Small Things Considered 2010
Purpose:
The purpose of this activity is for students to discover that bacteria can be found
everywhere. Most bacteria are beneficial and help maintain the environment by degrading
waste materials, man-made chemicals, and pollutants. Only a few bacteria can be harmful
or cause disease. Students will also gain an appreciation for the sheer number of bacteria
that can be found on them and in the world around them.
Activity:
Organize students into groups of 2-4. Each group should have 2 sets of color-coded
number cards: 16 “Bacterial Abundance” cards and 16 “Bacterial Distribution” cards.
Working with each set separately, students should work together to match the correct
number with the correct definition card. After students have had time to organize their
cards, go through the correct answers. Ask students what they found most surprising.
Answers:
Bacterial Abundance
Total bacteria on Earth
5 x 1030
Number of stars in the universe
7 x 1022
Age of the universe in seconds
4.4 x 1017
Bacteria in the human gut
1 x 1014
Global gross product ($/year)
7 x 1013
Cells in the human body
1 x 1013
Texts sent in 2009
1.5 x 1012
People on Earth
6.9 x 109
Bacterial Distribution*
Insect Species
Bacterial species in the soil
Bacterial species in the air
Bacterial species in the ocean
Bird Species
Bacterial species in the human mouth
Bacterial Species in the human gut
1
1-10 million
4 million
4 million
2 million
10,000
600
500
Minority Science Programs – School of Biological Sciences – University of California, Irvine
Small Things Considered 2010
Pathogenic Species
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CA Science Standards:
Grade 7.1. All living organisms are composed of cells, from just one to many trillions,
whose details usually are visible only through a microscope.
Grade 10.10. d. Students know there are important differences between bacteria and viruses
with respect to their requirements for growth and replication, the body’s primary
defenses against bacterial and viral infections, and effective treatments of these
infections.
*Note: Species numbers listed here are approximations and subject to change with various
species definitions. For a current assessment of the “species problem” and references,
please see the citation below (Hey 2001).
Curtis, T.P., W.T. Sloan, J.W. Scannell. (2002). "Estimating prokaryotic diversity and its
limits." Proceedings of the National Academy of Sciences 99(16): 10494-10499.
<http://dx.doi.org/10.1073/pnas.142680199>
Hey, J. (2001). "The mind of the species problem." Trends in Ecology & Evolution 16(7):
326-329. <http://dx.doi.org/10.1016/S0169-5347(01)02145-0>
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Minority Science Programs – School of Biological Sciences – University of California, Irvine
Small Things Considered 2010
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Minority Science Programs – School of Biological Sciences – University of California, Irvine