15-2
IDEAS THAT SHAPED
DARWIN’S THINKING
Objectives
1) How did Hutton and Lyell describe geological
change?
2) According to Lamarck, how did species evolve?
3) What was Malthus’s theory of population
growth?
INTRODUCTION
 People during Darwin’s era
thought the world was created
only a few thousand years ago
 People didn’t believe living
species or the Earth had ever
changed
 Scientists were discovering
new evidence to disprove
common beliefs
AN ANCIENT, CHANGING
EARTH
 2 scientists formed
important theories based
on evidence suggesting
that Earth was very old
and had changed slowly
over time
• Hutton and Lyell
AN ANCIENT, CHANGING
EARTH CONT’D
 Hutton and Lyell helped
scientists recognize that
• Earth is manly millions of
years old
• Processes that changed
Earth in the past are the
same processes that operate
in the present
HUTTON AND
GEOLOGICAL CHANGE
 Hutton published a detailed
hypothesis about the geological
forces that have shaped Earth in
1795
HUTTON AND GEOLOGICAL
CHANGE CONT’D
 Proposed
• Layers of rock form very
slowly
• Moved up by forces
beneath Earth’s surface
• Buried
• Pushed up from the sea
floor to form mountain
ranges
HUTTON AND GEOLOGICAL
CHANGE CONT’D
• Rocks are shaped by a
variety of natural forces
•
•
•
•
Rain
Wind
Heat
Cold temperatures
• Operate extremely slow
 Because of this he proposed
that Earth had to be much more
than a few thousand years old
LYELL’S PRINCIPLES OF
GEOLOGY
 Darwin was given a copy of Lyell’s book Principles of Geology shortly
before his voyage on the H.M.S. Beagle.
 This book inspired Darwin to ask questions
• If the Earth could change over time, might life change as well?
• Wouldn’t it have taken many, may years for life to change in the way Lyell
suggested?
•
This would only be possible if the Earth were extremely old
BLUE TICKET QUESTION
 What are some ways the
Earth has changed over time?
LAMARCK’S EVOLUTION
HYPOTHESES
 French naturalist
 Jean-Baptiste Lamarck
 Among the 1st scientist to
recognize
• Living things have changed
over time
• All species were descended
from other species
• Organisms were somehow
adapted to their environment
LAMARCK’S EVOLUTION
HYPOTHESES
 Lamarck proposed
• Selective use or disuse of organs, organisms acquired or lost certain traits
during their lifetime
• Traits could then be passed on to their offspring
• Led to change in a species over time
TENDENCY TOWARD
PERFECTION
 All organisms have an innate tendency toward complexity and perfection
• Continually changing and acquiring features that help them live more
successfully in their environments
USE AND DISUSE
 Organisms could alter the
size or shape of particular
organs by using their bodies in
new ways
INHERITANCE AND
ACQUIRED TRAITS
 Acquired characteristics could be inherited
• If during its lifetime an animal somehow altered a body structure, then it would
pass that change on to its offspring
EVALUATING LAMARCK’S
HYPOTHESES
 Lamarck’s hypotheses had flaws
• He did not know how traits are
inherited
• An organism’s behavior has no
effect on its heritable
characteristics
 He was one of the 1st to develop a
scientific hypothesis of evolution and
realize that organisms are adapted to
their environments
POPULATION GROWTH
 Thomas Malthus
• Reasoned that if the human population continued to grow unchecked, sooner or
later there would be insufficient living space and food for everyone
POPULATION GROWTH
CONT’D
• This hasn’t happened
because humans produce
fewer offspring
• Other organisms
• Majority of offspring die
• Only a few offspring
succeed in reproducing
15.2 EXIT TICKET