Transcript Section 1: Darwin`s Theory

Changes Over Time
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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?
Changes Over Time
Darwin’s Voyage
• Charles Darwin sailed on the Beagle, from
England to the Galápagos Islands.
Darwin’s Observations
• Darwin’s important observations included the
diversity of organisms, the remains of ancient
organisms and the characteristics of organisms
on the Galapagos Islands.
Diversity
• Today, scientists have identified more than 1.7
million organisms. MUCH more than Darwin
could have ever imagined.
• A species is a similar group of organisms that
can mate with each other and produce fertile
offspring.
Fossils
• Darwin saw the fossil bones of animals that
had died long ago. A fossil is the preserved
remains or traces of an organism.
Galapagos Organisms
• Many of the plants and animals resembled
those on the mainland.
• However there were important differences
between the mainland iguanas and the
Galapagos marine iguanas.
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Can you spot some differences
below?
Darwin’s Finches
• Darwin noticed differences in finches from
island to island
Tortoises too!
• Some islands had tortoises with dome shaped
shells, some with saddle shaped and some
that were more flat.
Adaptation
• An adaptation is any trait that helps an
organism survive and reproduce in its
environment.
• Finches beak structure helps it get food
• Flowers are brightly colored to attract bees
and other insects
Evolution
• Darwin reasoned that plants and animals that
arrived on the Galapagos Islands faced
environmental factors that were different
from those on the mainland. He hypothesized
that species gradually changed over many
generations to become better adapted to the
new environments. The gradual change in
species over time is called evolution.
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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.
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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.
Galapagos and Google Maps
• And now a video!
Questions
Give me 5! Outline your hand and give me five
things you learned today… one on each
finger!
Changes Over Time
End of Section:
Darwin’s Theory