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Chapter 15 Evolution
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What is evolution? Change in a population over time
Changes occur at genetic level mutations
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Mutations Change in the DNA code Can affect traits / phenotype
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The Darwin Dude? 5 year voyage on Beagle (1831-36)
Naturalist: surveyed coast of S.A. Wrote “Origin of Species”
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Galapagos Island Facts
Part of Ecuador 13 main volcanic islands Formed between MYA
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Darwin & Galapagos Organisms adapted to their environment
“Darwin’s Finches” Mechanism for evolution = Natural Selection
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Noteworthy Species
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Darwin’s Finches Adaptive Morphology
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Why do species change? Variations & adaptations help organisms survive
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Camouflage
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Camouflage
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Natural Selection Organisms with favorable traits survive & reproduce
Variation is key
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Natural Selection (cont.)
Struggle for existence Species become better fit for their environment
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Natural Selection (cont.)
4 Main Principles (pg 421): Variation Heritability Overproduction Reproductive Advantage
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Types of Natural Selection
1. Stabilizing Selection: Average phenotype favored Ex. Human baby weight
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Stabilizing Selection
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Types of Natural Selection
2. Directional Selection: increases “extreme” versions of traits Ex. Peppered Moth, Darwin’s finches
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Peppered Moth: Natural Selection
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Directional Selection
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Types of Natural Selection
3. Disruptive Selection: splits populations into 2 groups Both extremes favored Ex. Marine & Land Iguanas
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Disruptive Selection
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Evidence of Evolution Fossil Record Fossils: preserved evidence
Found in Sedimentary rock
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“Soft parts” don’t fossilize
Fossil Record (cont) “Soft parts” don’t fossilize Specific conditions needed to form fossils Lack of “transitional” fossils
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Evidence of Evolution 2. Homologous Structures:
Anatomically similar structures Evidence of common evolutionary origin
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Homologous Structures
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Evidence of Evolution 3.Comparative Embryology:
similarities in embryos
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Evidence of Evolution 4.Compararative Biochemistry: Organisms have similar DNA, genes and enzymes
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Evidence of Evolution 5. Vestigial Structures:
reduced in size, no longer have function
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What is Speciation? Formation of new species
Become genetically different
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What are Species? Group of organisms that can interbreed & produce fertile offspring
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Infertile Species Horse + Donkey = Mule
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Liger
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Species Loop Hole Not a perfect definition Used for classification
Some different species can produce fertile offspring
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Rate of Speciation Gradualism: Evolution occurring at slow rate
Punctuated Equilibrium: Evolution occurring at irregular rates
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Cause of Speciation Geographic Barriers Environment Changes
Mountains, Rivers, etc. Environment Changes
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