Sloths et al. teaching the "E" word:

using extant and extinct xenarthran cranial materials to exemplify for middle school students change

though time and how science works

Barbara J. ShawLuis A. Ruedas

Portland State University

AcknowledgmentsMy Advisory Committee:Dr. Debbie DuffieldDr. Lisa WeaselDr. Keith HadleyDr. Virginia Butler

Dr. Randy Zelick (Comprehensive Committee)

Most of all:Dr. Luis A. Ruedas, my major professor, for all his invaluable support, guidance, and encouragement

Dr. Richard B. Forbes whose memory I hold dear

Tom Lindsay and my Lab Mates

AcknowledgmentsFunding:

Collections Study Grant

ESIE Award #0119786 Collections:

American Museum of Natural History, New York, NYDr. Jin Meng Ms. Susan Koelle BellDr. John Wahlert Ms. S. Jean Spence

Museum of Vertebrate Zoology, Berkeley, CADr. Chris Conroy Dr. Jim Patton

Museum of Natural History, Gainesville, FLDr. Richard Hulbert Dr. Laura Wilkins

Museum of Vertebrate Biology, Portland, ORDr. Luis A. Ruedas

K-12 Battlefield

• Supernatural• Intelligent Designer • Irreducible

Complexity

vs• Rational• Descent with

Modification • Natural Selection

http://www.discovery.org/csc/

http://www.tortoisetours.com/files/Menu/gi_finches.1.JPG

Support for Evolution

Believe????

http://www.the-funneled-web.com/N&V_2005(Jan-Dec)/N&V_0504/news__views_item_april_2005-050428.htm

That can’t be right.

Evolution in Oregon

• The Oregon science Content Standards, adopted in April 2001, clearly require the teaching of evolution.

Student Graph

Oregon Standards on Inquiry

• Ask questions or develop hypothesis based on observations

• Design experiment

• Collect data

• Interpret results

Methods• 45 crania and mandibles

– 16 extinct xenarthrans skulls– 23 extant xenarthran skulls

• 15 Dasypus novemcinctus skulls for a control

– 6 outgroup skulls • 15 calipers – 150 mm• 5 calipers – 600 mm• Student notebooks• Pre and Post

assessment

01234567

nu

mb

er

of

sp

ec

ime

ns

85 to 88

88 to 91

91 to 94

94 to 97

97 to 100

100 to 103

103 to 106

over 106

length in mm

nine-banded armadillo skull length

Student Graph

Assessment• Identifying Testable Questions

• Biostratigraphy

• General Facts and Observations– About xenarthrans

– Similarities within xenarthrans

– Differences within xenarthrans

– Observations about a xenarthran

– Observations about a dinosaur

• Phylogenetic Tree

Pilosa Skulls

• Family Bradypodidae– Bradypus tridactylus

• Family Megalonychidae– Choloepus didactylus– Choloepus hoffmanni– †Megalonyx leptostomus – Florida

Pleistocene– †9 unknown small ground sloths specimens –

Argentina Miocene

Pilosa Skulls

• Family Mylodontidae – †Catonyx tarijensis Bolivia Pleistocene – †Glossotherium chapadmalensis – Florida

Pliocene – †Scelidodon sp. – Argentina Pleistocene

• Family Myrmecophagidae– Myrmecophaga tridactyla– Tamandua mexicana

Cingulata Skulls• Family Glyptodontidae

– Glyptodon calvipes – Uruguay Pleistocene– Panochthus tuberculatus – Argentina

Pleistocene• Family Pampatheriidae

– Holmesina septentrionalis – Florida Pleistocene

• Family Dasypodidae– Dasypus novemcinctus – Cabassous unicinctus– Euphractus sexcinctus– Priodontes maximus

Participants• Human Subjects Review approved• 78 students participated average 10.8 hr.• 35 signed permission • 3 students missed post-assessment• 32 participants total• Normally distributed• Paired Student-t test• Student-t test with equal

variance to assess student variables

Student Demographics

Student Demographics

Estimated Free and Reduced Meal

0

2

4

6

8

10

12

14

78.1 75.8 73.9 47.2 unk

Percentage per School

Nu

mb

er

of

Stu

de

nts

# Students~% FRM

Estimated 17 students on FRM

Results - Significant

• Assessment Questions– Testable Questions, p=0.330 df=31

Mis-identified testable, p=1.0000 df=9 *Mis-identified nontestable, p=0.0067 df=9 *Mis-identified non vs test, p=0.0002 df=19

Results - Significant

• Assessment Questions– *Facts, p=7.3x10-5 df=31

*Factual statements, p=0.004 df=31 *Xenarthran knowledge, p=0.005 df=31 *Same, p=0.05 df=31 *Different, p=0.005

Results - Significant

• Assessment Questions– *Total, p=0.003 df=31

• Significant gain under the following parameters:– Over 11 hours exposure to materials

p=2.79x10-7 df=30– Over 70% Free or Reduced Meals! p=0.038

df=30• Average gain for <50% = 1.65• Average gain for >70% = 5.79!

Results – Not Significant

• Assessment Questions– Biostratigraphy, p=0.325 df=31– Observations about a dinosaur, p=0.379 df=31– Phylogenetic tree, p=0.562 df=31

Conclusions

• Difficult for students to identify non-testable questions (>⅓ students thought that these were testable).– Are armadillos empathetic?– Are sloths slow because they are

deep thinkers?– Are sloths slow because they are

lazy?– Did anteaters lose all their teeth as a

punishment because they wanted to eat little animals?

Conclusions

• Students improved significantly in reciting facts about xenarthrans

• Number of hours of students participation was significant ( >10.5)

• Schools with >70% of student body in Free and Reduced Meal program gained significantly from the Pre to Post assessment

Conclusions

• Students did not show significance in biostratigraphy or phylogenetic trees however, most classes asked questions related to biomechanics

Student GraphNormalized Mandible as Lever

0.100.150.200.250.300.350.40

0.450.500.550.600.650.700.75

0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95

Normalized Mandible Length

Nor

mal

ized

Con

dyle

to M

uscl

e A

ttach

men

t Len

gth

Bradypus tridactylus

Cabassous uncinctus

Catonyx tarijensis

Choloepus didactylus

Choloepus hoffmanni

Dasypus novemcinctus

Euphractus sexcinctus

Glossotherium chapadmalensis

Glyptodon calvipes

Holmesina septentrionalis

Megalonyx

Myrmecophaga tridactyla

Panochthus tuberculatus

Priodontes maximus

Scelidodon

Tamandua mexicana

student 1

student 2

student 3

student 4

student 5

Thank You

Choloepus didactylus Choluis ruedas