Download 15-1 The Puzzle of Life*s Diversity

Where did they
originate ?
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Theory of Spontaneous
Generation
1.
2.
Living organisms arose
“spontaneously”
Believed to explain
“animalcules”
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Aristotle (384 –322 BC)
1. Proposed
theory of
spontaneous
generation
2. Also called
abiogenesis
3. lasted 2000
years
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Examples of
Spontaneous
Generation
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Example #1

Observation: Every spring, Nile
River flooded areas of Egypt,
leaving behind nutrient-rich mud
that enabled the people to grow
that year’s crop of food. However,
along with the muddy soil, large
numbers of frogs appeared that
weren’t around in drier times
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Example #1
Conclusion: perfectly obvious
that muddy soil gave rise to frogs
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Example #2

Observation: farmers stored
grain in barns with thatched
roofs
(like
Shakespeare’s
house). leaking. leads to
spoiled or moldy grain, and
of course there were lots of
mice around.
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Example #2
Conclusion: It was obvious to
them that the mice came
from the moldy grain.
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Example #3

Observation: for centuries
Sewage flowed down the
streets, and left over
food was thrown out into
the streets. Many cities
had major rat problems
and
a
disease
called
Bubonic plague.
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Example #3
Conclusion: sewage and garbage
turned into the rats.
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Example #4


Observation:
no
refrigerators
meant battling flies around meat.
Typically, carcasses were “hung by
their heels,” customers selected
which chunk the butcher would
carve off for them.
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Example #4
Conclusion: rotting meat was the
source of the flies.
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Abiogenesis Recipes

Recipe for bees:
Kill a young bull, and bury it in an
upright position so that its horns
protrude from the ground. After
a month, a swarm of bees will fly
out of the corpse.
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Abiogenesis Recipes

Recipe for mice:
Place a dirty shirt or some
rags in an open pot or
barrel containing a few
grains of wheat. In 21
days, mice will appear.
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Disproving
Spontaneous
Generation
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C. Francesco Redi (1668)
1. hypothesis was “rotten
meat does not turn into
flies”
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Redi’s Findings
2. Evidence against SG:
1. Unsealed – maggots on meat
2. Sealed – no maggots
3. Gauze –maggots on gauze only
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Results of Redi’s
Experiments

results only
accepted for
larger
organisms
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Disproving
Spontaneous
Generation of
Microbes
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D. John Needham (1745)
1. Showed
microorganisms
flourished in soups
exposed to air
2. Claimed a “life
force” could cause
spontaneous
generation
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Needham’s Results
3. bacteria were already present

didn’t boil long enough
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E. Lazzaro Spallanzani’s
(1765)
1. Boiled soups for an
hour and sealed
containers by melting.
2. soups remained clear.
3. Later, broke seals &
soups became cloudy
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Spallanzani’s Results
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Conclusion
4. Critics said sealed vials did
not allow “life force”
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The Theory Finally
Changes
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F.
Louis Pasteur (1822-
1895)
1. Performed experiments to
disprove Theory of SG.
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a. Pasteur's Experiment - Step
1
S-shaped Flask
 shape intended to trap
any dust containing
bacteria

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b. Pasteur's Experiment Step 2


Flasks boiled
Microbes Killed
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c. Pasteur's Experiment - Step 3


Flask left at various
locations
Did not turn cloudy
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Pasteur's Experimental
Results
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The Theory of Biogenesis

Proved biogenesis
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Figure 1.3
Evolution
Diversity of Life
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Evolution
“Nothing in
biology makes
sense EXCEPT
in the light of
evolution.”
Theodosius
Dobzhansky
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Charles Darwin in later years
History of
Evolutionary
Thought
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Early Ideas On Earth’s
Organisms
Aristotle
believed species
were fixed
creations
arranged by
their complexity
 Idea lasted
2000 years

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Early Ideas On Earth’s
Organisms



Linnaeus – 1st to
group similar
organisms and
assign them Latin
names
Two word name
(Genus species)
Known as Binomial
nomenclature
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Evolutionary Timeline
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Lamarck’s Theory of
Evolution




Jean-Baptiste Lamarck,
1809
Change Occurs Over Time
Changes Are acquired in
an organism’s lifetime
acquired changes were
passed to offspring
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Lamarck’s Theory of
Evolution
Idea called Law
of Use and
Disuse
 If a body part
were used, it
got stronger

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Lamarck’s Theory of
Evolution

Inheritance of Acquired
Characteristics
Traits Could Then Be Passed On To
Their Offspring
 Over Time This Led To New
Species

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Lamarck’s Theory of
Evolution


Use & Disuse - Could
Change The Size Or
Shape
Giraffe’s Necks
Longer from
stretching)
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Lamarck’s Theory of
Evolution

Inheritance Of Acquired Traits
– Traits Acquired During Ones Lifetime
Would Be Passed To Offspring
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Clipped ears of dogs could be passed to offspring!
Lamarck’s Mistakes
 Did
NOT Know traits were
inherited (passed through
genes)
 Mutation Occurs Before An
Organism Is Born
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Charles Darwin the
Naturalist
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Voyage of the Beagle
Charles Darwin




Born 1809
Joined Crew of HMS
Beagle, 1831
Naturalist
5 Year Voyage around
world
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Darwin’s Voyage of Discovery
A reconstruction of the HMS Beagle sailing off Patagonia.
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Darwin Left England in 1831
Darwin returned 5 years later in 1836
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The Galapagos Islands

West of South America
 Animals
On Islands Unique
»Tortoises
»Iguanas
»Finches
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The Galapagos Islands
More types of finches appeared on
the islands where the available food
was different (seeds, nuts, berries,
insects…)
 different types of beaks adapted to
their type of food gathering

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Darwin’s Observations
& Conclusions
The Struggle for
Existence
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Evidence for Evolution – The Fossil Record
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Definition
• Evolution is
the slow ,
gradual
change in a
population of
organisms
over time
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Darwin’s Observations
populations tend to remain
stable in size
 Environmental resources
are limited

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Darwin’s Conclusion
• Overproduction leads
to a struggle for
existence
• Only a fraction survive
each generation
• Survival of the Fittest
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Darwin’s Conclusion
• most fit for
environment leave
more offspring
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Darwin’s Theory of
Evolution
Organisms Change OverTime
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Common Descent with
Modification


organisms
descended from
common ancestors
diverge from a
common form
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Natural Selection


Driving force for
evolution
struggle for resources,
strongest survive &
reproduce
.
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Natural Selection
 Cannot
Be Seen Directly
 It Can Only Be Observed As
Changes In A Population Over
Many Successive Generations
– Radiation
– Fossil Record
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Descent With Modification
 Takes
Place Over Long Periods
of Time
 Natural Selection Can Be
Observed As Changes In
– Body Structures
– Ecological Niches
– Habitats
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Descent With Modification
 Species
Today Look Different
From Their Ancestors
 Each Living Species Has
– Descended
– With Changes
– From Other Species
– Over Time
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Descent With Modification
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Theory of Evolution
Today
Supporting Evidence
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Homologous Structures
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Evidence for Evolution - Comparative Embryology
Similarities In Embryonic Development
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Similarities in DNA Sequence
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Evolution
of
pesticide
resistance
in response
to
selection
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Evolutionary
Time Scales
Macroevolution:
Long time scale
events that
create and
destroy species
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Evolutionary
Time Scales
Microevolution:
Short time scale
events that change
the genotypes and
phenotypes of
populations
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Evidence of Evolution
Key Concept
Darwin Argued evidence Could Be
Found In:
– Fossil Record
– Geographical Distribution of Species
– Homologous Structures
– Early Development
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Fossil Record
Earth is Billions of Years Old
 Layers of Rock Showed Evidence Of
Gradual Change Over Time

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Geographic Distribution

Animals On
Different
Continents But
Similar Adaptations
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Homologous Body
Structures
 Similar
Structure
 Differ In Function
 Limb Bones Develop In Similar
Patterns
»Arms, Wings, Legs, Flippers
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Homologous Body
Structures
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Analogous structures

Butterflies or insects have wings but they are
very different from the birds.
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Anatomical studies show

Vestigial parts – why does a whale have a
pelvis and femur bones if it has no hind limbs?
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Vestigial structures
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Vestigial structures
Human vestigial structures
Ear muscles
Wisdom teeth
Appendix
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Vestigial Organs

Not All Serve Important Functions
» Appendix In Man
» Legs On Skinks
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Similarities In Early
Development
Embryonic Structures Show
Significant Similarities
 Embryo – early stages of
vertebrate development

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Human Fetus – 5 weeks
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Chicken
Turtle
Rat
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