answers- option e

8/2/2019 Answers- Option e

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Option E: Neurobiology and Behavior

Option E: Neurobio + behavior

E1 Stimulus and responseE.1.1 Define the terms stimulus, response and reflex in the context of animal behaviour.

Stimulus: change in the environment that is detected by a receptor and elicits a response Response: change in an organism due to the stimuli

Reflex: rapid, unconscious responseE.1.2 Explain the role of receptors, sensory neurons, relay neurons, motor neurons, synapses and effectors in the

response of animals to stimuli.

Receptor: transforms the stimuli energy into a nerve impulse

Sensory neurone: part of the peripheral nervous system; connects receptor to CNS; impulse travels along

the axon of the sensory neurone

Relay neurone: coordinator; part of spinal cord; a neurone of the CNS; cell body forms a synapse with

the incoming sensory neurone

Motor neurone: in peripheral nervous system; carries nerve impulse from CNS to effector

Synapse: junction btw 2 nerve cells or btw a nerve cell and effector; transmission of nerve impulse across

a synapse takes a chemical form

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.

CNS = brain and spinal cord Spinal cord: acts independently from brain during reflex actions

E.1.4 Explain how animal responses can be affected by natural selection, using two examples.

Natural selection: mechanism of evolution requiring:

o Variation in phenotypes

o Genetic basis to this variation

o Change in env’t



Ex1: European Blackcap bird migration patterns

o Phenotypic variation is in the direction of migration (behavior)

o Original behavior = migrating SOUTH

o New behavior = some migrate WEST (10%)

o Hypothesis: new behavior has genetic basis; increased fitness value of migration to WEST

Ex2: Prey preference of Garter Snake of Cali

o Hypothesis = difference in diet selection is behavioral and genetically inheritedo 2 populations have diverged due to difference in behavior (Costal and Inland snakes)

E2 Perception of stimuliE.2.1 Outline the diversity of stimuli that can be detected by human sensory receptors, includingmechanoreceptors, chemoreceptors, thermoreceptors and photoreceptors.

Mechanoreceptor (ear)

o Transforms mechanical or movement stimuli into nerve impulses

o Often takes form of pressure

Sound waves

Blood pressure

Air pressure

Touch Gravity

Stretch receptors

o Often stimulation changes the permeability of the receptor membrane, resulting in a depolarization or

hyperpolarization

Chemoreceptor (tongue)

o Chemical stimuli transformed into a nerve impulse

Chem. Might be dissolved- taste

Or chem might be a vapour – smell

Blood pH

O2 and CO2 receptors

Thermoreceptor (skin)

o Changes in temp produce nerve impulses that are sent to the posterior hypothalamus

Found in skin Photoreceptors (eyes)

o Transform visible light into nerve impulses

Rods

Cones

E.2.2 Label a diagram of the structure of the human eye. (sclera, cornea, conjunctiva, eyelid, choroid, aqueoushumour, pupil, lens, iris, vitreous humour, retina, fovea, optic nerve, and blind spot)



E.2.3 Annotate a diagram of the retina to show the cell types and the direction in which light moves.

Light: coming through eye from the RIGHT

3 layers of neurons shown: photoreceptors, bipolar cells, and ganglion cells

Ganglion and bipolar cells: transparent; don’t significantly reduce the intensity of light passing to the photo receptor

Photoreceptor: absorbs the light which changes the rate of neurotransmitter produced at the first synapse

Head of photoreceptor cell contains the light sensitive pigments

Bipolar cell: responds by changing rate of neurotransmitter released to the Ganglion cell

Ganglion cell: generates impulse which will travel along the axon of the ganglion to the brain.

Axons are grouped together, forming optic nerve.

Cell body of ganglion cell is in the retina.

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: pre-CNS processing of info on the retina itself. Not carried out by brain.

Contralateral processing: the way the brain collects and integrates info from the eyes to create the perception of

seeing.

E.2.6 Label a diagram of the ear. (pinna, eardrum, bones of the middle ear, oval window, round window,semicircular canals, auditory nerve, and 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.

How we perceive sound: sequences of changes of energy from one form to another.

o Initial: incoming sound is a pressure wave of air, transformed into a nerve impulse, a wave of sodium ions

traveling down the axon.

E3 Innate and learned behaviourE.3.1 Distinguish between innate and learned behaviour.

Innate: develops ind’tly of the env’tal context

Learned: develops as a result of experience

E.3.2 Design experiments to investigate innate behaviour in invertebrates, including either a taxis or a kinesis. Examples include:

• taxis— Planaria move towards food (chemotaxis) and Euglena move towards light (phototaxis)

• kinesis— woodlice move about less in optimum (humid) conditions and more in an unfavourable (dry)atmosphere.

E.3.3 Analyse data from invertebrate behaviour experiments in terms of the effect on chances of survival and

reproduction.

E.3.4 Discuss how the process of learning can improve the chance of survival.

If an animal has a nervous system that can allow it to change/modify behavior, it will have a survival

advantage over less flexible animals

LEARNING: behaviors can be acquired or modified during a life cycle, providing the animal with an

immediate increased chance of survival



Frequent learning behavior in a population must have a genetic component

Learning permits immediate satisfaction of needs without recourse to tedious process of selection over

several generations

Survival of the fittest

E.3.5 Outline Pavlov’s experiments into conditioning of dogs. P presents food (UCS) to dogs, they salivate (UCR) in anticipation of being fed

P rings bell (NS) each time dogs fed. Early experiment: dogs did not salivate when bell rung

After many repititions of ringing bell and presenting food, dogs began to salivate (CR) when bell rung ONLY

P describes this as “conditioned reflex”- stimuli produces the changed response

Reflex of salivation has had the stimuli changed from food smell to bell ringing

Provides animal with flexible behavior, allowing them to modify their behavior, improving survival chances.

E.3.6 Outline the role of inheritance and learning in the development of birdsong in young birds.

Male birds use song as a means of communication: attracting attention of female, or signaling territorial

boundaries

Bird song specific to species, and to individual birds

Young birds imitate older birds’ song if they find it successful in communication

Innate: innate template song prevents hatchlings from learning the wrong species song

Learned: allows the bird to modify the song to the correct local dialect

Summary:o Birds born with genetic component to their song, modified by experience

o Possession of template prevents young bird from learning from species song

o Learning phase: allows for adaptability to local dialect

E4 Neurotransmitters and synapsesE.4.1 State that some presynaptic neurons excite postsynaptic transmission and others inhibit postsynaptic

transmission.

Presynaptic neurons: excite OR inhibit postsynaptic transmission

E.4.2 Explain how decision-making in the CNS can result from the interaction between the activities of excitatory

and inhibitory presynaptic neurons at synapses.

Excitatory and inhibitory input decide if an impulse is passed on to create further neural activity

A neuron is on the receiving end of many excitatory and inhibitory stimuli.

Neuron: sums up the signal. If sum is inhibitory, then axon does not fire. If sum is excitatory, then axon

fires.

This is the interaction between activities of excitatory and inhibitory neurons at the synapses

Summation of the message is the way that decisions are made by the CNS

E.4.3 Explain how psychoactive drugs affect the brain and personality by either increasing or decreasing

postsynaptic transmission.



Psychoactive drugs: affect many different parts of brain, causing them to produce a degree of chemicals differing

from normal amount

o Dopamine makes brain change its thoughts and personality

o Some act as neurotransmitters and bind to receptors for that neurotransmitter in postsynaptic membranes,

blocking the receptor, preventing the neurotransmitter from having its usual effect

o Some have same effect as neurotransmitter, but aren’t broken down when they bind to the receptors, so the

effect lasts much longero Some interfere with the breakdown of neurotransmitter in synapses and prolong the effect of the

neurotransmitter

E.4.4 List three examples of excitatory and three examples of inhibitory psychoactive drugs.

Use the following examples.

Excitatory drugs: nicotine, cocaine, and amphetamines

Inhibitory drugs: benzodiazepines, alcohol, and THC

E.4.5 Explain the effects of THC and cocaine in terms of their action at synapses in the brain.

Include the effects of these drugs on both mood and behaviour.

THC: mimics anandamide (released in response to pain), which opens the flow of dopamine, releasing it

to bind to the synaptic cleft.

Cocaine: binds to dopamine transporters, which cause a flood of dopamine to the brain

E.4.6 Discuss the causes of addiction, including genetic predisposition, social factors and dopamine secretion.

Physical addiction: when body stops producing neurotransmitting chemicals and starts relying on outside

sources to initiate responses

Parent addiction can pass onto a child

Stress can increase addiction intensity

HL Material

E5 The human brain

E.5.1 Label , on a diagram of the brain, the medulla oblongata, cerebellum, hypothalamus, pituitary gland and

cerebral hemispheres.



E.5.2 Outline the functions of each of the parts of the brain listed in E.5.1.

E.5.3 Explain how animal experiments, lesions and FMRI (functional magnetic resonance imaging) scanning can

be used in the identification of the brain part involved in specific functions.

FMRI: gives a “map” of the brain, with use of magnetic field and radio frequency pulses. Tells what astroke, trauma, etc. has done to parts of the brain. Can keep track of changes occurring.

Animal experiments: can be used to look at brain development and brain parts in specific functions, but

with ethical issues. Lesions: injury within the brain. Different lesions caused by different injuries, ie stroke or trauma.

E.5.4 Explain sympathetic and parasympathetic control of the heart rate, movements of the iris and flow of blood

to the gut.

Heart rate: controlled by autonomic system, also divided into 2 parts: sympathetic and parasympathetic

nervous system

E.5.5 Explain the pupil reflex.

Regulates the amount of light being absorbed by the eye

Pupil either expands or contracts, depending on light intensity

Greater light = pupil contract; less light = pupil expanding



E.5.6 Discuss the concept of brain death and the use of the pupil reflex in testing for this.

To determine if the brain is still functional stimuli are presented such as shining light into the eye andlooking for the associated pupil reflex. A reflex would indicate some function at the basic brain level of

the medulla oblongata. E.5.7 Outline how pain is perceived and how endorphins can act as painkillers.

When a pain receptor in the skin is stimulated impulses are transmitted to the central nervous system to

the sensory areas of the cerebral cortex.

The pituitary secretes Endorphins into the blood stream and the hypothalamus secretes them into the brain

to block the receptor molecules at synapses. In doing so the pain is reduced.

An awareness of pain allows one to avoid acute injury been aggravated into chronic injury.

An awareness of pain allows one to avoid noxious substances.

Perception of pain is also used in aspect of social organisation e.g lion cubs mock fighting

Having the perception of pain has a distinct survival benefit however there comes a point at which the

pain needs to be blocked.

E6 Further studies of behaviourE.6.1 Describe the social organization of honey bee colonies and one other non-human example.

Honey Bee

Advanced nature of colony based on differentiation – 3 castes

Queen: responsible for egg production

Workers: female, gather food for the colony, tend to larva, live for 40 days Drones: male, contribute little to the colony

African Elephant

Herd: 10-20 females headed by matriarch female (oldest and biggest female)

Adult males pushed away from herd, and thereafter live alone or in loose male bands

E.6.2 Outline how natural selection may act at the level of the colony in the case of social organisms.

Natural selection acts on phenotypes of individuals

Individuals who survive to reproduce pass on their genes into the next generation successful genes

become more frequent in the population

All individuals within a population contribute their alleles to the gene pool of that population. Changes in

the frequency of alleles within a population are characteristic of evolution and evidence of the action of

natural selectionE.6.3 Discuss the evolution of altruistic behaviour using two non-human examples.

Altruistic behavior: when one puts itself at risk or pay in some way to save another, for another individual

to benefit

Ex: when squirrels make an alarm call to other squirrels when a predator is sited puts itself in

danger, but benefits the rest of the group by telling them to move to safety

Ex: when a mother elephant dies, a different female will suckle the baby elephant



E.6.4 Outline two examples of how foraging behaviour optimizes food intake, including bluegill fish foraging for

Daphnia.

Foraging behavior: to either maximize energy, or to minimize time consumption

Bluegill: eat small or large Daphnia, but usually larger ones

Limited amount: both

Abundance: conserve energy by eating only large ones

Sheep: graze on land most productive to minimize time in escaping by being in unobstructed views toescape

E.6.5 Explain how mate selection can lead to exaggerated traits. Ex: male peacock’s tail feathers

Good display chosen by female for reproduction

Exaggerated traits believed to have evolved by sexual selection

Sexual selection or natural selection?

E.6.6 State that animals show rhythmical variations in activity.

Animals show rhythmical variations in activity

Daily cycles

Seasonal cycles

Lunar cyclesE.6.7 Outline two examples illustrating the adaptive value of rhythmical behaviour patterns.

Grizzly bears: hibernate during the winter, as there is nothing to feed on till spring. This is adaptive to the

circumstance

Rabbit fish: only spawn on a new moon: reduces the cost of energy it takes to ensure the eggs and sperm

meet, as it only occurs in April and May.

answers- option e

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