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Patterns and Process: The Darwinian Revolution
Therefore, patterns inevitably emerge among our observations. Most patterns are the result of some process. Patterns comprise
Humans observe and measure their observations of the natural world. Humans have a long history of trying to make sense of observed patterns.
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Supernatural Explanations
1. Each of these stories is different from the others, 2. Empirical evidence for supernatural creation is lacking.
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Intellectual Stirrings in the Renaissancein which he set out to prove the existence of God as evidenced by the beauty and order of Nature.
This work reflected the prevailing belief that science should be
But that century also saw the first stirrings of ideas about
Let's visit a "Who's Who of Evolutionary Thought" (<-- required link) |
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Lamarck: Use it or Lose itSentiments interieurs ("inner feeling", Fr) was cited as a driving force of evolution:
the "inner feeling" of the individual will respond by altering the morphological traits necessary to meet that challenge.
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Lamarck: Use vs. Disuse
Acquired characteristics could then be passed on to the individual's offspring. Lamarck's theory was one of the first truly testable ideas about how evolution proceeds.
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NeoLamarckian Ideas?
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organic evolution
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the process by which a population undergoes genetic changes from one generation to the next
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gene
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a unit of inheritance, composed of DNA, that controls a physical trait
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alleles
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Different versions of the same gene.
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species
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A group of living organisms able to interbreed in nature to produce fertile, viable offspring;
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population
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All members of the same species living in a defined region or area
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deme |
a local, actively interbreeding subpopulation that shares a distinct gene pool
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gene pool
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all the genes at all loci in every member of an interbreeding population
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evolutionary adaptation
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1. the process by which a population evolves to become better suited to its environment
2. a character/trait that has resulted from the evolutionary process
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speciation
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the evolution of distinct, reproductively isolated species from an ancestral species |
microevolution
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genetic change within a species over generations |
macroevolution
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the evolution of taxonomic groups, from speciation to the formation of larger taxonomic groups;
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Individual organisms do not evolve.
Individual organisms change via short-term adaptations.
Only populations evolve.
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The Darwinian Revolution
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Charles Darwin
He was among the first to propose that all living species Like most scientists of the time, he was initially a creationist.
But his studies of the natural world led him to a different view |
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The Voyage of the BeagleH.M.S. Beagle for a five year voyage as "unpaid gentleman scholar and naturalist" and learned companion for Captain Robert Fitzroy. While the Beagle's crew mapped South American coastlines, Darwin went ashore and collected living specimens from every landing locality.
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Darwin and The Galapagos Islandsinspired the foundations of his theory. He returned to England, married his cousin Emma, and began to study and write. The works of
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Artificial SelectionDarwin observed and bred domestic animals.
He noticed that humans could generate animals He called this practice artificial selection. He wondered whether nature itself might operate on a similar principle:
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I Think...
He termed this gradual change of one species into another He believed that this occurred due to a process he called natural selection.
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Darwin's Observations |
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Final Inference: Natural Selection
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Darwin's inferences can be distilled into four tenets.
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1. Overproduction |
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2. Heritable Variabilityand some of those variations are heritable. |
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3. Competitionand those varied offspring must compete for their share. |
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4. Differential Reproduction
Those individuals whose inherited characteristics make them |
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Survival of the Fittest?![]()
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What is the Smallest Unit that Can Evolve?
Consider that overall phenotype is the product of
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The Immortal Gene
The end result of natural selection
Differential survival (inheritance) of "competing" alleles
This is the essence gene-centered evolution described by |
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Georges-Louis Leclerc, Comte de Buffon (1707-1788)
Buffon was among the first Age of Enlightenment philosophers to suggest that the earth might be older than 6000 years.
An expert in many sciences from astronomy to biology,
Instead of using conventional Biblical wisdom,
Evolution via migration |
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Jean Baptiste Lamarck (1744-1829)
In 1801, Lamarck presented his
Its main tenet: changes an organism acquired during its lifetime could be passed on to its offspring.
Lamarck said these changes were driven by
sentiments
interieurs ("inner feelings", Fr): environmental challenges would drive individuals to physically change to meet those challenges.
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Georges Cuvier (1769-1832)
Though his expertise was in natural history and zoology, Cuvier is best known as the "father of paleontology" for his work on fossils and their relationship to the earth where they were found.
He was the first to establish extinction as a fact by demonstrating organismal diversity in deeper sedimentary strata were different from that in more recent strata.
Like most scientists and philosophers of his time,
He proposed that periodic, catastrophic floods (generated by a divine creator) were responsible for the fossil record.
Catastrophism is the theory that sudden, relatively brief, violent events (floods, volcanic eruptions, etc.) are the main forces that shape the surface of the earth.
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![]() By Joseph Wright of Derby - Unknown, Public Domain, Link |
Erasmus DarwinCharles Darwin's grandfather, Erasmus Darwin, a physician, was a proponent of evolution.As a student, young Charles read his grandfather's writings and was inspired by them. But it was only after his voyage on the Beagle that Charles Darwin began to incorporate ideas from other sources into his own musings about evolution. |
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James Hutton (1726-1797)
Hutton was a Scottish geologist who challenged the catastrophism theory.
He proposed that slow, continuous processes such as erosion had been the major factors forming earth's topography.
He dubbed this theory gradualism
Some refer to Hutton as the "Father of Modern Geology".
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Sir Charles Lyell (1797-1875)
This Scottish geologist and author of Principles of Geology proposed the theory of uniformitarianism.
This was an expansion of Hutton's Theory of Gradualism.
Lyell contended that not only was earth shaped by slow, continuous processes,
His work challenged many of Cuvier's ideas, which were the geological "conventional wisdom" of the time.
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(Thomas) Robert Malthus (1766-1834)
Malthus was an English religious scholar.
In his work An Essay on the
Principle of Population he suggested that much of humanity's
suffering (disease, famine, homelessness and war) was the inevitable
result of overpopulation: humans reproduce more quickly than
their food supply and other resources can support them.
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Charles Robert Darwin (1809-1882)
One of the most influential scientists of all time,
On the Origin of Species is arguably the most important
Evolution by means of natural selection occurs when
This is the essence of natural selection.
Because of the theological controversy he knew his work would provoke,
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Alfred Russel Wallace (1823-1913)
Wallace was a British explorer, naturalist, geographer, anthropologist, and biologist.
Wallace independently conceived the idea of natural selection.
His friends Charles Lyell and botanist Joseph Hooker
Lyell and Hooker presented the paper for him,
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Motoo Kimura (1924-1994)
In 1968, Mtoo Kimura published his
The theory describes how random, neutral DNA mutations Kimura proposed that these neutral mutations could spread through populations via genetic drift.
Genetic drift is a random process by which some individuals
These "lucky" individuals are genetically overrepresented |
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Thus, "survival of the fittest" translates as "survival of the most reproductively successful".
Survival is only one aspect of evolutionary fitness.
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"Survival of the Fittest"
An individual's Darwinian fitness is defined as its reproductive output compared to that of its conspecifics.
It may not even be the most important aspect of reproductive success.
Modern biologists avoid using the phrase "survival of the fittest"
to describe Darwin's theory.