What Is a Phytolith?

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What Is a Phytolith?

• Unit 4 Activity 4.3
• Ginny King Brady
• bradyg_at_nscdiscovery.org

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Phytolith, n. A microfossil of a plant, created
by deposits of a mineral called silica in cell
walls. The silica remains after the plant dies,
forming a three-dimensional copy of the plants
cells. Paleobotanists studying such a copy can
recognize the kind of plant from which it came.
Most phytoliths are 10 to 100 microns long. (A
micron is one-millionth of a meter.)
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Purpose

• In this activity, you will use STRI scientist Dr.
  Dolores Pipernos methods and actual lakebed data
  to learn about Panamas past vegetation. You
  will then compare your results with Dr. Pipernos
  data and hypothesize about what youve discovered.

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Dolores PipernoStaff Scientist and CTPA
Director
Dr. Dolores Piperno, Director, Center for
Tropical Paleoecology and Archaeology
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Using Sediment Cores (Page 123)

• Long tubes 5 cm X 10 meters
• Sediment in lake bottoms
• Study core layers every 10 to 20 cm
• Radiocarbon dating

Lake La Yeguada
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Focus Questions

• How have people from different time periods used
  Panamas land resources?
• What methods do scientists use to examine
  Panamas past?
• How do humans affect tropical forests?

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Research Article (page 111)

• Dr. Dolores Piperno, a scientist at the
  Smithsonian Tropical Research Institute, is
  learning more about the farmers who began
  clearing the tropical forests to plant crops as
  early as 7000 years ago! She is researching what
  kind of crops they grew and where in tropical
  America they originated. She does this by
  searching lake sediments for tiny plant fossils
  called phytoliths.

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The Carbon Cycle
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The Marker Key

• What are the three main kinds of plant remains
  used to analyze land use and climate change?
• Phytoliths
• Pollen grains
• Particulate carbon

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Phytolith Magnolia

• A flowering tree now found in mountainous areas
  around Panama.

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Phytolith Chrysobalanaciae

• A family of trees now found in deep, lowland
  forests around Panama.

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Phytolith Trichomanes

• A fern now found in deep, lowland forests around
  Panama.

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Phytolith Podostemaceae

• A family of aquatic plants now found in lowland
  forests around Panama.

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Phytolith Heliconia

• A flowering herb that grows in deforested or
  burned areas

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Pollen Grain Oak (Quercus)

• A forest tree now found in mountainous areas
  around Panama.

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Pollen Grain Secondary Forest Trees

• These trees are the first to re-grow after
  original forest is cut down.

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Carbon Particle Charcoal

• Tiny piece of charcoal, indicating that
  vegetation in the area was burned.

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Hands-on Exercise

• Read Master F (page 123) and begin to examine
  your sample sediment core using the Marker Key.
• Separate out and identify all the markers in your
  sample.
• In paleobotany, a marker is something that
  suggests what kinds of climate and vegetation
  existed in the past.

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Next

• With a partner, record the number of each type of
  markers (seeds, grains, beans, and paper dots)
  on Master G.
• Create a bar graph for your sediment sample.

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Discuss with your partner

• What can you say about the land surrounding the
  lakebed when the sediments were forming?
• Write the answer on your graph.

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View the graphs on Master H

• What does the Y-axis show?
• The number of years before the present and the
  depth in centimeters at which the sample was
  taken.
• What does the X-axis show?
• The change in concentrations of each marker.

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• During what period were there mostly secondary
  growth forests?
• Magnolia and oak were at their peak between
  14,000 and 11,000 years ago a warmer, wetter
  climate less suitable for these species began
  about 11,000 years ago. Secondary growth was
  greatest 1,500 to 5,000 years ago.

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• When did particulate carbon first begin to appear
  in measurable quantities?
• About 11,000 years ago, when humans began using
  fire to clear land.

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• Why do you think heliconia was also abundant
  then?
• Heliconia was abundant 11,000 years ago, perhaps
  because it thrived in land deforested by humans.

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Cross-check with Graph on Master H

• In which time period would you place your
  sediment sample? Why?
• Within your group, create a model sediment core
  by pouring your sediments in to a 500 mL
  graduated cylinder in chronological order, with
  the oldest sediment at the bottom.
• Describe your sample as it is layered in the
  model core.

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More Questions

• If you had found starch grains from yams in a
  sample from 9000 years ago, what might you
  hypothesize about the area from which that sample
  came?
• It would be reasonable to hypothesize that the
  area was under cultivation.

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Conclusion

• What three types of plant remains do scientists
  use to study the plant history of an area, and
  what do they represent?
• Scientists use phytoliths, pollen grains, and
  charcoal dust (particulate carbon). Phytoliths
  and pollen grains mark past plant life.
  Particulate carbon marks the presence of burned
  areas.

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• What is a sediment core and how is it used?
• A sediment core is a cross-section of a lake-,
  stream-, or ocean-bed that is used to analyze
  what was present during different time periods.

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• Summarize what Dr. Pipernos data tells you about
  changes in the forest and human activity at Lake
  La Yeguada over this time period.
• The forest ecosystem changed from one
  characterized by cooler temperatures (today known
  as mountain forest) to one characterized by
  warmer temperatures (today known as lowland
  forest). Humans began to burn forest areas for
  hunting and gathering about 11,000 years ago.
  They began to farm about 9,000 to 8,000 years
  ago. The area was disturbed for thousands of
  years.

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Closure

• Reading from Jaguar by Roland Smith (pages 181
  186)
• Reflect on images described in this reading.
• Illustrate one of the images.
• Post your drawing on a mural.

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Multimedia use andJTO Integration

• Message Boards
• Chat Session with Scientist
• Earth Systems Digital Lab
• Carbon Cycle

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Novel Integration (page 127)

• Jaguar If a sediment core were taken of the lake
  bottom in the preserve, what information could it
  have provided?

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Standards and Assessments (page 108)

• Novice
• Apprentice
• Researcher

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Self Assessment (page 126)

• How Does Human Activity Influence Global Climate?
• Identified actions that might increase or
  decrease levels of carbon dioxide in the
  atmosphere.
• Identified carbon absorbers and carbon emitters.
• Yes
• No
• Not sure

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Teacher Preparation

• Pages 131 - 133

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Adaptations (page 132)

• Elementary
• If analyzing Dr. Pipernos data is too
  challenging, have students simply count the
  markers in their samples and help them to graph
  their own results. Then make a composite graph
  as a class for the entire core.
• High School
• After completing the exercise, have students
  write up a summary of what they think is
  happening during each 1000-year time period,
  using Dr. Pipernos graph.

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Key Skills

• Asking questions about how vegetation and climate
  have changed in an area over thousands of years.
• Collecting data on plant remains using a model
  sediment core.
• Analyzing graphical data from a paleobotanist and
  comparing them to data from a model.
• Explaining how plant remains, such as phytoliths,
  pollen, and particulate carbon, can be used to
  determine changing vegetation and land use.

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Credits

• Exploring the Environment http//www.cotf.edu/ete/
  modules/carbon/effig10_full.html
• Terry Ball's Phytolith Page http//reled2.byu.edu
  /ASCRIPT/TBall/index2.html
• Smithsonian Tropical Research Institute
  http//www.stri.org/Scientific_Staff/Piperno.html
  

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Sharing

• How could this activity be improved?
• Comments
• Questions

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Contact Holly

• hgarrett_at_cogeco.ca