Ecology and Evolution: Biology 301 -- Wethey and Woodin
Department of Biological Sciences

University of South Carolina

Darwin and the Theory of Evolution, and Artificial Selection

· Variation in Nature

· 1.3 billion species

· 750,000 insects, 250,000 plants, 4000 mammals, 5000 sponges

· Why is there such enormous variety in nature?

· Lamarck (1744-1829) -

• inheritance of acquired characteristics gave rise to evolution

· Darwin (1809-1882) - The Origin of Species (1859)

• Malthusian theory of population growth - more offspring than can survive.
• Artificial selection - breeders select more desirable individuals and allow them to reproduce
• Natural selection - natural analog of artificial selection - better adapted individuals leave more offspring.
• Rare "monstrosities" in animals or "sports" in plants arise (now called mutations). Darwin's estimate of mutation rate was 1 in 10⁶, which is close to modern estimates.
• "The laws governing inheritance are for the most part unknown..." (from Chapter 1 of the Origin of Species - Mendel's work was not known to him).

· Alfred Russell Wallace (1823-1913) -

• Co-discoverer of natural selection as primary mechanism of evolution.

· Gregor Mendel (1822-1884)

• Experiments in plant hybridization (1865)
• Patterns of inheritance

· Artificial Selection

• Darwin built his theory of Natural Selection from what he knew of Artificial Selection
• Domestic Dogs - argued that not all breeds have wild prototypes - "who could believe that greyhounds, bloodhounds, pug dog, Blenheim spaniel, so unlike all wild Canidae - ever existed in a state of nature?"
• Domestic Pigeons - ( Photos of breeds ) - Studied intensively by Darwin
• "I am fully convinced that all [hundreds of breeds] are descended from the rock pigeon (Columba livia)."
• "Hybrids or mongrels from between all breeds of pigeons are perfectly fertile, as I can state from my own observation.
• Within a breed, characters are variable
• Pigeons have been bred for 5000 years
• Pairs mate for life so multiple breeds can be kept together
• Adaptation in domesticated animals is "not indeed to the animal's or plant's own good, but rather to man's use or fancy."
• "We cannot suppose that all breeds were suddenly produced as perfect and a useful as we now see them, in many cases we know that this has not been their history. The key is man's power of cumulative selection: nature gives successive variations; man adds them up in certain directions useful to him"