Reviewing the Mystery…Why is the dark form becoming

more common in areas downwind of manufacturing centers?

1

The Peppered Moth

Biston betularia f. typica

Biston betularia f. carbonaria

2

1950Frequency of dark form Centers of pollution

1700

1800

1900

2000

1600

London

Manchester

Glasgow

3

Light & Dark Forms

lichen-covered treesoot-covered tree

4

Natural Section & the Mystery Phenomenon

E.B. Ford(1901-1988)

• 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.

J.W. Tutt(1858-1911)

5

Mystery PhenomenonPart 3

6

H.B.D. Kettlewell

(1907-1979)

The peppered moth Biston betularia

7

Kettlewell’s InvestigationsMark-release-recapture experiment

8

Film: Evolution in Progress

9

Kettlewell’s m-r-r results

2x as likely to survive.

10

Kettlewell’s m-m-r results

2x as likely to

survive.

11

Observations:bird predation order

12

What are experiments?

13

Are experiments necessary for progress in science?

14

Have Kettlewell’s experiments convinced you that Ford’s

theory is correct?

15

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

16

M. E. Majerus

Ford

17

Problems & Solutions

Biston betularia found at rest on a horizontal tree branch (M. Majerus 2009)

Kettlewell

18

Expectations

M.E. Majerus (1954-2009)

J.W. Tutt(1858-1911)

19

And What of the Moth?Frequency of dark form Centers of pollution

1700

1800

1900

2000

1600

20

London

Manchester

Glasgow

The Great Smog of 1952

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

21

Clean Air Act 1956

• Britain now had strict air pollution laws in place.

• What happened to the frequency of the dark form?

22

?Cooke

TuttHarrison

Kettlewell

The Mystery Phenomenon

165 years & countingFord

Majerus

23

?

Is that the Complete Story?

24

Details, details. 1’. The peppered moths has two dark forms, not one.

Biston betularia f. typica

Biston betularia f. carbonaria

Biston betularia f. insularia

25

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.

26

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?27