Population Dynamics (Day #2 of 3)

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Students will be able to explain how the complex set of interactions within an ecosystem can keep the numbers and types of organisms relatively constant over long periods of time under stable conditions. Students will also understand that, when encountering instability, populations can be resilient or severely challenged.

Big Idea

Populations of species are influenced by the abiotic and biotic factors present in the environment. However, feedback mechanisms help to adjust a population's size toward its "ideal" level.

Learner Goals

Note: I recommend that you first check out this resource in order to get the most out of this lesson!

In high school I took several drafting classes and, for a while, I had hoped to become an architect. With respect to planning instruction and teaching, I feel that I can still live out the detailed approach to building something intricate and complex even though the product is a lesson rather than a certain "built environment".

The lesson-planning document that I uploaded to this section is a comprehensive overview of how I approach lesson planning. This template includes the "Big Three" aspects of the NGSS standards: Disciplinary Core Ideas, Crosscutting Concepts, and Science Practices. Of course, there are many other worthy learning goals, skills, instructional strategies, and assessments that can be integrated into a class session. I don't feel compelled to check every box but, rather, use it as a guide to consider various options and tailor the lesson in light of these.

With regard to this particular lesson...

1. Carrying Capacity of Ecosystems (HS-LS2-1): Students will be able to use mathematical and/or computational representations to support explanations of factors that affect carrying capacity of ecosystems and different scales.

2. Interdependent Relationships in Ecosystems (LS2.A): Students will understand that carrying capacities limit population size due to the availability of living and non-living resources such as predation, competition, and disease. Were it not for limitations such as these, populations of great size would be rather commonplace.

3. Ecosystem Dynamics, Functioning, and Resilience (LS2.C): Students will understand that a complex set of interactions within an ecosystem can keep its numbers and types of organisms relatively constant over long periods of time under stable conditions. However, depending upon the extent of disturbance to the ecosystem, either a return to its original status or an extreme challenge to the basic functioning of the ecosystem will be observed.

I hope you get some value from my work!

Anticipatory Set ("Hook")

10 minutes

Please click here to navigate to the previous lesson in the series.

Teaching Challenge: How do I develop a classroom culture where students engage in meaningful and productive scientific discourse with peers?

Think, Pair, Share: Using the following National Public Radio (NPR) video titled Visualizing How A Population Grows To 7 Billion, students will explore the implications of an ever-increasing human population (on the carrying capacity of Planet Earth).

1. Think: On their own, carefully watch the video taking mental notes of key statistics or compelling pieces of evidence related to what many would term the "human population dilemma".

2. Pair: After the video has concluded, direct students to share their thoughts with a partner or with their small group (no more than four students).

3. Share: Solicit student responses in either an open-ended voluntary basis or by drawing student names (via popsicle sticks or name cards). Take note of the variety of key ideas that students took away from the video. These might naturally be interwoven with the lecture main idea to follow.


Instructional Input/Student Activities

40 minutes

Teaching Challenge: How do I support students to develop and use models?

1) Population Growth Lecture Main Idea #2: The (biotic) environment influences the size of a population


a. Mathematical growth formula with sample problems (slides #29-31)

b. Biotic factors affecting population size (slides #33-34)

In this min-segment of the multi-day lecture, I want to provide a mental and mathematical model with which to predict the effect on a given population based on specific changes in immigration, emigration, birth, and death statistics.


*As a side note, whenever I lecture in class, there is a specific format for students to follow; that is Cornell Notes. Please link to this lesson for a more thorough explanation of my expectations.

Teaching Challenge: How do I support my students in analyzing data in order to address a question of interest?

2) Lego Lab: Simulation The concept of feedback is ubiquitous throughout nature however I have discovered that students struggle understanding its nature and how it works. Specifically, comparing and contrasting positive and negative feedback. The change to a population over time is deeply rooted in the interplay between these two types of feedback. Therefore, I wanted to provide an opportunity for students to gain a concrete experience with feedback mechanisms. 

Who doesn't like Legos? Unsurprisingly, high schoolers haven't outgrown the affection for these simply manipulatives. So, I got to thinking about how to incorporate Legos into the concept of feedback. What if the building and dismantling of Legos could be likened to the birth and death of members of a population? And what if team members role played either birth or death? How might this interaction naturally play out and can its results be used to simulate the rise and fall of populations according to the mathematical models? I think it can!

Here is how it works:

1.Provide a container of loose Legos to each team; make sure that none are connected together.

2. Provide a copy of the job description for each member (a slip of paper with an icon for their role and a brief instruction to follow). Instruct each member to keep their instructions secret.

-Builder- Please connect any single Lego pieces into two-part units until there are no more single pieces remaining or you are told to stop by the Time Keeper or Instructor.

-Destroyer- Please keep track of the total number of Lego pieces that are connected in pairs. Once this number exceeds 20 built pieces, pull apart any connected pieces until there are no more than 20 built pieces. 

-Accountant- Please keep track of the total number of Lego pieces that are connected in pairs. Begin at time 0:00 and end at time 5:00. Record this number in a chart or table every 10 seconds.

-Time Keeper- Please use a timing device to keep track of the elapsed time of this activity. Begin at time 0:00 and end at time 5:00. Call out the time every 30 seconds.

3. Observe how each team gets started, works through the simulation, and ends all without any guidance other than what they were given.

What will typically happen is that the Time Keeper will automatically begin and end the session, the builder will start doing his or her thing and then get surprised and, in some cases, really mad that the Destroyer is undoing their work. Students won't understand the point of the activity but as long as the Accountant has a record of their activity then the next phase of the activity will be in good stead. With time permitting, students may choose to do the simulation again and even swap roles.

Once the simulation has been done at least once, students will be asked to graph the data. The X-axis ought to be elapsed time (0:00-5:00) and the Y-axis ought to show the total number of connected Legos at any point in time.

Click here for what one (pretty ideal) Lego graph looks like.

Spoiler: The graphs can look really different (and a bit chaotic) but many will resemble the logistic ("S shaped") growth curve. The completed graphs will be required for the next day's lesson so it should be finished by then.

Closure: What did we learn? Where do we go from here?

5 minutes

"Playing with a purpose."

On the heels of the Lego Lab experience, students will likely have a wide variety and number of thoughts about the purpose behind the simulation.

Turn & Talk: Prompt students to share their ideas about the real meaning behind the simulation (other to have fun, which is always an important part of learning).

Lesson Extension & Follow-Up Activities

If students have not yet finished the graphing of the Lego Lab Simulation, they are to do so for homework.

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