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Summary Evolution and Systematics
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Summary of the lectures of the course Evolution and Systematics at Wageningen University & Research.
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Chapter 2• Special Creation
o Species do not change
o Lineages do not split
o Each species is separately created
o Each species is indipendently created
o Earth and life are young (aprox 6000 years)
• Descent with Modification
o Species change over time (microevolution)
o Lineages split and diverge (speciation)
o New life-forms derive from older forms (macroevolution)
o All live-forms are related (common ancestry)
o Earth and life are old
▪ 4.6 billion years ago
• Homology
o Similarity due to inheritance of traits
▪ Always the same elements
▪ Not always the same function
• Analogy
o Similarity of character states not due to common ancestry
▪ Not always the same elements
▪ Same function
• Vestigial Structures
o Structures which are not functional in the species, but were functional in the
species’ ancestors.
• Molecular homology
o Shaded pseudogenes
▪ Non-functional genes.
• Uniformitarianism
o Geologic processes acted in the same manner and with the same intensity as today.
• Law of Succession
o The tendency of fossils, or living animals, resemble earlier fossils from the same area.
• Theory of Special Creation
o Species are immutable
o Species were created independently
o Are recent
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,Chapter 3
• Darwin’s Postulates
o Variation in phenotype within a generation.
o Phenotype is heritable.
o Differences in survival and/or reproduction (fitness).
o Correlation between phenotype and fitness.
• Darwinian fitness
o An individual’s ability to survive and reproduce.
o The “phenotype” on which natural selection acts
o Relative fitness is important for natural selection
o Different from physical fitness
• Nature of natural selection
o Populations evolve, not individuals
o Natural selection acts on phenotypes, but changes accumulate in genotype
o Exaptation
▪ Existing trait evolve new function
o May produce complex structures
o Traits that promote fitness become more frequent over time
o Does not always lead to the perfect design
▪ Leads to best possible short-term solution
▪ Depends on available variation
o Cannot adapt to a future event
• Darwin’s Problems
o The source of variation
o Understanding of inheritance
o Age of the Earth
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,Chapter 4
• Phylogenetic Tree
o Every node represents an common ancestor
▪ Reed back to nodes to determine common ancestry
o Are regarded as hypotheses
o Sister species
▪ Two closely related species that share a recent common ancestor
• Convergence
o Evolution of the same function in different non-related taxonomic groups.
▪ Wings in bats, birds and insects.
▪ Streamlined body in whales and sharks.
• Polytomy
o Uncertain relationship
o Into three or more species
• Sister Species
o Species which are more related to one another than to other species
• Plesiomorphy
o Ancestral character
o Phenotype of ancestor
• Apomorphy
o Derived characters
• Autapomorphy
o Derived character in single species
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, • Cataloguing on trait
o Not absolute
o Monophyletic
▪ An ancestor and all its descendants
▪ Synapomorphy
Derived character shared by two or more lineages.
o Paraphyletic
▪ An ancestor and some (but not all) descendants
o Polyphyletic
▪ Some descendants excluding the ancestors
• Three types of Evolutionary Trees
o Cladogram
▪ Branches Lengths have no meaning
o Phylogram
▪ Branch lengths represent evolutionary change.
o Time Tree
▪ Branch lengths represent time.
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