Exploring Resource Availability and Population Size

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SWBAT analyze and interpret data to provide evidence for the effects of resource availability on organisms and populations of organisms in an ecosystem.

Big Idea

Students explore the impact of resource availability on organisms in an ecosystem.


10 minutes

To engage students in lesson I show them a series of pictures showing the effects of California's current drought.  These dramatic pictures, only taken three years apart, show how water levels have decreased at alarming rates changing the physical landscape of locations.  What is not seen in the pictures is the impact that this drought is beginning to have on California's ecological communities. 

Next, I have students focus on the pictures above, showing the impact this drought is having on California's drinking water levels.  

I lead a whole group discussion around the following questions:

1.  Compare and contrast the two pictures.  What do you notice?

2.  What do you think is the major cause of this drought? 

3.  What do you think this impact is having and will have on the populations of organisms that live in California?

4.  What are some possible ways that we can help California recover from this drought?


25 minutes

To explore the effects of resource availability on populations of organisms in an ecosystem I have them complete Population Explosion, a module from The Concord Consortium.

Many factors influence the success and survival rate of a population of living things. Explore several factors that can determine the survival of a population of sheep in this NetLogo model. Start with a model of unlimited grass available to the sheep and watch what happens to the sheep population! Next try to keep the population under control by removing sheep periodically. Change the birthrate, grass regrowth rate, and the amount of energy rabbits get from the grass to keep a stable population.

Learning Objectives:

Students study how populations stay in balance with their environment and respond to various factors such as food supply (resource) and predators. (SP2 - Developing and Using Models: Develop or modify a model— based on evidence – to match what happens if a variable or component of a system is changed. & MS-LS2-1. Analyze and interpret data to provide evidence for the effects of resource availability on organisms andpopulations of organisms in an ecosystem.

Student Directions:

1.  Students complete module in pairs using student laptops.

Teacher Note:  You should download module before students enter to class to save time, having module preloaded on laptops increases lesson efficiency.  Teacher should walk around and check for understanding, in addition having module projected on screen is a good way of answering any questions that might come up during activity.


10 minutes

We now discuss the article, "How do predation and resource availability drive changes in natural populations?Stevens, A. (2010) Dynamics of Predation. Nature Education Knowledge 3(10):46.

The reason I choose to use this article is that it activates students knowledge from the prior lesson, Exploring Predator and Prey Relationships. After a brief review of predator and prey relationships the article discusses how resource availability has a direct relationship to population size. (CCC - Patterns -Patterns can be used to identify cause and effect relationships.) 

"Researchers found that when resources (food, nesting sites, or refuges) were limited, populations would decline as individuals competed for access to the limiting resources."

Specifically I show students the following graph Outcome of Snowshoe Hare Field Experiment. (I have attached the figure below in case you want to print it out for students to use in cooperative groups/pairs.) (SP4 - Analyzing and Interpreting Data)

Collaborative Group Discussion Questions:

1.  What are the 5 factors shown on graph?

2.  According to the graph, what environment leads to the highest survival rate of the snowshoe hare?

3.  How can abundance of food increase the survival rate of the snowshoe hare?

4.  Predict what would occur to the survival rate of the snowshoe hare if food availability decreases?


10 minutes

Students now elaborate on what they have learned about resource availability and its impact on populations of organisms by reading an article titled Drought hurting animals, plants by Jami Smith from California Academy of Sciences.

Students use Writing in the Margins as a strategy to access text.

Writing in the margins engages readers in the task by having them document their thinking while reading. Both writing and drawing in the margins engages students in actively thinking about the text they are reading. The power of this strategy is not the actual act of writing and drawing in the margins; instead, it is the thinking that students must process in response to their reading. 

The specific Writing in the Margin strategy they use for this reading is Respond:


Respond to ideas in the text as you read. Your responses can be personal or analytical in nature. Thoughtful responses will increase engagement and comprehension.

Readers will often respond to...

  • interesting ideas.

  • emotional arguments.

  • provocative statements.

  • author’s claims.

  • facts, data, and other support.  


10 minutes

Students complete an Exit Slip, which requires them to construct a scientific explanation addressing the relationship between resource availability and population dynamics. (SP6 - Constructing Explanations and Designing Solutions/RST.6-8.1 -Cite specific textual evidence to support analysis of science and technical texts.)