Transcript Ideas That Shaped Darwin`s Thinking

Bell Work
My, How You’ve Changed!

Prior to the 1800s, life scientists knew
that living things changed over
generations. They just didn’t know how
these changes were brought about.
Bell Work
1. Divide a sheet of paper into two columns and title the
first one Inherited Characteristics. Title the second
column Acquired Characteristics. In the first column,
list the characteristics that you believe you have
always had. For example, you may have brown eyes
or curly hair.
2. In the second column, list your acquired
characteristics. For example, you may have learned
how to play a musical instrument.
3. Which of the items in your lists do you think you might
pass on to your children? Explain your answer.
Ideas That Shaped Darwin’s
Thinking
Lyell and Hutton, Lamarck,
and Malthus
Ideas that shaped Darwin’s Thinking

Darwin’s voyage came at a critical time in
the history of science → explores were
traveling the world and great thinkers were
beginning to challenge established views
about the natural world

These ideas influenced Darwin’s thinking,
and in turn, Darwin’s ideas influenced others
Common Beliefs of the Time
1) Most Europeans believed the Earth and
all its life forms were created a few
thousand years ago
2) Neither the planet nor its living species
changed over time
 Many discoveries changed these views,
including the expanding fossil record
An Ancient, Changing World
Scientists studying the Earth began
uncovering evidence that suggested that
the planet was very old and had changed
slowly over time
* Hutton and Lyell helped scientists
recognize that the Earth is many millions
of years old and the processes that
changed Earth in the past are the same
processes that operate in the present

Processes that Shape the Earth


Rock layers are moved up or pushed
down (Plate Tectonics)
The Earth’s surface is shaped by a
variety of natural forces including rain,
wind, changing temperatures, etc.
(erosion)
Processes that Shape the Earth
Sea
level
Sea
level
Sedimentary
rocks form in
horizontal layers.
When part of Earth’s
crust is compressed,
a bend in a rock
forms, tilting the rock
layers.
As the surface
erodes due to water,
wind, waves, or
glaciers, the older
rock surface is
exposed.
New sediment is
then deposited
above the exposed
older rock surface.
Influence on Darwin

These ideas helped Darwin appreciate
the significance of geologic phenomena
that he had observed; this understanding
influenced Darwin in two ways:
1. Darwin asked himself: If the Earth can
change over time, might life change as well?
2. Darwin realized that it would take many years
for life to change as he suggested.
Lamarck’s Evolution Hypothesis

Lamarck was among the first scientists
to recognized that living things
changed over time – and that all
species descended from other species

Lamarck also realized that organisms
were somehow adapted to their
environment
Lamarck’s Idea About Evolution

Lamarck proposed that by selective use
or disuse of organs, organisms acquired
or lost certain traits over their lifetime.
These traits could then be passed on to
their offspring. Over time this process led
to change in a species.
Lamarck’s Idea About Evolution

Lamarck believed:
1. Organisms have a natural tendency toward
perfection
2. Organs can be altered through use or disuse
3. Acquired traits are inherited
* Lamarck’s hypotheses are incorrect in
several ways, but he was right in that he
recognized that organisms were adapted
to their environment.
Lamarck’s Idea About Evolution
Population Growth

Malthus reasoned that if the human
population continued to grow
unchecked, sooner or later there would
be insufficient living space and food for
everyone

Malthus observed that war, famine, and
disease worked against this population
growth
Influence on Darwin
Darwin recognized that this reasoning
applied directly to plants and animals,
which generally produce far more
offspring than humans
Examples: A maple tree produces thousands
of seeds in a single summer; an oyster
can produce millions of eggs each year
* Why isn’t the Earth covered with Maple
trees and oysters?

Main Ideas
1) The Earth is very old (~4.5 billion years
old); the planet and its living organisms
change over time
2) Organisms are adapted to their
environment
3) Organisms produce many more
offspring than survive to reproduce