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Nature of Science

Performance Benchmark N.8.A.3
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Nature of Science
Scientific Inquiry
  N.8.A.1
  N.8.A.2
  N.8.A.3
  N.8.A.4
  N.8.A.5
 

N.8.A.6

 

N.8.A.7

Science, Technology, and Society
Content Areas
Nature of Science (NOS)
Life Science
Earth Science
Physical Science

Students know different explanations can be given for the same evidence.    E/S

“Evidence is almost always incomplete, inconclusive, and amenable to multiple explanations...we always reason in the presence of uncertainty.”  —Robert Mislevy, Professor of Measurement, Statistics, and Evaluation at the University of Maryland

Evidence from the natural world is collected through observations and experimentation but it is up to the scientist to make sense of the data and draw conclusions.  Therefore, two different scientists may draw two different conclusions from the same evidenceScientific evidence is interpreted using reason and logic.  However, scientific interpretation is embedded within the dogma of the time.   To counter human nature, science requires that conclusions be validated by repeated experimentation and are subjected to peer review.  Lastly, scientific explanations (conclusions) are well founded in logic but are tentative as scientists must be willing to modify their ideas as new evidence is uncovered.

The extinction of the dinosaurs is a good example of how different explanations are derived from the same evidence.  Looking at the same evidence found in the rock strata, four dominant hypotheses are being further investigated:  asteroid impact, increased volcanism, mammal competition, and continental drift (climate change).  Figure one shows how evidence supports each of these hypotheses.

Hypothesis

High Iridium Level in Rocks

Melted
Rock

Fractured
Crystals

Fossil
Record

Impact
Crater

Lava
Flows

Sea
Level

Asteroid Impact

X

X

X

X

X

 

 

Volcanism

X

 

X

X

 

X

 

Mammal
Competition

 

 

 

X

 

 

 

Continental
Drift

 

 

 

X

 

 

X

Figure 1. This table shows how the abundant evidence supports multiple
hypotheses on the cause of the extinction of dinosaurs.
(From http://www.pbs.org/wgbh/evolution/extinction/dinosaurs/index.html)

Most scientists agree that an asteroid impact in the late Cretaceous off the Yucatan Peninsula was a dramatic event that sealed the dinosaur’s fate.  But many argue that increased volcanism, the rise of mammals, and gradual climate change (wet/hot to dry/cool) due to continental drift may have each contributed to the demise of the dinosaurs or one idea individually may have actually been the driving force that ended the Age of Dinosaurs.  Which idea is the right one?  All are equally valid and additional evidence may further support one hypothesis over another or completely discount one or more hypotheses.

A current issue that is being debated by scientists is global warming.  Most scientists agree that in the short run (last 100 years) global temperatures have increased significantly, but they disagree on the cause.  Some scientists say that the increase in temperature is solely anthropogenic caused by the burning of fossil fuels.  Other scientists say that human impact is minimal and that the climatic change is due to normal Earth cycles supported by long range (400,000 or more years) data.  Figure 2 shows the change in global temperature since 1860.  It shows that the last 30 years have exhibited warmer temperatures than the preceding 100 years.   Coupled with Figure 3, the change in atmospheric CO2, a relationship between temperature and CO2 is strongly suggested. 

16.jpg - 35713 Bytes

Figure 2. Global average surface temperatures since 1860. 
(From:  http://www.grida.no/climate/vital/17.htm )

http://www.rpdp.net/sciencetips_v3/images/n8a3/maunaloa.jpg

Figure 3.  Atmospheric CO2 since 1958
From ( http://www.exo.net/~pauld/workshops/
globalclimate/atmospherecarbondioxide.htm)

Plotting atmospheric data over 400,000 years, as shown in Figure 4, the debate becomes even more ardent.   A relationship between CO2 and temperature is also suggested since both parameters show the same trends over time.   Again, scientists present different explanations for the same data.  Some suggest that we are just living through a natural peak of CO2/temperature fluctuations, while others contend that humans are the current cause of the shown results.

http://www.rpdp.net/sciencetips_v3/images/n8a3/26_large.jpg

Figure 4. Global temperature and atmospheric CO2
concentrations over the last 400,000.
(From  http://www.grida.no/climate/vital/02.htm)

A scientific consensus as to cause and effect of CO2 and global temperatures does not exist.  Does the CO2 level cause the temperature change? Does the temperature change cause the change in CO2 level?  Is there a third factor affecting both?  Are we to blame for the climatic shift?  Is this just a natural long term Earth cycle?  Only time will tell.

For more information on Global Warming:

General information from the EPA, http://www.epa.gov/climatechange/   

General information geared to students, http://epa.gov/climatechange/kids/index.html

“The Other Side of Global Warming Debate:”
http://personals.galaxyinternet.net/tunga/OSGWD.htm

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Performance Benchmark N.8.A.3

Students know different explanations can be given for the same evidence.    E/S


Common misconceptions associated with this benchmark

1. Students incorrectly believe that “evidence accumulated carefully will result in sure knowledge”

 McComas, William, Ten myths of science: Reexamining what we think we know...., Vol. 96, School Science & Mathematics, 01-01-1996, pp 10
More information pertaining this misconception can be found at
http://www.geocities.com/otisbrown17268/scihist.html

Scientists are required to evaluate each new piece of data and modify their model to include the new data.  Any designed model must be flexible to allow the addition of newly discovered items or relationships. Science can only produce possible explanations for natural phenomena.  With new data collected with new technologies, tools, and techniques old models are replaced with new findings.  For example, the reclassification of Pluto has changed the model of our solar system. Models change as more information is discovered.


 2. Students incorrectly believe that there is only one accepted model for a given scientific  concept/belief.

Many models may be designed to explain a phenomenon using the same data set to meet the needs of the user.  One scientist may be interested in macro level relationships while another may design a model that shows micro level relationships.  Therefore, a model may be extremely simple or very complicated when more specificity is needed.

The following link can be used to show students the evidence and dominant theories associated with the extinction of the dinosaurs.
http://www.pbs.org/wgbh/evolution/extinction/dinosaurs/index.html


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Content Benchmark N.8.A.3

Students know different explanations can be given for the same evidence.    E/S

Sample Test Questions

1st Item Specification: Given an example, recognize that results can be explained in more than one way.

Depth of Knowledge Level 1

  1. The conclusions drawn from a set of data
    1. can vary from scientist to scientist.
    2. are generally accepted by all scientists.
    3. are not modified if based on careful experimentation.
    4. are often ignored if the data does not fit the previous model.
  1.  Different explanations can be given for the same evidence because scientists
    1. only look at the data that is important to them.
    2. work in different fields of science and draw conclusions from that expertise.
    3. use the evidence that supports their current working hypothesis.
    4. must consider how their government will react to the explanations.
  1. Which of the following statements is NOT true?
    1. All models must be accepted by all scientists working in field.
    2. All models must be supported by experimental data.
    3. All models must evolve as new data is analyzed.
    4. All models must show relationships between components.
  1. The mass extinction event happened in the late Cretaceous (144-65 million years ago).  This mass extinction event resulted in the loss of 85% of all species including the dinosaurs. Which of the following theories is the cause of the mass extinction?
    1. An asteroid impact created a layer of atmospheric dust that blocked the sun.
    2. Increased volcanism created a layer of atmospheric dust that blocked the sun.
    3. Slow climatic change from warm/wet to cool/dry environments lead to the decline of species.
    4. Any of the above events or a combination of events could have lead to the decline of species.
  1. Hypothesis and models are constructed to give the best explanation of a set of data. Models and hypothesis based on experimentation and research are
    1. generally accepted by all scientists who are experts.
    2. modified if necessary as new data and observations are collected.
    3. not modified once completed if based on careful experimentation.
    4. generally only accepted if scientists agree with collected data.

Depth of Knowledge Level 2

  1. Sources of evidences used to support hypothesis for the extinction of the dinosaurs.

Hypothesis

High Iridium
Level in Rock

Melted
Rock

Fractured
Crystals

Fossil
Record

Impact
Crater

Lava
Flows

Sea
Level

Asteroid Impact

X

X

X

X

X

 

 

Volcanism

X

 

X

X

 

X

 

Mammal
Competition

 

 

 

X

 

 

 

Continental
Drift

 

 

 

X

 

 

X

(From http://www.pbs.org/wgbh/evolution/extinction/dinosaurs/index.html)

Four competing hypotheses exist to explain the extinction of the dinosaurs.  How are these different conclusions possible if all of these scientists are looking at the same experiments and data?
  1. The scientists are experts in a narrow field so they ignore the data that is outside their expertise.
  2. There can be only one right answer.  One scientist has the correct answer and the rest are wrong.
  3. Each scientist was able to fit the data together into a logical conclusion even though the resulting models were not identical.
  4. Scientists pick a theory and then only use the data that supports their theory
  1. Some astrophysicists believe that the universe is expanding while others believe that it is shrinking. Others believe that the universe is not changing. How are these different conclusions possible if all of these scientists are looking at the same experiments and data?
    1. The scientists are experts in a narrow field so they ignore the data that is outside their expertise.
    2. There can be only one right answer.  One scientist has the correct answer and the rest are wrong.
    3. Each scientist was able to fit the data together into a logical conclusion even though the resulting models were not identical.
    4. Scientists pick a theory and then only use the data that supports their theory.
  1.  Use the following table to answer the next question.

 

Disease 1

Disease 2

Disease 3

Disease 4

Fever

X

X

 

X

 Red Bumps on Body

 

X

X

X

Swollen Tonsils

X

 

X

X

Ear Pain

X

 

 

 

A student asks to go to the nurse.  The nurse discovers that the students is running a fever and has swollen tonsils.  Presented with this data, which of the following diagnosis are possible?
  1. Disease 1 or 2
  2. Disease 1 or 4
  3. Disease 2 or 4
  4. Disease 1, 2, or 3
  1. Use the following table to answer the next question.  There are four species of insect eating birds on an island.  Wildlife biologists have noticed that Yellow bird population has dramatically decreased.  The biologist’s recorded the number of insects that the birds ate each day.

 

Insect 1

Insect 2

Insect 3

Insect 4

Blue bird

23

50

4

30

Yellow bird

3

75

50

1

Red bird

6

23

67

24

Green bird

9

11

50

52

Which of the following conclusions is NOT a probable explanation of why the Yellow bird’s population is decreasing?
  1. Red bird recently moved into Yellow bird’s habitat.  Therefore, Yellow bird’s supply of Insect 3 decreased.
  2. Insect 1’s population decreased significantly.  The decrease in Insect 1 significantly reduced the food available for Yellow bird.
  3. Blue bird moved into the Yellow bird’s habitat.  Blue bird preferred to eat Insect 2 which reduced the food supply for the Yellow bird.
  4. Green birds were better hunters of Insect 3 which reduced the food supply for Yellow bird
  1. Global warming is a hotly debated subject among scientists.  Some scientists support that human activities alone are dramatically warming the planet.  Other scientists conclude that human activities are only partly to blame.  Lastly, some scientists conclude that the earth is warming through normal planetary activities.  How are these different conclusions possible if all of these scientists are looking at the same experiments and data?
    1. The scientists are experts in a narrow field so they ignore the data that is outside their expertise.
    2. There can be only one right answer.  One scientist has the correct answer and the rest are wrong.
    3. Each scientist was able to fit the data together into a logical conclusion even though the resulting models were not identical.
    4. Scientists pick a theory and then only use the data that supports their theory.

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Performance Benchmark N.8.A.3

Students know different explanations can be given for the same evidence.    E/S

Answers to Sample Test Questions

  1. A, DOK Level 1
  2. B, DOK Level 1
  3. A, DOK Level 1
  4. D, DOK Level 1
  5. B, DOK Level 1
  6. C, DOK Level 2
  7. C, DOK Level 2
  8. B, DOK Level 2
  9. B, DOK Level 2
  10. C, DOK Level 2

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Performance Benchmark N.8.A.3

Students know different explanations can be given for the same evidence.    E/S

Intervention Strategies and Resources

The following is a list of intervention strategies and resources that will facilitate student understanding of this benchmark.

1. The Earth is Flat!!

This is a great activity that makes students evaluate data and draw logical conclusions.  According to the website, “Students are exposed to a compelling idea: the Earth really IS flat! They are challenged to provide the evidence for a spherical earth, then present the evidence (experiences) for a flat earth, discuss the relative strengths of the evidence, and reach conclusions. The Social Context of science is also explored, with the roles of collaboration and past experience biases being emphasized. “

To access this activity visit  http://www.indiana.edu/~ensiweb/lessons/flaterth.html

2.  Drawing Conclusions

This website provides a free downloadable activity appropriate for grades 6-12.  The activity walks students through how to draw a conclusion.  An extension to this activity is to have students draw their own conclusions from the available data and discuss and defend their conclusion.  This should drive home the point that multiple logical conclusions are possible from the same data.

This activity can be downloaded from, http://www.teachervision.fen.com/tv/printables/SISA00151_3.pdf


3. What killed the dinosaurs?

This website provides an interactive survey of the evidence that supports five different theories for the extinction of dinosaurs as discussed in the content section of this webpage.  Students can click on each piece of evidence and see how it supports one or more proposed hypothesis.  The information is supported with animations, hyperlinked glossary for vocabulary, pictures/diagrams, and grade level appropriate text.

This activity can be accessed at http://www.pbs.org/wgbh/evolution/extinction/dinosaurs/index.html
 

4.  Rickshaw or Rowboat? Is Climate Change Coming?

This webquest is a problem-based learning activity.  “The target class of this activity is eighth grade Integrated Science in Bangladesh but it could be adapted to higher levels and other locations very easily.  Students should have previous knowledge of the water and carbon-oxygen biogeochemical cycles, as well as local weather events, collecting data on them, and basic understanding of the role of the ocean in regulating regional climates.”  Students are assigned roles (environmentalist, climatologist, economist, and social scientist) and research climate change and draw their own conclusions on how rural Bangladeshis’ lives might be affected.  A construct a feasible proposal to the UN to assist where needed.

To access this webquest, go to http://teacherweb.com/BD/AIS_D/Rickshaw_or_Rowboat/index.html

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Benchmark
Support Pages

Misconceptions:
Click Here
Sample Questions:
Click Here

Intervention Strategies & Resources:
Click Here

Benchmark Related Vocabulary

Difference
Different
Evidence
Infer
Scientific evidence