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Evolution. Evolution= genetic change of a population over time. How do we know about evolution?.
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How do we know about evolution? In 1831, at the tender age of 22, Charles Darwin set sail on HMS Beagle. The original purpose of the voyage was to map out trade routes for Great Britain, but Darwin arranged to work as a field naturalist, recording details and illustrations of interesting flora and fauna as he sailed (read: job for slackers). The voyage did not return to England until 1836.
Interesting Galapagos Species Galapagos Tortoise “Lonesome George” Blue-Footed Booby! Marine Iguana Galapagos Penguin
Darwin began to notice that organisms in isolated locations (i.e., on islands) often bore resemblance to their mainland counterparts, but with slight morphological changes. He began to wonder about the long-held assumption that species were created in their present forms.
In 1859, Darwin published his magnificent work, The Origin of Species. • Two main points of the text were: • Descent with Modification (a fancy/non-controversial way of saying evolution!) - Darwin proposed that species were, in fact, not created in their present forms, but rather had common ancestry with other extant species. • Darwin proposed natural selection as the mechanism for this descent with modification. A word on Thomas Huxley
But wait… What took him so long?! 1. Natural theology had ruled the sciences for many years. 2. He was unsure about the nature of variation which natural selection acted upon (didn’t know about Mendel). “We are profoundly ignorant of the causes [of variations]…” - Charles Darwin 3. He was young and insecure about the idea (he was only 27 when he returned from trade voyage).
He was (sort of) forced to show his cards… Alfred Russel Wallace (1823-1913) A professional collector stumbled upon the ideas of Descent with Modification and Natural Selection while observing beetles in Malaysia. He wrote Darwin a famous letter in 1858 and disclosed his ideas.
Darwin’s magnum opus,The Origin of Species, laid out a clear and simple description of natural selection that helped to support their claims.
The two men presented joint letters to the Linnaean Society in 1859. This means they both got credit, but because Darwin had been working on this longer, and had more evidence, he got most of the credit. Think about it—do we call Wallace the Father of Evolution?
Darwin’s Four Postulates 1. In every population, there is variety.
2. Some of that variety is passed on to offspring. Aw, he has your eyes!
Some will die because of disease, predators, or resource availability 3. There are always more individuals produced than can survive.
4. So, over time, the individuals who are the most fit for their environment will survive better to reproduce. If that fitness is attributed to their genetics, this will lead to an increased representation of their alleles in future generations (genetic change/time) (not THIS kind of fit!)
Natural Selection Individuals with traits that allow them to survive, will go on to reproduce offspring with those traits.
No!!!!! Not only did Wallace have similar ideas, Darwin was influenced by the work of many scientists before him…
Carolus LinnaeusAKA Hot Pants(1707-1778) • Father of Taxonomy • Developed binomial nomenclature
Georges Cuvier(1769-1832) Okay, so this thing definitely doesn’t look like my dog… • Father of Paleontology • Described hundreds of fossils evidencing extinct life forms
True to natural theology, Cuvier described these fossils as a result of CATASTROPHISM. And, to be clear, many of them were the result of major catastrophes
James Hutton and Charles Lyell Fathers of Geology Gradualism Uniformitarianism
Jean-Baptiste Lamarck • “You get what you need” (use/disuse) • Inheritance of acquired characteristics
So, what’s the evidence?What convinced Darwin and what have we learned since?
Biogeography: Distribution of species around the earth Biological diversity results from descendants of a common ancestor becoming adapted to diverse environments.
The process of nuclear division that reduces the number of chromosomes by half • Start with somatic cell • End with gamete
Homologous Structures Homologous structures provide strong evidence that all four-limbed vertebrates have descended, with modifications, from a common ancestor.
Homologous Structures Similar structures, but different functions
Structures that were used by common ancestors, but are useless today Vestigial Structures
Vestigial Organs The organs of many animals are so reduced in size that they are just vestiges, or traces, of homologous organs in other species. (leftovers)
Fossils Fossils prove the existence of many different organisms through time that are related to existing organisms. Looked at fossils from each of the different strata and compared their morphologies.
Comparative Embryology There are many similarities in the early stages of development of vertebrates, which suggests common ancestry.
Molecular Biology • Protein synthesis is essentially the samein all organisms. • Proteins in all organisms are composed of the same 20 amino acids. • DNA is very similar between two closely related organisms • Compare amino acid sequences of 2 organisms • The more amino acids organisms share, the more closely related they are
