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Evolution
15
The Big Idea
The theory of natural selection
explains evolution and the
diversity of life.
Main Idea #1
Charles Darwin developed a theory of evolution
based on natural selection.
The 1st Scientific Hypothesis of Evolution
•
French biologist Jean Baptiste
de Lamarck offered the first
complete explanation of
evolution in 1809.
•
He was the first to argue that
fossils were the remains of
extinct animals.
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His concept was
transformational, meaning
individuals transform their
own traits in order to evolve.
Uniformitarianism
• Geologist Sir Charles Lyell the principle of
uniformitarianism.
•
Two parts:
•
laws of physics and chemistry
remain the same throughout earth’s
history
•
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past geological events occurred
by natural processes similar to
those that observed today
He said Earth’s age must be
measured in millions of years.
Charles Robert Darwin
1809-1882
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In 1831, Darwin sailed aboard the very
small ship the HMS Beagle.
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During his 5-year voyage, he collected
a wide variety of flora and fauna from
South America and surrounding
islands.
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He found long extinct fossils, including
seashells in the Andes Mountains at an
altitude of 13,000 feet.
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He also witnessed earthquakes and
severe erosion that helped to confirm
his ideas about geology.
Darwin & The Galapagos Islands
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These volcanic islands are on the
equator, 600 miles west of Ecuador.
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Each island varied in tortoises,
iguanas, mockingbirds, and ground
finches.
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The islands had similar climate, but
varied greatly in vegetation.
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Darwin inferred that island species
originated in South America, and
were modified over many years
under the varying conditions of
different islands.
Darwin (continued...)
• Darwin conducted the remainder of his work at
home in England, where all of his notebooks had
been sent home ahead of him in October 1836.
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His travel journal, The Voyage of the Beagle, was published three years later, but he
continued his research on the evolution of species by natural selection.
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Darwin first presented his ideas in a paper in 1844, but did not began writing the
larger volume until 1856. By 1858, he had received a manuscript from Alfred Russel
Wallace summarizing his ideas on natural selection.
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Geologist Lyell was instrumental in convincing Darwin to publish a joint paper with
Wallace.
•
Darwin’s book On the Origin of Species by Means of Natural Selection was published
in 1859. All printed copies sold out in one day.
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Darwin’s Theory of Evolution
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Darwin’s work actually included 5 separate theories
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Perpetual Change is the basic theory of evolution on which the
others are based stating that the world is constantly changing.
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Common Descent (controversial theory) states that all forms of
life descended from a common ancestor.
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Multiplication of Species - species divide and split into different
species, which can no longer interbreed
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Gradualism - large differences actually originate from an
accumulation of many smaller differences
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Natural Selection - explains the selective processes of the
environment, through a phenomenon called adaptation.
Natural Selection & Speciation
Natural Selection
•
The Ideas Behind Natural Selection
1. Individuals in a population show variations.
2. Variations can be inherited.
3. Organisms have more offspring than can survive
on available resources.
4. Variations that increase reproductive success will
have a greater chance of being passed on.
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Types of Evidence of Evolution
1. Fossil Record
2. Comparative Anatomy
• Homologous Structures - similar structures
inherited from a common ancestor
• Vestigial Structures - structures that are
reduced forms of functional structures in
other organisms; get smaller over
generations
• Analogous Structures - structures that have
similar function, but not similar shapes; not
inherited from a common ancestor
Evidence (continued...)
3. Comparative Embryology - many embryos share characteristics
that are not alike in the adult form
4. Comparative Biochemistry - the more closely related two species
are, the more amino acid sequences they will share
5. Geographic Distribution - evolution may be closely linked to climate
and geographical characteristics
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Speciation
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Speciation is the evolutionary process by which new biological
species arise.
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Allopatric speciation - a physical barrier divides one population
into one or more populations
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mountain ranges, lava flows, channels between islands,
wide rivers
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believed to be the most common type of speciation
Sympatric speciation - no physical barrier separates the
populations
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the ancestor species and new species live side by side
Types of Evolution
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Chemical Evolution - formation of organic molecules
from inorganic substances
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primordial soup; chemicals in the early ocean
giving rise to organic, and eventually, living matter
Organic Evolution - changing of a species into
something different by the accumulation of small
changes over time