Transcript OPTION E

OPTION E
NEUROBIOLOGY and
BEHAVIOUR
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E 1: STIMULUS AND RESPONSE
Stimulus: change in
environment
(internal or
external) that is
detected by a
receptor and ellicts
a response.
Response: change
in an organism,
produced by a
stimulus.
Reflex: a rapid,
unconscious response
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E.1.1: Stimulus/Response/Reflex
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E.1.2, E1.3: Neurons and Reflex Arc
PAIN WITHDRAWAL REFLEX
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Receptor: Part of the sensory neuron that detects the
stimulus.
Sensory neurons: Pass the message from the stimulus onto
the central nervous system.
Relay neurons: Pass the message from the sensory neuron
onto the motor neuron in the CNS.
Synapse: Fluid filled space between neurons. Message is
passed across the synapse via neurotransmitters.
Motor neurons: Sends message to effectors (muscles or
glands)
Effectors: Response from Muscles that contract or glands that
secrete hormones in response to message from motor 6
neuron.
E.1.4
For a particular behavior to evolve the
following conditions must exist:
*There must be variation for the behavior
*The behavior must be heritable (caused
by differences in alleles)
*Some variations of the behavior must
confer a greater reproductive advantage
than the others
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E.1.4 Behaviour and Natural
Selection
Sylvia atricapilla
Thamnophis elegans
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Example 1: European Blackcap migration patterns
Example 1:Bird: Sylvia atricapilla
Common name: Blackcap
Phenotypic variation is in the direction of migration (behaviour).
(a)The
original behaviour is that the Blackcap migrates SOUTH from its summer
breeding grounds in Germany to over winter in Spain.
(b) The new behaviour in some of the Blackcap population (10%)
in which they migrate to in a westerly direction to the UK.
*The hypothesis is that this behaviour has a genetic basis and that there is an
increased fitness value of migration to the west.
Experiment:
*The researcher collected the un-hatched eggs from parent birds that had visited the UK
in the previous winter.
Eggs collected
from both
groups
*The un-hatched eggs are incubated away from the parents and have no contact with
parent birds.
*Similarly, un-hatched eggs from parent birds that over wintered in Spain the previous
winter are collected, incubated and released as before.
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Results:
Birds of UK parentage flew west.
Birds of Spanish parentage flew south.
Conclusion:
The direction of migration is genetically determined and the population is diverging due
to behaviour (not speciation yet).
Discussion:
What is the advantage of flying west to the UK?
*Birds going to the UK to winter do not having to traverse the Alps in their flight path.
*The UK is much closer meaning that birds returning to the breeding grounds begin pair
bonding much earlier.
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Example 2: Prey preference in the Garter Snake of California Thamnophis elegans
*Coastal snakes diet includes amphibians and the Banana slug
(Ariolimus californicus)
*Inland snakes diet main component frog, leach and fish (slug is
absent)
Slugs eaten by
coastal snakes
no slugs eaten by inland
snakes
Hypothesis:
The difference in diet selection is behavioural and genetically inherited.
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Experiment:
•In an experiment pregnant snakes from the two regions have been collected.
•Inland and Coastal animals are isolated from each other.
•The hatchlings are offered Banana slug food along with other foods over a 10 day period
Results:
% of offspring that had a
preference for banana slugs
Coastal snakes
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Inland snakes
20
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Conclusion:
*Costal Garter Snake eat more Banana slugs than Inland Garter snakes
*Behaviour differences are genetically based
*Two populations have diverged due to a difference in behaviour (not speciation,
yet).
Discussion:
This experimental conclusion was followed up with an investigation looking for the
heritable aspect of the ‘slug smelling’ difference between coastal and inland Garter
snakes.
The difference between the coastal and inland Garter snake is genetic, the gene
allows the snake to detect the molecule that is the slugs ‘smell’. In other words the
sense of smell of the snakes is different.
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E.2: PERCEPTION of STIMULI
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E.2.1
SENSORY NEURON:
Sensory neurons convert the stimulus to an
electrical impulse
RECEPTORS
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E.2.1: Receptors
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MECHANORECEPTOR
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CHEMORECEPTORS
They measure changes in the
composition of arterial blood flowing past
it, including the partial pressures of
oxygen and carbon dioxide and pH
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THERMORECEPTOR
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PHOTORECEPTOR
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E.2.2: Human Eye
BLIND
SPOT
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E.2.3:Retina
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Individual cone cells send
signals to one neuron of optic
nerve
Groups of rod cells
send signals to one
neuron of optic nerve
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Rod cell: more sensitive to light,
monochromatic vision
E.2.3: Human Retina
Cone cell: less sensitive to light,
colour vision
Ganglion cell: A type of interneuron that
conveys information from the retinal
bipolar cells to the brain.
Bipolar neuron: Has two extensions:
connects rod or cone cells to
ganglion neurons
E.2.4: Rod and cones cells
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Cone cells
Rod cells
More sensitive to light and therefore they
get bleached in bright light
Less sensitive to light and therefore they
function well in bright light
One type of cell that can absorb all
wavelengths of visible light
Three types of cells that absorb red, blue,
or green light only
Monochrome vision and duller vision than Color vision and sharper vision than rod
cone cells
cells
More widely dispersed in retina and
therefore provide wider field of vision
Less widely dispersed in retina and
therefore provide narrower field of vision
Groups of rod cells send signals to one
neuron of optic nerve
Individual cone cells send signals to one
neuron of optic nerve
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E.2.5: Processing
Visual Stimuli
Three stages from when light
is detected until it reaches
the brain
1. Convergence
2. Edge enhancement
3. Contralateral processing
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1. Convergence: Bi-polar cells in the retina combine the
impulses from groups of photoreceptors and pass them
onto ganglion cells
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2. Edge enhancement
One ganglion cell
Receptive field: the
area of
photoreceptors that
pass their information
onto one ganglion
cell
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2. Edge enhancement: Ganglion cells are more stimulated if the edge
(light and dark) of what you are looking at falls within the receptive field
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Edge enhancement at work
The photopic cone system records and
enhances
edges.
(a) the annoying grey smudges (Hermann grid) that appear as we glance across the
figure cannot be easily counted because they disappear when fixed: they appear in
interstices not directly in our gaze.
(b) Why? Visual sharpness decreases as we move away from the fovea which is where
we see edges clearly so as we scan, the cells that are away from the center
overwhelm them (148) See next, search for “Hermann grid”
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3. Contralateral processing:
light entering each eye from the right side
of the person passes to the left side of the
brain, and vice versa.
Visual cortex processes the
information for us to see the image
Paris as seen with full visual fields
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Paris as seen with bitemporal
hemianopsia
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Paris as seen with binasal
hemianopsia
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Paris as seen with left
homonymous hemianopsia
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1. The folds of cartilage surrounding the ear canal are called the pinna and
cause sound waves to be reflected, and these changes of direction provide
information to help the brain determine the direction from which the sounds
came.
E.2.7
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2. The sound waves enter a simple tube called the auditory canal that amplifies
sounds. At the far end of the ear canal is the eardrum, which marks the beginning
of the middle ear.
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•3. Sound waves from the eardrum travel across the air-filled middle
ear cavity via a series of delicate bones: the hammer, anvil and
stirrup. These bones pass the sound waves onto the cohlear via a
membrane called the oval window.
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4. The round window is a membrane on the cochlea of the inner ear that
pulsates in accordance with vibrations entering the cochlea through the
oval window . It allows fluid in the cochlea to move.
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5. This in turn causes hair cells of the cochlea to be stimulated. Each
hair cell has a bundle of 100-200 specialized cilia at the top that act as
mechanoreceptors for hearing.
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E.3: INNATE and LEARNED
BEHAVIOUR
Innate behavior is behavior that
develops no matter what the
environment is like.
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E.3: INNATE and LEARNED
BEHAVIOUR
Learned behaviors develop as a result
of experiences during development.
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Innate behaviors are controlled by
genes, independent of learning. They
‘pre-program’ an individual for ‘success’
in its natural environment. In
evolutionary terms, ‘success’ means
surviving, reproducing and passing on
genes to the next generation.
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E.3.2: Taxis Kinesis
Taxis: The responsive movement
of a free-moving organism or cell
toward or away from an external
stimulus, such as light.
Kinesis: Movement or activity
of an organism in response
to a stimulus such as
humidity.
Sowbugs
Euglena sp
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Taxis
Dim light
Bright light
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E.3.2
Example of Taxis
In order to pass on his genes, a male promethia moth must avoid being eaten by predators
and he must find a fertile female to copulate with. This isn’t an easy task because females
spend most of their time hiding under branches, and they are distributed very sparsely over
large forest landscapes.
Through natural selection, male promethia moths have adapted two innate behaviors menotaxis and chemotaxis - to help them locate mates. Menotaxis refers to an animal in
motion that maintains a constant angle to a stimulus. Chemotaxis is movement in response to
chemicals.
•.
Male promethia moths fly at an angle (menotaxis) perpendicular to the direction of the wind
(stimulus). Once a male detects a female’s scent trail (stimulus), he turns upwind and follows
the chemical gradient (chemotaxis) of the trail, which leads to the female.
The menotaxis response increases the male’s chance of successful reproduction by: 1)
reducing his searching time; 2) lowering his energy costs; 3) decreasing his risk of being eaten
by predators; and 4) increasing his chance of finding a female.
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Menotaxis: refers to an
animal in motion that
maintains a constant
angle to a stimulus.
Chemotaxis: is
movement in response
to chemicals.
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E.3.2
Example of kinesis – the sowbug
Organisms that settle in more favorable areas enjoy a reproductive advantage over
those settling in less favorable areas. Therefore, natural selection favors animal
behaviors that help individuals to move to, and remain in, ideal habitat.
Humidity is one factor that affects the reproductive success and survival of the sowbug.
Sowbugs are land animals with external gills that must remain moist. Therefore,
sowbugs are restricted to humid areas and are commonly found under damp logs, rocks,
and fallen leaves.
To settle in a suitable habitat, a sowbug must perceive, and respond to, changes in
humidity. When humidity is favorable, a sowbug will remain (more or less) in the same
place. When humidity is unfavorable, a sowbug will emigrate to a new location.
Sowbugs respond to humidity with a form of kinesis called hygrokinesis. In hygrokinesis,
sowbugs respond to changes in humidity by altering the rate of locomotion and/or the
rate of change in direction.
When conditions are ideal, sowbugs move slowly and change directions frequently,
which has the effect of keeping them in the ideal microhabitat? When conditions become
dry, sowbugs increase their speed of travel and change direction less frequently, which
has the effect of taking them far away. Once a sowbug reaches a moister microhabitat it
will move slower and change directions more frequently.
Kinesis
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E.3.3
Identify the humidity range at which sow bugs remain in one place.
Identify the humidity range at which sow bugs travel the furthest.
State the preferred humidity of pill bugs
Compare the relationship between humidity and turns with the relationship
between humidity and speed.
Explain how natural selection could produce the observed innate behavior in
pill bugs.
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E.3.4: Learning improving survival
Habituation is a type of learning in which a behavior is reduced when no
reward or punishment follows. Deer become habituated in Canada’s
National Parks, for example. Deer are initially frightened by the sound of
highway traffic and therefore run from vehicles. Individuals that
habituate, however, learn to feed near highways. Therefore, habituated
deer gain greater access to food and produce more offspring than unhabituated deer.
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E.3.4
Conditioning is a type of learning in which an animal associates two
separate stimuli and then modifies its behavior. An example of
conditioning in nature involves birds that prey on butterflies: birds
that can distinguish between edible and toxic butterflies have a
survival advantage. For example, after eating a toxic Monarch
butterfly, a flycatcher feels ill and experiences an unpleasant taste.
The flycatcher learns to avoid monarchs by remembering the
butterfly’s appearance (a visual stimulus) and associating it with the
butterfly’s toxicity (a chemical stimulus).
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E.3.4
Imprinting is a type of learning that keeps goslings near their
mother, which helps them avoid predators and learn how to feed. In
his famous experiment, Lorenz divided the eggs of a graylag goose
into two groups: 1) eggs hatched by their mother and 2) eggs
hatched in an incubator. After hatching, the chicks that hatched with
their mother began to follow her around. The incubated chicks
however, began instead to follow Lorenz. The sign stimulus for the
goslings is any moving object the size of a mother goose.
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E.3.5: Pavlov
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E.3.: Birdsong
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Birdsong
Virtually all 9000 species of birds have the
ability to vocalize. Vocalizations with
extended melodies are termed, ‘song’.
Birdsongs can be compared by looking at
sonograms.
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Evidence for the role of inheritance in the development of
birdsong in white-capped sparrows
White-capped sparrows that are deafened are at birth can still develop
a song with some of the normal elements. This indicates the important
role of inheritance in song development.
White-capped sparrows can not learn to sing songs of non-sparrow
species which indicates the presence of a song template in the brain
(which must be inherited).
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Evidence for the role of learning in the development of birdsong in
white-capped sparrows
White-crowned sparrows have local song dialects. When a male
develops his song in a location where two sparrow populations overlap it
can become bilingual, meaning he can sing the two different songs. This
shows that song development requires learning the calls of a nearby
tutor during an early, sensitive phase of life.
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E4: Neurotransmitters and
synapses
STATE: Presynaptic
neurons either
excite/inhibit postsynaptic
transmission
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E.4.2: Decision making
Synapses and neurotransmitters
A nervous impulse is transmitted from one neuron to another across a
narrow, fluid-filled space called a synapse. The signal travels across the
synapse in the form of special chemicals called neurotransmitters, of which
there are many kinds.
Two neurotransmitters that control brain activity are glutamate (which
increases brain activity) and GABA (which decreases brain activity).
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Glutamate
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GABA
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E.4.2: Decision making
• When an excitatory neuron sends an impulse to the pre-synaptic
membrane an excitatory neurotransmitter will be released into the
synapse. When excitatory neurotransmitters bind to receptors on the
post-synaptic membrane, gated-sodium-channels open, causing
sodium ions to flow into the post-synaptic neuron. This depolarizes
the post-synaptic neuron, triggering an action potential.
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When an inhibitory neuron sends an impulse to the pre-synaptic
membrane an inhibitory neurotransmitter will be released into the synapse.
When inhibitory neurotransmitters bind to receptors on the post-synaptic
membrane, gated-chlorine-channels open, causing chlorine ions to flow
into the post-synaptic neuron. This hyperpolarizes the post-synaptic
neuron, preventing it from forming an action potential.
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The role of excitatory and inhibitory neurons in decision making
Pre-synaptic neurons only release one kind of neurotransmitter.
Therefore, a pre-synaptic membrane can either excite or inhibit a
post-synaptic neuron – it can’t do both.
Some post-synaptic neurons synapse with large numbers of both
excitatory and inhibitory pre-synaptic neurons. In this situation, a
post-synaptic neuron will form an action potential if it is receiving
more excitatory neurotransmitters (from excitatory pre-synaptic
neurons) than inhibitory neurotransmitters (from inhibitory presynaptic neurons). This is the basis of decision-making processes in
the central nervous system.
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E.4.3: Psychoactive drugs
A psychoactive drug is a chemical that
alters brain function, resulting in temporary
changes in perception, mood,
consciousness, or behavior.
psychoactive drugs may increase or
decrease transmission (to the
post-synaptic membrane);
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Psychoactive drugs are taken by some people: to treat neurological illnesses; for
‘recreational drug use’; or for spiritual purposes. Psychoactive substances can be
habit-forming, causing chemical dependency, often leading to substance abuse.
Personality, behavior and decision-making are the result of trillions of neurons in the
brain ‘talking’ with one another; ‘talking’ by means of neurotransmitters at the
synapses.
Drugs affect brain activity by interrupting the normal transmission of messages from
pre-synaptic membranes to post-synaptic membranes. Drugs can work by mimicking
neurotransmitters or influencing them in other ways.
Excitatory drugs increase post-synaptic transmission (e.g. cocaine). Cocaine works by
preventing the normal re-uptake of a neurotransmitter called dopamine.
Inhibitory drugs decrease post-synaptic transmission. (e.g. THC in marijuana). THC
binds to receptors in the pre-synaptic membrane thereby inhibiting the release of
excitatory neurotransmitters.
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E.4.4: Drugs
Excitatory psychoactive drugs
Inhibitory psychoactive drugs
Nicotine (cigarettes)
Benzodiazepines (valium)
Cocaine (crack)
Alcohol (San Miguel)
Amphetamines (ecstasy)
Tetrahydrocannabinol (THC)
Caffeine (coffee & tea)
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E.4.5: THC, cocaine
Cocaine blocks the dopamine pump
in the pre-synaptic membrane
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What should happen
Dopamine (the orange diamonds)
are taken back into the
presynaptic neuron
What happens with cocaine
The green is cocaine, blocking the
dopamine transporter and causing
increases in dopamine in the synapse.
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Cocaine
Usually makes the user feel euphoric, energetic, talkative, and mentally alert,
especially to the sensations of sight, sound, and touch. It can also temporarily
decrease the need for food and sleep.
Euphoria and Depression
- early side effects include euphoria lasting 5-15 minutes. This 'high' is followed by a
crushing 'low' (depression) that leaves the user craving more of the drug.
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THC in the brain
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Cannabinoid receptor
THC, the main drug in marijuana, works in this way: THC binds to
cannabinoid receptors in the pre-synaptic membrane thereby inhibiting the
release of excitatory neurotransmitters (orange diamonds with a X through
them).
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THC is an inhibitory psychoactive drug that decreases synaptic transmission.
THC affects synapses where the post-synaptic neuron releases a signal chemical
that binds to cannabinoid receptors on pre-synaptic neurons
THC also binds to cannabinoid receptors inhibiting the release of excitatory
neurotransmitters from the pre-synaptic neurons cannabinoid receptors are found in
various brain locations:
*cerebellum THC thus impairs motor functions
*hippocapus THC thus impairs short-term memory functions
*cerebral cortex THC thus affects higher order thinking
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Explain the effect of tetrahydrocannabinol (THC) on brain function
binds to cannaboid/pre-synaptic receptors;
inhibits neurotransmitter release;
therefore no excitation of post-synaptic membranes;
.
2 max
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E.4.5:
Cocaine is a powerful but short-acting stimulant drug (the high lasts no more than
40 minutes).
Cocaine is a white powder made from the leaves of the coca shrub, which grows in
the mountain regions of South American. Most users sniff it into the nostrils where it
is absorbed through the thin nasal lining.
Cocaine works by preventing the normal re-uptake of a neurotransmitter called
dopamine. Dopamine stimulates the pleasure center of the brain and thus functions
to give us a sense of well-being and happiness.
When cocaine is in the blood, dopamine accumulates in synapses, resulting in
repeated action potentials in the post-synaptic neuron. This over-stimulates the
pleasure center and the user feels euphoric.
While intoxicated, a cocaine user is likely to be talkative, alert, energetic and
euphoric. Repeated use of cocaine over extended periods of time causes the body
to produce less dopamine than normal; the result being a depressed person who
feels unhappy unless high on coke.
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Marijuana
Cannabis is a genus of flowering plant from northern India. It is smoked in the form of
dried flowers (marijuana) or resin (hashish). The high lasts 2-4 hours and the effects
vary amongst individuals.
THC, the main drug in marijuana, works in this way: THC binds to cannabinoid receptors
in the pre-synaptic membrane thereby inhibiting the release of excitatory
neurotransmitters.
Brain regions affected by THC include the cerebral hemispheres and the cerebellum.
Marijuana affects both mood and behavior. It makes some people talkative and silly with
laughter, while others become quiet and contemplative. A person intoxicated with
marijuana is likely to feel relaxed and calm.
Marijuana users often have an increased appetite while intoxicated and some report a
heightened sense of taste and touch, making food and sex more stimulating than
normal.
Repeated use of marijuana over extended periods of time can cause some people to
feel calmer than they normally would while other users may develop negative symptoms
such as lethargy and depression.
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Psychoactive Mechanism of
Drug
action
Inhibitory
or
excitatory?
Three
effects on a
person’s
mood
Three effect
on a
person’s
behaviour
anxiety, fear,
distrust, or
panic.
Distorted
perception (si
ghts, sounds,
time, touch)
Hallucination
s
Delusions
anxious
Cocaine
Marijuana
(THC)
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E.4.6: Drug addiction
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Drug addiction is a mental disorder characterized by:
Preoccupation: constant cravings and a urge to obtain and use the
drug
Binging: inability to control intake, using more of the substance than
necessary to experience the intoxicating effects
Withdrawal affect: emergence of a negative emotional state when
access to the drug is prevented; and reduced ability to respond to
naturally rewarding stimuli
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Drug addiction Definition:
Dependency on a substance
(such a s alcohol or other drugs).
Stopping is very difficult and
causes severe physical/mental
reactions.
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The biological basis of drug addiction
The biological basis of drug addiction involves the
neurotransmitter dopamine. The brain experiences pleasure
through the interaction of many brain parts, and dopamine is
the major neurotransmitter in this ‘reward circuit’.
Recreational drug use causes the release and prolonged action
of dopamine within the reward circuit. In other words, addictive
drugs produce a reward; the euphoric feeling resulting from
sustained dopamine concentrations in the synaptic cleft of
neurons in the brain.
Operant conditioning is exhibited in drug addicts as well as
laboratory mice, rats, and primates; they are able to associate
an action or behavior, in this case seeking out the drug, with a
reward, which is the effect of the drug.
Evidence shows that drug-addictive behavior is likely a result of
synaptic changes in the pre-frontal cortex – the decisionmaking part of the brain – which develops increased glutamate
receptors in drug addicts.
Drugs known to cause addiction include illegal drugs (like
cocaine) as well as prescription or over-the-counter drugs (like
nicotine, alcohol, and caffeine).
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Reward circuit of the brain (in blue)
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Genetic predisposition to drug addiction
Genetic predisposition is the increased chance of developing an
addiction based on the genes that a person has.
A person may have a genetic predisposition to engage in risktaking behavior. Such a person would be more likely to
experiment with drugs.
A person may have a genetic predisposition based on a gene
that affects brain chemistry. The DRD2 gene, for example, codes
for a dopamine receptor. Research shows that people with the A1
allele consume less alcohol on average than those with the A2
allele.
Genetic predisposition explains why some people never try
drugs, and why some people who do try drugs don't become
addicts.
Genetic link has also been
found with cocaine use
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Social factors in drug addiction
Certain drugs are important to some cultures. In Korea and Japan, for
example, alcohol is sometimes consumed to help complete business
deals. In France, wine is revered as an important aspect of French
culture. Cultural traditions can lead to increased rates of addiction.
Teenagers are especially vulnerable to peer pressure, which is a
common motivator for the use of nicotine, alcohol and marijuana.
Therefore drug prevention programs in schools often deal with peer
pressure.
Advertisers sometimes glamorize drugs like nicotine and alcohol.
They make these drugs seem ‘safe’, ‘cool’, and ‘fun’ even though they
are potentially dangerous.
Unemployment, poverty and traumatic life experiences may also be
contributing factors.
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Cocaine is a potent and dangerous. The
short-term and long-term effects of cocaine
are equally dangerous. The dangers of
experiencing cardiac arrest or seizures
followed by respiratory failure is equal in
both short and long term abuse.
Insomnia
Loss of appetite
Blurred vision
Vomiting
High anxiety
Irritability
Constricted blood vessels
Dilated pupils
Nasal infections
Nose bleeds
Rapid breathing
Sweating
Violent behavior
Twitching
Hallucinations
Chest pain
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Marijana
Distorted perception (sights, sounds, time, touch)
Problems with memory and learning
Loss of coordination
Trouble with thinking and problem-solving
Increased heart rate, reduced blood pressure
Sometimes marijuana use can also produce anxiety, fear, distrust, or
panic.
Hallucinations
Delusions
Impaired memory
Disorientation
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E.5.1
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E.5.2
Brain structure
Cerebellum
Medulla oblongata
Cerebrum
Functions
Controls muscle coordination, posture and balance
Controls automatic and homeostatic activities, such as
swallowing, digestion, vomiting, breathing and heart activity.
Learning, memory, emotions, language and reasoning
Hypothalamus
Maintains homeostasis, coordinating the nervous and
endocrine systems: helps to regulate water balance and body
temperature
Pituitary gland
The posterior lobe regulates many body functions by
secreting hormones that it produces (as well as hormones
that it receives from the hypothalamus and the anterior lobe).
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Animal studies
E.5.3
Experiments on living animals have provided additional
information on brain function. The brains of rats, monkeys and
other animals have been studied by observing the effects of
chemical injections and electric shocks in small brain regions.
This work has been criticized by animal rights groups.
A hole has been drilled in this monkeys skull and a cannula inserted, through
which fluids are drawn off from the brain. This device is also used to introduce
addictive drugs and other chemicals into the brain and such animal research
can extend over several months.
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CAROLINE DELGADO, shown monitoring encephalographic readings from a monkey,
has assisted her husband since their meeting at Yale University in the 1950s.
Delgado showed that stimulation of the
motor cortex could elicit specific physical
reactions, such as movement of the limbs.
By stimulating different regions of the
limbic system, which regulates emotion,
Delgado could also induce fear, rage, lust
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ELECTRICAL BRAIN-STIMULATION
DEVICES (above), invented by Jose Delgado for his research
into behavior and motor control, were implanted into apes, monkeys, bulls, cats and
humans. Electrodes could remain implanted for more than two years
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CAT LIFTED ITS HIND LEG in response to stimulation by an electrode implanted into the motor cortex of the brain.
The cat, Delgado says, displayed no discomfort in this experiment done in the early 1950s.
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E.5.3
Different parts of the brain are responsible for different
functions, although many functions require coordinated
communication of various brain parts.
Lesion studies
The first ‘brain maps’ were based on observations of patients
with brain tumors and brain lesions. Scientists learned that the
frontal cortex affects personality when a large metal bar sliced
through the skull and brain of a man named Phineas Gage.
The French physician Paul Broca discovered that speech is
controlled by a region at the back of the frontal cortex when he
found a brain lesion (caused by syphilis) in a patient that lost the
ability to speak. Since then, the effects of strokes and other
types of brain damage have been a key source of information
about brain function.
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Functional Magnetic Resonance Imaging (fMRI)
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E.5.3
Functional Magnetic Resonance Imaging (fMRI)
FMRI is a modern method used to study brain activity. It has two major
advantages: 1) it records brain signals non-invasively without health risks, and
2) it can provide information on an area smaller than 1mm2.
fMRI involves a high resolution brain scan before the subject is stimulated,
followed by a series of low-resolution scans whilst the subject is stimulated. The
scans show the brain regions that are activated by the stimulus.
fMRI shows changes of blood flow in response to neural activity in the brain or
spinal cord. When nerve cells are active they consume oxygen (carried by
hemoglobin in red blood cells) from local capillaries. The depleted oxygen
triggers a localized increase of blood flow, which the fMRI detects and shows.
This response rises to a peak over 4–5 seconds, before falling back to baseline.
122
This fMRI brain scan shows areas that respond
to familiar music (green), salient memories (red),
and music that is perceived as enjoyable (blue).
The yellow area, in the medial prefrontal cortex,
is a response both to music familiarity and
salient memory. (Petr Janata/UC Davis image)
123
In scan 1, a subject is asked to remember a face. Areas at the rear of the
brain that process visual information are active during this task, as is an
area in the frontal lobe. In scan 2, the subject is asked to "think about this
face." Surprisingly, the hippocampus is activated - the first time this has
been documented. The hippocampus was already known to be important
for memory, but these results show that this part of the brain is specifically
active during the time when we are remembering new information.
In scans 3 and 4, the subject was asked to compare another face to the
remembered face. Some of the same visual areas are activated as during
the initial memory task, but other areas, such as part of the frontal lobe,
are involved in making a decision about the memory.
124
bcm.bc.edu/issues/summer_2008
125
Can an fMRI like this one detect lies? [Credit: Washington Irvine, Wikimedia Commons]
126
Explain how fMRI (functional magnetic resonance imaging) scanning can be
used in investigation of how the human brain functions.
it records changes in blood flow;
active parts of the brain have increased blood flow;
but not all brain activity is detected by MRI;
a subject is given a stimulus which is designed to stimulate brain activity;
links stimulus with certain part of the brain;
brain activity visualized by coloured images;
degree of activity can be represented (by different colours);
temporal activities can be recorded as well;
allowing sequential use of the brain to be visualized;
collaboration between brain parts;
non invasive;
127
Discuss how brain lesions and fMRI (functional magnetic resonance imaging)
scanning can be used in the identification of the brain part involved in specific
functions of animals.
lesions (from accidents/birth) indicate effect of loss of area;
e.g. split brain patients/severed corpus callosum led to understanding
different functional roles of left and right hemispheres / other valid examples;
many actions of the body involve different areas of the brain;
damage may be to several/many parts so results unclear;
difficult to interpret due to complexity of reactions;
fMRI gives a more specific knowledge of stimulated area/activation;
e.g. used to study/diagnose ADHD/dyslexia/recovery from strokes/music
comprehension / other valid examples;
non-invasive / no damage to brain;
can study healthy subjects;
involves blood flow/supply/oxygenation;
not neuronal connections (so requires interpretation);
good spatial but poor temporal resolution;
problem of statistical interpretations of model;
Award [4 max] if either brain lesions or fMRI alone are discussed.
5 max
128
Technique of brain
mapping
Stimulus
Part of brain
associated with the
stimulus
Brain Lesions
Person’s brain was infected
with a bacterial infection
and person had lost the
ability to speak
Upon death dissection of
the brain reveled that the
back of the frontal cortex is
involved in speech.
Animal Experiments
Probes inserted into brain
and then stimulated
E.g. Cat had a probe
inserted into its brain and
when the brain as
stimulated the cat would
raise its leg indicating that a
motor region of the brain
was stimulated.
fMRI
Whilst in the fMRI a person
shown visual stimuli
Visual cortex region of brain
highlighted on fMRI scans
129
130
E.5.4
•The nervous system of vertebrates is divided into the central nervous system
(CNS) and the peripheral nervous system (PNS). The CNS consists of the brain
and the spinal cord. The PNS includes all the nerves outside the central
nervous system.
The peripheral nervous system is divided into the voluntary (or somatic)
nervous system (VNS) - which is under conscious control - and the autonomic
nervous system (ANS) - which is mostly under unconscious control.
131
132
•The ANS consists of sympathetic and parasympathetic motor
neurons, and it functions to maintain the homeostasis and normal
functioning of internal organs.
•The roles of the sympathetic nervous system and the
parasympathetic nervous system are largely
antagonistic.
•The parasympathetic nervous system is sometimes called the "rest
and digest system”. It functions during non-threatening situations to
slow and relax organs and body systems.
The sympathetic nervous system is sometimes called the "fight or
flight system”. It becomes active during threatening situations and/or
to prepare the body for periods of high activity (e.g. chasing prey,
being chased by predators, playing sports).
133
E.5.4
Effects of parasympathetic motor
neurons
Effects of sympathetic motor neurons
Circular muscles relax to increase the
Constricts pupil to reduce the influx of
diameter of the pupil. This maximizes
light, thereby allowing the retina to rest.
the influx of light thereby increasing
the sharpness of vision.
Speeds up digestion by increasing
blood flow to the gut by dilating blood
vessels that lead to the gut wall. This
allows the body to digest food a
during periods of low activity.
Constricts blood vessels leading to
digestive system when blood is needed
elsewhere, such as the muscles during
exercise.
Increases the frequency and strength
Reduces heartbeat (both strength and
of heartbeats, which sends more blood
frequency), which conserves energy.
to muscles thus improving muscle
performance.
134
Outline the unconscious control of the heart rate.
heart can contract without nervous stimulation/myogenic
contractions;
SA node is pacemaker/generates heart beat/initiates each
cardiac cycle;
epinephrine/adrenalin speeds up the heart rate;
autonomic/sympathetic and parasympathetic nervous system
control;
sympathetic speeds up heart rate;
parasympathetic/vagus nerve slows heart rate (back to normal/
resting rate);
135
Explain sympathetic and parasympathetic control of blood flow to the gut.
sympathetic and parasympathetic nervous systems are part of the
autonomic system;
have antagonistic actions;
smooth muscle in blood vessels/arterioles controlled by sympathetic and
parasympathetic nerves;
sympathetic system release norepinephrine/noradrenaline;
constricting blood vessels/arterioles to gut;
decreasing blood flow to gut;
parasympathetic system release acetylcholine;
dilating blood vessels/arterioles to gut;
increasing blood flow to gut;
136
E.5.5
The pupil reflex is a reflex that controls the diameter of the pupil, in
response to the intensity of light that falls on the retina of the eye.
Greater intensity light causes the pupil to become smaller (allowing
less light in), whereas lower intensity light causes the pupil to become
larger (allowing more light in). Thus, the pupillary light reflex regulates
the intensity of light entering the eye.
Emergency room physicians often assess the pupil reflex: lack of the
pupil reflex indicates optic nerve damage or brain death.
The sensory receptors responsible for the pupil reflex are
photoreceptor cells in the retina. When the photoreceptor cells are
stimulated by light, they excite sensory neurons of the optic nerve,
which send the message to the brain.
The brain relays the message to oculomotor neurons, which cause
neurons that innervate the constrictor muscle (the effector) of the iris
of the eye.
137
138
E.5.6
Brain death is a legal definition of death that refers to the
irreversible end of all brain activity (including involuntary activity
necessary to sustain life).
Brain death is due to the death of cerebral neurons following
loss of blood flow and oxygenation.
A brain-dead individual has no clinical evidence of brain
function upon physical examination. This includes no response
to pain and no cranial nerve reflexes such as the pupil reflex.
The concept of brain death emerged in the 1960s, as the ability
to resuscitate individuals and mechanically keep the heart and
lungs functioning became prevalent.
Most organ donation for organ transplantation is done in the
setting of brain death. The non-living donor is kept on ventilator
support until the organs have been surgically removed. If a
brain-dead individual is not an organ donor, ventilator and drug
support is discontinued and cardiac death is allowed to occur.
139
Discuss the concept of brain death and the use of the pupil reflex in testing for brain
death.
whole brain death is brain stem and cerebrum;
failure of pupil to respond to light indicates brain stem death;
without brain stem function, life cannot continue;
cerebrum involves higher order brain function;
non-functioning cerebrum with functioning brain stem is vegetative state;
some would argue this is the death of the person;
though brain stem function alone may be able to maintain homeostasis; 6 max
140
Discuss the concept of brain death and how it can be diagnosed.
it is a legal/medical definition of death;
some cases of coma are irreversible / some cases of coma may recover;
damage in the medulla (oblongata) is generally permanent;
doctors have to diagnose damage to decide treatment;
use tests of brain stem function to decide whether to preserve patient’s life /
without brain stem function life cannot continue;
test pupil reflex / shine light into eye;
if pupils do not constrict with light this suggests brain death;
more than one test used to diagnose brain death;
no response to pain or cranial reflexes;
legal/ethical definition needed for organ donation / long term use of life-support
machines may be inappropriate / bioethical considerations;
141
E.5.7
1. Pain receptors in the skin (and other parts of the body) send
pain messages to the sensory areas of the cerebral cortex.
2. The feelings of pain are due to the messages received by
the cerebral cortex.
3. Endorphins block the transmission of impulses at the
synapses involved in pain perception.
4. Having the perception of pain has a
distinct survival benefit however there
comes a point at which the pain needs
to be blocked.
142
endorphins (enkephalins) = pain-inhibiting neurotransmitters
produced by reticular formation in brain
descending fibers synapse at the spinal cord dorsal horn
release endorphins into synapse between sensory neurons and ascending pain
neurons
endorphins have specific receptor sites on post-synaptic neurons
inhibitory action
open K+ channels
close Ca+2 channels
hyperpolarizing post-synaptic membrane
act as pain killers by inhibiting pain signals along ascending pain neurons
143
Outline how endorphins act as painkillers.
endorphins released by pituitary gland (during stress, injury
or exercise);
endorphins block transmission of impulses at synapses involved
in pain perception;
bind to receptors in the membrane neurons (involved in)
sending pain signal;
block release of neurotransmitters;
144
145
E.6.1
The social behavior of naked mole rats
The naked mole rat has a complex social structure. Colonies are comprised
of 20 to 300 highly related animals living together in intricate systems of
burrows.
In each colony, all mating is done by one queen and 1-3 males.
There are two castes of non-reproductive mole rats: tunnel makers and
soldiers.
Naked mole rats display altruism in three ways:
1) mature females help to raise young that are not their own;
2) tunnel makers do all the work without getting to mate; and
3) soldiers squeak loudly to alert the colony of danger, which puts
them at risk of being eaten by predators.
146
The social behaviour of honey bees.
Caste
Gender
Task
Queen
Fertile female Lay eggs
Produce a pheromone to control
the activities of workers
Drone
Fertile male
Mate with virgin queen females
Worker
Infertile
female
Collect nectar and pollen
Convert pollen into honey
Guard the hive
Look after the queen
http://www.youtube.com/watch?v=x6rgWzYRXiI&NR=1
147
Mature bee colonies may grow to include as many as 60,000 workers, at
which point the hive will "reproduce" by swarming. This is a process of
colony division in which an established queen emigrates with a large
group of workers to establish a new nest site, while a young queen and
the remaining workers stay behind to occupy the old nest site.
148
E.6.2: Outline how Natural Selection may act at the level of the colony in the case of
social organisms.
Natural Selection is the mechanism of Evolution in which individuals who are able to
survive in their environment can then pass on their genes which allowed them to
survive to their offspring.
Geneticists/Evolutionary biologists disagree if Natural Selection works on the level
of the colony rather than the individuals.
Some biologist see the colony as a “super organism” with individuals having highly
specific roles; e.g. In a honey bee colony the queen just basically lays eggs, the
drones just basically fertilise the queen, the workers are dispensable and may be
viewed as “cells” of a multicellular organism. The queen could be seen as the
“ovary” of the organism and the drones as the “testes” and their survival depends
upon other parts of the colony.
Some biologists argue that Natural Selection operates with the “fittest” colonies
surviving while other biologists argue that Natural Selection operates at the level of
the gene and there is no need to bring in another level with Natural Selection
operating at the colony level.
149
E.6.3 and E 6.3
Altruistic behavior lowers the fitness of an individual (i.e., its
chance of passing on genes) whilst increasing the fitness of
another individual within the colony.
So how could natural selection favor altruism if it causes
individuals to have a reduced chance of passing on genes? This
riddle is resolved by the selfish gene theory, which states that
natural selection acts on the gene pool, not on individuals.
150
Altruistic Behaviour is when one organism
increases the risk of sacrificing its own life for
that of another individual.
Appears to go against Natural Selection.
151
Example 1
The naked mole rat is an example of an altruistic species that lives in colonies.
In a mole rat colony, every member is highly genetically related. On average,
two mole rats in a colony share 81% of the same genes. This means that
almost all the genes of an individual get passed on by the breeding of others.
So as long as the other mole rats are breeding there is no need for a virgin
mole rat to worry about sex. In fact, a soldier raises the fitness of his genes by
squeaking (and dying for it) if his warning increases the total number of
survivors (each of which carries his genes).
Over the great span of evolutionary time, colonies that had a high level of
altruism survived better than colonies that had a lower level of altruism. In this
way, nature selected altruistic alleles.
152
E.6.3
Altruistic behavior lowers the fitness of an individual (i.e., its chance of passing
on genes) whilst increasing the fitness of another individual. The naked mole rat
of East Africa and vampire bats of South America, provide good examples of
innate altruistic behavior.
Naked mole rats display altruism in three ways:
1) mature females help to raise young that are not their own;
2) tunnelers do all the work without getting to mate; and
3) soldiers squeak loudly to alert the colony of danger, which puts them
at risk
of being eaten by predators.
153
Under a stricter definition, altruism only includes acts that benefit
unrelated individuals.
Example 2:
Altruism between unrelated animals is common amongst vampire bats,
which feed at night by sucking blood from mammals. On most nights, an
individual bat is successful in obtaining enough food. On occasion,
however, a bat might go one or two nights without feeding success. In
such a case, the hungry bat will return to its cave to get nourishment from
the regurgitated blood of another bat. The act of ‘donating’ blood is
altruistic. In vampire bats, the act of donating blood is not helpful to the
donor in the short term but in the long-term it is beneficial because the
donor may need to be a receiver on another occasion. This is called
reciprocal altruism: one individual acts altruistically knowing that it will be
reciprocated later on.
154
In an altruistic act, the individual who
has sacrificed their potential to pass
on their genes directly has allowed
closely related members within the
colony to pass on their genes which
are shared with the individual who
has died. Therefore the individual
who has died has his genes passed
on indirectly through close relatives
within the colony.
155
156
157
Discuss the evolution of altruistic behaviour using two non-human examples:
a. altruistic behaviour is when one organism increases the risk of sacrificing/sacrifices its
own life/reproductive success for that of another individual/the colony / OWTTE;
b. appears to be against natural selection;
c. (as it) reduces the possibility of the altruistic individual passing on its own genes;
d. (but) allows other individuals to pass on genes of the same gene pool;
e. if the altruistic allele persists in the gene pool then that trait can be naturally selected;
f. named organism and altruistic behaviour;
(e.g. termites break a gland in their neck to
release a sticky substance)
g. benefit to others and risk to self;
(e.g. protects others from attacking ants but kills
themselves)
h. another named organism and altruistic behaviour;
i. another benefit to others and risk to self; [6 max]
Award [4 max] if only one example of altruistic behaviour given.
158
Discuss the evolution of altruistic behaviour in a non-human species.
altruistic behaviour may be harmful to the animal itself but beneficial to other
animals;
occurs in social animals;
usually occur in the same species;
need not happen between genetically related animals from one population;
altruistic behaviour often occurs in animals which are genetically closely related;
altruistic behaviour may increase the survival rate of the group and thus the species;
helping close relatives or siblings increases the chances of passing on genes to the
next generation;
due to natural selection;
this is called inclusive fitness;
enhancing reproductive success of relatives is called kin selection;
if altruism was a negative trait it would / may have disappeared;
altruistic species do just as well as non altruistic species belonging to the same
order;
159
E.6.4
Foraging theory
Foraging is the behavior of searching for food. Some animals (called
specialists) are highly selective, always feeding on the same food item. Other
animals (called generalists) can potentially feed on many food items. Thus
generalists can make decisions about what kinds of foods to go after.
Foraging theory is based on the theory of natural selection. It predicts that
generalist feeders will choose foraging options that deliver the highest payoff
(maximum calories in, for minimum calories out). Such behaviors would evolve
by natural selection because individuals with good genes (genes that help them
to make good foraging choices) will survive and therefore pass on their good
foraging genes.
Foraging theory allows biologists to predict how generalist feeders will change
their feeding strategies under different environmental conditions. Therefore
foraging theory is helpful in making conservation decisions, such as whether or
not to re-introduce wolves to Yellowstone National Park.
160
Foraging Example 1: Black bear foraging
The "spirit bear" is a subspecies of the American Black Bear
(Ursus americanus) living in the central coast of British Columbia.
About 1/10 of their population have white or cream-colored coats.
Spirit bears are omnivores whose diet includes plants, insects,
living animals and carcasses. During the salmon spawning
season, spirit bears gorge themselves on salmon because the
salmon provide the maximum calorie supply. When salmon are
not available, 80% of their diet consists of plant material because
meat is harder to find.
After catching a salmon spirit bears usually carry their fish away
from the stream where they can feed in seclusion. If the fish is a
female they begin feeding on the belly, which contains fat-rich
eggs. They also feed on the brains and certain organs, which are
also fat-rich.
161
The bear’s preference of feeding in seclusion reduces the chances of losing a
meal to a rival bear or wasting time fighting the rival. And their preference for
high-fat organs ensures that their bellies fill up with organs with the highest
energy content.
The spirit bear’s food preferences match foraging theory. Over evolutionary
time, natural selection has favored bears that prefer fatty meat because they
were able to consume more calories than bears that ate less fatty meat. In
bleak years, when competition for food was fierce, bears eating fatty foods
would have survived better than individuals consuming lower energy food
items.
162
Foraging Example 2: Bluegill fish foraging
When environmental conditions change, generalist feeders have an advantage
over specialist feeders because they can adjust their feeding behavior to
optimize their chances of survival.
A good example of this comes from studies on the bluegill sunfish (Lepemos
macrochirus), which feeds on small invertebrates like Daphnia.
When Daphnia is abundant the sunfish can afford to be choosy, and as such
they feed exclusively on larger prey items. However, when prey is scarce they
must eat whatever food items they can find.
The graphs indicate that average prey size increases as prey density increases.
163
E. 6. 5: Mate selection leading to exaggerated traits
1. A feature that is an indictor of good genes is “selected by the
females.
2. Over successive generation this feature becomes
exaggerated.
3. The exaggerated trait may be a hindrance to the individual e.g
peacocks feather’s in flying away from predators.
164
E.6.6
STATE: Animals show
rhythmical variations in
activity
165
E.6.7
Biological rhythms
Many animal species, including humans, have known
biological rhythms. A biological rhythm is a predictable cycle
in the behavior and/or biochemical processes of an
organism. Biological rhythms evolve in species to optimize
the timing of events such as: eating, sleeping, digesting,
mating, hibernating and migrating.
Most biological rhythms are circadian, which means they
take roughly 24 hours to complete the cycle. Examples of
biological cycles that are longer than 24 hours include:
annual migrations and the human menstrual cycle.
Examples of biological cycles that are shorter than 24 hours
include: the 90-minute REM cycle during sleep and the 3hour cycle of growth hormone production.
166
Using a named example, outline a rhythmical behaviour pattern with an adaptive value.
named example and behaviour;
adaptive value;
e.g. coral with coordinated spawning;
permits maximum results of fertilization/reproductive success/
survival of species;
Accept common or general names of organisms.
167
Outline two named examples illustrating the adaptive value of rhythmical behaviour
patterns.
name of organism and behaviour;
adaptive value;
e.g.
Baltic grey seal has diurnal activity;
allows them to find food;
e.g.
shore crabs are inactive during low tide/active during high tide;
hunt organisms that come in on tide;
Accept any other valid examples. 4 max
MAKE SOMETHING UP IF
YOU CAN’T REMEMEBER
168
Example 1: Krill
Krill are shrimp-like marine invertebrates. They are important sources of food
for certain whales, sharks, seals and penguins.
Krill typically follow a diurnal vertical migration. They spend the day at greater
depths and rise during the night towards the surface. The deeper they go, the
darker the water becomes, and this makes it more difficult for predators to eat
them.
The diurnal migrations of krill depend on accurate monitoring of daylight,
which is achieved by their circadian system.
169
Example 2: Insect-eating bats
The circadian "clock" in mammals is located in a part of the hypothalamus
called the SCN. The SCN receives information about daylight from special
photoreceptors in the retina.
The SCN sends a message to the pineal gland, a tiny structure in the brain,
which secretes the hormone melatonin. Melatonin causes mammals to feel
sleepy. In humans, secretion of melatonin peaks at night.
In bats, melatonin peaks in the daytime, which is why they are more active at
night? Being active at night is a benefit to bats because they feed on moths,
which mainly fly at night. Thus the circadian rhythm of bats helps them to hunt
and feed when their prey is most abundant.
170