Download Darwin`s Theory of evolution

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Darwin's Theory
of evolution
Ch 15
15.1 The Puzzle of life’s diversity
• Voyage of the Beagle
– Left port in 1813
– Traveled from The British Isles down the coast of South America around Cape Horn
to the Galapagos Islands.
– From there to New Zealand, Australia, around the Cape of Good Hope, and Britain.
15.1 The Puzzle of life’s diversity
• Darwin’s Observations
– He collected 68 species of beetles.
– He was amazed by how well suited species were to their environment.
– He collected many fossils.
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15.1 The Puzzle of life’s diversity
• The Galapagos Islands.
– It was his most influential stop.
– Despite their closeness they had very different climates.
– He was fascinated by the tortoises and marine iguanas.
– Tortoises on the different islands had unique shell shapes.
– He focused, however, on Finches of the islands.
15.2 Ideas that shaped his thinking
• Pre Darwin most people thought the earth was only a few thousand years old and
that life was created.
15.2 Ideas that shaped his thinking
• There were many advances going on in geology at the same time Darwin was on his
voyage.
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• James Hutton:
– Proposed it takes a long time for rock layers to form. He felt some layers were
buried others were pushed up to form mountains. Earth’s surfaces were shaped
by forces such as wind, rain, flooding heat, and cold, ect.
– For all this to happen the Earth must be millions of years old.
– Principle of Uniformitarianism: The geological processes that are going on now
have always gone on and operate the same way they do now
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15.2 Ideas that shaped his thinking
• Charles Lyell
– Published Principles of Geology
• Explained how earth processes worked.
15.2 Ideas that shaped his thinking
• Jean-Baptiste Lemarck
– Published his theory of inheritance of acquired traits.
• Tendency toward perfection: Organisms are constantly acquiring traits that help
them survive.
• Use and disuse: If a structure is used it is kept and improved upon if it is not
used it will disappear over time.
15.2 Ideas that shaped his thinking
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15.2 Ideas that shaped his thinking
• Jean-Baptiste Lemarck
• Inheritance of acquired traits: If a parent is disfigured by an injury the
disfigurement will be passed on to the offspring.
– Obviously there are some flaws with his theory
15.2 Ideas that shaped his thinking
• Thomas Malthus
– Deduced that the human population was growing rapidly and if left uncheck it
would exceed the earths carrying capacity.
– Darwin realized that this concept applied to all organisms, not just humans
15.3 Darwin Presents his Case
• Darwin looked at artificial selection an thought why could this not happen in nature.
– Artificial Selection: humans pick a desirable trait. They let plants with the
desirable trait breed and don’t let the others breed
– Natural selection: nature takes the place of humans in artificial selection
15.3 Darwin Presents his Case
• Natural selection
– Driven by struggle for existent: Everything is in competition for the resources they
need to live.
– Survival of the Fittest: the organism best suited to their environment will breed
and pass on their desirable traits .
• Fitness: the ability to an individual to survive and reproduce.
• Adaptation: an inherited characteristic that increases an organisms chance for
survival
Evidence of Evolution
• Fossil record: Shows that life changed over time.
• Geographic distribution: There are species on each continent that are similar to one
another, but differ in way that make them better suited for their environment.
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Evidence of Evolution
• Homologous Structures: Structures that originated from the same embryonic tissues.
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Evidence of Evolution
• Vestigial organs: Organs and structures that still remain although they have no
function
– Appendix, adipose fin
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Evidence of Evolution
• Similarities in embryos: show that organisms develop the same way. The same cells
are responsible for the homologous structures
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