California Agriculture in the Classroom

Good Taste: Honey Bee Forager Food Preference

Grade Level(s)

9 - 12

Estimated Time

Two 50-minute class periods

Purpose

In this lesson students learn about the foraging behavior of bees and hypothesize if the bee’s behavior is related to its ability to detect sugar. Students will then determine which type of foraging bee would be best for pollination or honey production. Students will learn about the process of gel electrophoresis as a genetic tool and analyze DNA to identify strains of bees who are better pollen-collecting bees or better nectar-collecting bees.

Materials

Interest Approach:

Activity 1 and 2:

Activity 3:

Activity 5: 

For the teacher to prepare ahead of time:

For each lab group:

Essential Files (maps, charts, pictures, or documents)

Essential Links

Vocabulary

response threshold: likelihood of reacting to task-associated stimuli

probiscis extension response (PER): a method for measuring a bee’s response threshold to sugar

deoxyribonucleic acid (DNA): molecules inside cells of all living things that carry genetic information and pass characteristic traits from one generation to the next

chromosomes: organized package of all DNA found in the nucleus of the cell

genes: sections of DNA on a chromosome that code for the proteins our body needs to function

DNA fingerprinting: tool used by biologists that analyzes an individual’s unique collection of DNA

restriction enzyme: enzyme that cuts DNA at a sequence of nucleotides

gel electrophoresis: procedure used to separate and analyze DNA fragments by placing a mixture of DNA fragments at one end of a porous gel and applying an electric voltage to the gel

Did you know? (Ag Facts)

Background - Agricultural Connections

Prior to this lesson students should be familiar with the steps in an experiment: formulating a research question, developing a testable hypothesis, gathering, recording, analyzing, and interpreting data, and drawing conclusions from evidence. Students should be familiar with what DNA is and aware that heritable traits are passed down from parents to offspring. This lesson will introduce genetic tools or techniques useful when examining genetic information.

Key STEM Ideas:

Heritable information is passed from parents to offspring via molecules of DNA. This information directs an organism’s growth, development, functioning, and reproduction. DNA of living organisms is responsible, in part, for characteristics or traits (such as sensitivity in taste perception). Genetic tools including gel electrophoresis can be used to analyze an organism’s DNA.

Connections to Agriculture:

Quality and yield of fruit, nut, and vegetable crops are improved with adequate pollination by insects such as bees. Honey bees add an estimated $19 billion in added value to agricultural crops.1

The proper functioning of a honey bee colony depends on all needs in the hive being met by a diverse group of workers. One of the key needs of the colony is foraging for nectar and pollen from flowering plants. Female worker bees accomplish the gathering of these food resources through a division of labor. Bees are genetically and environmentally predisposed to prefer either sweet nectar or not-so-sweet pollen. A more genetically diverse colony will stand a better chance of gathering all the food resources it needs for survival. In addition, successful honey bee colonies will be better pollinators of our fruits, nuts, and vegetables.

Even when colonies are healthy, some are better at pollinating than others. Genetics play an important role in determining the types of traits a colony possesses.

Genetic testing of bees for their pollen or nectar gathering preference can be used in research programs seeking out new and potentially valuable traits that can benefit the beekeeping industry and growers relying on honey bees for pollination services.

Interest Approach – Engagement

  1. Offer students a choice between a sweet and a salty food.
  2. After students have selected their choice, ask them why they chose the food they did. Allow a few students to share their answers and discuss reasons why some students chose sweet and others chose salty. Discuss with students what factors might impact our sense of taste and our preference.

Procedures

Activity 1: Foraging Behavior Experiment

  1. Give each student one Good Taste: Forager Food Preference student handout and one copy of the Activity 1 Field Notes
  2. As a class, begin reading on page 1 of the handout. Be sure students understand the different materials gathered by honey bees (nectar for energy, pollen for proper development, and water to cool the colony).
  3. After the reading, have students work individually to formulate a research question (question 1 on handout).
  4. Discuss the experimental set-up. Key points are listed below:
    • Plastic numbered tags are glued to the back of 50 worker bees
    • Bees are returned to the colony and allowed to forage as usual
    • As the bees return to the hive after foraging, the student captures and examines the bee to determine what resource has been brought home (pollen will be carried on the leg in a pellet, nectar or water can be regurgitated by the bee by gently applying pressure to the abdomen)
  5. Ask if students think that the type of resource brought home is randomly selected by the bees or if certain bees are specialized to bring home specific resources. Have students use their answers to develop a testable hypothesis (question 2 on handout).
  6. Have students work in pairs to complete the data table at the bottom of page 1 using the Activity 1 Field Notes. Once the table is filled out, students will use the data to answer the remaining questions.
  7. Discuss if the data supported their hypothesis or not (depending on their hypothesis, it may or may not be supported). Encourage critical thinking by having students discuss why water is brought back only in the afternoon (hotter temperature require cooling of the hive) and why some foragers returned to the hive with no resource (students don’t need to know this yet, just discuss possible reasons such as maybe they couldn’t find anything, maybe nothing was attractive enough to bring back, etc.)
  8. Discuss possible reasons why bees might specialize for certain resources. (It might be a learned response, it could be a genetic trait, etc.)

Activity 2: Proboscis Extension Response

  1. Read the introduction for Activity 2 located on page 3 of the handout. Review a few key points:
    • A proboscis is like the bee’s tongue.
    • Antennae act like the bee’s nose, but can also detect a resource’s level of sweetness.
    • Nectar is made of sugars and is sweet. Pollen is not made of sugar and is not sweet.
  2. Explain that a test can be performed to determine the point at which bees can detect sugar. This test is called the Proboscis Extension Response (PER) assay. Have students watch the video of a PER assay as you explain the following steps:
    1. A sugar solution is applied to the antenna of a restrained bee.
    2. The bee will reflexively extend its tongue to seek out the sugary reward IF it can detect the sugar content in the solution.
    3. A series of sugar concentrations are tested to determine the bee’s response threshold (the lowest sugar concentration that will elicit a positive response).
    4. Bees are then identified as having a relatively high or low response threshold depending on their sensitivity to sugar.
  3. Based on what students have learned about PER, have each student predict the foraging behavior for bees with high and low PER thresholds. Apply their predictions to the bees that were tested in the earlier experiment to determine which bees would have high and low PER thresholds by filling out the table at the bottom of page 3.
  4. Complete page 4 of the handout by having the students examine the graph showing data from a PER assay experiment. Apply information learned from this graph to determine if the student’s hypothesis was supported. (Yes, it was supported. A greater portion of pollen collecting bees responded to low concentrations of sugar. A smaller portion of nectar collectors responded to low concentrations of sugar. Instead, nectar collectors responded only to high concentrations of sugar.)

Activity 3: Gel electrophoresis and DNA fingerprinting as genetic tools

  1. Explain to students that now that we have learned that foragers specialize in what resources they bring home and that these specialized foragers also respond differently to sugar, we can start to examine what might be the reason or mechanism for these differences. Could there be a genetic component to explain this difference in ability to perceive sweetness?
  2. Have students read the introduction to Activity 3 located on page 5 of the handout. Students should then work through the DNA fingerprinting simulation.
  3. As the lab groups experience the simulation, have them write the purpose of each step in the DNA fingerprinting process in their handout.
  4. Discuss answers as a group and explain that DNA fingerprinting is one way of analyzing a DNA sample. The location of the cuts made by the restriction enzyme all occur at the same nucleotide sequence (or restriction site), but depending on the DNA sequence, the size of the resulting bands will be unique just like a fingerprint! The differences seen in the gel electrophoresis are a result of the different sizes of DNA.

Activity 4: Analyzing forager DNA

  1. Read with students about Activity 4. Explain that while the genes responsible for pollen collecting and nectar collecting are still being researched, the following activity simulates how DNA testing might one day be used to visualize the genetic differences between these two strains of bees.
  2. Instruct students to use the sample DNA cuts as a guide and mark the cuts on the pollen and nectar collector DNA on page 6 of their handout. Document the number of cuts and segments made by the restriction enzyme in the table. Answer the follow-up questions.

Activity 5: Using gel electrophoresis to identify unknown bees

  1. Split students up into lab groups. Have students read through procedures before they begin. Instruct groups to gather their lab materials and begin.
    1. Fill bowl approximately 1/2 full with water, add 0.5 tsp of washing soda solution. Mix with spoon.
    2. Dip card into solution until pink dots become visible and quickly remove it.
    3. Briefly sketch results into the data table.
  2. Using what they learned from the DNA fingerprinting simulation and their answers from Activity 4, have students answer the follow-up questions. 

Concept Elaboration and Evaluation

After conducting these activities, help students review and apply what they have learned:

Suggested Companion Resources

Sources/Credits

Author Affiliations:

Sources:

  1. $19 billion value of honey bees to U.S. agricultural value from Calderone, 2012 found here: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0037235
  2. AgNote: “Pollination of apples by honey bees” by Doug Somerville of New South Wales Department of Agriculture found here: http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0018/117108/bee-apple-pollination.pdf

Author(s)

Burke Morrow and Erin Ingram

Organization Affiliation

University of Nebraska-Lincoln