1. Reviewing the Mystery…
Why is the dark form becoming more common in areas downwind of manufacturing centers?

2. The Peppered Moth Biston betularia f. typica
Biston betularia f. carbonaria

3. 1950 Frequency of dark form Centers of pollution 1700 1800 1900 2000
Glasgow
Manchester
London
1700
1800
1900
2000
1600

4. Light & Dark Forms
lichen-covered tree
soot-covered tree

5. Natural Section & the Mystery Phenomenon
J.W. Tutt
( )
E.B. Ford
( )
The spread of the dark form is due to its physiological superiority over the light form.
The spread is limited to areas darkened by pollution owing to the handicap of dark coloration in unpolluted environments.

6. Mystery Phenomenon Part 3

7. The peppered moth Biston betularia
H.B.D. Kettlewell
The peppered moth Biston betularia
( )

8. Kettlewell’s Investigations
Mark-release-recapture experiment

9. Film: Evolution in Progress

10. Kettlewell’s m-r-r results
2x as likely to survive.

11. Kettlewell’s m-m-r results
2x as likely to survive.

12. Observations: bird predation order

13. What are experiments?

14. Are experiments necessary for progress in science?

15. Have Kettlewell’s experiments convinced you that Ford’s theory is correct?

16. The Mystery Continues Kettlewell’s Conclusions
Not universally accepted
Issues with experimental design.
Lack of knowledge of behavior & ecology of moth.
Other scientists worked on the moth

17. M. E. Majerus
Ford

18. Problems & Solutions
Kettlewell
Biston betularia found at rest on a horizontal tree branch (M. Majerus 2009)

19. Expectations
J.W. Tutt
( )
M.E. Majerus
( )

20. And What of the Moth? Frequency of dark form Centers of pollution 1700
Glasgow
Manchester
London
1700
1800
1900
2000
1600

21. The Great Smog of 1952 4- day smog event
Nelson's Column, London
4- day smog event
Reported that 4,000 people died
Recent research puts deaths at 12,000
10,000 people ill

22. Clean Air Act 1956 Britain now had strict air pollution laws in place.
What happened to the frequency of the dark form?

23. The Mystery Phenomenon?
Cooke
Majerus
Kettlewell
Tutt
Harrison
Ford
165 years & counting

24. Is that the Complete Story?

25. Details, details. 1’. The peppered moths has two dark forms, not one.
Biston betularia f. typica
Biston betularia f. carbonaria
Biston betularia f. insularia

26. When is it Enough?
Carbonaria is common in some rural areas (unpolluted).
Dark forms of other species have evolved for other reasons.
Scientific controversies not covered in detail.

27. What Should Science Teachers Do?
How much detail should science teachers give?
How can simplified versions of a scientific account be useful?
What problems can arise using simplified versions?
Is there ever a “complete” version?