fixity of species “design”

Evolutionary TheoryAn introduction

The Worldview of Early Modern Europe

Fixity of species “Design”

Nicolaus Copernicus; Galileo Galilei 1473 – 1543 1564 –1642

James Usher (1581-1656)

Carolus Linnaeus (1707-1778)

Jean Baptiste Lamarck (1744-1829)

Georges Cuvier (1769-1832)

Charles Lyell (1797-1875)

Thomas Malthus (1766-1834)

Charles Darwin (1809-1882)

Alfred Russel Wallace (1823-1913)

Natural SelectionDarwin’s big Idea

From Darwin’s intro to his Book On the Origin of Species

“…the Struggle for Existence amongst all organic beings throughout the world, which inevitably follows from the high geometrical ratio of their increase, will be treated of. This is the doctrine of Malthus, applied to the whole animal and vegetable kingdoms. As many more individuals of each species are born than can possibly survive; and as, consequently, there is a frequently recurring struggle for existence, it follows that any being, if it vary however slightly in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of surviving, and thus be naturally selected. From the strong principle of inheritance, any selected variety will tend to propagate its new and modified form.”

The key points

1. Excessive fertility2. Extensive variation of organisms3. Competition for resources4. “Natural selection” of advantageous

variants5. Reproduction of advantageous traits

The key points

1. Excessive fertility (observation)

2. Extensive variation of organisms (observation)

3. Competition for resources (inferred from #1)

4. “Natural selection” of advantageous variants

5. Reproduction of advantageous traits

The Concept

1. Excessive fertilitycombined with

2. extensive variation of organismscontributes to

3. competition for resourcesin which there is a

4. “natural selection” of advantageous variants

resulting in5. The reproduction of advantageous

traits.

The peppered Moths of Manchester