Example of Using the Power of Story: Eastern Deciduous Forest- Lyme Disease, Masting & Gypsy Moths

Example of using the power of story: Eastern deciduous forest (For students in another region of the USA or world, it might be better to start with the ecosystem for which they are most familiar.)

Pre-assessment: Ask students to draw labeled boxes and arrows with adjacent phrases to illustrate the relationship of these organisms from an eastern deciduous forest (USA): gypsy moth, deer, white-footed mice, white oak, red oak, red maple, earthworm, thrush (songbird). The drawing is a concept map of a food web. It will be rather sparse at the outset. Students may add other entities if they wish. They should use lines to link entities, and add a descriptive phrase by the link. The students should keep a copy of every map generated in the course, as a record of their progress. Student reflection about their maps will be an important part of their learning.

5E cycle #1

Major concepts: Population growth, cycles and models

Running themes: evolution of ecosystems, human impact, introduced species, species (interspecific) interactions, life history traits

Engage phase, part 1:

Lyme disease (caused by a spirochete) was first discovered in 1977 in Connecticut. Lyme disease is transmitted by ticks, which normally use mice, small birds and deer as hosts. Lyme disease is now the most important vector-transmitted disease in the USA. What explains the sudden appearance of this disease and its spread?

List ideas of students on board or overhead transparency. Alternatively, post questions on Blackboard for students to consider before class, and have them submit ideas, which are then summarized by instructor. Re-visit these after mini-lecture.

Likely ideas from students but don't discuss answers yet: disease introduced from another country (no), tick has changed hosts or expanded its use of hosts (no), deer population has increased and greater proportion of deer carry ticks (well yes, but more complicated than that), spirochete increased its virulence (no).

Now provide a mini-lecture punctuated by questions about the relationship of Lyme disease, mice, deer, oaks, habitat fragmentation. See the outline for Eastern Deciduous Forest.

Re-visit the question and their answers. Ask students to articulate new answers. Then have them draw a concept map for spirochete relationship with hosts and vectors. Before they draw, explain/review "basics" about developing concept maps. Have students pair-and-share.4 Ask for a few pairs to say what they learned from the pair-and-share. Re-inforce basics of developing concept maps. Sample below is a "concept" template from Inspiration Software.

New Concept

Total class time ~ 20 minutes

Engage phase, part 2:

Nut-producing tree species often produce huge numbers of nuts periodically and then little or no nuts for several years and, often within and even among species to some extent, are synchronized. What are the advantages and disadvantages of these patterns for nut-producing species? And what causes these patterns?

List ideas of students on board or overhead transparency. Alternatively, post questions on Blackboard for students to consider before class, and have them submit ideas, which are them summarized by instructor. Re-visit these after mini-lecture.

Likely ideas from students but don't discuss answers yet:
Advantages? Satiating seed predators during masting and limiting predator populations during non-mast years, masting for taking advantage of favorable growing/reproductive conditions, masting for attracting seed dispersers [all may play a role]
Disadvantages? Attracting predators with masting, germination/establishment conditions might not be favorable after masting so loss of many offspring [all possible]
Causes for patterns/syncrhony? build up of stores for reproduction with weather both limiting and enhancing build up, and so triggering reproduction [likely]; defoliation cycles of insects [gypsy moth may have effect]

Now provide a mini-lecture punctuated by questions about the evolution and ecology of nuts and masting. See outline for Eastern Deciduous Forest. Re-visit the question and their answers. Ask students to articulate new answers.

Then have students draw a 3-panel concept map of the effect of masting and non-masting years on risk of Lyme disease, using the entities from the first map plus the spirochete. Submaps for: year 1 with masting in fall, then year 2 and year 3. Have students pair-and-share. Ask for a few pairs to say what they learned from the pair-and-share. A series of cycles using "cycles" template in Inspiration Software works well for this.

Event

 

Total class time ~ 20 minutes

Explore phase, part 1:

Gypsy moth exhibits population cycle with peak ~7-10 years, can go from 1 to 5,000 egg masses/hectare, eat 200+ woody species but prefer oaks, at peak defoliation widespread, and with successive years of defoliation up to 20% of trees may die. Not so much a problem in Europe and Asia. Why do populations cycle to widespread defoliation levels here? And what causes population to decline or crash?

List ideas from students on broad or overhead transparency. Alternatively, post questions on Blackboard for students to consider before class, and have them submit ideas, which are them summarized by instructor. Re-visit after mini-lecture.

Likely ideas from students: not right kind of predators and/or parasites here to control gypsy moth (no), gypsy moth destroys its food, so food needs time to recover (no), abundance of sum of predators and parasites out of sink with abundance of gypsy moth (not really, different predators/parasites provide control at low vs high densities of gypsy moth), cyclic climate patterns (no), some combination of these (not really)

Now provide a mini-lecture punctuated by questions about the relationship of gypsy moths, their hostplants (including food quality and masting), their predators, their parasites, climate. See outline for Eastern Deciduous Forest.

Re-visit the question and their answers. Ask students to articulate new answers. Then have them draw a time line of effects of gypsy moth population on populations of "community" of first map.

Total class time ~ 20 minutes

Explore phase, part 2:

Besides gypsy moths, there are many other accidentally introduced insect herbivores in North American forests. That Europe and North America were once joined predisposes them to successful interchange of insect herbivores. But why have European insects been 100 times more successful at invasion into North America than vice versa?

List ideas from students on broad or overhead transparency. Alternatively, post questions on Blackboard for students to consider before class, and have them submit ideas, which are them summarized by instructor. Re-visit after mini-lecture.

Likely ideas from students: mismatch between insects and their enemies greater in North America (no), mismatch between insects and hostplants greater in Europe (okay, but why?), mismatch between insects and climate greater in Europe (okay, but why?), insects from Europe are better competitors (okay, but why?)

Now provide a mini-lecture punctuated by questions. List hypotheses, and evidence for each. In a chart, assign a probability or percent for each hypothesis/explanation's contribution to the skewed proportion of invasion into North America. Reflecting on the probability chart, discuss whether this is still a concern and, if so, what is/are the most reasonable course(s) of action? Ask students how they think this might play out for entire food web (to degree developed at this point). Looking for reasonable arguments. List additional ecological concepts to date. Ask for clarifications and/or examples.

[Hypotheses:5

General category 1: Number invaders going in any direction proportional to size of conduits of passage – can't examine because not enough quality data but probably not major factor

General category 2: Number invaders reflects fundamental differences in number species available for dispersal from donor continent – insect fauna estimated to be same size, so not factor

General category 3: Number successful invaders determined by ecological opportunities at arrival – major factor

a) Potential host plant species (taxonomically or chemically related), their abundance, morphological, ecological and phenological similarity to native hosts
b) In NA, larger number of potential host plants (north of 35o, 2x more tree species due to less extinction during glaciation due to north-south mountains rather than east-west), greater abundance (tree abundance 2x greater), less fragmented distribution than in Europe (with longer and intense disturbance by humans)
c) Abundant alien plants from Europe (30-60% during early succession) facilitates establishment by European insects

General category 4: Invaders are intrinsically competitively superior than natives – major factor
a) Since Alps, European biota more severely impacted than any other by cyclical severe climate changes driven by Earth's orbital fluctuations (e.g., glaciation from north and glaciers in east-west mountains left little refuge for plants and animals, and created aridity in southern Europe
b) Since last 10,000 years humans with invention of agriculture disrupted and even wholly eliminated many ecosystems in Europe
c) Selects for suite of traits that facilitate survival in patchy, fragmented, impoverished forests: high behavioral, morphological and physiological plasticity; uniparental reproduction (parthenogenesis) (40% of intro insects on woody plants compared to 11% native insects), large reproductive potential, auto- and alloploidy, strong dispersal capability, efficacy in dealing with competitiors, predators and parasites, special stress tolerance such as extended dormancy
d) Rapid and perfect synchronization of invader's life cycle to that of new environment and hosts, insects coming from 50o to 40o latitude (northern Europe to New England) no problem, but other direction is problem because summer day length in northern Europe too long to trigger diapause for a New England adapted insect ]

Total class time ~ 20 minutes

Explain phase:

Briefly discuss or review what insight population growth models can provide. Briefly discuss or review population cycles and lag effects. Ask students to review their concept maps to date to identify where population growth and population cycles are important. [Everywhere, but they need to explain.] Discuss carrying capacity and ask what it is for the species discussed so far. [Carrying capacity is not a constant.]

Ask students to list other ecological concepts involved (so far) in this "story"; ask for definition and example. Then have them draw a concept map of the hierarchy of all of these concepts. [There is no one or right answer. Mapping shows individual perception. What is important is that students have this practice and develop reasonable linking and sufficient complexity.]

Explain how to use standard criteria for evaluating such a "map". Have students either self-evaluate or as pairs evaluate each others' maps. Briefly discuss the evaluation (what students learned from it, what worked well, what didn't). This is a training session, so worth some time to ensure that students do it well.

Total class time ~ 55 minutes

Elaborate phase:

Pre-colonial northeastern forests were dominated by oaks and chestnut. Chestnut was wiped out by an Asian blight, and so the oaks have dominated until recently. Now red maple is taking over as a dominant. What explains this change?

List ideas from students on broad or overhead transparency. Alternatively, post questions on Blackboard for students to consider before class, and have them submit ideas, which are then summarized by instructor. Re-visit after mini-lecture.

Likely ideas from students, but do not comment on these: oaks dying from introduced insect pests and/or disease (no), oaks logged preferentially (no), abandoned agricultural land colonized by red maple before oaks (in part yes), gypsy moths defoliating oaks (in part yes), climate change (may be)

Now provide a mini-lecture punctuated by questions about the evolution of eastern deciduous forest during Pleistocene to present, role of seed predators, fire, gypsy moths, climate change.

Re-visit the question and their answers. Ask students to articulate new answers. List new concepts. Then have them draw a time line showing the dominant vegetation for the area that is now eastern deciduous forest, from 16,000 years ago through present to 100 years into future. Have students pair-and-share. Ask for a few pairs to say what they learned from the pair-and-share.

Total class time ~ 25 minutes

Evaluation phase:

Birds reduce densities of leaf-eating insect herbivores in forests. Birds by eating leaf-feeding insect herbivores increase growth of trees. Songbirds (many of which are insectivores) are vanishing from North America. Why?

Options for evaluation: Post-assessment, plus #1 or #1 & 2

Students read Terborgh6 article (on reserve; our library has "electronic reserve").

1) Application via identification of hypotheses, analyses and conclusions.

a) Answer set of questions, as pair-and-share, homework or essay exam: Concisely state each hypothesis given for why songbirds are vanishing from North America. Summarize the critical evidence for the hypothesis. Concisely state the conclusion drawn by the author for the likelihood of that hypothesis explaining why songbirds are vanishing. In a chart, assign a probability or percent for each hypothesis/explanation's contribution to the vanishing of songbirds. Based on your probability chart, what is/are the most reasonable course(s) of action? Does your analysis agree with the author's? Explain why or why not? List three things you would ask the author if you had the opportunity.

b) Alternatively, this work can be done by constructing a concept map ("problem solving" template from Inspiration Software works well) in class or outside class, or filling out a concept map form on a multiple choice exam.

Problem graphic

[The article provides several hypotheses and outlines the evidence. The author provides his conclusions but does not rank the hypotheses or give percent contribution to the problem. So students will have to assess that and sufficient information is provided for that. Reasonable ranking and appropriate rationale are the goals. The author provides some ideas about course of action; again students need to articulate well an appropriate rationale with sufficient and well-chosen detail. The list of questions for the author should reflect a clear and sophisticated understanding of the problem. It is appropriate to tell students these things before this assignment.]

2) Quiz or exam on concepts and application/identification of examples. Identify ecological concepts already discussed and provide an example from the article for each. Individual or individual-then-group quiz (the latter is a proven method that promotes both individual learning and teamwork).7

Total class time: typically a full class period

Post-assessment:

Outside of class, have students re-draw their concept map-food web for eastern deciduous forest. It will be quite complicated now. Students should use sub-maps (e.g., spirochetes on major map should refer to a submap to show host-vector cycle). There is no best way to do this and students can (and should) use their creativity (e.g., using colors to distinguish concepts from facts, transparent overlays, thematic series of maps, powerpoint features). The instructor, and/or student (self-evaluation) and/or student group can evaluate using standard criteria.3 Students should keep the set of maps developed in this series (from beginning to end) in a portfolio and asked to reflect on these either at this time or at end of course.

Total course time for this 5E cycle: ~ two weeks


Examples of how to implement the power of story:

Eastern deciduous forest: Lyme disease, masting, and gypsy moths
Eastern deciduous forest: Mutualisms and nutrient cycling
Outlines for Eastern deciduous forest material
References for Power of Story examples
Sample concept maps

 

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Last Updated: 1/28/15