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Darwin’s Theory
of Evolution
Chapter 15
Dr. Donna Howell
Biology I
Blacksburg High School
Evolution
• Wellsupported
scientific
theory
• Change
over time
Charles Darwin
• Scientist who, in
1831, traveled
on the HMS
Beagle around
the world to
study nature.
• He made
observations
and collected
evidence about
how life changes
over time.
Charles Darwin
• He observed that
plants and
animals all
seemed wellsuited to the
environment
they lived in
• He also noticed
that certain
species lived in
some places but
not in others.
Charles Darwin
• He collected many preserved fossils , and
wondered why some of these species had
disappeared from the earth.
The Galapagos Islands
• This was an area
in the Pacific that
intrigued Darwin
the most.
• He observed that
the animals on
the islands of the
Galapagos
differed in
predictable ways.
The Ancient Changing
Earth
• James Hutton
and Charles Lyell
propose that the
Earth is shaped
by geological
forces that took
place over
millions of years
• Darwin wondered
if the same could
be true for life
Lamarck’s Hypothesis
• Lamarck
hypothesized that
through use or
disuse of organs,
living beings
could add or lose
traits in their
lifetime.
Lamarck’s Hypothesis
• An example of
this is the fiddler
crab.
• He said that
because the male
crab uses its
large claw a lot,
it becomes larger
• This larger claw
is passed on to
offspring.
Population Growth
• Thomas Malthus,
in 1798, said that
if the human
population
continued to grow
like it is, sooner
or later there
would be
insufficient food
and living space
for everyone.
On The Origin of Species
• Darwin took all of
these ideas, and
came up with his
own theory of
evolution.
• In 1859, his book
was published
where he said a
mechanism called
natural selection
was responsible
for change.
Inherited Variation
• Darwin learned
from animal and
plant breeders
that some of this
change was due
to inheritance –
differences
passed from
parent to
offspring.
Artificial Selection
• When certain
plants and
animals are
deliberately bred
to produce a
superior
organism, this is
called artificial
selection.
Natural Selection
• Darwin realized
that artificial
selection takes
place in nature.
• There is a
struggle for
existence between
organisms, and
those that have
better traits win.
Natural Selection
• Darwin also said
that those
organisms that
were better suited
to their
environment
survived to
reproduce,
passing their
traits on.
• Survival of the
fittest
Natural Selection
• Darwin also said
that each living
species has
descended, with
changes, from
other species over
time to best suit
their habitat.
• Descent with
modification.
Natural Selection
• Darwin said that
if we trace the
lineage of each
animal back, we
would find that
all shared a
common ancestor.
• Common descent.
Evidence of Evolution
• There are multiple types of evidence for
evolution.
• Fossil record, homologous body structures,
and embryology.
The Fossil Record
• By comparing
fossils from
different rock
layers, scientists
can document the
fact that life on
Earth has
changed over
time.
Homologous Body
Structures
• Scientists have
noted that although
arms, wings, legs,
and flippers are very
different, they all
are constructed from
the same bones.
• Called homologous
structures.
Embryology
• The early stages of
animals with
backbones are very
similar.
• Same groups of
embryonic cells
develop in the same
order and similar
patterns to produce
tissues and organs.
Summary
• Individual variations
can be inherited.
• Only the fittest
survive
• Natural selection
causes species to
change over time.
• Species today are
descended with
modification from
ancestral species.

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