Transcript Chapter 7 Changes Over Time

Chapter 7 Changes Over Time
What factors have caused the evolution and diversity of
organisms?
You plant a packet of zinnia
seeds, and later, the zinnias
begin to bloom. You notice that
no two plants are exactly alike.
For example, some flowers have
different colors than others. What
accounts for these differences?
Write an explanation.
Chapter 7 Changes Over Time
Identify Multiple Meanings
Word
Everyday Meaning
Scientific Meaning
n. A guess; an idea of how
or why something might
happen
n. A well-tested concept that
explains a wide range of
observations
Example: Emily has a
theory that basketball is
harder to play than baseball.
Example: The cell theory says
that all organisms are made of
cells.
theory
Chapter 7 Changes Over Time
Apply It!
In the sentences below, identify which meaning of the word
theory was used—the everyday meaning or the scientific
meaning.
1.
The theory of evolution explains how organisms have changed
over time.
Theory (science use)
2.
Do you have a theory about why Sarah is a vegetarian?
Theory (everyday use)
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Changes Over Time
Section 1:
Darwin’s Theory
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?
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Changes Over Time
Darwin’s Voyage
Charles Darwin sailed on the Beagle, from England to the
Galápagos Islands.
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Darwin’s Discoveries
Comparisons to South American Organisms:
1. many island species were similar to mainland species.
2. species were different because of what they had to eat.
Comparisons among the islands:
1. Species varied from island to island.
Adaptation: A trait that helps an organism survive &
reproduce.
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EVOLUTION
Darwin’s Reasoning: Species gradually changed over many
generations & became better adapted to the new
environments.
Evolution- the gradual change in a species over time
Scientific Theory- a well-tested concept that explains a wide
range of observations.
Selected Breeding- (used by breeders) selecting to breed
species for certain traits (ex. Speed in race horses)
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Changes Over Time
Overproduction and Variation
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.
Overproduction:
Variation:
Producing a lot of
offspring.
Differences in
traits within a
species.
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Changes Over Time
Competition and Selection
Variations among turtles make some of them better able to
survive. Turtles that survive to become adults will be able to
reproduce.
Selection:
“survival of
Competition:
Species
compete against
each other to
survive.
the
FITTEST”.
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Environmental Factors: can effect an organism’s ability to
survive. (ex. Pollution, hunting)
Genes and Natural Selection: genes contribute to natural
selection.
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Changes Over Time
Links on Charles Darwin
Click the SciLinks button for links on Charles Darwin.
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Changes Over Time
End of Section:
Darwin’s Theory
(write summary)
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Section 2:
Evidence of Evolution
What evidence supports the theory of evolution?
How do fossils form?
What do scientists learn from fossils?
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Forms of Evidence
• Body Structure
•Comparative Anatomy- comparing body structures of
different organisms.
•Homologous structures- similar structures that related
species inherited from common ancestor.
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Homologous Structures
The structure of the bones in a dolphin’s flipper, a bird’s
wing, and a dog’s leg is similar. Homologous bones are
shown in the same color.
Chapter 7 Changes Over Time
Other Similarities:
• Similarities in Early Development- comparing how different
species develop before birth.
• Similarities in DNA & Proteins• Similar DNA = common ancestor
Chapter 7 Changes Over Time
A variety of species
Over time, different environments and genetic variation have
produced, through natural selection, the variety of
organisms that exist today.
Different Environments:
habitat: specific environment that provides the things
organisms need to LIVE, GROW & REPRODUCE.
Genetic Diversity: species are not completely identical.
-variations & mutations
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How do New Species Form?
New species can form when a group of individuals remain
isolated from the rest of it’s species long enough to evolve
different traits.
How?
Geographic Isolation- when some members of a species
become cut off from the rest.
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Kaibab and Abert’s Squirrels
These two kinds of squirrels have
been isolated from one another
for a long time. Eventually this
isolation may result in two
different species.
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Inferring Species Relationships
Similarities in DNAspecies inherited many of the same genes from common
ancestors.
Combining EvidenceSimilar DNA + Protein structure = common ancestor
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A Branching Tree
This branching tree shows how scientists now think that
raccoons, lesser pandas, giant pandas, and bears are
related. Related by shared-derived characteristics.
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Extinction of Species
Extinction is caused by a
change in species'
environment. The
members of a species
may not have adaptations
that allow them to survive
and reproduce in the
changed environment.
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Extinction and the Environment
Extinct: When no members of that species are still alive
• This is caused by the species environment
•New disease
•Predators
•Hunting
•Climate Change- the leading cause of extinction
• Adaptation and Survival•Some organisms have traits that will help them adapt to
the new environment and survive.
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A Branching Tree
Branching tree diagrams such as this show relationships
between groups of organisms. It also shows the order in
which specific characteristics may have evolved.
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Shared Derived Characteristics
A branching tree diagram shows evolutionary relationships
by grouping organisms according to shared derived
characteristic, a homologous structure shared by all in a
group.
Amphibians
Fishes
Reptiles
Egg with shell
Invertebrates
Four limbs
Backbone
Ancestor of animals
Chapter 7 Changes Over Time
Order of
Characteristics
Evolutionary
Groups
• The lower on the branch,
the earlier it developed
• Groups within groups
Amphibians
Fishes
Reptiles
Egg with shell
Invertebrates
Four limbs
Backbone
Ancestor of animals
Largest subgroup
Chapter 7 Changes Over Time
Constructing a Branch Tree
Group with 2 shared traits
Group with 1 shared trait
Group with none of characteristics
Shared trait
Shared trait
Common ancestor
Shared trait