Hypothesis Helper
17
Copyright 2009
description
Hypothesis Helper. An important process interconnected with Earth’s climate history is …. PLATE TECTONICS. Pangaea. Modern Continents. Animation courtesy of U.S. Geological Survey. EARLY SCIENTIFIC HYPOTHESIS - “CONTINENTAL DRIFT”. Glossopteris Fossil. - PowerPoint PPT Presentation
Transcript of Hypothesis Helper
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An important process interconnected with
Earth’s climate history is …
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PLATE TECTONICS
Pangaea Modern Continents
Animation courtesy of U.S. Geological Survey
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Glossopteris FossilPhoto courtesy of U.S. Geological Survey
EARLY SCIENTIFIC HYPOTHESIS - “CONTINENTAL DRIFT”
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Hypothesis : Glossopteris areas were once close together but then
broke apart & moved to the continents’ current positions.
Illustration credit: Peter Bockman
Distribution of Glossopteris plant fossils in Permian (250-299 mybp)
rocks(mybp = million years before
present)
But how do we know this is true?
Are there other possible explanations and
hypothesesfor finding this fossil
plant on widely separated continents?
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Let’s think about this …ACTIVITY 1: Hypothesis Helper
Which of the five species (if any) might provide the
best evidence for tectonic plate
movement?
Which species could have spread between Africa &
South America only if those continents were
once connected?
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Not the species that could have reproduced across the
ocean …
NOPE!
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… but the species that could have spread only on continuous
land which later broke apart
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A - Large triangular leaves; berries commonly
eaten by migratory animals B - Short, narrow, oval leaves; produces fewseeds, reproduces mainly by stolons C - Small thin feathery leaves; large seeds havespongy outer cover, allowing seeds to float andtravel easily in either fresh or salt water D - Thrives in swampy or watery environments;very large, heavy seeds sink and lodge inbottom sedimentsE - Long thin leaves; small fluffy seeds easilycarried by wind
stolons
WOOHOO!You have used ancient plants’ adaptations for reproduction & seed
dispersal (seed transport) to test a hypothesis about tectonic plate
movements!
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HOW DO THE SCIENTISTS KNOW SO MUCH ABOUT THEM?
IF THOSE PLANTS ARE FOSSILS &
ANCIENT & PROBABLY EVEN
EXTINCT …
WHOA!JUST A
SECOND!
I HAVE A QUESTION!
Earth processes that operated in the past are similar to those operating today.
“The present is the key to the past.”
PRINCIPLE OF UNIFORMITARIANISM
(UNIFORMITY)
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So earth scientists study modernvolcanoes to understand ancientvolcanic rocks … And modern rivers, glaciers, deserts,& coastlines and their sediments tounderstand how ancient sedimentaryrocks formed … And modern plants & their adaptationsto understand similar ancient plants &their adaptations.
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Based on its fossilremains and oncertain similaritiesto modern BaldCypress, scientistshave interpreted:
Tree shape & roots like modern bald cypressWarm, very wet environmentsSeeds too fragile to survive a long sea trip
FOR GLOSSOPTERIS, WHICH HAS NO MODERN REPRESENTATIVES
GLOSSOPTERIS
BALD CYPRESS
Illustration credits: Glossopteris, Rose Prevec, Rhodes University (South Africa); bald cypress, NRCS
