Transcript On the Origin of Species

Evolution
The Origin of
Species
Charles Darwin
1. Natural Selection/Survival of the
Fittest
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Adaptations-Allow organisms to survive
and reproduce in their environment
Variations-Differences
2. Principle of common descent
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All organisms come from a common
ancestor
3. Published Book: On the Origin of
Species
Darwin’s Theory of
Natural Selection
• 1. Populations have variations.
• 2. Some variations are favorable.
• 3. More offspring are produced than
can survive.
• 4. The offspring that survive have
favorable traits.
• 5. A population will change over
time.
Evolution & Life’s Diversity
FITNESS: The physical traits and behavior
that enable organisms to survive and
reproduce in their environment
 Fitness arises from adaptation
 Common Descent-Each species has
descended from other species over time
(Darwin)
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The Age of the Earth
The Age of The Earth
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The Earth is 4.6 billion years old;
determined by
radioactive/radiometric dating.
Relative Dating is a technique used
by scientists relative to fossils and
other ones in different layers of rock.
Half-Life-The length of time it takes
½ of a radioactive element to decay.
The Age of The Earth
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Elements with different half lives
provide natural “Clocks” that
“tick” at different rates
When interpreted correctly, they
help scientists date rocks and
specimen of different ages
Uranium 238, Potassium 40, &
Argon 40 are a few radioactive
elements
The Age of The Earth
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Carbon 14(C14)is used to
determine or date material that
was once alive, such as bones or
objects that contained onceliving materials; its half life is
5,700 years
Is not useful in dating
substances more than 60,000
years old
The Fossil Record
The Fossil Record
• Most fossils are found in
sedimentary rock.
• Sedimentary rock results when rain,
heat and cold breaks down existing
rocks into small particles of sand,
silt, and clay.
• Paleontologists are scientists who
study fossils
• Fossils are Evidence of
past life forms
The Fossil Record
• Fossil records also tell us of
major changes in the earth’s
climate
• Fossil shark teeth were found in
Arizona
• Giant fossil ferns were found in
Canada.
Fossil Discoveries
• Fossils – remains of dead
organisms (in rock, hardened
bones and wood, shells,
impressions of body forms)
Evidence From
Living Organisms
Evidence From Living Organisms
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Active genes (particular sequences of
genes) derived from a common
ancestor during early stages of
development are evidence in living
organisms that evolution has occured
Homologous structures- Structures
that develop from the same body part;
similar in appearance but have different
functions
Homologous Structures
Vestigial Organs
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Serve little or no purpose; Ex: human
appendix, tail bone
Similarities in chemical compound DNA,
RNA, and ATP
Provides powerful evidence that all
living things evolved from common
ancestors
Developing a Theory of
Evolution
Developing a Theory of Evolution
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Jean Baptiste de Lamarck- Thought
organisms had an inborn urge to better
themselves and become more fit to their
environment
Desire to Change
Use and Disuse
Inheritance of Acquired Traits
Developing a Theory of Evolution
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Thomas Malthus- Believed people were
being born at a much faster rate than they
were dying
Charles Lyell- a geologist who said the
earth was very old and had changed over
time.
Artificial selection-When animals are
bred for desired traits
Evolution by Natural
Selection
Evolution by Natural Selection
• Survival of the fittest-Individuals whose
characteristics are well-suited to their
environment to survive where as others
don’t
• A British ecologist,H.B.D. Kettlewell,
demonstrated natural selection with dark
and light peppered moth
Natural Selection and the
Peppered Moth
Genetics & Evolutionary
Theory
Genetics & Evolutionary Theory
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Genes- Units of variations; may occur from
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Population-A collection of individuals of the
mutations
same species in a given area whose members
can breed with one another
 Gene Pool-When organism share a common
group of genes
 Relative Frequency-The number of times an
allele occurs in a gene pool compared to the #
of times other alleles for the same gene occur
The Development of New
Species
The Development of New Species
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Species – basic unit of taxonomic classification
Population of closely related and similar organisms
In sexually reproducing organisms, the similar
organisms must be able to breed and produce viable,
fertile offspring
Speciation-How many species evolve from old ones
Niche-The combination of an organisms
“profession” and the place in which it lives.
Reproductive Isolation-The agent for the formation
of new species
The Development of New Species
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Darwin’s Finches
Step 1: Founding Fathers & Mothers;
descendants of a few ancestral finches
- originally lived in South America
Step 2: Separation of population.
- Some of the population flew to the
Galapagos island
Step 3: Changes in the Gene Pool
- The Gene Pool changed when the birds migrated
Step 4: Reproductive Isolation
- Prefer not to mate because of mating behavior
Step 5: Sharing the Same Island
- Coexistence, Extinction, or further evolution
Speciation & Adaptive Radiation
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Adaptive Radiation-Process by which a
species gives rise to many new species; also
known as divergent evolution. A number of
species diverge or move away from a common
ancestral form. (Start with one species and
make many)
Convergent Evolution- Adaptive radiations
among different organisms produce species that
are similar in appearance and behavior (Start
with many species and form a few similar ones)
Convergent Evolution
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Unrelated species
Similar environments
Similar adaptations (more alike)
Converge or come together
Divergent Evolution/Adaptive Radiation
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Related species
Different environment
Different adaptations
Develop new species
Diverge-move apart
Evolutionary Theory
Evolves
The Development of New
Species
• Genetic Drift-A random
change in the frequency of a
gene (an allele can become
common in a population by
chance)
New Species
Development
• Unchanging Gene Pools- A
species remains the same for a
long time
• Gradual and Rapid Evolutionary
Change
Gradualism- theory that
evolutionary change occurs
slowly and gradually
Gradualism vs
Punctuated Equilibrium
Rapid Evolution Can Occur
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Isolation
New Environment
Dramatic Changes in the earth
Mass Extinction-Phenomenon in
which many species vanish; some
are caused by changes in global
climates; others are uncertain
Punctuated Equilibria- Long stable
periods interrupted by brief periods
of change