the evolution of living things chapter 7 section 1
TRANSCRIPT
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The Evolution of Living Things
Chapter 7Section 1
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Adaptation
Definition: A characteristic that helps an organism survive and reproduce in its environment – Physical: long neck or striped fur– Behaviors: help an organism find food, protect
itself, or reproduce.
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The bright coloring of the strawberry poison arrow frog warns predators
that the frog is poisonous.
The smokey jungle frog blends into the forest floor.
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SpeciesDefinition: a group of organisms that can mate
with one another to produce fertile offspring – Example: all strawberry poison arrow frogs are
members of the same species and can mate with each other to produce more strawberry poison arrow frogs
• The species that live on Earth today range from single-celled bacteria, which lack cell nuclei, to multicellular fungi, plants, and animals.
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This diagram shows some of the many kinds of organisms that have
lived on Earth since the planet formed 4.6 billion years ago.
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Evolution
Definition: The process in which populations gradually change over time
• Scientists think that as populations change over time, new species form. Thus, newer species descend from older species
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Fossils
Definition: The remains or imprints of once-living organisms found in layers of rock
• Fossils can be:1. Complete organisms
2. Parts of organisms
3. A set of footprints
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The Fossil Record
Definition: the history of life in the geologic past as indicated by the traces or remains of living things
• Provide evidence about the order in which species existed
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A model of the proposed relationships between ancient and modern
mammals that have characteristics similar to whales.
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Case Study: Whales
• Whales seem similar to fish, but unlike fish, whales:
• breathe air• give birth to live young • produce milk
• ancient ancestor was probably a mammal that lived on land and that could run on four legs
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Skeletal Structure• Show similarities between animals
Similarities suggest that cats, dolphins, bats, and humans had a common ancestor
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DNA
• Used to further support the theory that organisms share a similar ancestry, scientists compare organisms’ DNA at a molecular level. – The greater the number of similarities
between the data sets for any two species, the more closely the two species are related through a common ancestor