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Lecture 2

PSYCH 1XX3 Lecture Notes - Lecture 2: Side Effect, Altruistic Suicide, Hymenoptera

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Joe Kim

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Adaptation: biological traits or characteristics that help an individual survive or reproduce in its habitat
Adaptation has a purpose → make themselves better suited to the environment
Adaptation always serve some function in the life of the individual. It enables organisms to
interact with a complex physical environment
Examples: Eyes enable us to recognize and respond effectively to things around by detecting and
analyzing reflected light, Nocturnal raccoons have good night vision, their front paws adapted to be so
sensitive they can distinguish if it is food or not
Cognitive psychologists study things like selective attention, and memory encoding and retrieval each
of which refers to a task that the mind needs to accomplish to do its job. They refer to the adaptive
functions of mental activity. Like biologists, cognitive psychologists are also adaptationist: they find it
helpful to break down large-scale cognitive processes into adaptive problems or tasks, and to then look
for the adaptations that solve those problems
Cognitive processes and behaviours are subject to selective pressures that satisfy particular goals
Adaptive functions that are served by our minds are served by our minds evolved like all other
adaptations-through natural selection
Evolution by Natural Selection
Natural Selection: Differential survival and reproduction of organisms as a result of the heritable
differences between them.
Three Essential Components:
1. Individual differences: There is variation among individuals for any given characteristic.
2. Differential Reproduction: This variation affects chances of survival; some individuals will produce
more offspring than others
3. Heritability: The offspring of successful reproducers will resemble their parents.
Selective Transmission: Occurs over successive generations when one trait is more favourable than
another. Eventually the entire population contains only the most favoured trait.
Stabilizing Selection: Selection against any sort of departure from the species typical adaptive design.
→ Blue coloured fish will be the most stabilizing selection because it’s adaptive and it gives higher
survival rate but when environment changes, selection favours traits are not typical and
evolutionary change could be observed
Changes due to natural selection is not always permanent.
Sometimes changes that arise through natural selection are more permanent and form a potential
foundation for diversification of related species.
Any behaviour that increases the chances of obtaining a mate is favoured by natural selection
Reproductive Success = Fitness
What natural selection favours is not simply those individuals who are best at surviving. It’s those who are
best at reproducing.
Darwinian Fitness: Average reproductive success of genotype relative to alternate genotypes
Fitness: How good a particular genotype is at leaving copies of its genes in the generation relative to
other genotypes
Evolution: change is gene frequency over generation
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Sexual Selection
Sexual Selection: The component of natural selection that acts on traits that influences an organism’s
ability to obtain a mate.
Ex. Peacock’s Tail: → females choice
Energetically expensive to produce
Harder to escape from predators
More conspicuous to predators
Increases risks of dying
This is why they will shed their feathers at the end of the breeding season
It contribute to fitness via increased chance of mating
Female peacocks prefer more eyespots and symmetry.
Ex. Elks(male red deer) → success in combat
Elks have horns to fight for mating purposes. Only male deers have antlers and muscles that they
need to carry the antlers. Stag who wins the contest gets to monopolize and “harem” of females
However, carrying around the antlers makes them more vulnerable to predators than females because
they don’t have as much stamina for running and are more likely to get stuck in the snow.
They also shed their antlers after the breeding season and grow new ones later
Similar to the peacocks, the trait has a negative effect on survival but it has a big positive effect on the
male’s chance of mating.
Differences: Peacocks don’t use tails to fight with. Females are choosy about mates but female elks do
not care about the size/appearance of the stag’s antlers.
Two ways of getting more access to mates than your rivals:
1. Being chosen by the opposite sex (attractiveness)
2. Beating up on your rivals in mating combat.
The evolution of the peacock was by female choice, whereas the evolution in the case of the stag was
success in combat.
If an anatomical trait differs between the sexes → sexual selected trait
If this trait only exists during breeding season → decreases their survival rate
Females may be choosy because they may have these preferences because they want to pick out males
with the greatest resistance to locally prevalent diseases, so their offsprings will also get the best
available genes passed down
Species-Typical Behaviour & The Comparative Approach
Behaviours are an evolved characteristic of a given species
Physical form
Habitat preference
Group size
Social system
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