Florida Scrub-jay Population Dynamics: Limiting Factors in the Scrub

Transcription

1 Lesson 3.2 Florida Scrub-jay Population Dynamics: Limiting Factors in the Scrub Adapted for the Florida scrub from The Ups and Downs of Populations at SCIENCE4INQUIRY.com To the Teacher The Florida scrub-jay is endangered and as of the early 1990s, the total population was estimated at about 4,000 pairs, a likely reduction of more than 90% from original numbers. Loss of habitat is the main problem. Additionally, as the Florida oak scrub is maintained by occasional fires, fire prevention has added to the effect of ongoing development. [1] Within the context of the oak scrub ecosystem, students will analyze the population dynamics of the Florida scrub-jay. Students will analyze population graphs, collect data to generate their own population graph, and experience limiting factors and their impact on carrying capacity in a scrub-jay population. Students will be able to identify, explain, and evaluate the impact that different limiting factors have on the population of organisms including food, shelter, predation, human interference, changes in birth and death rate, changes in immigration and emigration, disease, and reproduction. [2] References 1. Audubon. (n.d.). Florida scrub-jay. Retrieved from 2. Miller, H. (2016). The ups and downs of populations. Retrieved from smsfinal.pdf Objectives Students should be able to do the following: 1. Analyze how population size is determined by limiting factors (biotic and abiotic) that determine carrying capacity. 2. Refine their positions on the issue of saving endangered species, whatever the cost. 1

2 Time Needed Two 50-minute class periods Materials Ecosystem Dynamics and Interconnectedness of Living Things Materials per class o Computer with projector o Class set of Lesson 3.2 Science Notebook Template o Class set of Assessment Items Materials per pair or group o Copy of Population Graphs o Set of Carrying Capacity Cards, cut and placed in envelope o Copy of Scrub-Jay Survival Game o Online searchable device (BYOD) Materials per student o Science notebook or journal o Sentence Stems for Civil Discourse card from Unit 1 Procedure Advance Preparation 1. Before students arrive, arrange seating for collaborative groups of three to four students. 2. Pre-determine lab roles. 3. Print and cut population cards, per group, and place them in envelopes. Engage Population Graphs 1. Distribute copies of the Population Graphs to student pairs or groups. 2. Prompt students to look at the patterns in the two different graphs and to predict what they think could account for the differences between the two populations. 3. Allow for collaboration time and then randomly call on students to respond. Ask probing questions as misconceptions are revealed. See below for background information. Florida Scrub-jay: The Florida scrub-jay declined due to habitat destruction, degradation and fragmentation by agricultural conversion, development and disruption of natural fire regimes. Fire suppression caused increased shrub/tree encroachment and canopy closure. The bird's population declined from an estimated 27,000 breeding pairs in pre-settlement times to 13,800 by the late 1880s, then to about 6,000 when it was listed as endangered in It continued to decline to 4,000 in 1993 and 3,000 in [1] 2

3 Sample Population: When resources are limited, populations exhibit logistic growth. Initially, growth is exponential, because there are few individuals and ample resources available. As resources ben to become limited, the growth rate decreases. Ultimately, growth levels off at the carrying capacity of the environment with little change in the population over time. 4. In preparation for the exploration, instruct student pairs or groups to research the following questions (BYOD). (5-10 minutes) What do Florida scrub-jays need to survive? What interferes with Florida scrub jays survival? 5. Instruct students to choose one factor that limits the growth of scrub-jay populations and to complete the following hypothesis: If a population experiences then it will, because. Example: If a population experiences (a lack of water, an abundance of food, a lack of mates, habitat destruction, etc), then it will (increase, decrease, stay the same) because (scrub-jays need to have access to a consistent food supply to sustain a healthy weight, scrub-jays need to reproduce to maintain the population, the scrub-jays need a specific habitat to survive, etc). Remind students that there are no right or wrong answers and that the importance lies in the explanation of their reasoning. Note that the skills inherent to civil discourse must be practiced and that consistent and intentional use of the Unit 1 sentence stems is crucial throughout the year. Explore Scrub-jay Survival Game 1. Distribute a copy of the Scrub-jay Survival Game sheet to student pairs or groups and assign lab roles. 2. Explain to students that they will conduct their own population study with a population of 100 Florida They will be exposing their scrub-jays to factors that they commonly encounter in their natural ecosystem and will be evaluating how it impacts the scrub-jay population. 3. Instruct students to follow the directions on the game sheet. 4. Circulate while students are working, asking probing questions such as the following. Which factor(s) has/have had the most dramatic effect on your population so far? What is the highest your population has reached so far? Have you picked any cards that have surprised you? Explain Scrub-jay Survival Prompt students to use their data and graphs to respond to the following items. Items are listed on the Lesson 3.2 Science Notebook Template. Allow time for thinking, writing, and collaboration before randomly calling on students. 3

4 1. Give an overall description of your data and graph. Explain what factors accounted for the major increases or decreases in your population. Student responses will vary based on their graphs. Students should be able to identify what caused the increases and decreases in their population of 2. Based on the cards that you chose and in reference to your data table, what do you think a limiting factor is? Student responses should indicate that a limiting factor is anything in an organism s environment that can have a positive or negative impact on its population size. 3. Biotic factors are all of the living things in an ecosystem. What are some of the biotic limiting factors in the scrub-jay s ecosystem? Acorns, caterpillars, snakes, hawks, mates, shelter (if brush), blue jays, orange groves, and humans. Students may have additional responses that are correct as long as they are LIVING things. 4. Abiotic factors are all of the non-living things in an ecosystem. What are some of the abiotic limiting factors in the scrub-jay population? Water, air, cars, land development (buildings), lightning, and fire. Students may have additional responses that are correct as long as they are NON-LIVING things 5. Choose two limiting factors that had a positive effect on your population and explain why they had an impact on your population. Food, water, fire, shelter, mates, and more females than males all had a positive impact on the population. These allowed the scrub-jay to be healthy and reproduce which increased their numbers. 6. Choose two limiting factors that had a negative effect on your population and explain why they had an impact on your population. Predators, too many males, land development, humans, blue jays, and car traffic all had a negative impact on the population. These factors caused death or heightened competition which led to a decrease in numbers. 7. Carrying capacity is the maximum number of organisms that an ecosystem can support. Looking at your data table and graph, what would you predict is the carrying capacity for your ecosystem? Explain. Student responses will vary depending on their data and graphs. The carrying capacity should be represented somewhere around their maximum population. Once scrub-jays reach a certain population size, the resources in their ecosystem become stretched too thin amongst the birds and birds begin dying or are not born. 8. How is your graph similar to or different from the graph of another group? Student responses will vary depending on their graph and the graph they choose for comparison. 9. According to your data, was your hypothesis correct? Explain why or why not. 10. Scientific models are used to explain and predict the behavior of real objects or systems. Do you think you created a realistic graphical model of Florida Scrub-jay population growth? Explain why or why not. Although modeling is a central component of modern science, scientific models are, at best, approximations of the objects and systems that they represent they are not exact replicas. Thus, scientists constantly are working to improve and refine models. [2] 4

5 Elaborate Simulated Population 1. Refer students to the Elaborate section of the Lesson 3.2 Science Notebook Template. 2. Remind them that they now know about Florida scrub-jays and the limiting factors that affect their population sizes. Prompt them to think about one of their favorite animal species and what might affect its population sizes. Explain that they will be creating a simulated population study of the animal based on a little research and their knowledge of limiting factors. (BYOD) 3. Prompt students to record the name of their animal species and to construct a table including biotic factors, abiotic factors, factors that will increase the population, and factors that will decrease the population. Student tables will vary, depending on their chosen animal species. 4. Refer students to the Animal Species Population Graph. Imagining that the graph represents the population growth of their animal species, instruct them to explain the graph in terms of what caused the changes in the population fluctuations (increases, decreases, etc.). In general, graph explanations should state something along the lines of the population was relatively stable from In 1995 there was a huge jump in numbers. This could be due to available resources that year like excessive food, water, shelter, or mates. Beginning in about 2000, the population stabilized, with a relatively small dip in The dip may be due to unavailability of the same or other resources. In the end, the population appears to return to the stable population, which we can assume is near its carrying capacity. References 1. Center for Biological Diversity. (2016). Endangered bird trends: Florida scrub-jay. Retrieved from 2. Rogers, K. (2017). Scientific modeling. Encyclopedia Britannica. Retrieved from Closure Elaborate Refine Vote: Students have explored the population growth of the Florida scrub-jay, a threatened species, and found that limiting factors include those imposed by humans. Instruct students to readdress the unit question: Should we save endangered species, whatever the cost? Allow time for students to adjust their previous votes, with regard to the unit question by moving one of the sticky notes from yes to no or vice versa if so desired. Make note of any shifts or trends in student voting. Ask the question, Have you changed your vote? Why or why not? Randomly call on students to respond. Remind them that there are no right or wrong answers, all comments will be respected, and open-mindedness will be practiced. 5

6 Assessment Ecosystem Dynamics and Interconnectedness of Living Things Evaluate Students are monitored and assessed on mastery based on their participation in small group and class discussions. This formative assessment is ongoing in order to continually reveal misconceptions and to appropriately redirect instruction and questioning, so that the misconceptions are confronted in a constructive manner. Student accountability is additionally maintained through notebook checks. Note that intentional probing questions throughout the lesson are key not only to formative assessment, but to student s confrontation of misconceptions. 6

7 What do you think could account for the differences in the trends of the two populations? Pay close attention to the features of the graphs. The title, axes labels, and units will provide more clues than studying the lines alone. Ecosystem Dynamics and Interconnectedness of Living Things Population Graphs Credit: Center for Biological Diversity, Endangered Bird Trends: Florida Scrub-jay. Retrieved from Credit: Drawn by Lesson Writer 7

8 Scrub-jay Survival Game Problem: How is population size affected by different environmental factors? You will be conducting your own population study with a population size of 100 Florida You will be exposing your scrub-jays to factors that they commonly encounter in their natural ecosystems and will be evaluating how it impacts their population. Explore 1. Draw one card out of the envelope at a time. 2. Read what the card says and record the results on your data table. For example, if the card says that aliens have invaded and have killed 10 scrub-jays, subtract 10 scrub-jays from your population, record the new number of scrub-jays in your population, and then carry the new number into the row below for the next turn. Population Limiting Factor Effect on Population New Population 100 Aliens invaded DO NOT put the card back in the envelope. 4. Draw the next card and continue drawing and recording data until you have drawn 20 cards and completed the 20 trials. 5. When you are finished with the trials, put all cards back in the envelope. 6. Graph your data on a separate sheet of graph paper. 8

9 Carrying Capacity Cards A subdivision is developed in your Florida scrub. 25 scrub-jays die as a result. There has not been a lightning fire in many years and a tall pine forest divides your lowlaying scrub habitat. Half of your current population dies. A new family of indigo snakes is living in your area and eats 5 scrub-jays in your population. Credit: Credit: A new family of indigo snakes is living in your area and eats 5 scrub-jays in your population. Credit: You share hour habitat with the Cooper s hawk and it is your predator. 5 scrub-jays in your population die to feed the hawks You share hour habitat with the Cooper s hawk and it is your predator. 5 scrub-jays in your population die to feed the hawks. Credit: Credit: Credit: You share hour habitat with the Cooper s hawk and it is your predator. 5 scrub-jays in your population die to feed the hawks. You share hour habitat with the Cooper s hawk and it is your predator. 5 scrub-jays in your population die to feed the hawks. A blue jay family has moved into the scrub and is limiting your use of the habitat. 5 birds in your population die as a result. Credit: Credit: Credit: 9

10 There are too many males in your population and not enough females. Decrease your population by 20 There are more females in your population and most are of reproductive age. Increase your population by 20 A citrus grove is developed, separating your population. Decrease your population by 20 Credit: Credit: Credit: YOU FOUND SHELTER! YOU FOUND SHELTER! YOU FOUND SHELTER! Credit: Credit: Credit: YOU FOUND SHELTER! YOU FOUND SCRUB OAK ACORNS FOR FOOD! You bury these in the sand to eat in the winter and fall. YOU FOUND SCRUB OAK ACORNS FOR FOOD! You bury these in the sand to eat in the winter and fall. Credit: Credit: Credit: 10

11 A blue jay family has moved into the scrub and is limiting your use of the habitat. 5 birds in your population die as a result. Humans in your area are feeding your population by hand. As a result, members of your population are reproducing earlier in the year and their fledglings are not able to find caterpillars that are present only in the late spring and summer. 10 scrub-jays die of starvation. Humans in your area are feeding your population by hand. As a result, members of your population are reproducing earlier in the year and their fledglings are not able to find caterpillars that are present only in the late spring and summer. 10 scrub-jays die of starvation. Credit: Your fledglings disappeared and are no longer available to help you to raise the young. Decrease your scrub-jay population by 5. Credit: Your fledglings disappeared and are no longer available to help you to raise the young. Decrease your scrub-jay population by 5. Credit: There is a highway near your habitat that your population often crosses. Many are hit by passing cars. Decrease your scrub-jay population by 10. Credit: Credit: Credit: YOU FOUND WATER! YOU FOUND WATER! YOU FOUND SHELTER! Credit: Credit: Credit: 11

12 YOU FOUND SCRUB OAK ACORNS! You bury these in the sand to eat in the winter and fall. YOU FOUND SCRUB OAK ACORNS! You bury these in the sand to eat in the winter and fall. YOU FOUND SCRUB OAK ACORNS! You bury these in the sand to eat in the winter and fall. Credit: Credit: Credit: YOUR FLEDGLINGS FOUND GRASSHOPPER LARVAE! They cannot chew the hard acorns. YOUR FLEDGLINGS FOUND GRASSHOPPER LARVAE! They cannot chew the hard acorns. YOUR FLEDGLINGS FOUND GRASSHOPPER LARVAE! They cannot chew the hard acorns. Credit: Credit: Credit: YOU FOUND A MATE! Increase your population by 5 YOU FOUND A MATE! Increase your population by 5 YOU FOUND A MATE! Increase your population by 5 Credit: Credit: Credit: 12

13 Lesson 3.2 Science Notebook Template Engage Population Graphs Discuss the provided graphs with your partner or group and respond to each of the following in your Science Notebook. 1. What do you think could account for the differences in the trends of the populations of the Florida scrub-jay and the sample population? 2. What do Florida scrub-jays need to survive? (BYOD) 3. What interferes with Florida scrub jays survival? (BYOD) 4. Choose one factor that limits the growth of scrub-jay populations and complete the following hypothesis: If a population experiences then it will, because. Explore Scrub-Jay Survival Game Copy the following table in your science notebook. Follow the steps on the Scrub-jay Survival Game sheet to complete the table. Turn Population Size (Number of scrub-jays) Limiting Factor Effect on Population New Population Size (number of scrub-jays

14 Graph your data on a half sheet of graph paper. Explain Use your data and graph to answer the following questions. 11. Give an overall description of your data and graph. Explain what factors accounted for the major increases or decreases in your population 12. Based on the cards that you chose, and using your data table as reference, what do you think a limiting factor is? 13. Biotic factors are all of the living things in an ecosystem. What are some of the biotic limiting factors in the scrub-jay s ecosystem? 14. Abiotic factors are all of the non-living things in an ecosystem. What are some of the abiotic limiting factors in the scrub-jays population? 15. Choose two limiting factors that had a positive effect on your population and explain why they had an impact on your population. 16. Choose two limiting factors that had a negative effect on your population and explain why they had an impact on your population. 17. Carrying capacity is the maximum number of organisms that an ecosystem can support. Looking at your data table and graph, what would you predict is the carrying capacity for your ecosystem? Explain. 18. How is your graph similar to or different from the graph of another group? 19. According to your data, was your hypothesis correct? Explain why or why not. 20. Scientific models are used to explain and predict the behaviors of real objects or systems. Do you think that you created a realistic graphical model of Florida scrub-jay population growth? Why or why not. 14

15 Elaborate Simulated Population Now that you know a little about Florida scrub-jays and limiting factors that affect their population sizes, think about one of your favorite animal species and what might affect its population sizes. You will be creating a simulated population study of your animal species based on a little research and your knowledge of limiting factors. Record the following information in your Science Notebook. Animal Species: Biotic Factors Abiotic Factors Factors that will increase the population Factors that will decrease the population The graph below represents your organism s population and its change over time. Explain the graph in terms of what caused the changes in the population fluctuations (increases, decreases, etc.) for your animal species. Animal Species Population Graph Credit: CC BY-NC-SA 4.0 Elaborate Refine Vote Refine Your Vote: You have explored the population growth of the Florida scrub-jay, a threatened species, and found that limiting factors include those imposed by humans. Readdress the unit question: Should we save endangered species, whatever the cost? 15