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

Great Gravidity Home

CISEO Home

Materials Needed per group:

• 4-10 Petri dish habitats
• Bottle cage
• Colony of aphids on pea plant
• Eyelash brush
• Dissecting microscope or TriLens
• Data Collection Sheet
• 3-4 Aphid Observation Lab Sheets
• Sampling Methods Sheet

Class Time Required
Day 1

Approximately 45 minutes for project set-up.

Days 2-28
Approximately 15 minutes per day for observation and data collection

Exploring How Aphid Populations Grow
This long-term project and associated activities engage students in scientific research. The goal is to follow changes in aphid populations by counting the change in numbers of aphids over time. Students discover the impact of population growth in a closed ecological systemone in which nothing, except water and air, is introduced or removed. Students make initial

observations, then record data over a period of four weeks. By setting up experiments, they explore the following questions: How does a population grow? What factors affect the growth rate of populations?

At the beginning or end of each week, students meet with their groups to discuss their data. (See Data Analysis I.) They may share their observations with the whole class at that time. Then, have students make predictions about population growth for the next week. At the end of the four weeks, students interpret the data and make presentations about their findings. (See Data Analysis II).

Preparation
By now, you should have several healthy stock colonies of aphids on host plants. You or your students will need to have assembled the bottle cages. eyelash brushes and clip cages. Members of each group will be responsible for the care and maintenance of their bottle cages and aphid colonies over the course of the research project.

Day 1
Distribute one plant to each student group, and have students transfer one adult aphid from the stock colony to their plant. Also distribute the Aphid Observation and Data Collection sheets.

Groups can follow these sheets, or design their own methods to quantify and record data on population growth. Ask students how they would count a large number of insects or other organisms in a given area. (Samples of a population are counted and the overall population size calculated. See Sampling Methods.) Be sure groups record whatever method(s) they use.

On Day 2, circulate among the student groups and ask how they plan to collect data on their aphid colonies during the project. Ask each group to ensure that a different student observes colonies and records data each day, so that all students have an opportunity to observe and record data.

On Days 3-15, have students observe the behavior and growth of aphids on their whole plants and record their data. Make sure they water their plants when necessary. Have backup plants and aphids available in case of disaster.

Some students may want to isolate an individual adult aphid on a leaf with a clip cage to observe the reproductive capacity of a single aphid.

Students may notice the presence of other insects especially if wild caught aphids are used. See the Enforcers lesson for information and activities that explore the effects of predators and parasitoids on aphid populations.

Note
Aphids are small and fragile and are best handled with a small brush or eyelash brush. Gently prod the aphid with the eyelash brush until its mouthparts are removed from the plant. Then encourage the aphid to crawl onto the brush for transport.

Insect Note
You may have noticed the sticky droplets on the leaves below the aphids. This is called aphid 'honeydew.' The change in frequency ofhoneydew production by an aphid is a sensitive measure of the physiological influences affecting the aphid. Changes in light phase, temperature, humidity, and density of aphids on a leaf can affect the droplet production. For these reasons, measuring aphid honeydew can give an indication of how well the insect is doing on a particular plant. For example, measuring honeydew is a good way to determine how well the aphids survive on different varieties or species of plants in the pea or other appropriate host-plant family.

Ask the students to suggest ways to measure the rate of honeydew production.

A popular method for measuring honeydew is with bromophenol blue. Filter paper dipped in this solution and dried will stain bright blue when an acidic liquid touches its surface. Since honeydew is acidic, the bromophenol blue works as an indicator.

See the reference Klingler et al. for instructions on how to set up an experiment using this technique.