Core (for SL & HL) :
E1 – Stimulus and response;
E2 – Perception of stimuli;
E3 – Innate and learned behaviour &
E4 – Neurotransmitters and synapses
Additional Higher Level (for HL only):
E5 – The human brain &
E6 – Further studies of behaviour
E1 Stimulus and response
 E.1.1 Define the terms stimulus,
response and reflex in the
context of animal behaviour.
 E.1.2 Explain the role of
receptors, sensory neurons, relay
neurons, motor neurons,
synapses and effectors in the
response of animals to stimuli.
 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 cell, sensory
neuron, relay neuron, motor
neuron and effector.
 E.1.4 Explain how animal
responses can be affected by
natural selection, using two
examples.
E1 Stimulus and response
Definition of terms:
Stimulus; a change in the
environment (both
internal and (or)
external), that is detected
by a receptor and elicits a
response
Response; body’s reaction
to a stimulus.
Reflex; a rapid and
unconscious response to
a stimulus.
Draw a labelled diagram of a Reflex arc
receptor cell
sensory neuron
white mater
synapse
relay neuron
grey mater
effector
motor neuron
Components of a reflex arc
Components of a reflex arc & their role
in the response of animals to stimuli
Component
receptors
sensory neurons
relay neurons
Role in the response to stimuli
detect stimuli & transform it’s energy into a
nerve impulse
transmit nerve impulse regarding stimuli to the
CNS
transmit nerve impulse within the CNS from
sensory to motor neuron
motor neurons
transmit impulse from CNS to effector
Synapses
junction between two nerve cell or between a
nerve cell & an effector
receive messages from motor neurons & produce
a response to the stimuli
effectors
Effect of natural selection on animal
responses
 adaptation include
behaviour such as; mating,
hunting, migrating,
communication etc.
 Example; in a nest of chicks,
the chick which can call
louder and gape more
obviously is likely to be fed
 innate behavior patterns
more by its parents and
develop independently of the
survive
environment are inherited
 animals show variation in their  the alleles responsible for
successful behaviour are
behavior
eventually passed to the
 natural selection allows the
best-adapted animals to
offspring through
survive and reproduce
reproduction
Example: how natural selection
affect animal responses
 more food & mates in UK
 Blackcap (warbler) migrates to
UK from Germany due to severe
weather, food shortage & lack of
mates during winter
 there is warmer winters in UK
than in Germany
resulting in ‘selection for’
those birds migrating to UK
 migratory blackcap increase
in numbers due to greater
chances of survival
 the alleles responsible for
migration are eventually
passed to the offspring
through reproduction
 individuals that do not
migrate are ‘selected against’
Revision Questions:
 define the following terms:
stimulus; response & reflex
 explain the role of the
following; receptors, sensory
neurons, relay neurons, motor
neurons, synapses and effectors
in the response of animals to
stimuli
 draw labelled diagram of a
reflex arc for a pain withdrawal
reflex
 giving an example, explain the
effect of natural selection on
animal responses