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Changes Over Time
Chapter 5
Darwin’s Voyage
Chapter
5, Section 1
Pages 146-156
Make sure you know the following vocabulary:
1. species
2.
adaptation
3. evolution
4. scientific theory
5. natural selection
6. variation
Darwin’s Observations (page 147)
•When he was 22 years old, Darwin traveled
around the world on the ship HMS Beagle
•Darwin was amazed by the diversity of
animals that he saw
•A species is a group of similar animals that
can mate with each other and produce fertile
offspring
Similarities and Differences (page 148)
•On the
Galapagos Islands, Darwin observed organisms that were similar to ones on
mainland
South America
•The organisms on the islands had some
significant differences
•Darwin inferred that these organisms had
come to the islands from South America and then
changed over time
Adaptations (page 149)
•Darwin
observed the finches (small birds) of the Galapagos Islands
•He noticed that the beaks of the birds were
matched to the kind of food they ate
•An adaptation is a trait that helps an
organism survive and reproduce
Evolution (pages 149-150)
•After many
years, Darwin determined that species gradually change over generations to
become adapted to the surrounding conditions
•A scientific theory is a well tested concept
that explains a wide range of observations
•Darwin thought selective breeding must have
occurred on the islands, but he didn’t know what
could have caused it.
The Role of Genes in Evolution (page
154)
•If all
organisms for a species were exactly the same, natural selection could not
occur. Each
organism would have the exact same chance of
survival
•Only traits that are controlled by genes are
passed from parent to offspring
•During meiosis, mutations and gene shuffling
can occur, resulting in changes in traits
Evolution in Action (page 154)
•Scientists
have studied finches on one of the Galapagos Islands.
•When there is plenty of rain, more finches
have smaller, weaker beaks to eat small seeds.
When there is a shortage of rain, more finches
have larger, stronger beaks to eat large seeds.
•During the Industrial Revolution, moths in
England evolved from white to dark. Those with the
dark coloring were able to blend in with the
soot colored trees. They then survived and
reproduced at a higher rate than the white
ones.
How Do New Species Form? (page 155)
•Individuals
from a species are separated from the main population
•Over a long period of time, the separated
group acquires different traits through natural
selection.
Continental Drift (page 156)
•Hundreds of
millions of years ago, the supercontinent Pangaea was formed.
•Organisms of all species were able to move
to any part Pangaea
•Gradually Pangaea separated into today’s
continents
•Because organisms couldn’t cross the oceans
between the continents, they were separated
long enough to turn into different species
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