Download Evolutionary Scientists and Evidence for Evolution

The Evolution of an IDEA!!!
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Objectives:
Describe the contributions of early scientists to modern theories of
evolution
Explain the fundamental theory of evolution
Discuss some questions and ideas that shaped Darwin’s thinking
In your own words, describe
what YOU think the theory of
evolution means…
Charles Darwin
Darwin’s Theory of Evolution

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.
How did Darwin came up with his
theory?
• …well first we have to have a look at those
who came before Darwin.
• These people changed the way we look at the
world around us.
• Darwin’s theory was greatly influenced by the
following people.
Ideas that shaped Darwin’s
Thinking

James Hutton:

1795 - Theory of Geological
change
 Forces are changing the
shape of the Earth’s surface
 These changes are very
slow
 The Earth is much older
than the thousands of years
we once thought!
George Cuvier: Fossil Studies
• (1769 – 1832)
• He noted that fossils can be simple or complex
• Fossils of simpler organisms seem to be found in deeper
layers of rock and soil
• Fossils of more complex organisms seemed to be found at
relatively shallower depths
• The shallower the depth a fossil is found in, the more
closely it is likely to resemble a living species
• He also noted that some rock layers contained fossils of
organisms that didn’t occur in any other layer
• Theory of Catastrophism:
Catastrophes like floods caused
extinctions of species (which could be
found in the fossil layers) and these
species were replaced by new species.
Charles Lyell: Theory of Uniformitarianism
• 1797-1875
• Published ‘Principles of Geology’
• Earth has been changed in the past
and is still changing now
• Geological change is very slow
• Hypothesized that mountains were
and are still being formed by
gradual processes and areas of
land are being slowly worn/eroded
away
 Darwin thought if the Earth
changed over time, what about life
on the Earth?
Lamarck
Lamarck's Principles
1. Use and Disuse: Structures an animal used
became bigger and stronger, while structures
that were not used became smaller and
weaker.
2. Inheritance of Acquired Characteristics: An
animal could pass on the traits it had
acquired throughout its life to its offspring
What did we get from Lamarck??
• Lamarck hypothesized that…
• All species evolve over time.
• A species evolves in response to its environment
so that it is better able to survive (adaptation)
• Changes get passed on from generation to
generation
Lamarck’s theory, while flawed got the ball rolling
for modern day thinking about how and why
species change.
Population Growth – Why do
species need to change???


Thomas Malthus-19th
century English economist
If populations grew
indefinitely(more Babies
born than die)
 Insufficient living space
 Food runs out
 Darwin applied this
theory to animals
On to Darwin…The Voyage of the Beagle
Voyage of Beagle
Dates: February 12th, 1831
 Captain: Charles Darwin
 Ship: H.M.S. Beagle
 Destination: Voyage around the world.
 Findings: Evidence to propose a
revolutionary hypothesis/theory about how
life changes over time

Patterns of Diversity (Questions)

Darwin visited Argentina and Australia which had
similar grassland ecosystems.

Those grasslands were inhabited by very different
animals.

Neither Argentina nor Australia was home to the
sorts of animals that lived in European grasslands.

Why??? Wouldn’t similar environments be home to
similar species??
Patterns of Diversity

Darwin posed challenging questions.
 Why were there no rabbits in Australia, despite the
presence of habitats that seemed perfect for them?

Why were there no kangaroos in England?
Living Organisms and Fossils

Darwin collected the preserved remains of
ancient organisms, called fossils.

Some of those fossils resembled organisms that
were still alive today.
Living Organisms and Fossils

Others looked completely unlike any creature he had
ever seen.

As Darwin studied fossils, new questions arose.
 Why had so many of these species disappeared?

How were they related to living species?
Publication of Origin of Species

Russel Wallace wrote
an essay summarizing
evolutionary change
from his field work in
Malaysia

Gave Darwin the drive
to publish his findings
Your Task
• Read through your hand out and answer
questions 1-3.
• For HOMEWORK tonight!!
• Read Adaptive Radiation: Darwin’s Finches to
learn more about what Darwin discovered on
his voyage.
• Answer the questions
• I am away tomorrow. There will be a QUIZ
on Thursday based today’s lesson and your
work tomorrow!
Mechanisms for Evolution

Natural variation--differences among
individuals of a species

Artificial selection- nature provides the
variation among different organisms, and
humans select those variations they find
useful.
Artificial Selection
Other Mechanisms that Drive
Evolution
Sexual Selection: the process
by which a trait that enables
an organism to acquire more
mates becomes more
common.
 Males compete for females
(combat)
 Females chose males
(desirable traits)

Genetic Variation
Evolution requires genetic variation.
 New genes being introduced results in
diversity of offspring.
 Mutations: Source of genetic variation
 Light and Dark Moths
 Dark Moths increased in frequency
during industrial revolution because of
dark soot in air
 Dark Moths could hide from birds

Descent

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Descent with Modification-Each living organism has
descended, with changes from other species over time
Common Descent- were derived from common ancestors
Evidence of Evolution
 The
Fossil Record
 Comparative
anatomy/Homologous Body
Structures
 Similarities
in Early
Development
 Biochemistry and DNA
 Vestigial organs
 Observation of Direct Species
Change
Evidence for Evolution

The Fossil Record-Layer show
change

Shows numbers extinct animals
Shows similarities between extinct
animals and animals that are alive
today
The earth’s layers show a time
scale of species and when they
appeared on earth (and when they
died out)


Transitional fossils
are fossils that show
intermediary links
between groups of
organisms
 They can provide a
link between the past
and present

Biochemistry and DNA
When comparing
the DNA of one
species to
another, more
similarities are
found in species
that are more
closely related.
Direct observation of species
change

Bacteria become
resistant to
antibiotics

Wolves were bred over
many generations to
become dogs (artificial
selection) • and then
bred further to create a
variety of breeds
Your Task
With your partner, review the 4 mechanisms
for evolution that you learned about today.
 Explain each mechanism for evolution in
your own words. How do you think each of
these mechanisms drove evolution?
