Transcript Chapter 16: Darwin`s Theory of Evolution

CHAPTER 16: DARWIN’S THEORY
OF EVOLUTION
Section 16-2: Ideas the Shaped Darwin’s Thinking
AN ANCIENT, CHANGING EARTH
Many Europeans believed Earth was only a few
thousand years old, had not changed much
 Geology was new
 Geologists James Hutton and Charles Lyell
concluded that Earth is extremely old and that
processes that changed Earth in the past also
operate in the present

HUTTON AND GEOLOGICAL CHANGE
Connection between geological processes and
features
 Some rocks caused by sediments
 Earth shaped by natural forces
 Earth must be much older – deep time

LYELL’S PRINCIPLES OF GEOLOGY
Argued laws of nature are constant over time,
must use current, observable processes to explain
past events
 Uniformitarianism
 Built on Hutton’s work
 Darwin read Lyell’s book while on the Beagle –
witnessed a South American earth quake the
proved Lyell to be correct
 If Earth had changed over time, could life change
too?

LAMARCK’S EVOLUTIONARY HYPOTHESIS
French naturalist who proposed two early
hypotheses about evolution
 Suggested that organisms could change during
their lifetimes by selectively using/not using
various parts of their bodies
 Suggested individuals could pass these acquired
traits on to their offspring, enabling species to
change over time
 All organisms had an inborn urge to become more
complex/perfect and changed or acquired
characteristics to help them live more
successfully

LAMARCK’S EVOLUTIONARY HYPOTHESIS
Ex: Water birds acquired long legs because they
waded into deeper water to look for food
 Called acquired characteristics
 Inheritance of acquired characteristics
 Link between body structures and environment
 Incorrect:

No inborn drive to be “perfect”
 Evolution does not mean “becoming better” – no
predetermined direction
 Acquired traits cannot be inherited

POPULATION GROWTH
1798  English economist Thomas Malthus
noted humans were being born faster than people
were dying, causing overcrowding
 If the human population grew unchecked, there
would not be enough living space and food for
everyone
 Forces like war, famine, disease work against
population growth
 Darwin realized the same principle applies to all
organisms – most offspring die before reaching
maturity to reproduce

ARTIFICIAL SELECTION
Darwin looked for a natural, scientific
explanation
 Studied change produced by plant/animal
breeders
 Individual organisms vary, variations can be
passed from parent to offspring
