ACTIVITY
Pollen Puzzle
Materials
For each team of 3 students:
 Student worksheet, Pollen Puzzle – one per student
 Team Kit – see Instructions for Assembling Pollen Puzzle Materials
 3 laminated Pollen-Climate Keys
For the teacher:
 PowerPoint Presentation, Pollen Puzzle
 Answer Key for Student Worksheet, Pollen Puzzle
 Model of “Sediment Core” – see Instructions for Assembling Pollen
Puzzle Materials
Instructional
Strategies
1. Extensive explanatory notes accompany the PowerPoint Slides
2. Slide 2: Because they are not mobile, plants, their adaptations for climate
conditions, and plant communities are excellent indicators of climate and can
provide evidence in several ways. When the first bulleted item appears, ask the
students to recall the definition of a biome, before displaying the second bulleted
item, which defines biomes. Note that the climate is an integral part of the
definition of a biome, as are the plants adapted for a biome’s physical conditions.
Slide 3 asks the students for examples of biomes.
3. Slide 4 reviews/discusses the relationships among plant communities, biomes,
and climate change.
4. Slides 5 & 6 provide a hypothetical modern example of how plant communities
and biomes reflect a change in climate.
5. Slide 7 reviews the fundamental geologic Principle of Uniformitarianism – “the
present is the key to the past”. So the relationships among plant communities,
biomes, and climate can also be applied to fossil plants and plant communities.
6. Slides 8 & 9 illustrate this relationship in some fossil plant communities.
The upper left photo in Slide 8 shows a coal mine in the Netherlands where many
well-preserved plant fossils were found. (If you are using this lesson for an earth
science class, ask the students why one would expect to find numerous plant
fossils in coal beds & the associated rocks. Also point out the enormous size of
the mining machinery, compared to the two adult men.)
Point out that there are two rock layers evident in the photo – an older, darker
layer on the bottom, and a younger, lighter yellowish layer on the top. (For earth
science students, ask them what geologic principle suggests that the layer on the
bottom is older – Principle of Superposition.)
Note that the plant fossils are so perfectly preserved that one could almost
mistake them for modern fallen leaves glued to a piece of rock.
Palaeobotanists (scientists who study fossils plants & plant communities)
identified the plant species in Slide 8 as a community representative of a Subtropical Deciduous Forest biome – a somewhat warmer climate than Central
Virginia, more like Northern Florida or Gulf Coast areas.
The plant fossils in Slide 9 should look familiar to many students in Central
Virginia because they are almost identical to many leaves that students see on
the ground each autumn – not surprising, since these ancient plant species
represent the same biome as that in modern Central Virginia, Temperate
Deciduous Forest.
So the change in plant communities and biomes from Subtropical Deciduous
Forest in the older rocks to Temperate Deciduous Forest in the younger rocks
represents a cooling of climate during the time in the past that these layers were
deposited.
7. Slide 10 discusses why pollen is generally more useful than actual plant fossils in
studies of biomes and climate conditions. (Students are asked what the special
conditions are for plants to be preserved as fossils.)
8. Slide 11 is a photomicrograph of actual pollen grains, with size/scale indicated.
9. Slide 13 and its notes discuss how pollen from ice cores is used in climate
studies.
10. Slide 14 illustrates how pollen accumulating in layers of mud on a lake bottom can
record changes in biomes/climate, and how a the pollen extracted from a core of
this mud can be used to determine the climate trend during the time the mud
layers were deposited. The slide also reviews the Principle of Superposition and
its importance in pollen core studies.
11. Slide 15 uses a Play-Doh model to illustrate the use of a plastic pipe to obtain a
core of soft sediment. The photo at lower left shows scientists in southern
Mississippi doing this to obtain a sediment core.
12. Slides 16 and 17: Explain that students will use pollen analysis to determine
climate trends over 10,000 years, for an area in the southern Rocky Mountains
(based on actual data). They will do everything a palynologist does except
manipulate the excruciatingly tiny pollen grains under a microscope (which might
require weeks or months) – there is a substitute for the actual grains, i.e. foam
dots color coded to represent plant species. The map shows the location of the
lake.
13. Why the southern Rockies? Slide 18 introduces the concept that because of the
great variation in elevation, a single very high mountain commonly encompasses
several biomes from its peak to its base, and thus by using lake sediment cores
from such a mountain, scientists can observe several different biomes & their
shifts over time within a relatively small geographic area.
14. Slides 19-22 illustrate and describe the 3 major biomes present in the southern
Rocky Mountains along with the timberline. The illustration and descriptions are
important in the upcoming activity. Emphasize to the students that, although
they may not have encountered these biome names before, these are the
proper names to use for the Rocky Mountain biomes as they complete the
activity.
15. Slide 23 & 24 illustrate how climate changes in the area of a tall mountain in the
Southern Rockies would be reflected in the biomes & associated vegetation, in
the first instance if climate becomes colder, and in the second case if climate
becomes warmer. The X represents the location of a lake where sediment layers
are accumulating. Emphasize to the students that the lake does not move!!!
The biomes shift their location and extent on the mountain!!!
16. Slide 25 is a diagram of the sediment core from Black Hawk, indicating the
numbers assigned to each layer and the age of each layer. If you would like to
accompany the slide with a physical model to represent the core, construct the
model as detailed in the Instructions for Assembling Pollen Puzzle Materials.
17. Instructions for Activity
During the activity Slide 26 should remain projected on the screen, so that the
teams can consult it while they work on their pollen analysis.
For this activity, each team of 3 students will use the Pollen-Climate ID
Keys (photo credits), the white paper plates, the tweezers/forceps, and the three
“core samples” in the small plastic portion cups.
Instructions for the activity are included on the student worksheet. In the first part
of the activity, individual teams complete a pollen analysis for the core layer
samples they have been given. Each student on a team works with one of the
sediment samples. Each person should:
1)
2)
3)
4)
5)
Note the number of the sediment layer, on the label on the portion cup lid.
Dump the sediment sample onto the paper plate, and use the
forceps to sort through the sediment & separate the “pollen grains”.
On the paper plate, sort the pollen into piles by color.
Identify the plant species represented in the sediment layer by matching
the color of each pile of “grains” to the corresponding color on the PollenClimate ID Key (which is double-sided).
6) In the Pollen Analysis table on the Student Worksheet, find the column
corresponding to the sediment layer number, and, for that layer, record
the number of pollen grains for each plant species present in the sample.
7) Using the Climate Characteristics descriptions (on the Pollen-Climate
Key) for the species present in the sample, determine the likely biome at
the time the sediment was formed, and record the name of this biome for
the sediment layer in the appropriate row in the Biomes vs. Sediment Age
table.
8) Team members share and combine data from the two tables.
18. After all teams have completed the pollen analyses of their sediment samples,
proceed with the second part of the activity: data synthesis & summary,
conclusions, and class discussion. This part works well as a group activity.
.
19. Have teams answer and discuss Questions 5-7: What was/were the observed
climate trend(s)? What might have caused the observed trends or changes? Do
you have enough data from just one lake sediment core to generalize your
conclusions? What additional data might you need to confirm the possible trends
& causes?
As suggested in its wording, Question 6 may be somewhat difficult or obscure for
some students, depending on their grade level and classes they have taken.
Encourage them to make a reasonable guess based on their observations. Many
will respond “ice age”. Show and explain Slide 27 to the class. Possible cause
for the Little Ice Age are still debated. A series of volcanic eruptions has been
proposed, or a period of extreme sunspot activity. A limitation of these
hypotheses is the persistence of the cold trend over approximately 2.5 centuries.
Researchers from Stanford University recently proposed that reforestation of
agricultural land in the Americas following indigenous population collapse, due to
pandemics imported by European settlement, could have caused sufficient carbon
sequestration to trigger a period of global cooling (see
http://news.stanford.edu/pr/2008/pr-manvleaf-010709.html ). A scientist from the
University of Colorado recently proposed that a long series of volcanic eruptions
extending from the 1200s to the mid-1800s was responsible. There are still many
questions involving these two more recent proposed hypotheses.
20. Following discussion of the activity, show students Slide 28, an animation which
illustrates a pollen-climate study conducted from sediment cores in Glacier
National Park in Montana, for the years 1850-2000, and projecting to 2100 a
predicted pattern of changes in plant communities if the present day warming
climate trend continues at its current rate. Although the information is rather
detailed and the animation moves rapidly, the animation loops, and there are two
prominent patterns that students can observe: (1) Have them watch what
happens to the white color (which represents glaciers) as the animation proceeds
– by 2010 the glaciers for which the park is named have nearly disappeared, and
in the projected scenario to 2100 they vanish entirely. (2) Have them observe
what happens to the bright green, representing warmer climate grassland, as the
animation proceeds. This plant community/biome spreads farther upslope and
becomes much more extensive as the warming trend continues. In addition,
warmer climate plant communities encroach into the high elevation areas that
were previously rock & ice.