Transcript 10.1 Early Ideas About Evolution

10.1 Early Ideas About Evolution
10.1 Early Ideas About Evolution
• Spontaneous Generation – living things could come
from nonliving things
• Biogenesis – all living things come from other living
things
10.1 Early Ideas About Evolution
• Francesco Redi – questioned the belief that flies were
generated spontaneously from rotting meat
• Observation
– Tiny wormlike maggots turned into sturdy oval cases,
from which flies eventually emerge
• Experimental Group – jars with nets over them that
contained meat inside
– Netting allowed air to enter but not flies
• Control Group – uncovered jars with meat inside
• Result – maggots swarmed over the meat in the open jars
while the experimental remained maggot free
10.1 Early Ideas About Evolution
Control
Experimental A:
Independent Variable - cork
Experimental B:
Independent Variable - net
10.1 Early Ideas About Evolution
Spallanzani
• Hypothesis – microorganisms form not from air but from other
microorganisms
• Experiment – boiled broth in a flask to kill all microorganisms
in it
• Experimental Group – boiled then sealed flask
• Control Group – boiled then left open
• Result – sealed flask remained clear and free of
microorganisms; open flasks became cloudy
*Disagreed – heated the flasks too long, killing the
“vital force” in the air inside the flask
10.1 Early Ideas About Evolution
Louis Pasteur – Made a goose-neck flask that prevented
solid particles from entering but allowed air
– remained clear for up to a year – he broke the neck off & the
broth became cloudy
10.1 Early Ideas About Evolution
Fossil – trace of a long dead organism
• Found in sedimentary rock – deposited by wind & water
• Develop from hard body parts
• Overtime hard minerals replace the tissue leaving
rocklike structures
• Mold – imprint in the rock in the shape of the organism
• Cast – mold has been filled with hard minerals making a
rocklike model
10.1 Early Ideas About Evolution
Distribution of Fossils
• Law of Superposition – successive layers of rock or soil
were deposited on top of one another by wind or water
• Lowest stratum (rock layer) is the oldest
• Relative age – using law of superposition to figure out
the age of one fossil compared to another
10.1 Early Ideas About Evolution
Early scientists proposed ideas about evolution.
• Evolution is biological change over time
• A species is a group of organisms that can
reproduce and have fertile offspring.
10.2
Observations
10.1Darwin’s
Early Ideas
About Evolution
• There were many important naturalists in the 18th century.
Naturalist – collect specimens and keep careful records of
observations
Lamarck: Similar species descended from a common
ancestor
– Acquired Trait – trait not determined by genes but by
experience or behavior
– Believed acquired traits could be passed down
10.2
Observations
10.1Darwin’s
Early Ideas
About Evolution
Charles Darwin
• H.M.S. Beagle
• 5-year mapping and collecting expedition to South
America and South Pacific
10.1 Early Ideas About Evolution
10.2
Observations
10.1Darwin’s
Early Ideas
About Evolution
• Variation is a difference in a physical trait.
– Galápagos tortoises that live in areas with tall plants
have long necks and legs.
– Galápagos finches that live in areas with hard-shelled
nuts have strong beaks.
10.2
Observations
10.1Darwin’s
Early Ideas
About Evolution
• An adaptation is a feature that allow an organism to better
survive in its environment.
– Adaptations can lead to genetic change in a population.
– The change in genetic makeup of the population is
evolution
10.2
Observations
10.1Darwin’s
Early Ideas
About Evolution
Darwin’s Theories
• Descent with Modification – newer forms appearing in
the fossil record are actually the modified descendants of
older species
• Natural Selection – Organisms with favorable traits
survive, reproduce, and pass the variations to the next
generation
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10.3 Theory
Natural
Selection
10.4
Evidence
of
Evolution
• Artificial selection is the process by which humans
select traits through breeding.
neck feathers
crop
tail feathers
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10.3 Theory
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Evidence
of
Evolution
• The study of geography provides evidence of evolution.
– island species most closely resemble nearest mainland species
– populations can show variation from one island to another
 Biogeography - Study of the distribution of organisms around the
world.
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10.3 Theory
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10.4
Evidence
of
Evolution
• Embryology provides evidence of evolution.
– identical larvae, different adult body forms
– Similarites in Biochemistry: DNA, RNA, ATP. Etc
– Embryos of Vertebrates and gill slits?
Larva
Adult crab
Adult barnacle
10.1 Early Ideas About Evolution
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Evolution
10.3 Theory
Natural
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10.4
Evidence
of
Evolution
• Anatomy provides evidence of evolution.
– Homologous structures are similar in structure but
different in function.
Human hand
Mole foot
Bat wing
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10.3 Theory
Natural
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10.4
Evidence
of
Evolution
• The study of anatomy provides evidence of evolution.
– Analogous structures –similar function but different
Human hand structure
Mole foot
Fly wing
Bat wing
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10.3 Theory
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10.4
Evidence
of
Evolution
Vestigial structures are remnants of organs or structures
that had a function in an early ancestor.
• Ostrich wings are examples of vestigial structures.
10.1
Early Ideas
About Evolution
10.4 Evidence
of Evolution
Vestigial Structures
10.1
EarlySelection
Ideas About
Evolution
11.2 Natural
in Populations
Natural selection can change the distribution of a trait
in one of three ways.
• Normal Distribution – Frequency is highest near the mean
value (average) and decreases toward each extreme end of
the range.
10.1
EarlySelection
Evolution
10.3 Natural
Theory
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11.2
inSelection
Populations
– Stabilizing selection favors the
intermediate (average) phenotype
rather than either extremes.
10.1
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Evolution
10.3 Natural
Theory
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– Directional selection favors phenotypes at one
extreme.
10.1
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Evolution
10.3 Natural
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– Disruptive selection favors both
extreme phenotypes.
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10.3 Patterns
Theory
Natural
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11.6
Evolution
• Convergent evolution –
Evolution toward similar
characteristics in unrelated
species.
• Different species must adapt to
similar environments.
• Ex: Aquatic organisms
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10.3 Patterns
Theory
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11.6
Evolution
• Divergent evolution – 2 or more related populations
become more dissimilar.
– Response to differing habitats
kit fox
red fox
ancestor
How do convergent and divergent
evolution illustrate the directional
nature of natural selection?
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10.3 Patterns
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11.6
Evolution
Coevolution – change of 2 or more species in close
association with each
– occur in beneficial and competitive relationships.
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10.3 Patterns
Theory
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11.6
Evolution
Species can become extinct.
• Extinction is the elimination of a species from Earth.
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10.3 Patterns
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11.6
Evolution
• Mass extinctions are rare but much more intense.
– destroy many species at global level
– thought to be caused by catastrophic events
– at least five mass extinctions in last 600 million years
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Ideas
About Evolution
10.4 Patterns
Evidence
ofEvolution
Evolution
11.6
• Adaptive radiation – The diversification of one ancestral
species into many species.
– descendent species
usually adapted to
wide range of
environments
10.1 Early Ideas About Evolution
Punctuated Equilibrium
• A repeating pattern in the history of life
• reflected in the fossil record
• shows bursts of evolutionary activity that are followed by
long periods of stability.