From Eggs to Butterflies: How Does a Population Grow?
Teaching Suggestions

Overview

Introduction

A female monarch can lay hundreds of eggs. If every egg survived, the population could grow to a billion butterflies in only four generations.

 Essential Question What limiting factors keep the monarch population from growing exponentially?
Learning Outcomes

Goals:

• To explore population dynamics: the reproductive potential of monarch butterflies and the limiting factors that keep the population from growing exponentially.
• To invite students to record limiting factors that may impact the size of the population as they follow the migration live this spring.

Objectives:

1. Define the phrase "reproductive potential" and explain how it relates to monarch butterflies.
2. Identify and describe the limiting factors that keep the monarch population from reaching unsustainable levels.

Instructional Activities

1. Build Background Knowledge
Look at the graph One Monarch, How Many Eggs? and ask, What does the graph reveal?

Read aloud “How Much is a Million?” to conceptualize immense numbers and understand exponential growth.

2. Explore the Math
Place students in small groups. Provide each group the
handout, From One to One Billion Butterflies. Explore population growth and the reproductive potential of monarchs.

• Have students describe how the graphs help them understand the growth potential of monarch populations.
• Encourage students to write story problems for the class to solve using the data on the graphs.

3. Revisit Key Concepts
Write these two phrases on chart paper: “reproductive potential” and “limiting factors.” Have students explain how these words relate to monarchs using details from the slideshow. Reread the final page of the slideshow. Use guiding questions to discuss how limiting factors keep populations from reaching unsustainable levels:

• What factors might influence the number of eggs a monarch butterfly lays?
• Which factors might impact survival at each phase of the life cycle?
• egg
• larval
• chrysalis
• adult
• What limiting factors might impact survival at each stage of the annual cycle:
• spring migration
• fall migration
• breeding season
• overwintering season

4. Chart the Limiting Factors
Distribute the Monarch Annual Cycle and have students think about what challenges monarchs face during each stage. As students track the migration, have them record limiting factors that may impact population growth and decline on the chart. Display the chart and add ideas throughout each season.

5. Revisit Essential Question
Assess students' understanding by asking them to summarize their discoveries.

How Much is a Million?
by David M. Schwartz

Monarch Annual Cycle

Essential Question