Transcript 16.2 – Ideas That Shaped Darwin`s Thinking

16.2 – Ideas That Shaped Darwin’s Thinking
Warm Up
How did Lamarck propose organisms
evolve? Explain this process.
16.2 – Ideas That Shaped Darwin’s Thinking
Chapter 16: Darwin’s Theory
of Evolution
16.2 – Ideas That Shaped Darwin’s Thinking
Think about it!
 Many Europeans in Darwin’s time believed the
Earth was only a few thousand years old!!
 Darwin’s ideas relied upon the Earth being
much older. He based these thoughts off of the
research by several scientists.
16.2 – Ideas That Shaped Darwin’s Thinking
James Hutton and Geological Change
 Recognized connections between a number of geological
processes and geological features.
 Proposed two main ideas
1. Forces from under the Earth’s surface can push rock layers
up to create mountains.
2. Wind and water erosion can wear mountains away and
create valleys. (Grand Canyon – Rocky Mountains)
16.2 – Ideas That Shaped Darwin’s Thinking
James Hutton’s Conclusion
 All of these process took very long time to occur!
 Concluding that the Earth must be much older than a few
thousand years.
16.2 – Ideas That Shaped Darwin’s Thinking
Lyell’s Principles of Geology
 Stated that the laws of nature are constant over time and past
events can be explained by current observations!
 Examples
 Ancient volcanoes released lava and gases, just as
volcanoes do now.
 Ancient rivers slowly dug channels and carved canyons
in the past, just as they do today.
16.2 – Ideas That Shaped Darwin’s Thinking
Lyell’s Conclusion
 Lyell agreed with Hutton
 Argued that Earth was much older than a few thousand years
 Lyell’s book significantly impacted Darwin’s thinking.
16.2 – Ideas That Shaped Darwin’s Thinking
Lamarck’s Evolutionary Hypotheses
 Jean-Baptiste Lamarck also proposed that species change over
time:
 The Principle of Inherited Characteristics
 That organisms could change during their lifetimes by
selectively using or not using various parts of their bodies.
 He also suggested that individuals could pass these acquired
traits on to their offspring!
16.2 – Ideas That Shaped Darwin’s Thinking
Lamarck’s Ideas
 Example
 A giraffe with a 3’ long neck can only reach the
leaves at the bottom of the tree. After it ate all of
the leaves at the bottom it has to continuously
reach for higher leaves. Reaching for the higher
leaves all of the time caused its neck to grow
longer. Now it can easily reach the higher leaves.
The giraffe will then pass the long neck trait on to
its offspring.
 Principle of Inherited Characteristics
16.2 – Ideas That Shaped Darwin’s Thinking
Evaluating Lamarck’s Hypotheses
 Today, we know that Lamarck’s hypotheses were incorrect in
several ways.
 Evolution does not progress in a predetermined direction.
 Traits acquired by individuals during their lifetime cannot be
passed on to offspring.
16.2 – Ideas That Shaped Darwin’s Thinking
Population Growth
 Thomas Malthus – English Economist
 Conducted human population
studies.
 Noted the that there were more
births than deaths.
 This increased population would
create competition for resources!
16.2 – Ideas That Shaped Darwin’s Thinking
Population Growth
 Darwin knew that Malthus’s idea of competition applied
animals as well.
 Examples:
 A oak tree can produce thousands of seeds each
summer.
 One oyster can produce millions of eggs each year.
 Most offspring die before reaching maturity, and only
a few of those that survive manage to reproduce.
16.2 – Ideas That Shaped Darwin’s Thinking
Artificial Selection
 Artificial Selection = nature provides the variations, and humans
select the traits they find useful.
 Darwin put artificial selection to the test by raising and
breeding fancy pigeon varieties.
16.2 – Ideas That Shaped Darwin’s Thinking
Artificial Selection
 Darwin concluded that natural variation provided the raw
material for evolution.
 When Darwin published his scientific explanation for
evolution, it changed the way people understood the living
world.