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• What is the modern synthesis?
• How do we define evolution?
Modern Synthesis
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Questions
• What are the four forces of evolution?
• How does each change gene frequencies within and between populations?
• What is a population?
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The four forces• What is genetic drift?
• When is genetic drift most effective?
• Why is mutation so important?
• What is the role of gene flow in maintaining species?
• What are the different ways in which Natural selection works?
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Genetic Drift
• The random factor
• Greatest effect in small populations
• Founder effect
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Genetic Drift - Bottleneck
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Genetic bottleneck
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Natural selection
• differential reproductive success over multiple generations
• some variations are more successful than others, leading to a change in the entire population over time
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Natural Selection
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Pepper Moths
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Four Forces and Populations
Within Between
Mutation
Genetic Drift
Natural Selection
Gene Flow
=
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MICROEVOLUTION = the small changes in gene frequencies in a population from generation to
generation
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MACROEVOLUTION = the cumulative effect of these small changes over a long period of time - may lead to
SPECIATION
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What is a species?What is speciation?
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What is a species?
• an interbreeding group of animals or plants that are reproductively isolated though anatomy, ecology, behavior, or geographic distribution from all other such groups
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Reproductive Isolating Mechanisms
• Premating RIMsHabitat isolationTemporal isolationBehavioral isolationMechanical incompatibility
• Postmating RIMsSperm-egg incompatibilityZygote inviabilityEmbryonic or fetal inviability
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Theridon grallator
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Pan
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Common Chimpanzee Bonobo
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Gorilla
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Mountain Eastern lowland Western lowland
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X
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X =
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Species Concepts• Biological species concept: Defines species as
interbreeding populations reproductively isolated from other such populations.
• Evolutionary species concept: Defines species as evolutionary lineages with their own unique identity.
• Ecological species concept: Defines species based on the uniqueness of their ecological niche.
• Recognition species concept: Defines species based on unique traits or behaviors that allow members of one species to identify each other for mating.
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Modes of Evolutionary Change
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Cladogenesis
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Sympatric speciation
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Speciation creates clades
• clades are evolutionarily related groups
• Classification is the naming of these groups
• Started with Linnaeus
• tried to group organisms together based on relationship
• based on similarity
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Tempo of Speciation?• Gradualism?
• Punctuated Equilibrium?
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![Evolutionary Phylogenetic Networks: Models and Issues...1 Introduction In Charles Darwin’s Origin of Species [17], the depiction of an evolutionary history of species took the shape](https://img.pdfslide.net/doc/110x75/6003f8dcf6d8c3703e43d90f/evolutionary-phylogenetic-networks-models-and-issues-1-introduction-in-charles.jpg)
