PSYO 2160 Lecture Notes - Lecture 2: Natural Selection, Phenotype, Heritability
3 May 2018
School
Department
Course
Professor
Natural Selection
September 14 & 16, 2015
Artificial Selection of Dog Traits:
• Selectively breeding animals based on a desirable phenotype
• Phenotype: observable properties of an organism
o show dogs vs. working dogs
o selecting appearance vs. behaviour
• May have an effect on the genetic make up (genotype)
• Humans are the selective agent
Balyaevs Foxes
• In Russia 1959, Balyaev studied wild foxes by separating the foxes by behaviour (friendly,
aggressive)
• The friendly foxes bred together became more and more friendly across generations
• Bred for a behavioural phenotype but saw changes in appearance
o Friendly foxes became more dog looking
• Therefore, one gene must code for multiple things
o Genotype is not the phenotype
▪ Phenotype can be altered by the environment, learning/culture or illness
Natural Selection
• Nature is the selective agent
• Traits increase/decrease in frequency depending on how well they help the organism
survive in their current environment
• Those that survive, reproduce
Basic Principles:
• Animals can produce more offspring than the environment can support
• Therefore, competition among individuals of the same species for resources arises
• Only the best adapted to the environment survive to reproduce
• Genes that give animals an edge in their environment will increase in the population
Requirements:
• Variability in the trait (mutation, genetic, recombination, migration)
• Fitness consequences
• Mode of inheritance
• Limited resources
For example, Natural Selection in African Elephants
• Variability: Male (and some female) have tusks, both long and short.
• Fitness: Tusks are used for protection, fighting and foraging
• Heritability: adults with long tusks produce offspring with short tusks, gene codes for tusk
length are passed on
• Limited resources: limited number of females causes fighting for access to the females
between males
Selection is to maximize reproduction, not necessarily ones lifespan.
Ex. Mutant results in extra large tusks which increases reproductive success but shortens
lifespan.
Natural Selection has no end goal. Natural selection generates local adaptations – not necessarily
more complex.
find more resources at oneclass.com
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Document Summary
Selectively breeding animals based on a desirable phenotype: phenotype: observable properties of an organism show dogs vs. working dogs selecting appearance vs. behaviour, may have an effect on the genetic make up (genotype, humans are the selective agent. Natural selection: nature is the selective agent, traits increase/decrease in frequency depending on how well they help the organism survive in their current environment, those that survive, reproduce. Requirements: variability in the trait (mutation, genetic, recombination, migration, fitness consequences, mode of inheritance, limited resources. For example, natural selection in african elephants: variability: male (and some female) have tusks, both long and short, heritability: adults with long tusks produce offspring with short tusks, gene codes for tusk. Fitness: tusks are used for protection, fighting and foraging length are passed on. Limited resources: limited number of females causes fighting for access to the females between males. Selection is to maximize reproduction, not necessarily one(cid:495)s lifespan. Natural selection generates (cid:523)local(cid:524) adaptations not necessarily.
