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.
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.
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.
[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:
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The
Ecosystem