Population Dynamics (Day #1 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")

15 minutes

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

To kick off this series on population dynamics, I want to get the blood flowing, brains processing, and kids on their feet. To do so, I use the strategy called either the "Line Game" or "The Line". Essentially this requires students to stand (by default) on a piece of rope lying on the floor and dividing the classroom. When presented with a statement in the Population Survey, students will agree with it by remaining on the rope or step off of the rope should they disagree.

Alternatively, the "Four Corners" strategy would require students to more keenly discern their answers. Instead of simply stepping on or off of the line, students will need to move to one of four corners in the classroom with signage labeled:

4: Strongly disagree

3: Disagree

2: Agree

1: Strongly agree 

The trick with this entry task is to get students to think about different scenarios and to look for different ways to frame an answer. Many of the scenarios are designed to be answered from multiple points-of-view. And this is O.K.! Furthermore, it is advisable to probe student thinking between each of the prompts to uncover student thinking in various ways.


Instructional Input/Student Activities

30 minutes

Turn and Talk:

-Longevity (slide #3)

-P.O.V.: "Is human overpopulation the root cause of all other environmental problems?"

What did they say?

-"It's not just about the number of people who live on the planet, its about their lifestyle and what they consume."

-"Yes, human population is the issue. More people eat more food, make more waste and negatively affect the environment."

Population Growth Lecture Main Idea #1: Population size is controlled by (abiotic) non-living factors


1. Describing various aspects of "community" (slide #19)

2. Population density: comparing regions and discussing impacts on populations (slides #20-23)

2. Abiotic factors affecting population size (slide #24)


*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.

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

10 minutes

Parking Lot: Using a Post-It note, students will identify four factors that affect (+, -) population size. Once completed, students will post their answer to a visible wall or board space. These can be collected (by instructor) en masse and analyzed for trends in the fashion of a formative assessment. In this case, I randomly select three to five responses and read them aloud as class wraps up.

Some typical responses might include:

+ Factors are...plentiful food and water supplies; available mating partners (involving sexual reproduction); available habitat

- Factors are...pathogens; hurricanes, droughts, deep freezes; limited access to mating partners

Essentially it comes down to abiotic and biotic limiting factors (either needed and plentiful or otherwise)

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