Darwin

Objectives

• Distinguish evolution from natural selection
• Explain artificial selection
• Describe the role of Wallace
• Summarize Darwin's reasoning
• Explain how a species can evolve

2 Major Ideas of the Theory of Evolution

• Evolution occurs
• Evolution occurs by natural selection

Natural selection is the process by which organisms with beneficial traits produce more offspring than other organisms.

Scientific Expedition

• Set sail in 1831 on the HMS Beagle
• Darwin was a naturalist
• Visited tropical rainforests
• Found rocks containing sea fossils
• Visited rock ledges that used to be beaches

Scientific Expedition

• Uncovered fossils of extinct ground sloth

Galapagos Islands

• Off the coast of Ecuador
• Observed that the islands were different
• Saw the plants and animals were different too

Who influenced Darwin

• Jean Baptiste Lamarck 1744-1829
• Thomas Malthus 1766-1834
• Charles Lyell 1797-1875

Lamarck

• French naturalist
• Proposed a species changes over time
• Was wrong about HOW species change
• (inheritance of acquired characteristics)

Malthus

• English economist
• Wrote essay: On Population
• Argued human population grows faster than others
• When population is too big, famine and disease occur
• This kills off weakest members

Lyell

• English geologist
• Wrote "Principles of Geology"
• Darwin took Lyell's book on his voyage
• Argued geological processes have shaped Earth
• Inferred Earth must be older than people believed

Other influences

• Was aware humans could breed organisms for useful traits
• Called this artificial selection

Alfred Russel Wallace

• English naturalist
• Had same idea as Darwin
• Sent Darwin a paper he'd written
• Confirmed Darwin's thoughts

Putting it all together

Like Lamarck, Darwin thought species could change over time. Fossil evidence helped confirm this.

Lyell convinced Darwin that Earth and life were very old. Thus, there was enough time to produce great diversity.

From Malthus, Darwin knew that a species could grow faster than its resources. Darwin turned this into "struggle for existence."

Darwin coined the term fitness to refer to an organisms ability to survive and produce offspring.

Darwin referred to nature's selection of the most useful variations as natural selection.

Darwin knew artificial selection could change a domestic species over time and inferred that natural selection would change a species over time.

Darwin thought that if a species changed enough, it would evolve into a new species.

Darwin published his own book, On the Origin of Species, in 1859.

Example

• Giraffes used to have short necks