Activity for Some Animals are More Equal than Others

Resource Type
Description
This activity explores the content and research discussed in the film Some Animals are More Equal than Others, which tells the story of the ecologists who first documented the role of keystone species in ecosystem regulation.
The short film explores the work of ecologists Robert Paine and James Estes. Robert Paine’s experiments showed that removing starfish from tidal pools has a big impact on the population sizes of other species. James Estes and colleagues discovered that the kelp forest ecosystems of the North Pacific are regulated by the presence or absence of sea otters, which feed on sea urchins that consume kelp. These direct and indirect effects of starfish, sea otters, and other so-called keystone species describe a phenomenon known as a trophic cascade. These early studies were the inspiration for hundreds of subsequent investigations on how population sizes are regulated in a wide variety of ecosystems.
The “Student Handout” probes students’ understanding of the key concepts addressed in the film. The “Educator Materials” document provides suggested pause points in the film with questions for students, background information, and detailed discussion points; a list of related resources and references; and an answer key for the “Student Handout.”
The “Resource Google Folder” link directs to a Google Drive folder of resource documents in the Google Docs format. Not all downloadable documents for the resource may be available in this format. The Google Drive folder is set as “View Only”; to save a copy of a document in this folder to your Google Drive, open that document, then select File → “Make a copy.” These documents can be copied, modified, and distributed online following the Terms of Use listed in the “Details” section below, including crediting BioInteractive.
Student Learning Targets
- Use evidence to explain why some species play the role of keystone species in their ecosystems.
- Explain the concept of a trophic cascade using examples from different ecosystems.
Estimated Time
Key Terms
apex predator, food web, keystone species, trophic cascade
Primary Literature
Dyer, Lee A., and Deborah K. Letourneau. “Trophic cascades in a complex terrestrial community.” Proceedings of the National Academy of Sciences 96, 9 (1999): 5072–5076. https://doi.org/10.1073/pnas.96.9.5072.
Estes, James A., Martin T. Tinker, Terrie M. Williams, and Daniel F. Doak. “Killer whale predation on sea otters linking oceanic and nearshore ecosystems.” Science 282, 5388 (1998): 473–476. https://doi.org/10.1126/science.282.5388.473. To access this article, set up a free AAAS account.
Paine, R. T. “Intertidal community structure: Experimental studies on the relationship between a dominant competitor and its principal predator.” Oecologia 15, 2 (1974): 93–120. https://doi.org/10.1007/bf00345739.
Terms of Use
Please see the Terms of Use for information on how this resource can be used.
Accessibility Level (WCAG compliance)
Version History
NGSS (2013)
HS-LS2-1, HS-LS2-3, HS-LS2-6, HS-LS4-5; SEP6
AP Biology (2019)
ENE-4.B, SYI-1.H, SYI-2.B, SYI-3.F, SYI-3.G ; SP1, SP2, SP4
IB Biology (2016)
4.1, 4.2, C.1, C.2, C.3, C.4, C.5
AP Environmental Science (2020)
Topic(s): 1.9, 1.11, 2.7
Learning Objectives & Practices: ENG-1.B, ENG-1.D, ERT-2.I, SP1, SP2, SP4, SP5
IB Environmental Systems and Societies (2017)
2.2, 2.3, 2.4, 3.3
Common Core (2010)
ELA.RST.9-12.2, ELA.WHST.9-12.9
Vision and Change (2009)
CC4, CC5; DP1