Descent with Modification: A Brief History

1. Descent with Modification: A Brief History • Carolus Linnaeus (father of taxonomy, 1707-1778) • arranged organisms by genus and species largely by physical characteristics. • Called a binomial system the naming of organisms is still used today. • Inference - species that shared similar characteristics were created at similar times and did not necessarily share a common ancestor. • Ironically it was the detailed work of Linnaeus that led Darwin to connect the dots of evolution.

2. Paleontology • The branch of paleontology largely began around the time of Darwin as Georges Cuvier (1769-1832) began noticing that as the strata (layers of the Earth) change going deeper into Earth, fossils become more dissimilar to present day organisms. • Cuvier was a staunchly opposed to the theory of gradual evolution but rather clung to the idea of catastrophism to explain the differences between strata. It was his belief the changing Earth caused mass extinctions of organisms.

3. Descent with Modification: A Brief History • In contrast to Cuvier's catastrophism was the idea of gradualism. • Scottish geologist James Hutton (1726-1797) proposed the concept of gradualism. • Gradualism simply stated that the process that changed Earth's strata are still at work today and that these ecological pressures are what cause a change in the species. • This led to the comprehensive theory of uniformitarianism by Charles Lyell (1797-1875). • These ideas greatly influenced Darwin to publish his famous papers.

4. Descent with Modification: A Brief History • Jean-Baptiste de Lamarck (1744-1829) published on the theory of use and disuse to explain the difference in the fossil record. • He believed that if a physical trait was useful to an organism it would be passed on and that if it was not it was not. • Although he lay the ground work to what would become evolution, he missed the mark as he believed that acquired traits were passed on and not necessarily genetic frequencies.

5. Descent with Modification: A Brief History • In 1859 Charles Darwin changed the ancestral view when he published on the Origin of Species. • In it he challenged the whole organism theory (organisms were created just as you find them today) offered by Aristotle and offered a new one. Organisms may be quite different than there ancestors due to natural selection. • Natural selection simply means that nature selects which phenotypes are most suited to leave offspring. • Those offspring will pass on the genetic traits that made them more fit (able to adapt to environmental changes). • Natural selection leads to evolution within a species. • Evolution of a species is the change in gene frequencies in a population over time. • It leads to evolutionary adaptation which is an accumulation of adaptations that lead to an increase of fitness. • This descent with modification became the focus of now classifying organisms trying to find a common descent.

6. Artificial Selection • From Darwin's research came the idea of artificial selection which allows us to select for traits that are desired from selective breeding of individuals possessing desirable characteristics. • Over time Darwin's theme of evolution has caused taxonomy to be replaced with phylogeny. As with taxonomy individuals are grouped by relatedness. Unlike taxonomy as a means of classification, phylogeny classifies individuals based on their genetic as well as physical make-up Darwin’s Finches