Lesson 1. Lesson 1: Introduction to Ecosystems and Models

Sugat Dabholkar, Kevin Hall, Philip Woods, Connor Bain
Biology, Environmental Science
1 class period (45 minutes)
Introductory High School Biology
v3

Overview

Lesson 1 Teacher Guide

Purpose

To teach students to understand biological systems using individual- or agent-level behaviors and interactions.

Prerequisite Knowledge

  • Food is a source of energy and building blocks for organisms
  • Food is necessary for animals to survive
  • Plants make their own food while animals and decomposers must consume other organisms
  • Familiarity with food webs and trophic levels

Lesson Description

Students will use their prior knowledge of food webs to examine the specific ecosystem of Isle Royale.  They will make predictions about how the populations of wolves and moose change over time, and attempt to construct a simple agent-based model based on the ecosystem.

Lesson Outline

  1. Introduction
  2. Think about differences between ecosystems broadly
  3. Think about interaction between populations broadly
  4. Think about Isle Royale broadly
  5. Predictions about wolf and moose populations
  6. Brainstorm rules for the model
  7. Revisiting predictions about wolf and moose populations
  8. Think about how and why models are useful
  9. Wrap-up

Standards

Next Generation Science Standards
  • Life Science
    • [HS-LS2] Ecosystems: Interactions, Energy, and Dynamics
    • [HS-LS4] Biological Evolution: Unity and Diversity
  • NGSS Crosscutting Concept
    • Patterns
    • Systems
    • Stability and Change
  • NGSS Practice
    • Analyzing Data
    • Using Models
    • Conducting Investigations
Computational Thinking in STEM
  • Data Practices
    • Analyzing Data
    • Manipulating Data
    • Visualizing Data
  • Modeling and Simulation Practices
    • Using Computational Models to Find and Test Solutions
    • Using Computational Models to Understand a Concept
  • Computational Problem Solving Practices
    • Troubleshooting and Debugging
  • Systems Thinking Practices
    • Investigating a Complex System as a Whole
    • Thinking in Levels
    • Understanding the Relationships within a System

Credits

Unit designed/developed by Dabholkar, S., Hall K., Woods P., & Bain C.

Acknowledgement

CODAP is developed and built by The Concord Consortium at https://codap.concord.org/  

Lesson 7 is based on the lesson Evolution in Action: The Galápagos Finches Authored by Paul Strode for Howard Hughes Medical Institute based on data collected by Peter and Rosemary Grant, Princeton University.

This work is supported by the National Science Foundation (grants CNS-1138461, CNS-1441041 and DRL-1020101) and the Spencer Foundation (grant 201600069). Any opinions, findings, conclusions, and/or recommendations are those of the investigators and do not necessarily reflect the views of the funding organizations.

Activities

  • 1. Introduction
  • 2. Interactions Between Populations
  • 3. Studying Simpler Systems
  • 4. Predicting Population Sizes on Isle Royale
  • 5. Simulating Isle Royale
  • 6. Revisiting Population Sizes on Isle Royale
  • 7. The Purpose of Using Models
  • 8. Summary

Student Directions and Resources


Students will develop an understanding of how populations interact with each  other within a community, discussing ideas concerning carrying capacity, competition, and interdependence. From there students will use models to explain the connection between genetic drift, natural selection, and speciation.

1. Introduction


Modeling Interactions in Ecosystems

Purpose

What are the types of interactions that affect populations of organisms in an ecosystem?

 

Procedure

Brainstorm a list of organisms you might find in each of the forests that are pictured below.


Question 1.1

What type of organisms might be found in the tropical rainforest?



Question 1.2

What type of organisms might be found in the temperate deciduous forest?



Question 1.3

Why might you find different types of organisms in each forest?

2. Interactions Between Populations


Populations of organisms are often heavily influenced by their environments.  However, other populations within an environment can also have a large influence.  In the questions below, you will examine some of the ways in which populations can influence each other.


Question 2.1

How might a change in the size of one population affect the amount of resources available in the forest for other populations?



Question 2.2

Why might the change in the amount of resources available in the forest affect the size of other populations?



Question 2.3

How might a change in the size of a population indirectly affect the size of another population in an ecosystem? For example, how do you think a change in the population of mice in a forest might affect the population of moths?

3. Studying Simpler Systems


Background Information

Ecosystems are often difficult to understand because they usually include interactions between a large number of species. Isle Royale is different. It is a relatively simple island ecosystem, located 24 km from the shore of Canada in Lake Superior.

 

While there are many types of small animals on the island, and almost 20 types of mammals, only two species of the mammals that live on the island are relatively large. These are the wolves and the moose. On this island, wolves are the only predator of moose, and moose are essentially the only food for wolves.

  

To understand nature, it helps to observe an ecosystem where human impact is limited. On Isle Royale, there are no towns and people do not hunt wolves or moose or cut the forest. It is a very rare place on the planet where wolves, their prey, and the plants that support the prey are all left unharvested by humans. Isle Royale is remarkable, because nature runs wild there.

Moreover, because the wolves and moose on Isle Royale are isolated from the mainland by the surrounding water, they are unable to leave and new individuals are unable to come to the island except in very rare cases.  Since scientists began observing the island in 1959, only one migration has occurred, which was a single wolf joining the island.  Therefore, any population changes we might observe therefore are not the mere wanderings of wolves and moose to or from the island.

You're going to make some predictions about how the size of the wolf and moose population might change over time.


Question 3.1

Since moose can’t typically migrate on or off the island, what other factors might cause the size of the moose population to change from year to year?



Question 3.2

Since wolves can’t typically migrate on or off the island, what other factors might cause the size of the wolf population to change from year to year?



Question 3.3

Thinking about this community of wolves and moose in Isle Royale, do you believe that the size of the wolf population will change from one day to the next?

  Yes
  No


Question 3.4

Do you believe that the size of the wolf population will change from one month to the next?

  Yes
  No


Question 3.5

Do you believe that the size of the wolf population will change over the course of 30 years?

  Yes
  No


4. Predicting Population Sizes on Isle Royale


Scientists counted the number of wolves and moose on Island Royale every year starting in 1959. Here is the data for 1959 and for 2010.

In order to compare data from two populations, scientists plot the data using two different y-axes on the same graph. The y-axis on the left side of the graph below is the scale for the size of the wolf population. The y-axis on the right side of the graph below is the scale for the size of the moose population.


Question 4.1

Sketch the shape of the graph that you predict you will see for the size of the wolf population between 1959 and 2010.

In a different color, sketch the shape of the graph that you predict you will see for the size of the moose population between 1959 and 2010.

Note: Draw your sketch in the sketchpad below


Question 4.2

What is the maximum number of moose that can be plotted on this graph according to the axis labels and intervals?



Question 4.3

What is the maximum number of wolves that can be plotted on this graph according to the axis labels and intervals?

5. Simulating Isle Royale


Based on the information you have been provided and the questions you have thought about, brainstorm a possible set of behavior rules for the wolves and moose and record them using the questions below.  Don't worry about trying to come up with the 'right answer'.  There are many possible answers which are valid, so just try to come up with a plausible, reasonable set of rules.

Discuss your rules with your classmates.  Have some students behave as wolves and others behave as moose according to the rules established by the class, and think about what observations you can make about the ecosystem.

The model that we will end up using gives the same simple instructions to each type of organism, in this case moose, wolf, and plant.

What simple rules could you give to each of these types that would lead to a natural ecosystem? Think of simple commands like move, direction etc,,

Remember all organisms of the same type will follow the same rules.


Question 5.1

Please provide the rules for wolf behavior that your group came up with.



Question 5.2

How could you improve your rules (code) to more similarly mimic a real ecosystem?

6. Revisiting Population Sizes on Isle Royale


Based on your observations during the class simulation, do you have new thoughts about the population trends on Isle Royale?

Sketch the population trend you expect to see below.


Question 6.1

What did you notice about the wolf and moose populations and how they changed over the course of your model?  Please provide at least one observation.



Question 6.2

Sketch the shape of the graph that you predict you will see for the size of the wolf population between 1959 and 2010.

In a different color, sketch the shape of the graph that you predict you will see for the size of the moose population between 1959 and 2010.

Note: Draw your sketch in the sketchpad below


7. The Purpose of Using Models


Now that you have worked on developing a model of the Isle Royale ecosystem, you may have gained some insight into how and why models are useful in a variety of contexts.


Question 7.1

The Isle Royale ecosystem is very simple compared to many others available to scientists.  What are some advantages to studying a simple ecosystem instead of a more complicated one?



Question 7.2

Why might studying an ecosystem with simple relationships between the organisms help us understand more complex places?

8. Summary


The original purpose of this activity was to answer: "What type of interactions affect populations of organisms in ecosystems?"


Question 8.1

What is the one big idea that you have discovered in this lesson?