# Population Dynamics (Day #3 of 3)

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## Objective

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 support my students in analyzing data in order to address a question of interest?

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

Write, Pair, Share: Using the completed graph (itself a model) from yesterday's Lego Lab simulation, students are prompted to annotate the graph.

1. Write: On their own, students will reflect on what the Builder and Destroyer did in each time interval (every 30 seconds) that led to the various "ups" and "downs" evident in the graph.

2. Pair: After this period of reflection and writing 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). I use an Elmo document camera in class. Using this technology, students will present their graph and annotations to the class and explain the overall pattern of the graph and the causal events behind the pattern.

Take note of the variety of key ideas that students took away from the Lego Lab Simulation. These might naturally be interwoven with the lecture main idea to follow. In particular, students ought to see the the likeness between the Lab and logistic growth. Building on this, students should be able to interpret population graphs in light of carrying capacity, competition, predation, and the human population.

Source: https://students.ga.desire2learn.com/d2l/lor/viewer/viewFile.d2lfile/1798/12674/graph-comparisons.png

Note: Our focus was on modeling Logistic Growth (right-hand graph)

## Instructional Input/Student Activities

35 minutes

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

Population Growth Lecture Main Idea #3: Feedback mechanisms help to adjust population size toward an "ideal" level.

Emphases:

a. Carrying capacity (slides #37-41)

b. Logistic growth curves (slides #42-45)

c. Competitive exclusion (slides #46-47)

d. Predator-prey interactions (slides #48-50)

e. Exponential growth curves (slides #51-53)

f. Human population dilemma (slides #54-55)

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*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

Peer Instruction Protocol: According to the protocol outlined here, conduct a brief review of the two questions concluding the lecture.

Exit Task: Please answer the following questions on the sheet of paper provided. This is due by the end of class. (Sample of student responses in bold)

1) What variables help to change a population’s size?
Birth, death, emigration, immigration

2) Is there a limit to population size? If so, list three factors (things) that limit it.
Yes, there is. When disease, famine, or lack of mating partners exist, the population will fall.

Yes. Either abiotic or biotic factors can cause a population to shrink. Things like fire, tornadoes, and earthquakes all impact (-) populations

3) How well do you understand the topics of the lecture so far? Not very well (1) --> very well (5)
Class Average=4