Download Ch 15 Darwins Theory of Evolution

CH 15 Darwin’s Theory of
Evolution
15-1 The Puzzle of Life’s Diversity
15-2 Ideas that Shaped Darwin’s Thinking
15-3 Darwin presents his Case
15-1 The Puzzle of Life’s Diversity
 Evolution, or change over time, is the
process by which modern organisms
have descended from ancient
organisms
 A scientific theory is a well-supported
testable explanation of phenomena that
have occurred in the natural world
15-1 The Puzzle of Life’s Diversity
 During his travels, Darwin made numerous
observations and collected evidence that led
him to propose a revolutionary hypothesis
about the way life changed over time
15-1 The Puzzle of Life’s Diversity
 Darwin saw patterns in evolution not
only in living organisms but also in
comparing their ancestors fossils or
preserved remains
 Darwin observed that the characteristics
of many animals and plants varied
noticeably among the different
Galapagos Islands
15-1 The Puzzle of Life’s Diversity
 Pg 372 (1-5) Don’t Fall Behind
15-2 Ideas that Shaped
Darwin’s Thinking
 Most Europeans believed
Earth and life had been
created a thousand years
ago
 Before setting sail on the
Beagle, Darwin studied the
rich fossil record and started
changing his beliefs about
life’s creation
15-2 Ideas that Shaped
Darwin’s Thinking
 Before Darwin’s voyage, James Hutton
and Charles Lyell showed the Earth to
be millions not thousands of years old
due to geologic record
 This led Darwin to having 2 ideas
 If the Earth can change, so can life
 This change would have taken a very long
time
15-2 Ideas that Shaped
Darwin’s Thinking
 Lamarck proposed that by selective use or
disuse or organs, organisms acquired or lost
certain traits during their lifetime
 These traits could be passed on to their offspring,
overtime leading to changes in species
15-2 Ideas that Shaped
Darwin’s Thinking
 Lamarcks ideas
 Animals are always changing to become
more complex and closer to perfection
 Animals will gain or lose organs by using
their bodies in specific ways (arm  wing)
 Inheritance of acquired traits lift weights
and get strong you will have strong kids
 Even though he was wrong about most
of his ideas, they led to better theories
15-2 Ideas that Shaped
Darwin’s Thinking
 Last influence on Darwin-Thomas
Malthus
 Malthus reasoned that if the human
population continued to grow unchecked,
sooner or later there would be insufficient
living space and food for everyone
 Humans have a couple kids, trees can
have millions why is the Earth not
completely covered in trees? Why…..
15-2 Ideas that Shaped
Darwin’s Thinking
 Pg 377- (1-5)
15-3 Darwin presents his Case
 Darwin returned to England-1836
 Darwin released “On the Origin of Species” in
1859
 In Artificial Selection nature provided the
variation, and humans selected those variations
that they found useful
15-3 Darwin presents his Case
 The Struggle for existence means that
members of each species compete
regularly to obtain food, living space, and
other necessity of life
 Darwin called the ability of an individual to
survive and reproduce in its
specific environment Fitness
15-3 Darwin presents his
Case
 Fitness results from Adaptations or any
inherited characteristics that increases
an organism’s chance of survival
 Best suited animals have a higher survival
rate in the process- Survival of the Fittest
 Over time, Natural Selection results in
changes in the inherited characteristics
of a population
 These changes increase a species fitness
15-3 Darwin presents his Case
 The principle that all living and
extinct animals have one
common ancestor is known as
Common Descent
 Evidence that animals have
been evolving for millions of
years on Earth are the fossil
record, geographic distribution
of animals, homologous
structures, and similarities in
early development
15-3 Darwin presents his Case
 Structures that have
different mature forms but
develop from the same
embryonic tissue are called
Homologous structures
15-3 Darwin presents his
Case
 The organs of many animals are so
reduced in size that they are just traces
of homologous organs in other species
are called Vestigial Organs
 Pg
 386
 (1-4)