CRIM 402 Lecture Notes - Lecture 2: Peppered Moth, The Boy Who Cried Wolf, Reinforcement

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14 Aug 2016
Chapter 2
Basic Biological Concepts
Natural Selection
-Natural selection = evolution
-All living organisms adapt to their environments, which leads to increased survival/reproductive success
oAdaptations occur over many generations
Anything modified by evolution has a genetic component
Evolution selects individuals with genes that result in traits that help them survive/reproduce
These favorable traits are passed on, and such favorable traits are chosen based on the
environment and time frame
*i.e. Galapagos Island Finches (wide beak vs. average beak vs. narrow/long beak)
- All living organisms are adapted to their environment, and this adaptation takes many forms:
oStructural modifications
Enhance survival and reproduction
i.e. an orchid has a flower that looks like a female wasp, so male wasps try to reproduce with it
and other orchids, thereby pollinating them
oBiochemical pathways
Development of metabolism or photosynthesis or respiration
oBehavioral adaptations
Increase survival and reproductive success
i.e. learning to avoid predators or developing mating rituals in order to find strong/suitable
-The process that results in these adaptations is called natural selection
oThe differential survival/reproduction of individuals within a population
Some have better chance of surviving/reproducing and of having offspring with the same traits that help
the parents survive/reproduce
Adaptations are behavioral, structural, and biochemical
-Three conditions necessary for natural selection to occur
(if all 3 are met certain individuals will leave more offspring because they are better able to survive/reproduce and the trait
will become increasingly represented in subsequent populations)
Must be variation among individuals
Variations can be structural, behavioral, physiological, biochemical
The variation must be a heritable trait
Under genetic control so it can be passed on to the next generation
oIndividual must differ in its ability to survive/reproduce depending on this trait
The trait must give the individual a better chance of surviving/help it produce more offspring
-Most famous example of natural selection – English Peppered Moth
o2 varieties
1 is light with splotches of dark pigment
1 is dark all over
This is an example of variation in a population that is inherited
oThese moths rest during the day on light coloured lichens on trees/rocks
The light coloured moths were more easily camouflaged from predators, and therefore the dark moths
were rarer as they had a worse chance of surviving because they were more easily noticeable by
However after the industrial revolution, there was heavy pollution and the lichens died off, leaving the
dark background of the bare bark
The environment changed, and now the dark moths had the advantage and after a while there became
more dark moths than light ones because the light ones had lower survival rates and therefore lower
reproduction rates
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-Constraints on the ability of natural selection to produce adaptation of organisms to their environment
oAdaptations are often compromises
Organisms must do many things, and an organism that develops a new structure/behavior carries a cost
because it requires energy to develop/carry out the change and it may also reduce the ability to do
something else
i.e. peacock tails… “expensive” because it reduces the ability to flee from predators but it also
greatly increases the birds ability to reproduce, so the cost is made up for
humans have engaged in unnatural selection  breeding race horses (long legs and fast= thoroughbred)
oNatural selection can only work on existing traits
Modifies existing traits as environment/conditions change (doesn't rebuild from scratch)
Behavior in Humans and Other Animals
-Nature and Nurture
oAn interaction (rather than a dichotomy)
oWe are a product of what we are biologically and of the environment we’ve been exposed to throughout our life
-Behavior: what an animal does and how it does it
oThe study of behavior loos at the action itself and its motor components
The brain function and how the animal actually performs the behavior
oBehavior is adaptive
Natural selection adapts an organism to its environment, and acts on everything we inherit from our
parents including behaviors
An animal must
*Feed in a way to maximize fitness
*Reduce the risk of predation (being eaten)
*Increase chance of mating
-Behavior must has a genetic basis because behaviors do evolve
oEven learned behaviors depend on genes that create a neural system receptive to learning
oExample for genes influencing behavior: birds nesting techniques
-Genetics and environment should be regarded as a continuum
oAll behaviors have some genetic and some environmental contribution
Amount of input from each varies with different behaviors, but nearly all have components of both
-Behaviors can be divided into two main groups
oInnate behaviors: governed entirely by genes
oLearned behaviors: require experience, still have genetic component but are strongly affected by environment
and experience
Innate behaviors
-All animals carry out many behaviors without having ever seen them performed
oBecause they couldn't have learned them, the didn't come from the environment which means they are innate
These behaviors tend to be constant and are performed the same way by every individual of that species
This is called fixed action patterns (FAPs)
This can be seen in animals:
When the animal has little opportunity for learning
*i.e. fly that has one day to mate, lay eggs, and then die… wouldn't survive if it had to
learn how to go about it
When it is critical for the animal to perform the behavior correctly the first time, even when there
is opportunity to learn
*i.e. baby bird’s first flight
-Innate behaviors are often related to predation, reproduction or other important activities, and are triggered by a
stimulus of some kind (a sort of sign) that will reliably occur under conditions that should lead to the appropriate
i.e. male stickleback fish have red under bellies, so when a male is protecting a nest of eggs and sees red
he becomes aggressive (only thing in their environment that is red so it is a simple cue there’s an enemy)
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