Evolution by Natural Selection 2003-2004

Charles Darwin 1809-1882 British naturalist Proposed the idea of evolution by natural selection Collected clear evidence to support his ideas 2003-2004

Voyage of the HMS Beagle 1831-1836 Travels around the world Makes many observations of natural world main mission of the Beagle was to chart South American coastline After graduation Darwin was recommended to be the conversation companion to Captain Robert FitzRoy, preparing the survey ship Beagle for a voyage around the world. FitzRoy chose Darwin because of his education, his similar social class, and similar age as the captain. Darwin noted that the plants and animals of South America were very distinct from those of Europe 2003-2004

Voyage of the HMS Beagle Stopped in Galapagos Islands The origin of the fauna of the Galapagos, 900 km west of the South American coast, especially puzzled Darwin. On further study after his voyage, Darwin noted that while most of the animal species on the Galapagos lived nowhere else, they resembled species living on the South American mainland. It seemed that the islands had been colonized by plants and animals from the mainland that had then diversified on the different islands 2003-2004

Darwin’s finches 13 species of finches in the Galápagos Islands Was puzzling since only 1 species of this bird on the mainland of South America, 600 miles to the east, where they had all presumably originated Darwin noted that the plants and animals of South America were very distinct from those of Europe. Organisms from temperate regions of South America were more similar to those from the tropics of South America than to those from temperate regions of Europe. Further, South American fossils more closely resembled modern species from that continent than those from Europe. 2003-2004

Darwin’s finches Differences in beaks associated with eating different foods adaptations to the foods available on their home islands Darwin concluded that when the original South American finches reached the islands, they adapted to available food in different environments 2003-2004

Darwin’s finches Finches with beak differences that allowed them to… successfully feed successfully compete successfully reproduce pass the successful traits onto their offspring 2003-2004

Darwin’s finches Over many generations, the finches changed anatomically and separated into different species adaptive radiation 2003-2004

Origin of Species On November 24, 1859, Charles Darwin published On the Origin of Species by Means of Natural Selection 2003-2004

In historical context 2003-2004

What did Darwin say? Every population of organisms includes variation differences between individuals 2003-2004

What did Darwin say? Organisms reproduce more than the environment can support some offspring survive some offspring don’t survive competition for food for mates for nesting spots to get away from predators 2003-2004

Natural selection Put together variation and competition and you get natural selection survival of the fittest fittest are the ones that survive to reproduce The dodo is probably the world's most famous extinct bird. Dodos lived on the island of Mauritius, where over many years they became flightless. Unfortunately, when humans arrived on Mauritius -- off coast of east Africa in Indian Ocean -- bringing pigs and monkeys, the dodo was rapidly exterminated. 2003-2004 Dodo bird

Survival of the fittest Who is the fittest? traits fit the environment the environment can change, so who is fit can change Peppered moth 2003-2004

Peppered moth Year % dark % light 1848 5 95 1895 98 2 1995 19 81 1848 5 95 1895 98 2 1995 19 81 2003-2004

Support for Darwin’s ideas Fossil record layers of sedimentary rock contain fossils new layers cover older ones, creating a record over time fossils within layers show that a succession of organisms have populated Earth throughout a long period of time 2003-2004

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Archaeopteryx A fossil of Archaeopteryx (Smithsonian Museum, Washington, DC), a reptilian bird ancestor that lived about 150 million years ago. 2003-2004

Fossil record Today’s organisms descended from ancestral species 2003-2004

Descent with modification The history of life is like a tree with multiple branches from a common trunk Closely related species — the twigs of the tree — shared the same line of descent until they branched off from a common ancestor 2003-2004

Support for Darwin’s ideas Homology similarities in characteristics resulting from common ancestry 2003-2004

Homologous structures The forelimbs of human, cats, whales, and bats share the same skeletal structures but different functions branched off from common 4-limbed ancestor homologous structures 2003-2004

Support for Darwin’s ideas Artificial selection Artificial breeding can take advantage of differences between individuals “descendants” of the wolf 2003-2004

Support for Darwin’s ideas Artificial selection Artificial breeding can take advantage of differences between individuals “descendants” of the wild mustard 2003-2004

Support for Darwin’s ideas Natural selection in action Insecticide & drug resistance insecticide didn’t kill all individuals resistant survivors reproduce resistance is inherited insecticide becomes less & less effective The evolution of resistance to insecticides in hundreds of insect species is a classic example of natural selection in action. The results of application of new insecticide are typically encouraging, killing 99% of the insects. However, the effectiveness of the insecticide becomes less effective in subsequent applications. The few survivors from the early applications of the insecticide are those insects with genes that enable them to resist the chemical attack. Only these resistant individuals reproduce, passing on their resistance to their offspring. In each generation the % of insecticide-resistant individuals increases. 2003-2004

Theory of Evolution Theory of evolution by natural selection well-supported idea not “just a theory”! Natural selection is widely accepted in science because its predictions have withstood thorough, continual testing by experiments & observations 2003-2004

Unity & diversity Only evolution explains both the unity & diversity of life By attributing the diversity of life to natural causes rather than to supernatural creation, Darwin gave biology a strong, scientific, testable foundation 2003-2004

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