BIOL 1020 – CHAPTER 22 LECTURE NOTES
Chapter 22: Descent with Modification: A Darwinian Viwe of Life
I. Darwin’s voyage
A. Charles Darwin (1809-1882) received a degree in theology, but also was trained in the type of field biology common in the early 19th century (most prominent biologists of the time were field biologists who studied and classified organisms in their natural environments)
B. Darwin signed on as the captain’s companion on board the H.M.S. Beagle, on which he took a five-year voyage from 1831-1836 exploring South America and surrounding islands, as well as islands in the South Pacific
C. His private work on the voyage was as a naturalist, collecting and cataloging thousands of species
D. He was most impressed by the similarities between species in the Galapagos islands (in the Pacific west of Ecuador) and their similarities to species from South America; this did not fit well with the divine design model that he had been trained under and that was still prominent at the time
E. There was much discussion by immediate predecessors and contemporaries of Darwin about how the divine design model did not mesh well with observation of the extremes of variation among species, the idea of extinct species represented in the fossil record, and the functional similarities between the anatomy of extremely divergent species; the idea that evolution occurs thus was “in the air” at the time, but attempts to find a convincing mechanism fell short (such as Lamarck’s acquired characteristics model)
F. Recall Darwin’s theological training – Darwin was well aware of the impact that a workable, testable theory of evolution would have, and the intense controversy and scrutiny it would draw; thus, while he worked out most of his theory of evolution shortly after his trip on the Beagle, he spent 20 years accumulating evidence and doing experiments before finally publishing the idea
G. Darwin was spurred on to publish when Alfred Russel Wallace shared his independent work where he had reached similar conclusions to Darwin; they first presented the theory of evolution by natural selection together in 1858
H. Darwin published his first version of the book On the Origin of Species by Means of Natural Selection in 1859; in it, he laid out the entire argument with all of the evidence that he had been gathering ever since his voyage on the Beagle
I. Darwin’s book had immediate and dramatic impact; the force of his argument and evidence convinced many scientists quickly, but of course it stirred tremendous controversy as well; Darwin made several revisions of his work in response to some of the most reasonable criticisms, as well as focusing on human evolution in The Descent of Man (1871)
II. Evidence supporting the theory of evolution
A. the fossil record
1. fossils provide direct evidence for change over time
· fossils range from mineralized casts or imprints (most commonly of bone, teeth, and shells, but sometimes of softer tissues) to actual body parts...
