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Chapter 7 Changes Over Time
Changes Over Time
Section 7-1:
Darwin’s Theory
Pages 224-231
What important observations did Darwin make on his
voyage?
How did Darwin account for the diversity of species
and the differences between similar species?
How does natural selection lead to evolution?
Chapter 7 Changes Over Time
5.1 Natural Selection
Charles Darwin
Simple Definition of Evolution -- Change over time.
Classical Definition of Evolution –
Common decent of all life upon earth from a single
ancestor as a result of mutations and natural
selection. Molecules to man theory.
Microevolution – Small changes within a species.
Macroevolution - Major changes from one kind of
animal into another
Chapter 7 Changes Over Time
Charles Darwin (cont.)
Darwin explored South America and its remote islands, such
as the Galapagos, on the HMS Beagle during a 5 year
journey.
Chapter 7 Changes Over Time
5.1 Natural Selection
Darwin’s Observations
Darwin made observations about the diversity and
uniqueness of organisms.
Many of the animals on the Galapagos were
similar, but not the same as organisms in
mainland South America.
Darwin reasoned that perhaps the organisms
in the Galapagos originally came from
South America and over time, they had
evolved or changed.
Chapter 7 Changes Over Time
Chapter 7 Changes Over Time
5.1 Natural Selection
Tortoises
Darwin found giant tortoises on all the Galapagos Islands, but nowhere else.
He reasoned that each new population changed slightly, or
evolved, to fit its unique environment on the island.
Chapter 7 Changes Over Time
Changes Over Time
Natural Selection
Natural selection is the process by which individuals who are
better adapted to their environment are more likely to survive
and reproduce than other members of the same species.
Although resources are
limited, animals
often produce more
offspring than could
survive.
Sometimes changes occur
in genes and a new
trait is created.
Chapter 7 Changes Over Time
Changes Over Time
Overproduction, Variations, Competition and Selection
Genetic variations (differences in traits) among turtles make
some of them better able to survive. Turtles that survive to
become adults will be able to reproduce.
Natural selection does not give a new species what it needs to
survive
Natural selection merely chooses for a trait that is already there.
Over time, it may make a trait better or more distinct but it does not
create it.
Chapter 7 Changes Over Time
Finches
Darwin was also
impressed by the diversity
of finches on the
Galapagos.
He reasoned that the finches changed over time
because they adapted to the different habitats and
food sources on the islands.
Chapter 7 Changes Over Time
Chapter 7 Changes Over Time
Galapagos Finches
Chapter 7 Changes Over Time
Sharpbeaked
Ground
Finch
Chapter 7 Changes Over Time
Large
Ground
Finch
Chapter 7 Changes Over Time
Warbler Finch
Chapter 7 Changes Over Time
Galapagos Woodpecker Finch
Chapter 7 Changes Over Time
Chapter 7 Changes Over Time
Chapter 7 Changes Over Time
Chapter 7 Changes Over Time
Chapter 7 Changes Over Time
6.2
Species change over time.
Reviewing Darwin’s theory of natural selection and evolution.
Copy the red sections down on a clean sheet of paper
Natural Selection Notes
Four principals of natural selection are
• OverproductionMore offspring are
produced than can
survive
Chapter 7 Changes Over Time
6.2
Species change over time.
Darwin's theory of natural selection explains evolution.
Four principals of natural selection are
• Overproduction
• Genetic VariationThere may be slight
variations in the
offspring.
Chapter 7 Changes Over Time
6.2
Species change over time.
Darwin's theory of natural selection explains evolution.
Four principals of natural selection are
• Overproduction
• Genetic Variation
• Competition – The offspring
Compete for survival in their
unique environmental
conditions.
Chapter 7 Changes Over Time
6.2
Species change over time.
Darwin's theory of natural selection explains evolution.
Four principals of natural selection are
• Overproduction
• Genetic Variation
• Competition
• Selection - Those with the best
traits for a particular environment
(adaptations) will survive and
reproduce. This is commonly
called “survival of the fittest.”
More fish with the beneficial notch
survive to reproduce
Chapter 7 Changes Over Time
Darwin’s Theory of Natural Selection
Natural selection is the process by which individuals who
are better adapted to their environment are more likely to
survive and reproduce than other members of the same
species.
Two factors that lead to natural selection – Genetics and the
environment
Chapter 7 Changes Over Time
Virtual Labs- How can natural selection be
modeled?
http://www.glencoe.com/sites/common_assets/scie
nce/virtual_labs/LS16/LS16.html
http://science.discovery.com/interactives/literacy/da
rwin/darwin.html
Chapter 7 Changes Over Time
Environmental changes can affect populations.
III. Environmental changes can affect populations.
A. Population size is limited by environmental
conditions.
B. Populations increase through births and
immigration.
C. Many factors limit population size.
1. Competition
2. Predators
3. Disease
4. Catastrophic events
D. The survival of a species depends on its
ability to adapt to change.
1. How Extinction Happens
Chapter 7 Changes Over Time
Environmental changes can affect populations.
III. Environmental changes can affect populations.
A. Population size is limited by environmental
conditions.
B. Populations increase through births and
immigration.
C. Many factors limit population size.
1. Competition
2. Predators
3. Disease
4. Catastrophic events
D. The survival of a species depends on its
ability to adapt to change.
1. How Extinction Happens