Chapter 20: Introduction to Evolutionary Theory

Biological evolution

Occurs in populations when specific processes cause organisms to differ from their ancestors

Heritable changes (& the phenotypic modifications they cause)

Products of evolution

Three forms of evidence suggesting evolution

Biogeography, comparative morphology, fossils

Biogeography

Similar species despite being in different regions

Comparative morphology

Reveals homologous structures, ex. Bats, whales, cheetah, and humans have similar bone structure of arm

Fossils

Finding fossils of animals that don’t exist today, ex. Older fossils are deeper and less similar to existing species

Aristotle

First person to try to make sense of living things and laws that govern life only based on observation, first biologist

Scale of Nature/Great chain of being

Animals put in a scale from least to best, not based on evolution, implies progress or value, ancient Greece - Middle Ages

Chronological Order of Evolutionary Thinkers

Aristotle, Carolus Linneaus, Georges Leclerc, Jean-Baptiste de Lamarck, Charles Lyell, Thomas Malthus, Charles Darwin

Carolus Linneaus

establishing the foundational principles of modern biological classification and for creating binomial nomenclature

Georges Leclerc

Species are produced by nature and produced by time, introduces vestigial structures

Vestigial structures

Structures that had a purpose in the past but now don’t have a function anymore

Erasmus Darwin

Jean-Baptiste de Lamarck

First to propose a mechanism for evolution (why), it was wrong, principle of use and disuse, inheritance of acquired characteristics

Principle of use and disuse

More you use a structure, the more sophisticated it becomes within the lifetime WRONG

Inheritance of acquired characteristics

The characteristics built up during lifetime transfers to offspring WRONG

Charles Lyell

Proposed that Earth changed very slowly over a very long period of time (gradualism) through the same processes that operate today (uniformitarianism)

Thomas Malthus

Human population increases exponentially but food production stays constant -> Struggle for survival idea -> natural selection & scientific racism and eugenics

Charles Darwin

First to propose a plausible mechanism for evolution, natural selection, and to propose common descent, that all life is connected

Charles Darwin fun facts

Really smart (got facts from different sources into one theory), never worked bc nepo baby, chronically ill, pre-med dropout, collected beetles, went on the HMS Beagle and that’s where he found Galapagos

Charles Darwin and Galapagos

Observed finches/mockingbirds with similar morphologies and different beak shapes, observed marine iguana on Galapagos vs green iguana on mainland, observed dome-shaped and saddle-shaped tortoises

Charles Darwin Pastime After Galapagos

Breeding pigeons (artificial selection), worms, and something about barnacles

Charles Darwin and Alfred Wallace

Had idea of natural selection and procrastinated like crazy until Alfred Russell Wallace, who was also on an expedition as a naturalist, came up with a very similar theory of natural selection. He wrote a letter to Darwin showing him his idea, Darwin was gagged and scared his idea would be stolen from him. Wallace & Darwin’s mutual friend found a way for both of them to be published at the same time.

The Descent of Man and Selection in Relation to Sex by Darwin

Sexual Selection