E.1.1

Define the terms stimulus, response and reflex in the context of animal behaviour.

1

A stimulus is a change in the environment (internal or external) that is detected by a receptor and elicits a response. A reflex is a rapid, unconscious response.

E.1.2

Explain the role of receptors, sensory neurons, relay neurons, motor neurons, synapses and effectors in the response of animals to stimuli.

3

Aim 7: Data logging using an EKG sensor to analyse neuromuscular reflexes could be used.

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.

1

Include white and grey matter, and ventral and dorsal roots.

E.1.4

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

3

Use of local examples is encouraged.

The bird Sylvia atricapilla (blackcap) breeds during the summer in Germany and, until recently, migrated to Spain or other Mediterranean areas for winter. However, studies show that 10% of blackcaps now migrate to the UK instead. To test whether this change is genetically determined or not (and, therefore, whether it could have developed by natural selection or not), eggs were collected from parents who had migrated to the UK in the previous winter and from parents who had migrated to Spain. The young were reared and the direction in which they set off, when the time for migration came, was recorded. Birds whose parents had migrated to the UK tended to fly west, wherever they had been reared, and birds whose parents had migrated to Spain tended to fly south-west. Despite not being able to follow their parents at the time of migration, all the birds tended to fly in the direction that would take them on the same migration route as their parents.

This and other evidence suggests that blackcaps are genetically programmed to respond to stimuli when they migrate so that they fly in a particular direction. The increase in the numbers of blackcaps migrating to the UK for the winter may be due to warmer winters and greater survival rates in the UK.

TOK: There are many poor examples of supposed links between animal responses and natural selection. It is easy for us to guess how the behaviour of an animal might influence its chance of survival and reproduction, but experimental evidence from carefully controlled trials is always needed to back up our intuitions.

E.2.1

Outline the diversity of stimuli that can be detected by human sensory receptors, including mechanoreceptors, chemoreceptors, thermoreceptors and photoreceptors.

2

Details of how each receptor functions are not required.

TOK: Other organisms can detect stimuli that humans cannot. For example, some pollinators can detect electromagnetic radiation in the non-visible range. As a consequence, they might perceive a flower as patterned when we perceive it as plain. To what extent, therefore, is what we perceive merely a construction of reality? To what extent are we dependent upon technology to “know” the biological world?

E.2.2

Label a diagram of the structure of the human eye.

1

The diagram should include the sclera, cornea, conjunctiva, eyelid, choroid, aqueous humour, 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.

2

Include names of rod and cone cells, bipolar neurons and ganglion cells.

E.2.4

Compare rod and cone cells.

3

Include:

• use in dim light versus bright light

• one type sensitive to all visible wavelengths versus three types sensitive to red, blue and green light

• passage of impulses from a group of rod cells to a single nerve fibre in the optic nerve versus passage from a single cone cell to a single nerve fibre.

E.2.5

Explain the processing of visual stimuli, including edge enhancement and contralateral processing.

3

Edge enhancement occurs within the retina and can be demonstrated with the Hermann grid illusion.

Contralateral processing is due to the optic chiasma, where the right brain processes information from the left visual field and vice versa. This can be illustrated by the abnormal perceptions of patients with brain lesions.

E.2.6

Label a diagram of the ear.

1

Include 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.

3

The roles of the other parts of the ear are not expected.

E.3.1

Distinguish between innate and learned behaviour.

2

Innate behaviour develops independently of the environmental context, whereas learned behaviour develops as a result of experience.

E.3.2

Design experiments to investigate innate behaviour in invertebrates, including either a taxis or a kinesis.

3

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.

3

E.3.4

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

3

E.3.5

Outline Pavlov’s experiments into conditioning of dogs.

2

The terms unconditioned stimulus, conditioned stimulus, unconditioned response and conditioned response should be included.

TOK: The extent to which Pavlov’s theory can be applied to different examples of learning could be considered.

E.3.6

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

2

E.4.1

State that some presynaptic neurons excite postsynaptic transmission and others inhibit postsynaptic transmission.

1

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.

3

E.4.3

Explain how psychoactive drugs affect the brain and personality by either increasing or decreasing postsynaptic transmission.

3

Include ways in which synaptic transmission can be increased or decreased. Details of the organization and functioning of the entire brain, and theories of personality or explanations for personality, are not required.

E.4.4

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

1

Use the following examples.

• Excitatory drugs: nicotine, cocaine and amphetamines

• Inhibitory drugs: benzodiazepines, alcohol and tetrahydrocannabinol (THC).

E.4.5

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

3

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

Aim 8: The social consequences of these drugs could be considered, for the user, his or her family and the wider society.

E.4.6

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

3

E.5.1

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

1

E.5.2

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

2

Medulla oblongata: controls automatic and homeostatic activities, such as swallowing, digestion and vomiting, and breathing and heart activity.

Cerebellum: coordinates unconscious functions, such as movement and balance.

Hypothalamus: maintains homeostasis, coordinating the nervous and endocrine systems, secreting hormones of the posterior pituitary, and releasing factors regulating the anterior pituitary.

Pituitary gland: the posterior lobe stores and releases hormones produced by the hypothalamus and the anterior lobe, and produces and secretes hormones regulating many body functions.

Cerebral hemispheres: act as the integrating centre for high complex functions such as learning, memory and emotions.

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.

3

Include one specific example of each.

Aim 8: There are some important ethical issues involved in animal experimentation.

TOK: The construction of controlled FMRI experiments has proved very difficult because of the development of conditioned reflexes in experimental subjects. Investigating the human mind will always be a challenging field.

E.5.4

Explain sympathetic and parasympathetic control of the heart rate, movements of the iris and flow of blood to the gut.

3

E.5.5

Explain the pupil reflex.

3

E.5.6

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

3

E.5.7

Outline how pain is perceived and how endorphins can act as painkillers.

2

Limit this to:

• passage of impulses from pain receptors in the skin and other parts of the body to sensory areas of the cerebral cortex

• feelings of pain due to these areas of the cerebral cortex

• endorphins blocking transmission of impulses at synapses involved in pain perception.

E.6.1

Describe the social organization of honey bee colonies and one other non-human example.

2

Detailed structural differences and the life cycle of honey bees are not expected.

E.6.2

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

2

E.6.3

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

3

E.6.4

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

2

E.6.5

Explain how mate selection can lead to exaggerated traits.

3

An example of this is the peacock’s tail feathers.

E.6.6

State that animals show rhythmical variations in activity.

1

E.6.7

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

2

Examples could include the diurnal activity variation of hamsters, coordinated spawning in corals, or seasonal reproductive behaviour in deer.