unit 11 evolution of populations
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10.5 Evolutionary Biology Today
KEY CONCEPT New technology is furthering our understanding of evolution.
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10.5 Evolutionary Biology Today
Fossils provide a record of evolution.
• Paleontology is the study of fossils or extinct organisms.
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10.5 Evolutionary Biology Today
• Paleontology provides evidence to support evolution.
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10.5 Evolutionary Biology Today
Molecular and genetic evidence support fossil and anatomical evidence.
• Two closely-related organisms will have similar DNA sequences. What would you expect to find the differences code for?
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10.5 Evolutionary Biology Today
• Pseudogenes are sequences providing evidence of evolution.– no longer function– carried along with functional DNA– can be clues to a common ancestor
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10.5 Evolutionary Biology Today
• Hox genes indicate a very distant common ancestor.– control the development of specific structures– found in many organisms
• Protein comparisons, or molecular fingerprinting reveals similarities among cell types of different organisms.
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10.5 Evolutionary Biology Today
• Scientists from many fields contribute to the understanding of evolution.
• The basic principles of evolution are used in many scientific fields. Some for good purposes and some for less ethical – give an example of each.
Evolution unites all fields of biology.
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11.1 Genetic Variation Within Population
KEY CONCEPT A population shares a common gene pool.
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11.1 Genetic Variation Within Population
Remember me?
• Genotypic• Phenotypic
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11.1 Genetic Variation Within Population
Genetic variation in a population increases the chance that some individuals will survive.
• Genetic variation leads to phenotypic variation. Why?• Phenotypic variation is necessary for natural selection.
Why?• Genetic variation is stored in a population’s gene pool.
– made up of all alleles in a population– allele combinations form when organisms have offspring
– How?
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11.1 Genetic Variation Within Population
• Allele frequencies measure genetic variation.
– measures how common an allele is in population– can be calculated for each allele in gene pool
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11.1 Genetic Variation Within Population
Genetic variation comes from several sources.
• Mutation is a random change in the DNA of a gene.
• Recombination forms new combinations of alleles.
– can form new allele– can be passed on to
offspring if in reproductive cells – why not from body cells?
– usually occurs during meiosis – parents’ alleles
arranged in new ways in gametes
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11.1 Genetic Variation Within Population
Genetic variation comes from several sources.
• Hybridization is the crossing of two different species.– occurs when individuals can’t find mate of own
species– topic of current scientific research
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11.2 Natural Selection in Populations
KEY CONCEPT Populations, not individuals, evolve.
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11.2 Natural Selection in Populations
Natural selection acts on distributions of traits.
• A normal distribution graphs as a bell-shaped curve.
• Traits not undergoing natural selection have a normal distribution.
• Give an example of a trait that could have a normal distribution.
– highest frequency near mean value
– frequencies decrease toward each extreme value
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11.2 Natural Selection in Populations
Natural selection can change the distribution of a trait in one of three ways.
• Microevolution is evolution within a population.– observable change in the allele frequencies – can result from natural selection
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11.2 Natural Selection in Populations
• Natural selection can take one of three paths.
– Directional selection favors phenotypes at one extreme. What’s happening in this graph?
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11.2 Natural Selection in Populations
– Stabilizing selection favors the intermediate phenotype.
– What’s happening in this graph?
• Natural selection can take one of three paths.
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11.2 Natural Selection in Populations
• Natural selection can take one of three paths.
– Disruptive selection favors both extreme phenotypes.
– What is happening in this graph?
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11.2 Natural Selection in Populations
Where does genetic variation come from? • A. Mutation only • B. Both mutation and recombination • C. Recombination only • D. Mitosis only
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11.2 Natural Selection in Populations
Where does genetic variation come from? • A. Mutation only • B. Both mutation and recombination • C. Recombination only • D. Mitosis only • Correct Answer = B
Where is the most common phenotype found in a normal distribution? • A. In the middle range • B. At the low range • C. At the high range • D. Equally across the distribution range
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11.2 Natural Selection in Populations
Where does genetic variation come from? • A. Mutation only • B. Both mutation and recombination • C. Recombination only • D. Mitosis only • Correct Answer = B
Where is the most common phenotype found in a normal distribution? • A. In the middle range • B. At the low range • C. At the high range • D. Equally across the distribution range• Correct Answer = A
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Review
• Paleontology is the study of fossils – it provides evidence for evolution in a predictable fashion
• Genetics gives evidence of evolution – similar gene sequences are found in related organisms
• Pseudogenes are segments of DNA that no longer function but give clues to evolutionary history
• Evolution unites the study of Biology in a similar way as Einstein’s famous E=mc2 unites Physics.
• Genetic variation increases the chances that some individuals will survive.
• Allele frequencies measure the variation in a species
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Review
• Genetic variation comes from several sources– Mutations– Recombination– Hybridization
• Populations evolve – not individuals• Natural Selection can take one of three paths
– Directional – moving towards one extreme– Stabilizing – moving towards the mean value– Disruptive – moving towards both extremes