PSYC 3280 Chapter Notes - Chapter 2: Silent Mutation, Mutation, Phenotype
26 Sep 2018
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Chapter 2- The Evolution of Behaviour
• Artificial Selection- the process of humans deliberately choosing certain
varieties of an organism by implementing breeding programs that favor
one variety over another
o Over generations, by only allowing those organisms with the
favored traits to reproduce, the frequency of this trait increases
• Natural Selection- the process by which traits conferring the highest
reproductive success to their bearers increase in frequency over time as
they are passed down to future generations
• Phenotype- the observable properties of an organism
• Genotype- genetic makeup
• Allele- a gene variant, one of two or more alternative forms of a gene
Natural Selection
• Traits, including behavioural traits, increase or decrease in frequency as
a function of how well they suit organisms to their environments
• an individual’s phenotype is a result of its genotype and the way that
genotype manifests itself in the environment
• Ex Pack Hunting; Wolves that hunted in a pack got more meat than those
who hunted alone. The more food a wolf consumed, the more offspring
they’d produce. Therefore, those hunting in packs produce more
offspring, and pass on the behavioural variant of pack hunting to the
next generation
• The process of natural selection operating on a specific trait behaviour
requires
o Different varieties of the trait (different alleles)
o Fitness consequences of the trait
2
o A mode of inheritance
o Resources must be limited with respect to the trait being studied
• Variation can be caused by genetic and environmental factors
o Mutation- change in genetic structure
▪ Addition/deletion mutations (single nucleotide from a
stretch of DNA), causes the production of an inactive
enzyme
▪ Base mutation (one base in a nucleotide replaces another),
can change protein function and therefore reproductive
success
▪ Silent mutations (base mutation that doesn’t change the
production of amino acids)
o Genetic Recombination- when pairs of chromosomes line up
during cell division in sexually reproducing organisms, and
sections of one chromosome swaps position/crosses over with
sections of the other chromosome
o Migration- the introduction of new trait variants by individuals
coming from other populations
• Narrow-sense Heritability can be measured
o By designing a truncation selection experiment
▪ Step 1: measure the mean score of the behavioural trait
for generation 1
▪ Step 2 (truncate): cut off the population variation in the
behavioural trait by allowing only those with a specific
variation to breed; calculate the mean score of the
behavioural trait of those individuals
▪ Selection Differential (S)- the difference between the
mean scores of the group in step 1 and the group in step 2
(the group we have allowed to breed)
