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Biston betularia
Distribution Map Biston betularia f. typica 1700 1800 1900 2000 1600
Discovery Biston betularia f. carbonaria 1848 - Manchester, UK 1700 1800 1900 2000 1600
James W. Tutt (1858-1911) Manchester in 1843 1700 1800 1900 2000 1600
1950 Frequency of dark form Centers of pollution 1700 1800 1900 2000 Glasgow Manchester London 1700 1800 1900 2000 1600
Mystery Phenomenon Part 2
Unpolluted vs. Polluted Forest
Unpolluted Woods & Moths
Polluted Woods & Moths
Three Theories 1. Physiological Response to Changed Environment 2. Natural Selection 3. Mutation
Three Theories 1’ . Lamarck’s Theory of Acquired Inheritance 2’. Darwin’s Theory of Natural Selection 3’. De Vries’ Mutation Theory
Lamarckian Inheritance All creatures have a natural tendency to become more complex. Changes in behavior can result in morphological changes inherited by offspring Jean Baptiste Lamarck (1744-1829)
Lamarckian Inheritance Applied to the Mystery Phenomenon This trend is the result of the moths adapting to environmental conditions that have led to a general darkening of their resting sites, such as pollution and increased humidity. Individuals adapt to local circumstances and these changes are passed to their offspring. Nicholas Cooke (1818-1886) 1700 1800 1900 2000 1600
Natural Selection There are small heritable variations within populations. Some variations give their possessors a better chance at surviving and reproducing. Over time the favored variation will become more common. Charles Darwin (1809-1882)
Natural Selection & the Mystery Phenomenon Increase of the dark form is due to crypsis or the protective advantage of dark color in soot- darkened environments. J.W. Tutt 1858-1911) 1700 1800 1900 2000 1600
Natural Selection & the Mystery Phenomenon The spread of the dark form is due to its physiological superiority over the pale form. The spread is limited to areas darkened by pollution owing to the handicap of dark coloration in unpolluted environments. E.B. Ford (1901-1988) 1700 1800 1900 2000 1600
Mutation Theory Speciation is the result of large discontinuous changes caused by mutations that produce offspring radically different than their parents. Hugo De Vries (1848-1935)
Mutation Theory & the Mystery Phenomenon Lead salts in the pollutants covering the foliage of trees have mutagenic properties. Exposure to these salts has led to this mutation. Heslop Harrison (1881-1967) 1700 1800 1900 2000 1600
To Sum it Up…
Cooke’s Theory Increasing Pollution
Tutt & Ford’s Theory Increasing Pollution
Heslop Harrison’s Theory Increasing Pollution
What is a theory?
How do scientists choose between competing theories?