Year 7 Science

Lesson Title 

Tragedy of the Commons- A Lesson in Conservation Issues  


This activity is intended to be undertaken after the class has been introduced to the concept of sustainability. It is assumed that students have a basic understanding of relationships between organisms in the environment and follows the lesson “Food Webs”

Cross-Curriculum Priority: Sustainability 

 Content Descriptions

Interactions between organisms, including the effects of human activities can be represented by food chains and food webs (ACSSU112). The activity focuses on the elaboration of ‘investigating the effect of human activity on local habitats, such as deforestation, agriculture or the introduction of new species’ and then leads into the elaborations of ‘using food chains to show feeding relationships in a habitat’ and ‘constructing and interpreting food webs to show relationships between organisms in an environment’ and how these food webs can be impacted by human activity. 

 This lesson sequence provides opportunities to gather information about students’ understanding related to the sections in bold in the achievement statement below:

Achievement Standard

By the end of Year 7, students describe techniques to separate pure substances from mixtures. They represent and predict the effects of unbalanced forces, including Earth’s gravity, on motion. They explain how the relative positions of Earth, the sun and moon affect phenomena on Earth. They analyse how the sustainable use of resources depends on the way they are formed and cycle through Earth systems. They predict the effect of human and environmental changes on interactions between organisms and classify and organise diverse organisms based on observable differences. Students describe situations where scientific knowledge from different science disciplines and diverse cultures has been used to solve a real-world problem. They explain possible implications of the solution for different groups in society.

Students identify questions that can be investigated scientifically. They plan fair experimental methods, identifying variables to be changed and measured. They select equipment that improves fairness and accuracy and describe how they considered safety. Students draw on evidence to support their conclusions. They summarise data from different sources, describe trends and refer to the quality of their data when suggesting improvements to their methods. They communicate their ideas, methods and findings using scientific language and appropriate representations.

Teacher Information (Explanation of concepts, common misunderstandings, alternative conceptions)

This activity is designed to allow students to experience and investigate Hardin’s (1968) tragedy of the commons phenomenon. It addresses the misconception that there is an unlimited amount of fish in the world’s oceans; when in fact fish are a renewable resource only if appropriate numbers remain to reproduce and fulfil a given species role in a food web. This concept can be applied to the locally appropriate conservation issue such as deforestation, hunting etc. Fishing is chosen for the Darwin region as it is a popular past time and many students have vested interests in fish populations.

Global fish stocks have declined drastically in the past few decades such that some people’s livelihoods and wellbeing are now being negatively impacted (Daw et al. 2012). Accepting this information and understanding the causes are essential steps necessary in attempts to rectify the issue. This activity promotes an understanding of sustainable harvesting of fish stocks.

Materials and Equipment


Small pieces of scrap paper ( draw on paper to represent fish) or small fish toys if available

Books and writing utensils 

Safety Advice

 This is a seated group activity and requires no additional safety measures. 

Teaching Sequence

Lesson Objective

 To have students understand the concept of the tragedy of the commons and how it impacts conservation efforts in fishing, and be able to apply this knowledge to new and unfamiliar contexts. 


 The concept of commons is explained to the class. The class is told that they will be doing an activity that is designed to investigate if there are any potential human impacts upon fish stocks.


 Organise class into 5 roughly even groups around tables. Each student is assigned the role of the member of a family responsible for providing food. Place 25 small pieces of ripped paper in the centre of each table. The table represents the local sea that contains the only available food source, the paper represents the fish populations. Have the students record the number of fish in the sea (count the pieces of paper).

1.      Each table operates in turns, each turn represents one year, students may take between 1-4 fish per turn with the result that:

1 fish = the students family starves2 fish = the students family survives 3-4 fish = the students family is fed and makes a profit

Have each table add half the number of remaining pieces of paper to the table at the end of each turn. Ask students to record the number of fish in the bowl at the end of each turn.

2.      After each student completes 5 turns (use a timer as appropriate) the class stops the game and each group is asked to send forth a representative to mark upon the class whiteboard the total number of fish left in their bowl at the end of each of the five turns. 

Write the following questions on the board. Groups discuss questions, one person writes down answers:

1.      How did your fish stock change over the turns? Dependent variable

2.      Why do you think that your fish stock changed? Open ended answer.

Why were fish added to the stock at the end of each turn? Answer: to represent reproduction


After the students have had 5 minutes to think about the questions, host a class discussion around their answers. Ask what they think may happen to their fish stocks if they continue to fish at the same rate in the future.

IF there is still time: Ask groups to discuss and devise a way in which they could have altered their fishing practices to maintain their fish stock.

PROMPT: have students to work out the total number of fish they can take without there being a population reduction by the end of the year. Ask groups to discuss the elephant in the room, human population growth. What would happen if humans were added to the population fishing at each table every turn?

PROMPT: how many fish per turn are sustainably available this turn? What about next turn if there are two added people? What would happen if you continued this trend into the future?

Lesson Resources

Digital Resources

ABC (2016). ABC Spash. Retrieved from

Useful Links

Hardin, G. (1968). The tragedy of the commons. Science, 162(3859), 1243-1248.

Adapted from Etienne Littlefair’s Lesson Plan (2018) 

Tragedy of the Commons