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E.1.1 Define the terms stimulus, response and reflex in
the context of animal behavior
Stimulus – a change in the environment (internal or external) that
elicits a response
•Examples – sound, pain, blood sugar change
Response – the action that results from the stimulus.
•The total of all responses to a certain set of stimuli is often called
behavior
Examples of stimuli/response
•external – an animal running away from a predator
•internal – secretion of enzymes in response to food in the stomach
E.1.1 Define the terms stimulus, response and reflex in
the context of animal behavior
Reflex – a rapid unconscious response
•Example – pain reflex
E.1.2 Explain the role of receptor, sensory neurons,
relay neurons, motor neurons, synapses and effectors
in the response of animals to stimuli
1. Receptors
E.1.2 Explain the role of receptor, sensory neurons,
relay neurons, motor neurons, synapses and effectors
in the response of animals to stimuli
2. Sensory Neuron
E.1.2 Explain the role of receptor, sensory neurons,
relay neurons, motor neurons, synapses and effectors
in the response of animals to stimuli
3. Relay Neuron
E.1.2 Explain the role of receptor, sensory neurons,
relay neurons, motor neurons, synapses and effectors
in the response of animals to stimuli
4. Synapses
E.1.2 Explain the role of receptor, sensory neurons,
relay neurons, motor neurons, synapses and effectors
in the response of animals to stimuli
5. Motor Neuron
E.1.2 Explain the role of receptor, sensory neurons,
relay neurons, motor neurons, synapses and effectors
in the response of animals to stimuli
6. Effector
A muscle or a gland that results in s response
E.1.3 Draw and label a diagram of a reflex arc for a pain
withdrawal reflex, including the spinal cord and its
spinal nerves, the receptor cells, sensory neuron,
motor neuron and effector
http://4.bp.blogspot.com/-zeepaOYQ7PU/ThEWWfZyX8I/AAAAAAAAACA/kbnwhUhcjaI/s1600/Untitled.png
E.1.4 Explain how animal responses can be affected by
natural selection, using two examples
Natural selection can also act on behaviors of organisms. If a particular
behavior helps an animal survive, this animal will likely become parents
and pass the behavioral trait to its offspring
These behaviors are called “Fixed Action Patterns” (FAP), or instincts,
and are genetically coded.
Examples of FAP’s include:
•Migration patterns
•Feeding beavior
E.1.4 Explain how animal responses can be affected by
natural selection, using two examples
Example 1: European Blackcap migration
patterns
Phenotypic variation is in the direction of
migration (behaviour).
•
•
The original behaviour is that the
Blackcap migrates SOUTH from its
summer breeding grounds in Germany to
over winter in Spain.
The new behaviour in some of the
Blackcap population (10%) in which they
migrate 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.
E.1.4 Explain how animal responses can be affected by
natural selection, using two examples
Example 2 – Fighting rituals in male
marine Iguanas (Amblyrhynchus cristatus)
•fighting behavior among male iguanas on
the Galapagos is favored by natural
selection
•most vertebrates have this fighting
behavior to prevent overcrowding or fight
for a mate
• fighting between animals of the same species rarely results in death or
even injury
• when there is a fight (ritual) the “loser” exhibits a submissive posture and
retreats
• both animals survive and have the possibility to pass their traits on to the
next generation
E.2.1 Outline the diversity of stimuli that can be
detected by human sensory receptors, including
mechanoreceptors, chemoreceptors, thermoreceptors
and photoreceptors.
Receptors detected the changes in both internal and external
environment.
The function of receptors is to transform the stimuli into a nerve impulse
that can be sent to the central nervous system which in turn
coordinates an appropriate response.
Remember all forms of stimuli are changed into nerve impulses
(electro-chemical)
E.2.1 Outline the diversity of stimuli that can be
detected by human sensory receptors, including
mechanoreceptors, chemoreceptors, thermoreceptors
and photoreceptors.
Chemoreceptors
Chemoreceptors have special proteins in their membranes.
These proteins can bind to a
particular substance and this will
result in a depolarization of the
membrane leading to an action
potential being sent to the brain.
Chemoreceptors are responsible for
our sense of smell and taste but also
detect the blood pH. taste buds on
the tongue contain chemoreceptors.
http://static.ddmcdn.com/gif/taste-6.gif
E.2.1 Outline the diversity of stimuli that can be
detected by human sensory receptors, including
mechanoreceptors, chemoreceptors, thermoreceptors
and photoreceptors.
Electroreceptors
Electroreceptors are found, for example, in sharks. Muscle contractions
generate electrical fields which are conducted by the water.
The shark can sense these fields
with its electroreceptors and detect
its prey. As air is a poor conductor,
terrestrial organisms would not have
much use for this sense organ.
E.2.1 Outline the diversity of stimuli that can be
detected by human sensory receptors, including
mechanoreceptors, chemoreceptors, thermoreceptors
and photoreceptors.
Mechanoreceptors
Mechanoreceptors are those that are sensitive to some kind of
movement. In fish, they are found in the ‘lateral line system’, which
detects vibrations in the environment.
We have a similar system in our
inner ear to inform us of our body’s
position and movement.
E.2.1 Outline the diversity of stimuli that can be
detected by human sensory receptors, including
mechanoreceptors, chemoreceptors, thermoreceptors
and photoreceptors.
Photoreceptors
Photoreceptors are the rods and cones in our eyes (Topic E.2.2).
Rods and cones contain photopigments that are broken down when
exposed to light.
This causes the cells to send an action potential to the brain.
E.2.1 Outline the diversity of stimuli that can be
detected by human sensory receptors, including
mechanoreceptors, chemoreceptors, thermoreceptors
and photoreceptors.
Thermoreceptors
• Thermoreceptors are found, for
example, in the skin.
• Cold receptors, just under the surface
of the skin, will send an action
potential when the temperature drops.
• Warm receptors, located a little
deeper, will send an action potential
when the temperature increases.
• The temperature center in the
hypothalamus of the brain also
contains thermoreceptors to monitor
the temperature of the blood.
E.2.2 Label a diagram of the structure of the human
eye.
E.2.3 Annotate a diagram of the retina to show the cell
types and the direction in which light moves.
There are three layers of
neurons:
• Photoreceptors (rods and
cones) In this image the
rods are blue and cones
orange
• Bipolar cells (named after its two
processes at either side of the cell body)
responds by changing rate of
neurotransmitter released to the Ganglion
cell
• Ganglion – A ganglion cell generates the
impulse which will travel along the axon of
the ganglion to the brain. These axons are
grouped together to form the optic nerve.
The cell body of the ganglion cell is in the
in the retina.
E.2.3 Annotate a diagram of the retina to show the cell
types and the direction in which light moves.
E.2.4 Compare rod and cone cells.
E.2.5 Explain the processing of visual stimuli, including
edge enhancement and contralateral processing.
Edge Enhancement - makes the edge of something dark even darker
and creates a “halo” of light around it, enhancing the contrast.
•Edge enhancement occurs within the retina.
E.2.5 Explain the processing of visual stimuli, including
edge enhancement and contralateral processing.
E.2.5 Explain the processing of visual stimuli, including
edge enhancement and contralateral processing.
E.2.5 Explain the processing of visual stimuli, including
edge enhancement and contralateral processing.
E.2.5 Explain the processing of visual stimuli, including
edge enhancement and contralateral processing.
Contra-lateral processing - refers to fact that some of the nerve fibres
in the optic nerve will cross before reaching the brain (optic chiamsa).
• the information from the left half of the
visual field, arrives on the right side of the
retina in the left eye.
• The nerves from this section are processed
by the right side of the brain.
• Information from the right half of the visual
field, arrives on the left side of the retina in
the left eye.
• The nerves from this section are processed
by the left side of the brain.
E.2.5 Explain the processing of visual stimuli, including
edge enhancement and contralateral processing.
• Overall, it means that
information of the right side of
the visual field is processed
by the left hemisphere of the
brain and information from the
left side of the visual field is
processed by the right
hemisphere.
• This “stereoscopic vision”
allows for 3-D vision and
depth perception.
E.2.6 Label a diagram of the ear.
E.2.7 Explain how sound is perceived by the ear,
including the roles of the eardrum, bones of the middle
ear, oval and round windows, and the hair cells of the
cochlea.
How’s your hearing?
Loudness vs pitch
E.2.7 Explain how sound is perceived by the ear,
including the roles of the eardrum, bones of the middle
ear, oval and round windows, and the hair cells of the
cochlea.
E.2.7 Explain how sound is perceived by the ear,
including the roles of the eardrum, bones of the middle
ear, oval and round windows, and the hair cells of the
cochlea.
Sound is captured by the
pinna (like a satellite
antennae)
Sound travels as
pressure waves in the air
which push the
membrane of the
eardrum, causing it to
vibrate
The ear drum pushes on the bones of the middle ear (the ossicles), which
magnify the vibrations (~ 20 times)
E.2.7 Explain how sound is perceived by the ear,
including the roles of the eardrum, bones of the middle
ear, oval and round windows, and the hair cells of the
cochlea.
The ossicles push against
the oval window,
displacing fluid within the
cochlea
Movement of the cochlear
fluid affects the position
of cilia on sensory hair
cells
Cilia on hair cells vary in
length and each
resonates to a different
frequency of sound
E.2.7 Explain how sound is perceived by the ear,
including the roles of the eardrum, bones of the middle
ear, oval and round windows, and the hair cells of the
cochlea.
Activation of the hair cells
generates nerve impulses
which are transmitted via
the auditory nerve to the
brain
The kinetic motion of the
cochlear fluid is
dissipated (or absorbed)
by the movement of the
round window