Teacher sheet · Ages 15–16 · about 45–50 minutes
Reading trackways: dinosaur speed, evidence and uncertainty
Lesson page: echoesof.science/school/dinosaurs/ages-15-16/ · Pupil worksheet: echoesof.science/school/dinosaurs/ages-15-16/print/
Learning aims
- Define dinosaurs by ancestry and anatomy.
- Use Alexander's equation with correct units and powers.
- Evaluate the method and its uncertainty using published test results.
- Describe how evidence was weighed for the end-Cretaceous extinction.
Lesson plan
| Time | Activity |
|---|---|
| 5 min | Starter: show a photo of a trackway. What can we know for sure? What do we have to infer? |
| 10 min | Read the text; worked example of Alexander's equation. |
| 20 min | Testing the equation on yourselves. |
| 5 min | Play Observation or inference? |
| 5 min | Quiz and discussion of uncertainty. |
Materials for the experiment
- A straight, flat 20 m track (playground or hall)
- Tape measure (at least 10 m) and metre rule
- Stopwatch
- Chalk or bean bags to mark footfalls
- Calculator or spreadsheet
Safety: Use a dry, level surface with no obstacles. Jog, do not sprint; only one pair on the track at a time. Wear suitable shoes.
Common misconceptions
| Pupils may think… | Actually… |
|---|---|
| A formula gives the dinosaur's real speed. | It gives an estimate with large uncertainty; tests on living birds in mud found large errors. |
| All dinosaurs died out 66 million years ago. | Non-avian dinosaurs did; birds are dinosaurs that survived. |
| A scientific idea that changes was wrong science. | Changing ideas with new evidence, as with Iguanodon's posture, is how science works. |
Worksheet answers
- Answers vary; % difference = (predicted − measured) ÷ measured × 100%; uncertainties from timing (reaction time, about ±0.2 s) and stride marking; compare walking and jogging.
- For example: hip height is only estimated (4 × footprint length); the equation assumes a straight leg; soft ground changes footprints and strides; the equation was fitted to living animals; tests with guineafowl in mud found large errors.
- Birds are dinosaurs and they survived, so only the non-avian dinosaurs died out.
- Four alternating prints with footprint length marked on one print, λ between two prints of the same foot, and h ≈ 4 × footprint length.
Quiz answers
- A trackway has λ = 3.0 m and footprints 0.30 m long. Using h ≈ 4 × footprint length, what does Alexander's equation predict? About 4.0 m/s. h = 1.2 m; u = 0.25 × 3.13 × 3.0^1.67 × 1.2^−1.17 ≈ 4.0 m/s.[10][9]
- At the same hip height, the stride doubles. By about what factor does the predicted speed rise? About 3.2. 2^1.67 ≈ 3.2.[10]
- What is the stride length in a trackway? The distance between two prints of the same foot. A stride is a full cycle of one foot.[9]
- What did the guineafowl study find? None of the equations accurately predicted speed in mud. Trackway speeds carry major uncertainty.[10]
- Which definition makes birds dinosaurs? Descendants of the common ancestor of Diplodocus, Triceratops and the house sparrow. This definition by ancestry includes birds.[1]
- Why did the 2010 panel judge the Deccan Traps not to be the primary cause? They reviewed 20 years of evidence and found the asteroid impact fitted best. 41 experts weighed the evidence and favoured the Chicxulub impact.[4]
Going further
Use a spreadsheet to plot predicted against measured speed for the whole class. Draw the line 'predicted = measured' and discuss where the points lie.
Sources used in this lesson
- [1] What Makes a Dinosaur a Dinosaur (US National Park Service (NPS)): reliability High
- [2] What is a dinosaur? (Australian Museum): reliability High
- [3] Dinosaur summary (Encyclopaedia Britannica): reliability High
- [4] Asteroid killed off the dinosaurs, says international scientific panel (Imperial College London (news, March 2010)): reliability High
- [7] The Bernissart Iguanodons at a glance (Royal Belgian Institute of Natural Sciences (Museum of Natural Sciences, Brussels)): reliability High
- [9] The speed of extinct organisms (The Open University (OpenLearn)): reliability Medium-high
- [10] Speed from fossil trackways: calculations not validated by extant birds on compliant substrates (Liverpool John Moores University research repository (peer-reviewed article)): reliability High
Full list with links and a note on each source's reliability: echoesof.science/school/dinosaurs/sources/
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