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STEM
Teacher’s Guide: Food Webs and Species Interactions
The Stem Context
“Science may be described as the attempt to give good accounts of the patterns in
nature. The result of scientific investigation is an understanding of natural
processes….” The Massachusetts Science and Technology/Engineering Framework:
2006 (p. 7)
Life Sciences Context
“Organisms both cooperate and compete in ecosystems. The interrelationships and
interdependencies of these organisms may generate ecosystems that are stable for
hundreds or thousands of years.”
The National Science Education Standards: 1996 (p. 186)
“Living organisms have the capacity to produce populations of infinite size, but
environments and resources are finite. This fundamental tension has profound effects
on the interactions between organisms.” p. 186
The National Science Education Standards: 1996 (p. 186)
Examples of Related National Science Education Standards
Teaching Standard B: Teachers of science guide and facilitate learning. In doing this
teachers
 Challenge students to accept and share responsibility for their own learning. (p.
30).
Content Standard C:
As a result of their activities in levels 5-8, students should develop understanding of
 Structure and function of living things
 Reproduction and heredity
 Regulation and behavior
 Populations and Ecosystems
 Diversity and adaptation of organisms
www.umassk12.net/ipy
A STEM ED Program at the University of Massachusetts, funded by the National Science Foundation and supported by the
Climate System Research Center in conjunction with the International Polar Year
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As a result of their activities in levels 9-12, students should develop understanding of
 The cell
 Molecular basis of heredity
 Biological evolution
 Interdependence of organisms
 Matter energy and organization in living systems
 Behavior of organisms
Examples of Related Massachusetts Science and Technology/Engineering
Framework Standards
Life Science (Biology) Standard 3, Grades 3-5, Recognize that plants and animals for
through predictable life cycles that include birth, growth, development, reproduction and
death.
Life Science (biology) Standard 13, Grades 6-8: Give examples of ways in which
organisms interact and have different functions within an ecosystem that enable an
ecosystem to survive.
Life Science (Biology) Standard 14: Grades 6-8: Explain the roles and relationships
among producers, consumers, and decomposers in the process of energy transfer in a
food web.
Life Science (Biology) Standard 6.2: Grades 9-10: Use a food web to identify and
distinguish producers, consumers, and decomposers, and explain the transfer of energy
through trophic levels.
Life Science (Biology) Standard 6.3: Grades 9-10: Identify the factors in an ecosystem
that influence fluctuations in population size.
The following activity will take approximately 1 hour to complete (although it could be
divided into different sections and expanded to cover more than one class period).
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Reading and Research Activity: Food Webs and Species Interactions
In architecture, a keystone is the stone that is found at the top of an arch. When
the keystone is in place, the arch is structurally stable. When it is removed, the arch
collapses. In the past, species have been labeled “keystone species.” These are
species that in spite of their potentially low biomass have a strong influence on the
structure of the ecosystem where they were found. When the term was first suggested,
it was in reference to a top predator in a food web that helped to maintain a diversity of
organisms through reducing interspecific competition among prey species (Paine 1969).
Like many terms in science, the meaning has evolved and expanded to refer to any
species that are important because if removed, a chain reaction would be triggered
leading to the loss of many other species in the environment where the key species are
found. For example, without certain prey species, predators would have nothing to eat
and their populations would decline.
Using the concept and term, ‘keystone species,’ directs attention towards the
strengths of the interactions of species in a food web. The goal of this activity is to
identify different species of animals that are part of the Arctic and Antarctic ecosystems
and to create a basic food web including these species. Each member of a team will
take on the responsibility of researching at least one organism and identifying its role in
the ecosystem: i.e. where it can be found, what that organism eats and what might eat
it, is it a producer, consumer, carnivore, herbivore, omnivore or a decomposer.
Examples of species for a Land-based Arctic Food Web could include: Polar Bears,
Caribou, Moose, Wolves, Lemmings, Ptarmigan, Mice, and Snowshoe Hare. Examples
of species for an Ocean-based Antarctic Food Web could include: Krill, Adélie or
Emperor Penguins, Baleen Whales (Blue or Humpback Whales), Fur or Leopard Seals,
Antarctic Cod, and the South Polar Skua.
The teams then construct a food web and discuss the roles of the organisms.
The next step will be for the team to identify the strengths of the interactions among
species. Based on what is known about the biology and behavior of each species, what
might happen to the populations of the other species if one species was removed from
the web? What is currently known about the status of these species? For example,
what would happen if suddenly there were no Krill to be found in the Antarctic waters?
The goal will be for the smaller teams to report back to the larger group on what they
have learned 1) about individual species, 2) about food webs in the Arctic and Antarctic,
3) what changes to the populations of species within those ecosystems could do, and 4)
current threats to specific species (e.g. overfishing of krill or melting of pack ice and
impact on polar bears). This lesson could be expanded to include a discussion of
conservation ecology and the reasoning for why certain species are protected.
References
Paine, R. T. 1969. A note on trophic complexity and community stability. American
Naturalist 103: 91-93.
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Some Web Resources for this exercise:
http://www.nationalgeographic.com/sealab/antarctica/mission.html
A National Geographic site that gives information about the life history of many
Antarctic species including: Krill, baleen whales, penguins, fish etc.
http://www.nationalgeographic.com/xpeditions/lessons/08/g68/antarcticeco.html
National Geographic site that details an exercise exploring what might happen if
there were no more Krill in the Antarctic waters. Has links to life science and geography
sites.
http://www.coolantarctica.com/Antarctica%20fact%20file/wildlife/krill.htm
This is an interesting site that gives more information about Krill and their role in
the Antarctic oceanic ecosystem.
http://www.sciencedaily.com/releases/2008/02/080225122334.htm
More current information about Krill and the Antarctic
http://www.mongabay.com/reference/environment2/Keystone_species.html
A site that gives some links to examples of keystone species in different types of
ecosystems.
http://news.mongabay.com/2008/0219-antarctica.html
A site with photographs of some bizarre creatures found in the waters around
Antarctica.
http://www.ulapland.fi/home/caes/Course2000/course00.htm
This site explains how caribou or reindeer can be considered a keystone species
in the Arctic.
http://news.mongabay.com/2008/0215-sharks.html
What would happen if sharks disappeared from the Antarctic waters?
http://www.vtaide.com/png/foodchains.htm
A website that has been selected and approved by NSTA’s (National Science
Teacher Association) network of teacher-webwatchers. This site has a good
explanation of food chains and food webs as well as examples that can be built using
different ecosystem types. There are also links to other websites about this topic.
http://www.70south.com/information/antarctic-animals
An interesting website with information about may Antarctic species and topics.
http://www.usgs.gov/newsroom/special/polar_bears/
This site is from the USGS newsroom and talks about the current population
status of Polar Bears.
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http://www.fws.gov/home/feature/2006/12-27-06polarbearnews.pdf
An article that proposals that the Polar Bear be listed under the endangered
species act. It has now been declared ‘threatened’ but the USFWS.
http://www.amnh.org/sciencebulletins/?sid=b.s.polar_bears.20070108&src=/earth/polar/
b
Interactive information from the American Museum of Natural History
http://www.pbs.org/wnet/nature/arcticbears/resources.html
PBS Nature – polar bear connections – lists web-links to other resources about
polar bears.
http://www.panda.org/news_facts/education/high_school/species/index.cfm
Info geared toward ages 12-17 from the World Wildlife Fund about endangered
species.
http://forces.si.edu/arctic/index.html
Website developed by the Smithsonian covering their Polar Exhibit titled: Arctic:
A Friend Acting Strangely. The site gives some information on the impact of melting ice
on some species of animals (e.g. Caribou). Also places climate changes in a human
context.