Download Evolution - Southmoreland School District

Evolution
Natural Selection and Evidence
for Evolution
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Life
• How did we come from this?
• To this.
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What is Evolution?
• Change in a population over a long
time or MANY generations
• A population is a group of a single
species
– Humans…or Lions
• Evolution occurs through
Natural Selection (“That is the Key!”)
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What is a Species?
• A Species is defined as a group of
organisms that share similar
characteristics and that are capable of
interbreeding and producing fertile
offspring
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Lamarck
• French scientist Jean Baptiste de Lamarck
(1744 – 1829)
• First to propose a unifying hypothesis of
species modification
• Acquired Traits – trait that is not
determined by genes
• Lamarck – these were passed on to
offspring
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Charles Darwin
• Darwin –
– individuals struggle to survive
• (competing for food and space,
escaping predators, finding mates,
locating shelter).
– Only some individuals survive the
struggle and produce offspring
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Charles Darwin
• Darwin –
– Descent with Modification
– Modification by Natural Selection
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Darwin and Natural Selection
• Four things that drive N.S.
– Fitness
• Ability to survive and reproduce
– Variation
• Differences among species
– Adaptation
• Variation that improves chances of survival
• Adaptations develop over many generations
– Competition
• Fight for survival (food, shelter)
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Selection
• Artificial Selection
– Breeding organisms with specific traits
• Natural Selection
– Mechanism for change in population
– Organisms with certain variations survive,
reproduce and pass their traits to offspring
• Survival of the Fittest!
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Variation
A variation is an inherited trait that makes an
individual different from other members of
the species.
Some traits are “better” or more favorable than
others
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Adaptation
• Adaptation: any variation that aids an
organism’s chances of survival in its
environment
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Evidence of Evolution
1. Structural Adaptation:
– allow a species to defend
against predation.
Monarch
– Mimicry:
• The ability species to
resemble another species;
two types.
Viceroy
– Camouflage:
• The ability of species to
blend in with their
surroundings
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What is this?
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Structural Adaptations cont
• Mimicry
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Leafhoppers
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Treehopper
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Leaf Hopper
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Ants
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Warning Coloration
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Other Evidence
2. Physiological Adaptations:
– Develop rapidly…(antibiotic resistance;
pesticide resistance)
– This is Direct Evidence
• 3 – 6. Indirect Evidence
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3. Fossils
• Fossils show
evolutionary
history
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4. Anatomy
• Homologous Structures
– Common ancestry
• Analogous Structures
– No Common ancestry
• Vestigial Structures
– No visible function or use
any longer
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Anatomy Revisited
• Homologous Structures
– Common Ancestor
– Can have similar arrangement
and function
• Analogous Structures
– No common ancestor
– Similar function; different
anatomy
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Vestigial Structures
• Flightless Cormorant
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Vestigial Structures
• Human Ear Muscles
• Baleen Whale
Pelvic Bone
• Vestigial Video
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5. Embryology
• Similarities in Embryos
– Suggest a common
ancestor
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Embryology and Evolution
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6. Biochemistry
• Comparison of DNA and RNA
• Determine evolutionary relationship
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Evolution and History
How Evolution Happens - YouTube
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Industrial Melanism
• Peppered moths –
• Before the Industrial
Revolution
• After the Industrial
Revolution
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Mechanisms of Evolution
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Disruption of Equilibrium shows Evolution
• Mutation – change in the DNA of an organism
• Genetic Drift
– Alleles frequency changes by random events or chance
• Non-Random Mating
– Assortative Mating – Selection of mate based on similar
characteristics
• Migration
– into or out of population
– Gene Flow: genes moving from one pop to another
• Natural Selection – See Below
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Assortative Mating
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Review Natural Selection
• Natural Selection –
– The idea that organisms with traits best suited to
their environment are more likely to survive and
reproduce
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Types of Natural Selection
• Stabilizing Selection
– Favors average
individuals
• Disruptive Selection
– Favors both extremes of
a variation
• Directional Selection
– Favors a single extreme
variation
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Speciation
• What is Speciation?
– The evolution of new species
• Geographic Isolation
– Occurs when a small part of the
population becomes separated; over
generations, different variations become
more common
• Reproductive Isolation
– Members of a species change from one
another over time so much that they can
no longer reproduce fertile offspring
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How long does speciation take?
• Gradualism
– The model that describes
evolution as a slow ongoing
process
• Punctuated Equilibrium
– States that rapid evolution
comes about when the
mutations of a few genes
results in the appearance of a
new species over a relatively
short period of time
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Patterns of Evolution
• Divergent Evolution
– Adaptive Radiation
– Single species evolves
into an array
• Convergent Evolution
– The acquisition of the
same biological trait in
unrelated lineages
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