Direct Observations of Natural Selection: The Peppered Moth

Introduction

• Sixth line of evidence for evolution.
• Focus on the peppered moth, Biston Betularia.

Historical Background

• Historically, moths were predominantly white with black spots.
• Lived in England; English naturalists have paid close attention to them.

First Melanic Form

• 1848: First recorded melanic (black) form, called the Carbonaria type.
• Original white type called Bistan Betularia Typica.
• By 1900, 90% of moths in some parts of England were Carbonaria type.

Environmental Changes

• Industrial pollution changed tree colors, creating a selective environment.

Kettlewell's Experiments

• Conducted to determine the role of environmental change.
• Released moths in polluted and unpolluted areas.
• Polluted Areas: More Carbonaria released; higher recapture rate for Carbonaria.
• Unpolluted Areas: Equal release; higher recapture rate for Typica.
• Demonstrated survival differences based on coloration.

Natural Selection

• Pollution didn't turn moths black; survival differences due to environmental changes caused evolution.
• When pollution reduced, frequency of Carbonaria decreased.
• Reflects natural selection adapting to environmental changes.

Ongoing Research

• Identifying genetic differences is ongoing.
• 2011 study indicates a simple genetic basis for color difference.
• Science is an evolving field, continuously seeking details.

Summary

• The case of the peppered moth is a classic example of natural selection.
• Illustrates how environmental changes drive evolutionary adaptations.
• Science continues to explore and refine understanding of these processes.