## Reflection: Real World Applications Population Dynamics (Day #2 of 3) - Section 3: Instructional Input/Student Activities

Modeling. According to A Framework for K-12 Science Education: Practices, Crosscutting Concepts, and Core Ideas (a key resource used to support NGSS implementation), "By Grade 12, students should be able to construct drawings or diagrams as representations of events or systems... and use it as the basis of an explanation or to make predictions about how the system will behave in specified circumstances." (p. 58)

In this lesson, the system represents a population of organisms (represented by Legos) whose size increases, decreases, and remains constant under certain circumstances. The equation for population change (+ or -) is governed by birth, death, immigration, and emigration. In the simulation, emigration and immigration were excluded therefore any change to the population resulted in births (connected or "built" Legos) and deaths (Legos that became disconnected or "destroyed").

So for students the real objective was to model how these two processes worked together (even when they weren't aware of the "real" motive of the exercise). An even more pressing objective is the concept of feedback (which can snarl up even the brightest minds and I see misconceptions related to it crop up in my AP Biology classes too). So by establishing the threshold of 20 connected Legos and restraining the "Destroyer" until this point was reached ("equilibrium" that they will come to know as carrying capacity) helped them to see later on (via class discussion) how the population was controlled by negative feedback. Students should also be able to determine the future course of population growth when manipulating the (B+I)-(D+I) formula and how carrying capacity is affected as a result.

Footnote: After our first "trial" we discussed the meaning of the simulation and students wanted to redo it. Armed with full knowledge, I must say that it was quite hilarious to see the various strategies that the builders and destroyers invented and implemented to outwit, outplay, and outlast each other: I am talking about hording Legos, Builders using body parts to shield their "precious" (a la Gollum of LOTR fame) Legos from the Destroyers. Normally mild mannered young ladies got really mad when their creations were unmade. Definitely a fun and memorable day in my class!

Real World Applications: Hands-on, Minds-on Learning (I)

# Population Dynamics (Day #2 of 3)

Unit 7: 7) Ecology ("Population Interactions")
Lesson 5 of 16

## 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.

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Subject(s):
Science, Populations and Ecosystems, abiotic factors, carrying capacity, exponential growth, Ecology, Biotic Factors, feedback, logistic growth, competitive exclus, predator and prey
55 minutes

### Mitchell Smith

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