Overview & Lesson Sequence

Focus on Standards & Assessment

Materials Needed, Preparation & Planning, Management Strategies

Background Info

Intro Activity
Why Study Populations?

Meet the Aphids

Research Project
Aphid Population Growth

Data Analysis I

Data Analysis II

Optional Activity
The Power of Exponential Growth

References

Glossary

Suppliers

Resource Sheets

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Overview

Insects make excellent models for introducing the fundamental concepts in population ecology. They compete with humans for food and fiber, making many species agricultural pests. An understanding of insect population growth is essential to their management. Many species of insects are extraordinarily fecund: they can produce incredible numbers of offspring in a short amount of time. This reproductive capacity allows many insect populations to recover quickly from episodes of pesticide application, predation, and climatic variation. Aphids, in particular, make superior models since they have the ability to reproduce rapidly both sexually and through parthenogenesis, i.e., eggs develop without being fertilized. They are also pests.

In this lesson students will discover the basic principles of

population ecology by observing and collecting data on aphid population growth during a four-week research project and integrated learning activities.

This lesson's long-term research project and associated activities mirror real-world scientific research in that students will be collaboratively setting up an experiment, collecting, organizing and interpreting data, then presenting the results to a larger audience. There are ample opportunities for students to ask their own questions, develop hypotheses and design experiments based on the initial experimental set up.

Lesson Sequence
The lesson involves introductory activities, a long-term research project, and two data analysis activities. An optional activity relates what students have learned in the lesson to the global human population.

Introduction: Assess students' prior knowledge and develop a list of students' questions about populations and population growth.

Meet the Aphids: Students are introduced to aphid biology and the laboratory techniques they will use during data collection.

Research Project--Exploring How Aphid Populations Grow: Students set up and observe controlled aphid habitats in order to investigate population growth rates in a "closed" ecological system. Note that a closed system does not reflect natural conditions since there is no immigration or emigration of individuals. In addition, no new resources (other than water and air) are added. Over the course of four weeks, students collect and

analyze data on the condition of the insects, record insect

development and reproduction, and document the condition of the habitat. Students will discover that at some point the

environment is no longer able to support the population of aphids, that is, the environment reaches its carrying capacity.

Data Analysis I: After each week of observations, students do a data analysis, discuss their data with their groups and share with the rest of the class. They predict future growth of their aphid populations for the coming week, and continue to collect data over the four weeks of the investigation.

Data Analysis II: Students do a final data analysis and give a formal presentation of their data, with interpretations and conclusions to the class. Through extended discussions about findings, they come to understand the limits of an environment's ability to support a population or its carrying capacity.

Optional Activity--The Power of Exponential Growth: This activity provides an opportunity for students to apply their new knowledge of population dynamics to other systems such as the human population and its effect on the earth's ecosystem.