Darwinism as a dual meaning

Darwinism

• Darwinism as a dual meaning.

• It refers to evolution as the explanation for life’s unity and diversity.

• It also refers to the Darwinian concept of natural selection as the cause of adaptive evolution.

Viewed from the perspective of descent with modification, the history of life is like a tree with multiple branches from a common trunk.

• Viewed from the perspective of descent with modification, the history of life is like a tree with multiple branches from a common trunk.

• Closely related species, the twigs of the tree, shared the same line of descent until their recent divergence from a common ancestor.

The other major point that Darwin pioneered is a unique mechanism of evolution - the theory of natural selection.

• The other major point that Darwin pioneered is a unique mechanism of evolution - the theory of natural selection.

• Ernst Mayr, an evolutionary biologist, has dissected the logic of Darwin’s theory into three inferences based on five observations.

• These observations include tremendous fecundity, stable populations sizes, limited environmental resources, variation among individuals, and heritability of some of this variation.

Observation #1: All species have such great potential fertility that their population size would increase exponentially if all individuals that are born reproduced successfully.

• Observation #1: All species have such great potential fertility that their population size would increase exponentially if all individuals that are born reproduced successfully.

• Observation #2: Populations tend to remain stable in size, except for seasonal fluctuations.

Observation #5: Much of this variation is heritable.

• Observation #5: Much of this variation is heritable.