Chemicals cue behavior

This exercise is a part of Educator Guide: Chemical Coaxes Locusts to Swarm / View Guide

Directions for teachers:

Ask students to read the online Science News article “A single molecule may entice normally solitary locusts to form massive swarms” and answer the questions below about the chemical makeup of the pheronomone described in the article. Then, in the section titled “Cued behaviors,” students will select and research a pheromone that interests them and answer questions about the pheromone’s role in species behavior. You may need to review concepts related to molecular formulas and structure before beginning the exercise. Have students partner up to discuss the last four prompts, which ask them to think about other factors that may influence behavior. Bring the class back together as a group and discuss questions of your choice.

Want to make it a virtual lesson? Post the online Science News article “A single molecule may entice normally solitary locusts to form massive swarms” to your virtual classroom. Ask students to answer the first set of prompts individually, and have them post the pheromone they chose to your online discussion board. When you’re ready to pair students up, have them discuss the final prompts using a video-conferencing platform, or talking by phone. They can collaborate in a shared document during the conversation. After posting the answers to an online discussion board, have students give feedback on another pair’s responses.

A pheromone’s chemistry

1. What is the pheromone identified in the Science News article? Give both the common name and formal scientific name.

The locusts’ aggregation pheromone identified by sciencetists has the common name of 4VA. It’s formal scientific name is 4-vinylanisole, or 4-methoxystyrene.   

2. Using PubChem, find and state the molecular formula of the pheromone. What elements does the molecule contain? How many atoms of each element does one molecule contain?

The molecular formula of 4VA is C9H10O. One molecule of it contains nine atoms of carbon, ten atoms of hydrogen and one atom of oxygen.  

3. Use PubChem to list two additional properties given for your molecule. Are the properties physical or chemical? Explain.

4VA has a boiling point of 205.0 degrees Celsius and a molecular mass of 134.17 g/mol. Both of these properties are physical — they can be observed and measured without changing the chemical composition of the substance.  

4. Using the “3D Conformer” section on PubChem along with the pheromone’s molecular formula, draw the pheromone’s molecular structure. Label each element within the molecule (make sure to use elemental symbols) and include all bonds. How many single bonds does the molecule contain? What about double bonds? Triple bonds?

See the 4-methoxystyrene page for the molecular structure of 4VA. The molecule contains 16 single bonds, four double bonds and no triple bonds.  

5. What information does the molecular structure tell you that the molecular formula doesn’t?

The molecular structure shows you the types of bonds that exist and which elements are bonded to other elements and how. The molecular formula tells you only how many atoms of each type of element exist in one molecule. 

6. Optional extension question: What types of bonds exist within the molecule? If bonds are covalent, are they likely nonpolar covalent or polar covalent? Explain.

There are nonpolar covalent bonds between carbon atoms and between carbon and hydrogen atoms. The bonds between the oxygen atom and carbon atoms would likely be polar based on the relatively large electronegativity difference between the atoms.

Cued behaviors

7. What pheromone have you chosen to research? Why does it interest you?

Student answers will vary.

8. What organism releases the pheromone? What behavior does the pheromone appear to cue?

Student answers will vary depending on the pheromone they choose. For 4VA, the pheromone appears to signal solitary migratory locusts (Locusta migratoria) to congregate into swarms.  

9. How might the behavior cued by the pheromone benefit the organism?

Student answers will vary depending on the pheromone they choose. In regards to 4VA, group formation can aid locusts in foraging, reproduction, migration and increased survival from predators.

10. What do scientists know about how the pheromone is produced or detected by individuals?

Student answers will vary depending on the pheromone they choose. For 4VA, scientists think that the protein that detects the pheromone sits on certain sensory hairs that extend from the locusts’ antennae.

11. How might humans benefit from knowing about this pheromone? Explain. 

Student answers will vary depending on the pheromone they choose. For 4VA, knowing more about the pheromone that may cue locust swarm formation could help determine ways to help control swarms and thus prevent them from destroying crops. 

Final group prompts

12. Based on what you have learned from this exercise, how would you define a pheromone?

A pheromone is a chemical released by an individual organism that impacts the behavior of other individuals of the same species.

13. Why is it beneficial for scientists to know the structure of the pheromone molecule? Include the terms physical and chemical properties in your answer.

The chemical structure of the pheromone determines the chemical and physical properties of the pheromone. Physical properties such as boiling point and vapor pressure can explain how long the chemical will remain on a surface or in the air. Chemical properties such as its reactivity with other compounds could be used to create molecules that could consume or block the pheromone to prevent its spread.

14. List as many other examples of group and individual behavior as you can think of. Indicate which category (group or individual) each behavior belongs to. If a behavior could be categorized as group and individual, explain why.

Other group behaviors include: flocking, herding, migrating, swarming, etc.
Other individual behaviors include: mating, fleeing from a potential threat, eating, etc. Hunting and hibernating are examples of behaviors that could be group or individual behaviors, depending on the species exhibiting the behavior. For instance, arctic ground squirrels are solitary hibernators while some species of bats hibernate in groups.

15. What factors besides chemicals might influence behavior?

Environmental conditions such as climate or weather changes, the availability or lack of resources, the presence of other organisms (especially possible predators or threats) and the circadian rhythm of an animal may influence behavior.