Collapse: A Problem-Based "Ecology" Unit for Biology (PBL)

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Collapse: A Data-Driven Problem-Based Ecology Exploration (PBL) for High School Biology

The Case:

Though Northern Sea Otters were nearly hunted to extinctions by fur traders throughout the 18th and 19th centuries, a few colonies survived in isolated coves of the Aleutian Islands. With hunting banned in the early 20th century, the sea otters began to stage a come-back, their number rebounding to a stable population. Then, in the early 1990s, researchers began to notice that the Aleutian sea otters were once again disappearing. The questions is, “Why?”

Students learn about interactions that occur within an environmental system while looking for answers to why the Aleutian sea otter population has continued to decline. Students also evaluate ethical considerations in conservation and create an “Action Plan” to help the sea otter population recover.

Please look at the preview file to see a list of materials, the first day's lesson, and additional information. The Day 2 simulation "Kelp Forest Simulation" is offered as a free product here.

This unit comes with a "Classroom" version and "Distance Learning (or Absent)" version. Both the classroom version and the distance learning version follow the outline below. In the distance learning option, the case is presented using readings, virtual simulations, and videos. All versions are offered as a PDF and a Word file.

General Objectives: (from Texas State Standards)

- Summarize the role of microorganisms in both maintaining and disrupting the health of both organisms and ecosystems.

- Describe how events and processes that occur during ecological succession can change populations and species diversity.

- Interpret relationships, including predation, parasitism, commensalism, mutualism, and competition, among organisms.

- Compare variations and adaptations of organisms in different ecosystems.

- Analyze the flow of matter and energy through trophic levels using various models, including food chains, food webs, and ecological pyramids.

- Describe the flow of matter through the carbon and nitrogen cycles and explain the consequences of disrupting these cycles.

- Describe how environmental change can impact ecosystem stability.

NGSS Objectives: HS-LS2-1, HS-LS2-2, HS-LS2-4, HS-LS2-6, HS-LS2-7, HS-LS2-8, HS-ESS3-5


Day 1

Introduction: Reading introduces the scenario. Students brainstorm possible causes of sea otter decline.

Food Chains Activity: Students use information about the Aleutian ecosystem to draw food chains.

Day 2

Trophic Cascade Video: Video with worksheet introduces the idea of a trophic cascade.

Kelp Forest Simulation: Simulation looks at how sea otters, sea urchins, and kelp are interconnected. Students graph data.

Day 3

Food Webs Activity: Students use their food chains to build a food web.

Food Chain Vocabulary: Students are introduced to ecosystem vocabulary and read about changes to the Arctic Ocean.

Day 4

Kelp Forest Data: Students analyze data about the relationship between sea otters, sea urchins, and kelp in the Aleutians as well as the abundance of sea otter prey over a 30-year period.

Prey CER: Student use their data to analyze the claim, “A lack of prey led to the Aleutian sea otter collapse.”

Food Chain Practice WS: Students practice with ecosystem vocabulary and read about keystone species.

Day 5

Other Ecosystem Relationships Activities: Students read about and then complete an activity to classifyorganism relationships as predator-prey, mutualism, commensalism, or parasitism.

Parasite and Disease Data: Students look at common parasites and diseases that might affect sea otters.

Parasites and Disease Students use the provided data to analyze the claim, “Parasites or CER: disease caused the Aleutian sea otter collapse.”

Day 6

Modelling Competition: Students work with an on-line simulation to model the effects of competition on barnacles.

Food Web Practice: Students practice reading a food web and read about parasite mind control.

Day 7

Sea Otter Competitors: Students use their food webs to identify potential competitors.

Sea Otter Competitors-Man: Students evaluate data to look at man as a competitor.

Competition CER: Students use the provided data to analyze the claim, “Competition from another predator caused the sea otter collapse.”

Ecosystem Interactions WS: Students practice identifying organism interactions and read about the complex relationship between aphids, red ants, and spruce trees.

Day 8

Ecological Pyramid Notes: Notes about ecological pyramids.

Predator Suspect 1–Killer Whales: Worksheet activity has students evaluate the killer whale as a sea otter predator.

Killer Whales CER: Students use their findings to analyze the claim, “A change in the behavior of killer whale led to the sea otter collapse.”

Day 9:

Predator Suspect 2– Bald Eagles: Students complete a simulation to learn about biomagnification in terms of DDT and bald eagles.

Bald Eagle Data: Students analyze data related to changes in bald eagle diet.

Bald Eagle CER: Students use their findings to analyze the claim, “A change in the behavior of bald eagles led to the Aleutian sea otter decline.”

Pyramid WS: Student practice with ecological pyramids and learn about tree communication.

Day 10

Invasive Species Reading: Discusses the role of Arctic foxes and rats in altering the nitrogen cycle.

DIY Nitrogen Cycle: Students use informational cards to create a model of the nitrogen cycle.

Nitrogen Cycle in the Ocean: Students use the nitrogen cycle to look for potential effects on the kelp ecosystem and read about the role of salmon in the terrestrial nitrogen cycle.

Day 11

Climate Data: Students look for trends in climate data at the time of the sea otter collapse.

Greenhouse Gases: Students are given a basic overview of the role of greenhouse gases.

Carbon Cycle: Students use a model of the carbon cycle to determine how changes in the carbon cycle would affect the concentration of greenhouse


Climate CER: Students use provided data to analyze the claim, “Climate caused a decline in the Aleutian sea otter population.”

Day 12

Initial Cause Discussion: Students discuss their theories of the sea otter collapse with a group.

Initial Cause Report: Students begin to write a report about their conclusions.

Day 13

Ecological Succession: Students work with an on-line simulation to learn about succession. They determine whether succession is possible in a barren kelp ecosystem.

Day 14

Rough Draft Review: Students work with a partner to review their Initial Cause Report

Conservation Ethics: Students talk about why conservation is important and learn about several principles of ethics.

Presentation Prep: Groups are given a scenario describing a conservation method used with an endangered species. Students prepare to present the scenario to the class and talk about the ethical implications.

Day 15

Presentation: Students present their scenario.

Changing Oceans: Students exchange information about the future climate predicted for the Aleutians.

Day 16

Action Plan: Students create an action plan describing actions that could be taken to conserve the sea otter.

Copyright © E. Stubbe (The Wasp Whisperer)

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Total Pages
173 pages
Answer Key
Teaching Duration
3 Weeks
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to see state-specific standards (only available in the US).
Design, evaluate, and refine a solution for reducing the impacts of human activities on the environment and biodiversity. Examples of human activities can include urbanization, building dams, and dissemination of invasive species.
Use mathematical representations to support claims for the cycling of matter and flow of energy among organisms in an ecosystem. Emphasis is on using a mathematical model of stored energy in biomass to describe the transfer of energy from one trophic level to another and that matter and energy are conserved as matter cycles and energy flows through ecosystems. Emphasis is on atoms and molecules such as carbon, oxygen, hydrogen and nitrogen being conserved as they move through an ecosystem. Assessment is limited to proportional reasoning to describe the cycling of matter and flow of energy.
Analyze geoscience data and the results from global climate models to make an evidence-based forecast of the current rate of global or regional climate change and associated future impacts to Earth's systems. Examples of evidence, for both data and climate model outputs, are for climate changes (such as precipitation and temperature) and their associated impacts (such as on sea level, glacial ice volumes, or atmosphere and ocean composition). Assessment is limited to one example of a climate change and its associated impacts.
Use mathematical and/or computational representations to support explanations of factors that affect carrying capacity of ecosystems at different scales. Emphasis is on quantitative analysis and comparison of the relationships among interdependent factors including boundaries, resources, climate, and competition. Examples of mathematical comparisons could include graphs, charts, histograms, and population changes gathered from simulations or historical data sets. Assessment does not include deriving mathematical equations to make comparisons.
Evaluate claims, evidence, and reasoning that the complex interactions in ecosystems maintain relatively consistent numbers and types of organisms in stable conditions, but changing conditions may result in a new ecosystem. Examples of changes in ecosystem conditions could include modest biological or physical changes, such as moderate hunting or a seasonal flood; and, extreme changes, such as volcanic eruption or sea level rise.


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