Chapter 16 – Darwin’s Theory of Evolution. 16.1: Darwin’s Voyage of Discovery Darwin was born...
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- Chapter 16 Darwins Theory of Evolution
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- 16.1: Darwins Voyage of Discovery Darwin was born on February
12, 1809 in England. Darwin was the first man to develop and
publish a theory of evolution. Evolution: a scientific theory that
explains how modern organisms evolved over long periods of time
through decent from common ancestors. This theory arose first when
he visited the Galapagos islands and other locations around the
world in 1831 on the ship H.M.S Beagle and collected samples of the
life there.
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- On his journey, Darwin noticed three general patterns of
biological diversity 1. Species vary globally Different, yet
ecologically similar, animal species inhabit separated, but
ecologically similar, habitats around the globe Example- the
flightless bird the rhea in the grasslands of South America and the
flightless bird the emu in the grasslands of Australia.
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- On his journey, Darwin noticed three general patterns of
biological diversity 2. Species vary locally Different, yet
related, animal species often occupied different habitats within a
local area. Example- the tortoises of the Galapagos.
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- On his journey, Darwin noticed three general patterns of
biological diversity 3. Species vary over time By collecting
fossils (preserved remains or traces of ancient organisms) Darwin
came to realize that fossils of extinct animals were similar to
living species. Example- the armadillo and the long-extinct
Glyptodont.
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- 16.2: Ideas that Shaped Darwins Thinking Geologists James
Hutton and Charles Lyell greatly influenced Darwins thinking Hutton
and Lyell concluded that the Earth is extremely old and that the
processes that changed Earth in the past are the same processes
that operate in the present.
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- James Hutton Hutton explained geological change of rocks,
mountains, and pressure.
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- Charles Lyell Lyell published a book called Principles of
Geology in 1830 that explained the theory of uniformitarianism-
that the geological processes we see today shaped the Earth long
ago, as well.
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- Jean-Baptiste Lamarck Lamarck suggested that organisms could
change during their lifetimes by selectively using or not using
various parts of their bodies. He also suggested that individuals
could pass these acquired traits on to their offspring, enabling
species to change over time. His ideas were published in 1809. His
hypotheses was concluded incorrect in several ways.
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- Thomas Malthus In 1798, English economist Thomas Malthus noted
that the world was becoming overcrowded. He reasoned that if the
human population grew, unchecked there wouldnt be enough living
space and food for everyone.
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- Artificial Selection In artificial selection, nature provides
the variation, and humans select those they find useful. Most
common example is with plant and animal breeders
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- 16.3: Darwin Presents his Case Described his theory in a book
called On the Origin of Species published in 1859. He spoke about
the struggle for existence The theory of adaptation- any heritable
characteristic that increases an organisms ability to survive and
reproduce in its environment. Survival of the fittest and fitness-
describes how well an organism can survive and reproduce in its
environment.
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- Natural Selection And, most importantly, as the mechanism for
evolution, natural selection- the process by which organisms with
variations most suited to their local environment survive and leave
more offspring. Natural selection occurs in any situation in which
more individuals are born than can survive, there is a natural
heritable variation, and there is variable fitness among
individuals.
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- Common Decent According to the principle of common descent, all
species living and extinct are descended from ancient common
ancestors.
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- 16.4: Evidence of Evolution Biogeography is the study of where
organisms live now and where they and their ancestors lived in the
past. Patterns in the distribution of living and fossil species
tell us how modern organisms evolved from their ancestors.
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- There are two biogeographical patterns 1. Closely related
species differentiate in slightly different climates. Example-
finches (birds) of the Galapagos. 2. Very distantly related species
develop similarities in similar environments. Example- similar
ground dwelling birds in the grasslands of Europe, Australia, and
Africa.
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- The Age of Earth and Fossils Radioactive dating indicates that
the Earth is about 4.5 billion years old plenty of time for
evolution and natural selection to take place. Many recently
discovered fossils form series that trace evolution of modern
species from extinct ancestors. Example- a fossil of the Eocene
whale Ambulocetus natans dates back to 49 million years old.
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- Homologous Structures Structures that are shared by related
species and have been inherited from a common ancestor are called
homologous structures, Evolutionary theory explains the existence
of homologous structures adapted to different purposes as the
result of descent with modification from a common ancestor.
Example- common structures are found in chicken wings and alligator
legs, probably dating back to an ancient, lobe-finned fish.
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- Structures Vestigial Structure: inherited from ancestors but
have lost much or all of their original function due to different
selection pressures acting on the descendant. Analogous Structure:
body parts that share a common function, but not structure.
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- Embryology Similar patterns of embryology, or the study of the
similarity of embryos provide further evidence that organisms have
descended from a common ancestor.
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- Genetics and Molecular Biology At the molecular level, the
universal genetic code and homologous molecules provide evidence of
common descent. The genetic code of RNA and DNA is nearly identical
in bacteria, yeast, plants, fungi, and animals. Genes, proteins,
and cells can be homologous, too.
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- Real Life Most changes take place over millions of years, and
evidence wont be seem overnight. Bacteria in a lab can display the
effects of natural selection, so scientists can understand
evolution through a lab setting.
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- Darwins Finches Darwins finches are the most stunning example
of natural selection. First Darwin hypothesized Then, he collected
evidence for over 35 years The Grants took over his work and have
documented that natural selection takes place in wild finch
populations frequently, and sometimes rapidly.
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- Further Study The Grants work shows that variation within a
species increases the likelihood of the species adapting to and
surviving environmental change It is important to understand that
any questions that remain are about how evolution works not whether
evolution occurs.