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Artificial Selection

Chapter 2 The Evolution of Behavior. Artificial Selection. Natural Selection. When nature is the selective agent, traits, including behavioral traits, increase or decrease as a function of how well they suit organisms to their environment.

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Artificial Selection

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  1. Chapter 2 The Evolution of Behavior Artificial Selection

  2. Natural Selection When nature is the selective agent, traits, including behavioral traits, increase or decrease as a function of how well they suit organisms to their environment. If an animal’s trait variation allows for better survival and reproduction that trait is bound to be passed on. Small differences in fitness can accumulate into large changes in gene frequencies.

  3. The process of natural selection requires three prerequisites to operate: 1. Variation Can be caused by genetics, i.e. genetic variation - Mutation - Genetic recombination Or can be caused by environment - Migration

  4. 2. Fitness Consequences The trait must affect reproduction success 3. Mode of Inheritance Truncation selection experiment Xo = mean value Truncation line-only birds above this speed allowed to breed X1 = mean of Truncation line S = selection differential X2 = mean value of 2nd generation

  5. Behavioral Genetics Behavioral geneticists are involved in many activities linked to ethology: 1. Mendel’s Laws Used to better understand the underlying genetics of behavioral traits. Satellite males vs. Independent male ruff birds (Philomachus pugnax) 2. Mapping Genes for Behavioral (Polygenic) Traits Behavioral geneticists often search for a set of genes responsible for the expression of polygenic traits. QTLs are quantitative trait loci. Jonathan Flint and his colleagues’ work found evidence of QTLs associated with fear on 14 different chromosomes of mice.

  6. 3. Determining What Variation of a Trait is due to Genetics & What is Due to Environment Cross-fostering experiment Cliff swallows (Petrochelidon pyrrhonota)

  7. Modern Theoretical Framework for Animal Behavior The Selfish Gene Any gene that codes for a trait that increases the fitness of its bearer above and beyond that of others in the population will increase in frequency.

  8. Antipredator Behavior in Guppies Upstream from waterfalls – low predation pressure Downstream from waterfalls - severe predation pressure Most guppy studies are conducted in the Northern Mountains of Trinidad and Tobago.

  9. Differences in the two populations include antipredator behavior, color, number of offspring in a clutch, offspring size, aging patters, & age at reproduction.

  10. Antipredator behavior - Predator inspection - Shoaling

  11. 1957 Transfer of guppies demonstrated evolution via natural selection Demonstrates that Natural Selection can act fairly quickly

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