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Lecture 2

BIO120H1 Lecture Notes - Lecture 2: Jerry Coyne, Special Creation, Botany


Department
Biology
Course Code
BIO120H1
Professor
Jean Jiang Nash
Lecture
2

Page:
of 2
BIO120 - Lecture 2 - Darwins big idea and how it changed biology
Required readings: Chapter 2 of Why Evolution is True by Jerry Coyne!
Recommended Reading: http://www.iflscience.com/plants-and-animals/new-species-human-
discovered-south-africa
Theory of evolution: living things change gradually from one form into another over time!
- a theory is a body of knowledge that is known to be true!
- special creation = direct creation of all things in effectively their present form, challenged
evolution
Evolution involved two controversial ideas:!
- concept of a changing universe (not static)!
- evolution has no purpose (replaced view that the causes of all phenomena had to have a
purpose)
Jean-Baptiste de Lamarck (1744-1829):!
- first to use the term “evolution” (disregarded special creation, realized organisms were
related by descent)!
- got the mechanism wrong: linear rather than branching view of evolution!
- first to provide a casual mechanism - the inheritance of acquired characters (e.g. the giraffe’s
neck: changes occur in the individual giraffe, grows a longer neck and will pass on that
acquired character to its offspring)
Why was Lamarck wrong?!
- August Weisman's Germplasm Theory:!
1) Inheritance only by germ cells (gametes); somatic cells (soma/body cells) do not function
as agents of heredity.!
2) Thus genetic info cannot pass from soma to gametes and onto next generation.!
3) Modern interpretation stated in molecular terms genetic info flows in one direction only from
DNA to protein but never in reverse.
Charles Darwin and Alfred Ruseell Wallace co-discovered Natural Selection
“On The Origin of Species” = possibly most important scientific book ever written
Darwin’s parents wanted him to be a doctor, but he was not interested in medicine and
couldn’t handle blood. He was always interested in nature and while at Cambridge, he had
the opportunity to travel on the Beagle.!
- took him 20 years after returning from the Beagle to published “Origin”!
- 1844: wrote but did not publish an essay on natural selection (important because it proves
that he had the idea recorded before Wallace)!
- 1858: received Wallace’s essay on same topic
Two key components of “Origin of Species”!
1) All organisms have descended with modification from common ancestors (idea of the tree
of life)!
2) The major agent of modification is natural selection operating on variation among
individuals
Darwin was influenced by the Cambridge botanist John S. Hounslow - prompted Darwin to
voyage on the Beagle for 5 years!
- after travelling the world for 5 years, Darwin never left England again!
- he was dedicated to writing many scientific texts, 25 in total
Darwin developed the idea of change from Charles Lyell’s book “Principles of Geology”!
- Lyell argued that present day geological processes can explain the history of the earth -
gradualism inspired Darwin, that changes occur gradually!
- The notion of a dynamic rather than a static world emerged in Darwin’s thinking
Darwin observed mockingbirds on Galapagos, noted that species varied, were not all identical
Darwin also read Malthus’ “Essay on the Principle of Population”!
- Malthus was worried about population growth and the strain it would put on resources!
- prompted Darwin to believe that favourable variations would be preserved while
unfavourable ones would be destroyed (idea of natural selection)
“Down House” = Darwin’s family home where “On the Origin” was written, other research and
writing as well (in Kent, England)
Essence of a Darwinian world-view:!
- recognition that variation among individuals is not deviation from a type (imperfection), but
the material from which natural selection fashions better adapted forms of life (move away
from typology and the notion of an “ideal” species to population thinking)
Requirement for Darwin’s theory to work (IMPORTANT!):!
1) Variation - variation among individuals in a population!
2) Heredity - progeny (offspring) resemble their parents more than unrelated individuals!
3) Selection - some forms are better at surviving and breeding than other in their given
environment
Creationism:!
- literal reading of the Book of Genesis!
- idea that the creation of all living organisms occurred by divine order in 6 days!
- all types of organisms were individually created and designed by a purposeful creator
Creationism is not science because:!
- it is not supported by empirical observations!
- it does not infer its principles from observation!
- its assumptions lead to no testable or falsifiable hypotheses
For those struggling with the idea of evolution vs. creationism, Douglas J. Futuyma’s Science
on Trial is a recommended read
Key things to know: Dobzhansky, Lamarck, Weismann, Darwin, Wallace, Lyell, Malthus,
inheritance of acquired characters, germ plasm theory, publication of “Origin of Species,”
gradualism, descent with modification, natural selection, requirements for evolution, creation
“science” is not science.