What makes honey bees work together?

Transcription

1 What makes honey bees work together? How genes and environment affect behavior Lesson 3: How do bees heat the hive? I. Overview Lesson 3 explores the influence of the environment on animal behavior, and how collective behaviors can modify the environment. In this lesson, students explore how a specific environmental factor, temperature, influences bee behavior. Additionally, they will consider how the concept of homeostasis can be applied to multiple levels of biological organization, and how group behavior can be used to modify the environment. Students design and carry out an investigation using a NetLogo simulation. From the simulation and a reading activity that follows, they collect and organize data and use it to support a scientific claim that addresses the driving question for this unit. By the end of this lesson, students will synthesize the concepts of genetic and environmental influences on behavior, and appreciate how these two influences interact. Connections to driving question This lesson uses a NetLogo simulation to model how an environmental factor, temperature, influences the performance of hive heating or cooling behavior by individual bees. Students also explore a reading that discusses the impact of climate and temperature-related behaviors on honey bee ecology. Connections to previous lesson In lesson 2, students considered how many factors, including environmental factors, can act through gene expression to influence the social behavior of individual bees. In this lesson, they consider a specific environmental factor (temperature) and its effects on social behavior. II. Standards National Science Education Standards 12ASI1.1 Identify questions and concepts that guide scientific investigations. Students should form a testable hypothesis and demonstrate the logical connections between the scientific concepts guiding a hypothesis and the design of an experiment. They should demonstrate appropriate procedures, a knowledge base, and conceptual understanding of scientific investigations. 12ASI1.2 Design and conduct scientific investigations. Designing and conducting a scientific investigation requires introduction to the major concepts in the area being investigated, proper equipment, safety precautions, assistance with methodological problems, recommendations for use of technologies, clarification of ideas that guide the inquiry, and scientific knowledge obtained from sources other than the actual investigation. The investigation may also require 1

2 student clarification of the question, method, controls, and variables; student organization and display of data; student revision of methods and explanations; and a public presentation of the results with a critical response from peers. Regardless of the scientific investigation performed, students must use evidence, apply logic, and construct an argument for their proposed explanations. 12CLS6.2 Organisms have behavioral responses to internal changes and to external stimuli. Responses to external stimuli can result from interactions with the organism s own species and others, as well as environmental changes; these responses either can be innate or learned. The broad patterns of behavior exhibited by animals have evolved to ensure reproductive success. Animals often live in unpredictable environments, and so their behavior must be flexible enough to deal with uncertainty and change. Plants also respond to stimuli. 12CLS6.3 Like other aspects of an organism s biology, behaviors have evolved through natural selection. Behaviors often have an adaptive logic when viewed in terms of evolutionary principles. Benchmarks for Science Literacy 12D/H7* Use tables, charts, and graphs in making arguments and claims in oral, written, and visual presentations. III. Learning Objectives Learning objective Assessment Criteria Location in Lesson Describe how the environment Individual bees respond to changes in environmental temperature by performing Activity 1 influences social behaviors that contribute to regulation of hive temperature. behavior. Exposure to high or low environmental temperatures will produce different types of behaviors in honey bees. Bees also produce different behavioral responses depending on the size of their group. Apply the concept of homeostasis to temperature regulation in a social group. Colonies exposed to cold environments must maintain a minimum temperature that allows survival of as many individuals as possible. Behaviors induced by changes in environmental temperature act to counteract those changes and maintain an appropriate temperature inside the hive. Activity 1 2

3 Design and carry out an investigation using a model to test the effect of temperature on honey bee behavior. Elaborate on the concept of the honey bee colony as a superorganism, and summarize the benefits of eusocial behaviors. Develop a model for how genetic and environmental factors can affect each other. The magnitude of the behavioral response reflects the magnitude of the difference between the ambient and desired hive temperatures. Environmental temperature and group size are independent variables; frequency of behavioral performance and hive temperature are dependent variables At low environmental temperatures, smaller groups of bees are less able to regulate hive temperature than larger groups of bees. The colony represents a higher level of biological organization, where cells:body::bees:colony. Individual bees, which are exothermic, exhibit behaviors that work together to produce an endothermic colony. Natural selection acts on the level of the colony; the colony s survival determines whether the genes of the reproductive members will be passed on. Bee colonies with different genetic backgrounds have different degrees of ability to withstand cold temperatures. Subspecies of bees that have lived in either temperate or tropical environments exhibit heritable adaptations to those environments. Specific genes are involved in bees behavioral response to extreme temperatures. Activity 1 Activities 1 and 2 Activity 2 IV. Adaptations/Accommodations The timeframe for the Netlogo simulation can be adjusted by assigning different groups to investigate different temperature ranges, and then sharing and discussing data as a class. The reading on Africanized bees can be done in class, or completed as a homework assignment. 3

4 Depending on the grade level and the presence of ELL students, some classes may need additional support for the reading in Activity 2, as for other readings in this Unit. The activity, and accompanying research question, can be assigned as homework over multiple days if students might need more time, or students can work together on the project. V. Timeframe for lesson Opening of Lesson Class discussion in which you review basic concepts of division of labor and behavior-related gene expression from previous lesson 15 minutes Main Part of Lesson Activity 1: NetLogo Hive Temperature Simulation 45 minutes Activity 2: Africanized bees and climate reading 45 minutes, plus time for research question if in class Conclusion of Lesson Wrap up discussion of lesson 15 minutes VI. Advance prep and materials Activity 1: NetLogo Hive Temperature Simulation Materials: Pre-reading (1 per student), U8_L3_PreReading_HoneyBeeClustering.docx Student worksheet (1 per student), U8_L3_StudentSheet_BeeNetlogo.docx Computers with Netlogo Hive simulation (1 per 2-4 students), U8_L3_NetLogo_HoneyBee.nlogo Rulers, pencils for graphing Graph paper Preparation: Make enough copies of the worksheet for each student to have one. Make sure enough computers are available. Activity 2: Africanized bees and climate reading Materials: Africanized bee reading (1 per student), U8_L3_Reading_AfricanizedBeeInvasion.docx Student worksheet (1 per student), U8_L3_StudentSheet_AfricanizedBeeInvasion.docx Preparation: Make enough copies of the reading and worksheet for each student to have a copy of each. 4

5 Homework and Assessments Materials: o N/A VII. Resources and references Teacher resources Winston, M. L. (1987). The biology of the honey bee. Harvard University Press. Cambridge Massachusetts. References Rinderer, T. E., Oldroyd, B. P., Sheppard, W. S. (1993). Africanized bees in the U.S. Scientific American West Mountain Apiary. (n.d.). The winter cluster. Retrieved from 5

6 VIII. Lesson Implementation Opening of Lesson: Review with the students the concepts they were introduced to in the previous lesson. Review the structure of the honey bee colony and the different tasks of the workers o What are some tasks that workers perform, and why are they important to the colony? For example: nursing, guarding, foraging. Each is important for a different function necessary for the function of the whole colony, for example: guarding protects the colony s population and food stores from intruders, foraging adds to food stores. o Higher or lower expression of specific genes in the brain can be associated with certain behaviors. Expression of PKG, aka the foraging gene, is higher in the brains of honey bee foragers than bees performing tasks inside the hive, such as nurses. Consider as a class what types of factors influence animal (or human) behavior, using the activities from Lessons 1 and 2 as a starting point. o What aspects of the environment might influence behavior? Students may mention physical factors such as season, temperature, or time of day; biological factors such as nutrition or illness; or social factors such as behavior of conspecifics o How might genetics influence behavior? Students may mention the idea of heredity indirectly; e.g. similarities between behavior of parents and children. Why is it important for animals to respond to changes in the environment with changes in behavior? o Some environmental changes may represent an opportunity for the animal to gain something (more flowers in bloom mean more available nectar for bees to collect, presence of a queen bee is a chance for drones to mate and pass on their genes). o Other environmental changes may be hazards that the animal must avoid or address (confront or flee from predators, return to shelter to escape inclement weather). o In some cases, animals may respond by modifying their environment (some animals respond to approaching winter by creating dens or nests). How do changing seasons affect bee colonies? Remind students that insects are ectothermic, and that the hive s internal structure is made of wax. o In the winter, bees must maintain a minimum temperature inside the hive to avoid freezing to death. o In the summer, bees must protect the colony from extreme heat. Activity 1: Netlogo Hive Temperature Simulation Assemble students into small groups of 2-4. Ask them to complete the pre-reading individually, or as a group. Explain that they will be using a computer simulation to learn more about how bees respond to changes in environmental temperature. The simulation, and the data that groups collect from it, will 6

7 help them understand why the size of a colony (number of bees) is important for its survival in extreme temperatures. Groups will work together to come up with hypotheses for the two questions posed in the student worksheet, design experiments to test those hypotheses, and analyze the data that they collect. Teacher Pedagogical Knowledge Students can gain important experience through graphing by hand on graph paper, but it can also be valuable for students to gain experience using Excel or a similar program for graphing. Since students are already using computers for this activity, it may be convenient to have them enter their data into Excel. Students can then print their graphs to share with the class, or their data can easily be pasted into a single document and the class data plotted in one graph. The following resource may be a helpful guide for graphing the data from this activity in excel: Many others are also available online. Once students have completed their graphing, discuss the results as a class. Have each group describe their results in words, or have students share their graphs (ie by drawing them on overheads or on the board, or by shuffling students between groups). Give students time to answer questions on the final page of the student sheet and then discuss the data as a class: How did group size and environmental temperature affect hive temperature? o Lower environmental temperatures lower the hive temperature. o Hive temperature lowers more for smaller groups of bees. o Fewer bees have a harder time counteracting cold and warming the inside of the hive, although even the largest group of bees will experience some drop in temperature. Activity 2: Reading on Africanized bee invasion In this activity, students complete a reading that discusses the introduction to the Americas of a subspecies of honey bees, commonly referred to as Africanized or killer bees, that is adapted to tropical climates and can be more aggressive than subspecies adapted to temperate climates. Student Misconceptions Students may think of killer bees as insects that act as a predatory unit, hunting down prey. They may also overestimate the lethality or likelihood of an encounter with Africanized bees. Although Africanized bees are more easily aggravated than European bees, and have a more extreme aggressive response, they attack only in 7

8 response to a perceived threat to their nest site. In addition, mortality rates are low and result when individuals are allergic to bee venom (a condition not specific to stings from Africanized bees) or are unable to flee. Students may work alone or in groups of 2-4 to complete the reading, and to answer questions on the associated student sheet. These questions, as well as other questions and ideas that students have developed while reading, can then form the basis of a whole-class discussion. Possible discussion points include: Was the introduction of Africanized bees positive or negative overall? What types of evidence did the authors use to argue that Africanized and European bees can hybridize? Did all these types of evidence agree? How does the behavior of the Africanized and European bees provide evidence that appropriate behavioral responses to changing environmental temperature are influenced by genetics? Conclusion of Lesson What are some ways that temperature affects honey bee behavior? What are some ways that honey bee behavior changes the environment? o This could start with the context of the experiment, i.e. bee behavior changes the hive temperature, but then branch out to other examples: bees create a hive, pollinate plants, etc. How is homeostasis for a single organism similar to (or different from) homeostasis for a honey bee colony? What are other environmental factors that individual bees might need to respond to, to maintain homeostasis for the colony? o Disease: Remove diseased workers to prevent the spread of pathogens o Predators: must be attacked or removed o Rain/moisture: use plant material to block or patch holes o Colony population too large or small: colony divides in half to form a new colony/queen lays more eggs to produce more bees What are some direct and indirect ways that behavior was measured in the simulations used? How might gene expression act as a connection between hive temperature (or other environmental factors) and behavior? How might bees that have adapted to different areas of the world, or bees with different colony sizes, respond differently to changes in temperature? Homework and Assessments 8

9 The research question on the final page of the student sheet for the Africanized bee reading may be assigned as a homework project. Student sheets for both the Netlogo simulation, and this reading, may be collected as assessments. 9