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Chapter 6: Change Over Time
Lesson 1: Darwin’s Theory
 Studied in the Galapagos Islands
 Saw a variety of living organisms and compared them
to organisms from around the world.
 Convinced that a species changes over time.
 Species: group of similar organisms that can mate with
each other (more than 1.6 million species).
 He mostly studied tortoises and birds.
 Darwin thought that all finches must be related
through a common ancestor, and that the changes
they had in their beaks was a result to the
environment.
 Adaptation: a trait that increases an organism’s
ability to survive and reproduce.
 Darwin came up with a
hypothesis of evolution:
the process of change over
time.
 He thought species change
over many generations to
become better adapted to
new conditions.
 “When we read in Genesis the account of Creation, we risk
imagining that God was a magician, with such a magic
wand as to be able to do everything,” he said. “However, it
was not like that. He created beings and left them to
develop according to the internal laws that He gave each
one, so that they would develop, and reach their fullness.”
 The creation of the universe, Francis said, was not a singular
event, but rather “went forward for centuries and centuries,
millennia and millennia until it became what we know
today.”
 “God is not... a magician, but the Creator who brought
everything to life,” Francis said. “Evolution in nature is not
inconsistent with the notion of creation, because evolution
requires the creation of beings that evolve.”
 Natural selection: the process by which individuals
that are better adapted to their environment are more
likely to survive and reproduce more than other
individuals.
 Several factors affect this process.
 Most species produce too many offspring, and there are
not enough resources for them all.
 The stronger species that get the resources will survive.
 Survival of the fittest
 Variation: any difference between individuals of the
same species.
 Some organisms have certain traits that make them
more likely to survive.
 Members of the same species living in the same area
have to fight for the same resources.
 Organisms with more desirable traits will be chosen as
mates by other organisms, and the desirable traits
could be passed on.
 A change in the environment could lead to certain
species or members of a species having better chances
of survival.
 Only traits that are inherited (genetically passed on)
can be acted upon by natural selection.
Chapter 6: Change Over Time
Lesson 2: Evidence of Evolution
Fossils
 Fossils show differences
between organisms from
the past and organisms
today.
 Show when/how new
species evolved
Early Development
 Similarities early on suggest that organisms have the
same ancestor.
Body Structure
 Similar body structures also suggest a common
ancestor.
 Homologous structures: are similar structures in
different species; could have different functions.
DNA and protein structure
 The more closely related the DNA is, the more closely
related the organisms are.
 Usually DNA evidence supports the other types, or
reinforces what scientists already believe to be true.
Chapter 6: Change Over Time
Lesson 3: Rate of Change
 Sometimes part of a species becomes isolated, or
separated, from the rest of the species.
 When this happens, they can slowly, over a long time,
evolve to have different traits that prevent
reproduction.
 Gradualism: small changes that add up to major
changes over a long period of time.
 Sometimes, a species remains unchanged for its
existence.
 After extinction, a similar species appears that remains
unchanged for a long period of time.
 This is called punctuated equilibrium.