# Lesson: Investigating factors that effect population sizes (limiting factors)

David Kujawski Bird Middle East Walpole, MA
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### Lesson Objective

YWBAT: 1) Explain, in detail, at least three factors that can affect the size of a population. 2) Define limiting factors and explain how they can impact the size of a population.

### Lesson Plan

1.)    DO NOW: What is required for organisms to survive?  Field responses; possible answer include: space, water, air, food, shelter, etc.

2.)    State: We are going to do an activity that investigates the way that the abundance or shortage of resources can affect population sizes.  A resource is anything that is required for life, and without it, a population of organisms could decrease in an area.

3.)    Give out handouts (Student graph activity one). Students will complete the worksheet with a partner.  They will have to determine what a hypothetical graph of the population would look like given the scenario that they’re presented.  Students may struggle with this because they will be used to making a graph based on collected data.  There will be no data provided; they will simply have to determine the best shape of the graph, based on the situation.

4.)    Students complete activity and answer questions at the end and review as a class.  Have students defend why they chose to make their graphs in that particular way.  Challenge their decisions—make them think!

5.)    State: we are now going to do an activity to see the affect that space has on supporting a population of organisms.

6.)    (Ahead of time) Make 3 squares on your classroom floor.  One should be 1 meter x 1 meter.  The next should be .5 meter x .5 meter.  The last square should be .25 meter x .25 meter.

7.)    Ask for volunteers to fit their feet into each square.  Record on the board how many students each square can support.

8.)    State: What we just modeled was the idea of limiting factors.  In this case, the amount of space available determined how many organisms in a population could be supported.  In ecology, there is a theoretical limit to the amount of organisms that can be supported for a certain population.  This limit is called carrying capacity.  Define on board: Carry Capacity- the amount of organisms of a certain species that can be supported in a certain area.

10.)   Review worksheet with class, review what they learned that day, hand out homework and then dismiss.

### Lesson Resources

 Using graphs to teach limiting factors   Activity 6,782