psoriasis, and acne. The Human Microbiome Project has identified over
50,000 different species of bacteria that live on the skin, but not every human has the exact
same species. Characteristics of the environment of an individual’s skin—such as whether it
is oily, moist, or dry—attract different types of bacterial species that prefer to live there. Oily
skin has the most biodiversity. The area of the entire body having the most biodiversity is the
forearm, while the least biodiversity is located behind the ears.
Over 1,000 species of bacteria make their home in the mouth alone. An imbalance or
introduction of foreign bacteria in the mouth can cause oral diseases such as infections,
dental caries (tooth decay), and bad breath. The diagram below provides examples of a
few common microorganisms found in different environments of the human body.
http://www.advisoranalyst.com/glablog/2013/11/25/the-human-microbiome.html
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Changing Conditions Within the Body
The human microbiome changes drastically throughout an individual’s lifetime. There is a
natural succession of biodiversity and populations as an individual ages. The womb is a
sterile environment, and newborns have no microbiome when they are born. At birth,
microorganisms from the mother and other individuals who interact with the newborn begin
to colonize the baby. The microbiome changes most drastically from birth until about 2
years of age. It will generally remain fairly stable from that point, but life events, such as
pregnancy or disease, can impact biodiversity. In addition, the microbiome can also be
changed by the human host’s choices. For example, the microbiome could be changed by
the host’s environment, diet, lifestyle, disease, or even antibiotic use.
http://www.actionbioscience.org/images/microbes_over_time_sized.jpg
Review Questions – answer questions on a separate sheet of paper
1.
2.
3.
4.
5.
6.
7.
8.
9.
What are carrying capacities? Give an example of a factor that limits carrying capacity.
What is biodiversity? What part of the Earth has the most biodiversity? Why?
What percentage of the world's plant and vertebrate species are located in hot spots?
Which biodiversity hot spot has lost the most habitat? How much has it lost?
Which biodiversity hot spot has lost the least habitat? How much has it lost?
How can human activity impact biodiversity? Give an example.
What is the greatest impact on biodiversity caused by agriculture? Climate change?
How many different species of bacteria live on the skin? In the mouth?
Why do you think the biodiversity of microorganisms living on the human body changes depending on
the environment? For example, why is there more biodiversity on oily skin, rather than dry skin?
10. How does the human microbiome change throughout an individual's lifetime?
11. Is the microbiome of a baby different if he or she is breast-fed, formula-fed, or eating solid food?
12. How is the microbiome of a toddler different than that of an elderly individual?
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HASPI Medical Biology Lab 10
Scenario
The goal of this lab will be to collect, culture, and observe some of the normal flora in the
mouth and skin of the human body. Your lab team will also decide on an “environmental
change” to test on the normal flora, and observe how this change impacts the populations
and species that grow on the nutrient agar plate.
Materials
Petri plate w/ nutrient agar (2)
Skin “environmental change”
Cotton swabs
Mouth “environmental change”
Permanent marker
Procedure
Your lab team will be given tasks, or directions, to perform on the left. Record your questions,
observations, or required response to each task on the right.
Part A. Preparing the Plates
Task
Response
Obtain 2 petri plates. Your instructor has already poured nutrient agar into the petri
plates, or if not will provide instruction. DO NOT OPEN YOUR PLATE UNTIL DIRECTED!
Using the permanent marker, label the top of one plate
2
“Skin” and include your group name (see upper image).
Notice the plate is split into two sides. On the bottom of the
Skin
plate, in very small writing, write “A” on one side and “B” on
Group E
3 the other as close to the edge as possible. You do not want
to have to look through your labeling to see what grows on
the plate.
Using the permanent marker, label the top of the other
4
plate “Mouth” and write your group name.
Notice this plate is also split into two sides. On the bottom
5 of this plate, in very small writing, write “A” on one side and
“B” on the other as close to the edge as possible.
6 Choose one individual in your group to be the test subject.
Have the test subject swirl a cotton swab in his or her mouth
A B
7
!
for at least 5 seconds.
Whenever removing the lid from the plate, it is important to
not remove the lid completely! Hold the lid over the plate.
8
Contaminants in the air can easily settle and grow in the
dish if the lid is completely removed.
The nutrient agar in the plate is similar in consistency to
9
Jello. Try not to break the surface of the agar.
On side A of the “Mouth” plate, starting at the middle, very
10 gently brush the cotton swab back and forth in a zig-zag
motion (see lower image).
Remove and discard the cotton swab. Place the lid back
11
on the plate.
B
A
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Choose an “environmental change” for the mouth. Suggestions include: mouthwash,
soda, food, or anything else that could be placed and moved around in the mouth.
Have the test subject put the choice in his or her mouth, and swish around the
13 “environmental change” for 30 seconds. For example, a soda can be swished just like a
mouthwash. After 30 seconds, spit the choice into the sink or trash.
A B
Immediately have the test subject swirl a cotton swab in his!
14
or her mouth for at least 5 seconds.
On side B of the “Mouth” plate, starting at the middle, very
15 gently brush the cotton swab back and forth in a zig-zag
motion (see image). Remember not to break the agar.
Remove and discard the cotton swab. Place the lid back
on the plate, and set the plate aside.
16
12
17 Choose one individual in your group to be the test subject for the “Skin” activity.
Whenever removing the lid from the plate, it is important to not remove the lid
18 completely! Hold the lid over the plate. Contaminants in the air can easily settle and
grow in the dish if the lid is completely removed.
Remember, the nutrient agar in the plate is similar in consistency to Jello, so you are trying
19
to avoid breaking the surface of the agar here as well.
On side A of the “Skin” plate and starting at the middle, have the test subject very gently
20
brush an index finger back and forth in a zig-zag motion. Place the lid back on the plate.
Choose an “environmental change” for the skin. Suggestions include: lotion, soap,
21
disinfectant, or anything else that could be used on the skin.
Have the test subject put the choice on both hands, and wait for 3 minutes. For example,
22
if the choice is lotion, have the test subject apply lotion to the hands in the usual way.
On side B, starting at the middle, have the test subject very gently brush the index finger
23
back and forth in a zig-zag motion. Place the lid back on the plate.
Turn both plates in to the instructor. If an incubator is available, the bacteria and fungus
24 will have grown by the following day. If not, it will be 2-3 days before the plates will be
ready for observation.
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Part B. Observing the Plates
Task
1
2
3
Collect your plates. DO NOT REMOVE
THE LIDS FROM YOUR PLATES!!!
Observe the bacterial and fungal
growths on the plates. Bacterial growth
will be evidenced by small round
colonies, while fungal growths normally
have a more complex structure, variety
of colors, and can even look like mold.
Record your observations on the right;
use color if needed.
Record in Table 1 and Table 2 how
many different types of organisms
appeared, with a description of each
on sides A and B of the respective
plate. If there are more than 5
organisms, continue Tables 1 and 2 in
the space below.
Date:
Response
Draw the growths that appear on each plate below.
Mouth
!
Side A, B,
or both?
A B
Table 1. Normal Flora Growth: Mouth
Abundance
Description
(how many)
Once finished, return the plates to your
teacher for disposal.
Skin
!
Side A, B,
or both?
A B
Table 2. Normal Flora Growth: Skin
Abundance
Description
(how many)
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Analysis & Interpretation
Analysis Questions – answer questions on a separate sheet of paper
1. What environmental change was chosen for the skin plate? Be specific
(brand/variety).
2. How did the environmental change impact the population and/or types of growths
that appeared on the skin plate?
3. If the environmental change were to be consistently used (i.e. daily or hourly use),
do you think it could change the environment and biodiversity of the skin? Explain
your answer.
4. What specific environmental change was chosen for the mouth plate? (Brand/flavor)
5. How did the environmental change impact the population and/or types of growths
that appeared on the mouth plate?
6. If the environmental change were to be consistently used, do you think it could
change the environment and biodiversity of the mouth? Explain your answer.
Connections & Applications
Your instructor may assign or allow you to choose any of the following activities. As per
NGSS/CCSS, these extensions allow students to explore outside activities recommended by
the standards.
1. RESEARCH MICROBIOTA INTERACTIONS: Species within ecosystems interact with one
another, even on the microscopic level. Specific interactions, such as predation,
competition, and symbiosis occur between microbiota. Corynebacterium and
Staphylococcus are two families of bacteria that commonly colonize the human
body. Use the Internet to research and answer the following questions. Cite ALL of
your references.
a. Provide two specific species of Corynebacterium and Staphylococcus that
colonize the human body.
b. What part of the human body does each family colonize?
c. How does each family live in symbiosis with the human body? Provide a specific
example.
d. How do these two families interact with one another? Provide a specific
example.
e. Can species from either of these families cause disease? How?
2. HUMAN MICROBIOME PROJECT: The Human Microbiome Project (HMP) is a large-scale
research project aimed at discovering and sequencing all of the microorganisms that
make up the human microbiome. Using the Internet, research and answer the
following questions related to the HMP. Cite your references.
a. What is the Human Microbiome Project, and why is it important to health and
medicine? Give at least three examples.
b. How many microorganisms that are part of the human microbiota have
currently been identified?
c. Summarize at least two articles that outline how the HMP has provided insight or
implications on human health.
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3. GRAPHICAL COMPARISONS OF MICROBIOTA: Graphical comparisons of biodiversity
and populations in ecosystems can assist researchers in predicting interactions
between species. Two species of bacteria, Bacillus subtilis and Staphyloccus aureus
have been found in the nasal passageways of humans. In an experiment to
determine how these two bacteria interact with one another, B. subtilis and S. aureus
were grown in petri plates both independently and also together. The numbers of
organisms in the populations were counted at 12-hour intervals for a week. The data
collected can be found in Table A below. Create a single graph to represent the
data in Table A, and then answer the questions below. (Title/label your graph!)
Table A. Bacterial Species Growth Rate
Grown Separately
Grown Together
Time
B. subtilis
S. aureus
B. subtilis
S. aureus
0 hour
0
0
0
0
12 hours
5
3
4
2
24 hours
10
5
18
8
36 hours
22
16
47
12
48 hours
45
32
112
20
60 hours
94
68
282
44
72 hours
184
156
296
124
84 hours
348
254
260
210
96 hours
542
415
210
342
108 hours
786
563
154
410
120 hours
891
708
113
424
132 hours
935
800
81
429
144 hours
968
852
62
425
156 hours
975
868
49
428
168 hours
970
870
36
430
a. Compare the growths of B. subtilis and S. aureus when grown separately and
grown together.
b. Hypothesize how B. subtilis and S. aureus interact with each other based on the
graph. Explain your reasoning.
Resources & References

NHGRI. 2009. Study Finds Unexpected Bacterial Diversity on Human Skin. National Institutes of Health,
National Human Genome Research Institute. http://www.genome.gov/27532034.

Reed, A. and Green, S. 2013. Human Microbiome FAQ. American Academy of Microbiology.
http://microbio.me/americangut/img/FAQ_Human_Microbiome.pdf.
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