Animal Behaviour and Physiology Flashcards
1
Q
What are brains composed of?
A
They are composed of many neurons.
2
Q
How is Golgi staining done?
A
It is produced by a reaction of potassium chloride and silver nitrate to produce silver chromate crystals in aldehyde-prefumed tissues.
3
Q
What does Golgi staining allow for?
A
It allows for neurons to be visualised.
4
Q
What species has the neural networks mapped?
A
An adult Drosophila fly.
5
Q
How similar are invertebrate and vertebrate neural networks and how have these arised?
A
Some aspects are similar and these have arisen through convergent evolution.
6
Q
What is a neural circuit?
A
A population of neurons in an animal’s nervous system that carries out a specific behaviour or set of behaviours.
7
Q
What does the GAL4-UAS system enable?
A
It enables one to turn genes on and off that are important for studying processes and neurons.
8
Q
How does the GAL4-UAS system work?
A
You have a GAL4 transcription activator, and the UAS is enhancer to which the activator binds to transcribe the gene of interest.
9
Q
What areMBONs?
A
Mushroom body output neurons.
10
Q
What is used to image specific neurons in the Drosophila brain using the GAL4-UAS system?
A
GRP and other associated fluorophores.
11
Q
How can neural circuits be studied?
A
Using electrophysiology or imaging.
12
Q
What does electrophysiology use?
A
It uses ‘spike trains’, which are voltage recordings of action potentials.
13
Q
What does imaging of the brain sometimes use?
A
It sometimes uses calcium fluorophore from transgenically modified individuals.
14
Q
Why are invertebrates a good model to study neural circuits?
A
They have large neurons, simplified circuits, and are easy to dissect and use in lab experiments.
15
Q
What is a good organism to study the reflex circuit on and what are they attacked by?
A
Crayfish are a good organism and they are attacked by dragonfly nymphs.
16
Q
What are the two main types of the crayfish defence mechanism and when are they activated?
A
- Medial giant tail-flip (threat from front activates the medial giant neuron)
- Lateral giant tail-flip (threat from back activates the lateral giant neuron)
17
Q
Where are most attacks at crayfish aimed at and what response does this lead to?
A
Most attacks are aimed at the thorax, so most responses are mediated by the medial giant neuron.
18
Q
What do crayfish have to enable them to tail-flip?
A
Big lateral abdominal muscles.
19
Q
What is the organisation of the ventral nerve chord of crayfish?
A
There is one ganglion per segment.
20
Q
What is the organisation of the medial giant neuron of crayfish?
A
It extends the entire length of the crayfish.
21
Q
What is the organisation of the lateral giant neuron of crayfish?
A
It is a series of segmentally distinct neurons that are connected by synapses, making it a slower response than the medial giant neuron.
22
Q
What is seen in a cross section of the crayfish nervous system?
A
The giant neurons are much bigger than the local neurons.
23
Q
How fast are chemical synapses and how does it work?
A
It is 0.5-4ms and it works by there being a unidirectional change in voltage.
24
Q
How fast are electrical synapses and how does it work?
A
They are less than 1ms, and they work through bi-directional or unidirectional changes in voltage depending on the type of gap junction.
25
What type of synapses does the crayfish neural circuit have?
It has both electrical and chemical synapses.
26
What does it mean to be a rectifying synapse?
It means that signals can be relayed very rapidly in one direction without backpropagation.
27
How do the giant fibres in crayfish evoke the tail-flip?
They evoke it through rectifying electrical synapses with the motor neurons.
28
What type and how many synapses are there between the mechanosensory input and the motor output in crayfish?
There are 2 electrical synapses between the input and output.
29
How quickly does the behavioural output occur after input stimulation?
It occurs within 10ms.
30
How do you work out if a neuron is rectifying?
By injecting positive and negative currents and see which one elicits a reaction.
31
What happens as specialisation in sensory input happens?
Locomotion circuits complexify.
32
What do the mushroom bodies do?
They integrate information from the senses to control motor output.
33
What is most behaviour more complex than?
It is more complex than a reflex.
34
What happens if there is a spike in input but not al of the impulses are stimulated in additive synapses?
It will act to inhibit the reaction and lower the potential of the giant neuron.
35
What cells in the mushroom body receive olfactory input?
Kenyon cells.
36
What does the olfactory stimulation from foods lead to?
The dopaminergic neurons having a reaction of it being a good or bad smell.
37
How are circuits modified during learning?
Through synaptic plasticity at chemical synapses.
38
What does using synapses allow for?
It allows for signals to be amplified, summed, or subtracted (spatially or temporally).
39
What is a reflex?
A simplified circuit that often bypasses the CNS to activate behaviour quickly.
40
How is memory of smells achieved in flies?
By synaptic depression in the fly reward circuit.
41
What is the locust visual escape response?
It is a reflex-like behaviour embedded in a larger network that controls locomotion.
42
What different levels can behaviour be studied at?
It can be studied at many levels, from movements of individual body parts, to interactions between individuals, to movements of whole flocks and herds.
43
What do nervous systems allow animals to do?
It allows animals to behave rapidly and in more complex ways.
44
What do action potentials provide?
They provide rapid communication between different parts of the body and multiple connections between neurons allow for many different functions.
45
What is behaviour studied through?
Tinbergen's 4 questions.
46
What is the nervous system of jellyfish, sea anemones, and starfish?
They have simple nervous systems in a nerve net, with no or few centralised nervous systems.
47
What are the 3 parts of invertebrates sensory systems?
- the somatic nervous system
- the peripheral nervous system
- the visceral nervous system.
48
What is the somatic nervous system composed of?
A ventral chain of bilaterally segmented ganglia.
49
What is the structure of vertebrate ganglia?
They have cell bodies inside dendrites and axons outside.
50
What is the structure of invertebrate ganglia?
They have an outer rind of cell bodies and an inner core consisting of axons and dendrites, forming a dense neurophil.
51
What is a supraoesophageal ganglia?
A ganglia that is associated with brain and anterior portion of the gut.
52
What is the suboesophageal ganglia?
It is involved in controlling mouthparts and neck muscles and influences motor patterns in walking, flying and breathing.
53
What is the thoracic ganglia?
It is involved in innervate muscles, so wings, flight muscles, leg muscles etc.
54
What is the abdominal ganglia?
It controls movements of abdominal muscles, like the anus, genitalia, and cerci etc.
55
What is each ganglion surrounded by and why?
Each ganglion is surrounded by a neural lamella, and this provides an ionic barrier, so ionic concentrations surrounding neurons are different from haemolymph.
56
What is the organisation of an insect brain?
It is a complex of six fused ganglia in 3 pairs.
57
What is the main part of the insect brain?
The Protocerebrum.
58
What is the first pair of ganglia in the insect brain associated with?
It is largely associated with vision, and they innervate the compound eye and ocelli.
59
What is the compound eyes features?
It has a large view angle, detects fast movement and polarisation of light.
60
What is the ocelli sensitive to and what is it used for?
It is sensitive to light and used for flight control.
61
What are the two major regions in the mushroom bodies in the protocerebrum?
- the cap-shaped calyx
- the stalk-shaped peduncle.
62
What are the mushroom bodies in the protocerebrum involved in?
- processing olfactory signals
- olfactory learning
- learning
- memory
- high order processing.
63
What is the central complex in the proteocerebrum?
A region where nerve fibres pass from one hemisphere to the other, but little information on type of process that occurs.
64
What do the optical lobes in the proteocerebrum process?
Visual signals from compound eyes in a series of neurophil layers.
65
What are the second pair of ganglia in the brain and what do they do?
They are the Deutocerebrum and they are really important in processing sensory information collected by the antenna, olfactory, and mechanosensory signals.
66
What is the tritocerebrum?
It is not very well understood but it seems to integrate sensory inputs from the first 2 pairs. It links the brain with the rest of the ventral nerve cord and visceral nervous system that controls internal organs.
67
What does the peripheral nervous system consist of?
- the axons and terminals of the motor neurons
- the terminals and cell bodies of sensory neurons.
68
What does the visceral nervous system consist of?
A series of small ganglia which are distinct from but linked to the main segmental ganglia of the somatic nervous system.
69
What does the visceral nervous system innervate?
The internal organs of the: gut, salivary glands, spiracles, heart, reproductive organs etc.
70
What has the hindbrain become divided into over evolutionary time?
It became divided into the ventral medulla oblongata, and the dorsal cerebellum.
71
What did the midbrain become?
It became specialised optic lobes and visual centres.
72
How has the forebrain changed over evolutionary time?
There was the anterior cerebrum with olfactory bulbs, posterior thalamus and hypothalamus, with it later gaining the cerebral cortex and the neocortex.
73
What does the spinal cord transmit?
It transmits neural signals between the brain and the rest of the body.
74
What does the spinal cord contain?
It contains neural circuits that independently control reflexes and neural networks that act as central pattern generators.
75
What are central pattern generators?
Neural networks that endogenously produce rhythmic patterned outputs.
76
How does neural rhythmicity arise?
- through interactions among neurons, where rhythmicity is a property of a circuit and neurones are the pace makers
- through interactions amongst currents in individual neurons.
77
What are the 2 classes of cells in the nervous system?
Neurons and glial cells.
78
How is impulse conduction propagated in unmyelinated fibres?
It is propagated by local circuits of ion current.
79
How does impulse conduction work in myelinated fibres?
The circuit flow jumps to the next node of Ranvier.
80
Do vertebrates or invertebrates have myelin sheath?
Vertebrates do, invertebrates don't, but they can have giant axons for rapid conveyance.
81
What do glial cells do?
They provide:
- structure neural groups
- separate neural groups
- insulate neural groups
- produce myelin in vertebrates
- remove debris after neuronal injury of death
- guide giant neurons during development
- help form the blood brain barrier.
82
What is Ohm's law?
V = I x R.
83
What is current?
The rate of movement of electrical charge through a conductor.
84
What is potential (voltage)?
The force on a charge particle.
85
What is conductance?
The ease with which current will flow.
86
What is the resting potential normally?
-65mV.
87
What are the 2 distinct types of channels?
Leaky channels and gated channels.
88
What is the K+ equilibrium?
Inside the neuron are several types of large anions, which can't cross the membrane. As potassium ions flow down chemical concentration gradient and out of the cell, they are simultaneously attracted back into the cell because of the electrical gradient. An equilibrium that reflects a compromise between these 2 forces is achieved, giving rise to a higher potassium ion concentration inside than outside.
89
What is the Nerst equation?
The membrane potential for an ion at which there is no net flow of that particular ion from one side of the membrane to the other.
90
How is the K+ potential computed and what does it typically give an EK of?
It is computed by the Nernst equation, and typically gives an EK of -75mV.
91
How would you describe an action potential?
It is an all or nothing response, with a threshold potential.
92
What is the action potential driven by?
It is driven by a large increase in sodium ion conductance through voltage-gated channels which are opened by membrane depolarisation.
93
What happens anytime there's an increase in the conductance of an ion?
The membrane potential moves in the direction of the equilibrium potential for that ion.
94
How can neurons be classified according to their electrophysical characteristics?
- Tonic or regular spiking, which are typically constantly active
- Phasic or bursting, which fire in bursts
- Fast spiking, which have high firing rates.
95
What does electrical transmission involve?
Gap junctions and it is incredibly fast but doesn't have much plasticity and flexibility.
96
What does chemical transmission involve?
It involves neurotransmitters, and it is slower but has plasticity.
97
What do many neurotransmitters involve?
- acetylcholine
- amino acids (glutamate, GABA glycine)
- peptides (neuromodulates)
- biogenic amines (catecholamines, serotonin, and histamine).
98
Why is plasticity of neurons possible?
Because of the use of synapses, which allow for signals to be amplified, summed, or subtracted.
99
How can neurons be classified by function?
- Afferent (sensory), convey information from tissues and organs to CNS
- Efferent (motor), transmit signals from CNS to effector cells
- Interneurons, connect neurons.
100
What are examples of sensory organs?
- electroreceptors
- baroreceptors
- chemoreceptors
- photoreceptors
- mechanoreceptors
- nociceptors
- proprioceptors
- thermoreceptors.
101
What do sensory organs act as?
An interface between the environment and the CNS.
102
Who was the first person to do experiments in the mid-19th century to understand hormones and what did he find?
Arnold Berthold did the first experiments and he found that castrated male chickens displayed few male morphological traits and behaved like females.
103
What is a hormone?
A chemical messenger that is released into the bloodstream or tissue fluid system that affects the function of target cells some distance from the source.
104
What do hormones coordinate and how?
They coordinate the physiology and behaviour of animals by regulating, integrating, and controlling its bodily functions.
105
How do hormones act?
They act by binding with receptors within cells and on the membranes of target cells or tissues.
106
Which is quicker: hormonal messages or neuronal messages?
Neuronal messages.
107
How long can hormones be sustained?
They can be sustained over minutes, days, or months.
108
What are the 3 classes of hormones from vertebrates with examples?
- Amine-derived hormones, e.g. melatonin, seratonin, ephinphrine.
- Peptides, e.g. insulin, gonadotropin RH, leptin, LH.
- Lipid and phospholipid-derived hormones, e.g. androgens, oestrogens.
109
What are endocrine cells?
Cells that secrete hormones directly into the bloodstream.
110
What are exocrine cells?
Cells that secrete peptides or other chemical signals directly into a duct prior to release into the bloodstream.
111
What are chemical signals defined by?
The distance from the secretory point to the target.
112
What are hypothalamic hormones?
'releasing hormones' that control and regulate hormones.
113
What are pituitary hormones?
Regulating hormones in the thyroid.
114
What is the pineal gland?
It is derived from photoreceptor cells and, in mammals, it produces serotonin and melatonin, and it is involved in our circadian rhythm.
115
What are thyroid and parathyroid hormones involved in?
They are involved in metabolism and growth/differentiation.
116
What are pancreatic hormones involved in?
They are involved in sugar metabolism.
117
What are adrenal hormones involved in?
They are involved in emotional arousal, salt and carbohydrate metabolism, and inflammation reactions.
118
What are gastrointestinal hormones involved in?
They are involved in circulation and digestion.
119
What are gonadal hormones involved in?
They are involved in sex, reproduction, growth and development.
120
What is homeostasis?
The ability to regulate one's internal state to a stable or optimal condition.
121
How can hormones influence behaviour?
They can influence behaviour endogenously or reciprocally as a change in the amount of a hormone present.
122
What can hormone secretion affect?
- function and structure of the nervous system
- sensory perception
- tissue development
- expression of sex-specific traits
- metabolism
- biological and circadian rhythms
- reproduction.
123
What are 2 processes that both influence hormones and are governed by hormones?
Biological/circadian rhythms and nutritional state.
124
What cycle do plasma hormone levels follow?
They follow a diurnal cycle.
125
What is motivation?
The biological, social, and cognitive forces that activate behaviour.
126
Why might motivation to perform a behaviour arise?
- from a physiological need to maintain nutritional homeostasis
- as a result of another internal need
- due to circadian rhythms or hormone cycles.
127
How much more plasma testosterone do human adult males have than females?
They have levels that are 15 times greater.
128
How does dust-bathing in birds work?
It is not a result of external stimuli like oil in feathers as chicks still have the motivation when they lack feathers. Furthermore, chickens on glass who can see sand to dust bathe will also try to dust bathe on the glass.
129
How do androgen levels in males change and how can one see it?
The vary as a function of age and you can see this through the masculinization of facial features as a function of androgens.
130
What is chromosomal sex?
Sex which is determined by the sex chromosomes that an individual receives at fertilisation.
131
What is gonadal sex?
Sex determined by the possession of gonads.
132
What is hormonal sex?
Sex determined by the concentration of plasma androgens and oestrogens.
133
What is morphological sex?
Sex determined by body form or sex-specific traits.
134
What is behavioural sex?
Sex determined by the exhibition of male-typical or female-typical behaviours.
135
What is key in taking testosterone and making masculinizing or feminizing hormones?
Enzyme expression.
136
What is the default sex in mammals?
It is female, with feminizing and masculinizing hormones both being present in females.
137
What can affect sexual differentiation in adult birds?
In ova hormone levels.
138
Why are there temperature-dependent differences of sex in fish and reptiles?
It is due to the effect of temperature on the activation or aromatase and/or reductase.
139
What is a sequential hermaphrodite?
When a single organism begins life as one sex and then changes to the other sex as an adult in response to environmental or genotypic factors.
140
What are the 2 morphologies of males in many fish species?
- large
- small, where these often resemble females in morphology and behaviour.
141
What must you establish to study the effects of hormones on behaviour?
You must establish a causal link between the presence of the hormone and behaviour.
142
How can one establish a causal link between the presence of a hormone and behaviour?
- blockade, where the source of the hormone is removed or the actions of the hormone are blocked
- reinstatement, where after the behaviour stops the hormone is reinstated and so is the behaviour
- concentration dependence, so the concentration of the hormone is reflected in the behaviour.
143
What are 2 techniques that are commonly used in behavioural endocrinology?
- ablation (removal of a gland or tissue expected to be producing the hormone, or knockout of its gene)
- bioassay (injection of different doses of hormone).
144
Why is timing important to consider when looking at hormones and behaviour?
Timing can effect hormones and behaviour and it should be considered if it is long-term, short-term, or cyclical.
145
What will affect the depression of behaviour and development of sexual adult traits in rodents?
Androgen exposure during "critical periods" of development.
146
What do pre-natal androgens influence in female rhesus monkeys?
The expression of rough play behaviour.
147
What eggs do mothers provision more to in canaries and why?
In canaries, mothers provision the youngest eggs with the most testosterone and it means the last laid eggs are more socially dominant and demanding.
148
What are sex hormones often?
They are often cyclic.
149
Why can the oestrus cycle synchronise?
It can synchronise depending on the context and it tends to happen with females in close proximity. It can improve offspring survival in certain contexts, e.g. mice in high populations.
150
What do socially dominant goats express during the luteal phase of ovulation?
They express higher levels of progesterone.
151
How do hormones effect courtship displays in male doves and pigeons?
It is facilitated by testosterone, and successful mating induces progesterone in males which then influences brooding and nest-making behaviour.
152
What happens when the testes of a bird are removed?
It causes a decrease in testosterone, but it doesn't always control sexual behaviour.
153
Why might testosterone be important in some bird species?
It can be important in facilitating aggression and territoriality than in maintaining sexual behaviour.
154
Where can the relationship between testosterone and aggression be seen?
In red deer, horses, and humans.
155
What does perinatal and pubertal testosterone prime the brain to do?
It primes the brain to respond to elevated testosterone levels during adulthood.
156
Where has testosterone been seen to be influenced by conflicts and dominance?
In cichlids, where males that have had territorial conflicts and been defeated have a drop in testosterone.
157
What have winner-loser effects on hormone expression and behaviour been observed in?
They have been observed in male-to-male contests in many species, from mammals to birds and fish.
158
How does one start to investigate behaviours?
One will start by asking what evolutionary advantage does the behaviour have, so how its survival and/or reproduction is increased.
159
How can one investigate how and when a behaviour evolved?
It can be investigated by looking at close relative species and looking at if the behaviour is present in those species, so you can use phylogeny to work it out.
160
What are the problems of studying adaptiveness of behaviour?
- the fact that behaviour is ephemeral
- selection doesn't just act on behaviour so one needs to look at where, when and how it acts
- there are big differences between lab and field studies
- it is often difficult to establish direct fitness effects, so many studies use 'proxies'.
161
What are ways of making adaptive comparisons?
- experiments where you compare artificial 'mutants' with existing animals
- comparisons within species so compare different individuals
- comparisons between species so looking at different species with different ecologies
- optimality and design features approach where you compare animals machinery or models designed to optimise known features.
162
What is an example of experiments using artificial species?
Looking at tail length in long-tailed widow birds, cutting and extending come tails and then to look at breeding.
163
What do you look at when comparing within species?
You look at the fitness consequences and these differences but if seeing these is problematic, one can look at short-term benefits which might be a good proxy indicator of fitness.
164
What is a real challenge when testing adaptive hypothesis?
Working out if it is correlation or causation.
165
Why can multiple alternatives be seen in nature?
It can be due to geographical variation, and the fact that there can be more than one way of being successful.
166
What do you do when using the comparative method?
You look at if the differences in behaviour and appearance is correlated with differences in environments. To do this, multiple examples of convergent evolution will need to be looked at.
167
What happens in the design features/optimality approach?
One can ask an engineer how to design an animal body or behaviour so that it optimises some design criterion. From this, one can see how closely a real animal matches the engineer's design. The more closely it matches, it suggests more that natural selection has effectively designed the animals to the same criterion.
168
What are problems with studying behavioural adaptations?
- experiments give control but may not reflect the natural environment
- comparisons within and between species is more natural but no control may lead to misleading correlations without care.
169
What are the 2 key problems when looking at adaptive mechanisms?
- how the animals recognise patterns
- how animals make decisions about what to do next.
170
When are sign stimuli effective?
- if the sign stimulus is unique
- when the response has to be made quickly
- when a young animal has to respond soon after birth or hatching.
171
What do sign stimuli become more of over time?
They become more exaggerated and more distinctive.
172
What does pattern recognition discriminate between?
Things that are similar and recognising something that may look different from different views.
173
What can't most behaviour be neatly divided into?
'innate' and learnt behaviour.
174
What is learning?
An acquisition of knowledge.
175
What is performance?
A change in behaviour.
176
How is development different from learning?
Because it is a behavioural change that is dependent on a special/specific experience.
177
How is learning distinguished from motivation?
Motivation behavioural changes are reversible and is state-dependent while learning permanently changes an organism.
178
What is a good definition of learning?
It is an inferred change in the organism's mental state which results from experience and which influences in a relatively permanent fashion the organism's potential for subsequent adaptive behaviour.
179
What is non-associative learning?
A modification of a response to a single stimulus.
180
What is habituation?
A decreased innate response towards a stimulus without consequences.
181
What is extinction?
A loss of learned response when stimulus ceases to have consequences.
182
What is sensitization?
Increased responding to a stimulus following non-specific stimulation.
183
What are the general principles of habituation?
- course of habitation
- effects of time
-dishabituation
- effects of stimulus intensity
- effect of inter-stimulus.
184
Why is habituation considered to be non-associative learning?
Because it involves only one stimulus and one pre-existing response.
185
What is an unconditioned stimulus?
A biologically relevant stimulus that elicits a characteristic response.
186
What is an unconditioned response?
A characteristic response to the unconditioned stimulus.
187
What is a conditioned stimulus?
A stimulus that initially does not elicit the unconditioned stimuli.
188
What is a conditioned response?
A response elicited by the conditioned stimuli after pairing the unconditioned stimuli.
189
What can conditioning be enhanced by?
- contiguity
- appropriateness
- contingency.
190
What did the discovery of blocking lead to?
Models of learning connected to its function, to predict events.
191
What is the main associative learning model?
It is the Rescoria-Wagner model.
192
What happens in Operant conditioning?
The animal associates its own behaviour with its consequences. Relation between behaviour and subsequent biologically relevant events. Behaviour is instrumental in obtaining the reinforcer, and reinforcement is obtained by operating on the environment.
193
What is concept learning?
Generalisation within a class of stimuli and discrimination between classes of stimuli.
194
What is feature theory?
The idea that animals could solve the problem by looking for a unique feature that is present in each category.
195
What is exemplar theory?
The idea that animals may classify images by their similarity to images that have been classified previously.
196
What is prototype theory?
Th idea that this may form representations that correspond to the average of the members of the category.
197
What is imprinting?
Learning occurring at a particular life stage that is rapid and apparently independent of the consequences of behaviour.
198
What is filial imprinting?
Where newborns learn to recognise parents.
199
What is sexual imprinting?
Where juveniles learn characteristics of desirable mates when reaching sexual maturity.
200
What does recognition allow an animal to discriminate between and respond appropriately to?
- self and non-self
- relatives and unrelated individuals
- familiar individuals and strangers
- same-sex and opposite sex
- friends and enemies
- rivals and mates
- conspecific and heterospecific
- predators and prey.
201
What is discriminating and categorising individuals often crucial for?
Maximising the fitness payoffs from interactions.
202
What is kin-discrimination?
Discrimination of individuals that are genetically related to a receiver.
203
What are genetically related individuals?
Individuals that share more genes identical by descent with each other than the average relatedness between individuals of a population.
204
What are the 2 main drivers of kin recognition?
- boosting direct fitness by avoiding inbreeding depression
- boosting indirect fitness by cooperating with kin/avoiding competition with kin.
205
When is selection for kin recognition expected to be strongest?
Where individuals are likely to encounter both kin and non-kin, but also where payoffs of discriminating kin from non-kin are large.
206
What is the strength of kin-biased cooperation determined by across species?
The benefits of kin-directed cooperation.
207
What mechanisms do kin tend to use to recognise kin?
- simple rules of thumb, e.g. who I grew up with
- phenotypic traits, genetic or environmental.
208
What does homogenisation of recognition cues reduce?
It reduces the costs of group recognition but makes within-group discrimination harder.
209
When is using phenotypic cues helpful for recognition?
When there is not a lot of variation within and between groups.
210
What is self-referent matching?
When one's own cues are learnt and stored as a template.
211
What is family-referent matching?
When cues are learnt from conspecifics and these are stored as internal templates.
212
What is phenotypic matching based on in terrestrial arthropods?
It is based on the cuticular hydrocarbons.
213
What must phenotypic cues be when kin are recognised on the basis of phenotypically similarity?
- strongly correlated with genotype
- robust to and detectable against other changes
- variable.
214
What is the major histocompatibility complex?
A tightly linked set of extremely polymorphic genes playing a fundamental role in vertebrate adaptive immunity.
215
How are olfactory cues used as recognition in humans?
'self' peptide antigens presented molecules activated a region in the right middle frontal cortex, which suggests that humans have the ability to detect and evaluate MHC peptides in body odour.
216
What is self-referent matching based on in mice?
It is based on major urinary protein genes.
217
What are greenbeard genes?
Genes that can identify the copies of themselves in other individuals, and cause their carrier to behave nepotistically toward those individuals.
218
How does indirect fitness effect arise with the greenbeard gene?
It arises whenever social partners share a gene in common even when they are dissimilar at other loci in the genome.
219
When is recognition tricky?
When the phenotypes of desirable and undesirable individuals overlap.
220
What does the acceptance threshold model suggest?
That acceptance thresholds are shaped by the relative costs of rejection and acceptance errors.
221
What is a key example of recognition strategies and parental care?
Long-tailed tits and their song recognition of relatives and non-relatives and choosing who to help or who to mate with.
222
How do paper wasps identify individual nestmates?
They identify nestmates by unique facial features.
223
When can the ability to recognise individuals be adaptive?
Whenever there are repeated social interactions among multiple individuals with differing fitness.
224
How does individual recognition work?
The receiver identifies signaller according to its individually distinctive characteristics and the signaller is recognized by unique recognition cues, and the receiver learns the cues and uses them to identify the signaller during future interactions.
225
What can individual recognition lead to?
The evolution of complex cognitive representations of conspecifics.
226
What can individual recognition do when there is repeated aggressive interaction between small numbers of individuals?
- Promotes appropriate parental behaviour in large or high-density populations. - Facilitate territorial defence: territory holders can preferentially direct their aggression toward strangers.
- Enables animals to predict the outcome of contests and reduce conflict costs so that contests between familiar individuals are settled with less aggression.
- Mediates formation and maintenance of social hierarchies, by providing a non-cheatable method of assessing individual fighting ability and allowing mechanisms such policing and punishment.
227
What are the results of the mirror self-recognition test paradigm?
The results suggest varying degrees of evidence consistent with self recognition in varying species.
228
What terms can some form of answer been given to each of Tinbergen's 4 questions?
Some form of answer can be given in terms of genetic differences, or genetic causation.
229
What does the extent to which evolution will result from selection depend on?
It depends on genetic variance and maybe covariance between traits.
230
What is genetics crucial for?
It is crucial for making sense of evolutionary paths as it determines how selection translates into change between generations.
231
What is variation due to genetic differences between individuals within populations and what can it look at?
It is a population-specific estimate, and is can look at the genetic 'architecture' or the variance.
232
What does quantitative genetics aim to do?
It aims to partition variation in a population into its component sources.
233
What plots can help to think about genetic variation and what can they include?
They can help to think about genetic variation, and a simple plot can include the reaction norm plots.
234
What are the 2 levels that phenotypic plasticity has a basis on?
- elasticity genes, the genes that underlie the plastic response
- genetic variation in plasticity, individuals differ in the extent to which they respond to the environment.
235
What does the V(G*E) term refer to?
It refers to the variance resulting from the interaction between G and E.
236
Do behavioural or morphological traits have a lower hereditability?
Behavioural traits have a lower hereditability.
237
Why is it thought that behavioural traits have a lower hereditability?
Due to the plastic nature of behavioural traits, and the environmental stochasticity.
238
What is the hypothesis-based testing method that allows for gene function to be studied in multiple species and why is this possible?
It is where the function of a gene is known in one species, so discovering functions linked to one behaviour in one species can easily be tested on another species as the function of genes can be highly conserved between species.
239
What is an example of a candidate gene study?
An example includes Rover-sitting polymorphisms in Drosophila larvae, and a honey bee ortholog is associated with controlling the switch between brood care and foraging outside the hive, and an ortholog is involved in influencing nutrition-dependent foraging in C.elegans.
240
What data-intensive methods can we use to estimate the likely genetic basis of traits when we have no information?
- QTL, quantitative trait loci
- GWAS, genome-wide association study
- Polygenic Scores, predicted effect based on individual's genotype at each locus.
241
How does a genome-wide association study work?
With very many genetic markers, we can simply ask how variation at each position on the genome explains variation in the behaviour we're interested in. It is frequently used in human association studies and there are many different approaches which can detect loci of small and large effect.
242
What is one challenge with genome-wide association studies?
They can have a lot of false positives, so that needs to be taken into account.
243
What can genome-wide association studies estimate and reveal?
They can estimate when interactions were important, and it reveals highly complex genetic architecture, with many genes having a small/moderate effect.
244
What are pedigree-based methods typically used for?
They are typically used for long-term breeding records or for populations studied in the wild.
245
What can we model using pedigree-based methods if we know the relationship between pairs of individuals?
We can model the extent to which similarity results from shared genes versus other effects on any phenotype.
246
What is an example of pedigree building?
An example is the egg laying date data pedigree in great tits in Wytham woods.
247
What is the principle of artificial selection experiments?
It is that if we choose which parents produce offspring based on some phenotypic measure of behaviour, we can estimate how much genetic variance contributes to the trait from how strongly the trait responds to selection.
248
What is an example of an artificial selection experiment?
An example is when scientists took young wild great tits into captivity and measured the rate that juveniles explored a 'novel environment' sand selected from the upper and lower tails of the distribution and did this for 4 generations.
249
How can genetic and environmental effects be disentangled?
It is very difficult and the genotypes and environment can interact with each other, which means that it doesn't make sense to treat them as if they are independent.
250
What is behavioural genetics?
It is a field particularly associated with trying to explain variation in behaviour is human populations as a function of genetics.
251
How can individual variation in characters be extensive?
They can be genetically variable, developmentally plastic and phenotypically plastic.
252
What can one look at when explaining variation when given a sample from a population?
They can question how much of the variation around the mean is non-adaptive or adaptive.
253
What is a question that can be asked when given the variation within a population?
One can ask if it is the case that all individuals can produce all phenotypes, or are individuals restricted in the phenotypes that they produce.
254
Why might discrete behavioural variation arise?
- individuals differ in their abilities, and the ability determines relative pay-offs from behaviour.
- alternative behaviours have equivalent fitness at ESS, but selection is negative frequency-dependent.
255
What is a good example of discrete behavioural variation?
The producer-scrounger division in spice finches, which showed a bimodal distribution with phenotypes being stable over time. It could be stable due to task specialisation, but it seems which phenotype is chosen may be quite stochastic.
256
What are conditional strategies?
Behaviours associated with phenotypic differences.
257
What are examples of conditional strategies?
- Ruffs, which have permanent genetically based morphs
- Marine isopods, where there are three size morphs
- Blue-gill sunfish, where there are three male tactics of being parental, a sneaker, or a satellite.
258
What's an important question when looking at male polymorphisms?
Why are behavioural polymorphisms linked to differences in male behaviour often linked to striking differences in phenotypic appearance?
259
What is often likely to be needed to maintain variation?
Negative frequency-dependence.
260
When might developmental polymorphisms be the only case?
Where you don't need fitness equality.
261
What happens with discrete behavioural types?
They can switch rapidly, but most often, discrete behavioural types are fixed and sometimes are associated with suites of other traits.
262
What happens with continuous behavioural variation in populations and individuals?
Most behavioural traits vary continuously within populations, and individuals sometimes seem to be constrained with respect to which parts of the distribution they occupy.
263
What is found if one measures the behaviour of an individual multiple times?
It is found that behaviour is consistent over repeated measures.
264
What is found when one measures multiple behaviours?
It is often found that they are correlated with each other, both across individuals and within individuals.
265
What are synonyms used to refer to the concept of suites of behaviours that correlate with each other across contexts?
- personality
- syndrome
- strategy
- coping style.
266
What are examples of animal personality models?
- goats
- crustaceans
- fish
-birds.
267
How is genetic variation linked to personality?
Genetic variation has been seen to be related to personality, but also variation might be entirely non-genetic.
268
What is an example of non-genetic variation?
An example is clonal Amazon mollies, where they reared the fish singularly or in groups and tested them for swimming and for exploration of a novel environment. They had strikingly consistent behaviour, with no influence of social environment. But, there were different individual differences even with clonal fish, so genetic variation can't be the only factor acting on the fish.
269
What can behavioural correlations do?
They can constrain evolution.
270
What was found from a comparison across stickleback populations?
It was suggested that the structuring of behaviour evolves in response to the environment.
271
What are 2 outstanding questions in personality research?
- What maintains variation within populations?
- Why are there personalities at all?
272
Why do we look at individual variation in cognitive performance?
Cognitive differences between species are a familiar concept, and one we treat as evolutionarily relevant.
273
What is an important question to ask about innovation?
Innovation can create new opportunities but are these always advantageous?
274
What is migration?
Regular, long-distance movements each year to track changes in resources and habitats.
275
How are resources and/or predators distributed in space and time?
They are heterogeneously but predictably distributed.
276
What do migrations connect?
They connect ecosystems globally.
277
What are the ultimate causes of multi-generation insect migration?
- escaping conditions that are incompatible with development
- to escape high density.
278
What is nomadism?
A tendency of adults as well as juveniles to move widely in search for food, and to settle and breed where it is locally abundant.
279
What is nomadism seen in?
It is seen in Quelea, Crossbills, and Desert Locusts.
280
What is philopatry?
If resources are predictable, animals might benefit from returning to the same place and this requires navigational ability.
281
What displays natal philopatry?
Sockeye salmon do, and they spawn high up in river systems after which the adults die. The offspring then migrate to the ocean and spend several months to years there. When mature, they home precisely to the river system where they were spawned.
282
What are factors influencing population-level patterns of migration?
- cost of migration
- competition between individuals
- Bergman's principle
- variation in the reliability of seasons across latitudes.
283
What is partial migration?
Where the proportion of the population that migrate is proportional to the winter vs summer site resource differences.
284
How does migration impact diseases?
It can lead to the spread of important zoonoses, but it can also allow for escape from diseases. It can lead to a reduction in immunocompetent and migration and disease needs ecological considerations for human disease management.
285
What can happen when there is migration through a body of water?
There can be mass drownings which can lead to different nutrient compositions of rivers downstream which can have trophic consequences.
286
How can one calculate the latitude and longitude of a bird?
It can be calculated using a light sensor and working out dawn and dusk. However, a week either side of the equinoxes, the latitude is difficult to distinguish.
287
What is a way birds deal with long periods of travel?
The long periods require high energy which leads to the gizzard, liver, kidneys and gut being assimilated, which leads to their organs then being regrown at stop-over sites to allow for feeding. Their flight muscles are also assimilated for energy by arrival at the stopover site.
288
What are methods for studying migration?
- radar
- colour ringing
- genetic analysis
- geolocator tracking
- lab experiments
- selective breeding
- GPS/ARGOS satellite tracking.
289
What are some benefits of living in a group?
- anti-predator
- foraging
- energy saving
- navigation.
290
What are the costs of being in a group?
- predators
- parasites
- foraging
- sharing.
291
Why does living in a group lead to increased anti-predator vigilance?
Because 'many eyes' allow for animal groups to have a higher chance of detecting predators. Detecting more predators sooner allows more animals a chance to escape.
292
How does group vigilance increase which individuals spend less time on the task?
Because individuals are vigilant at random times but when someone is eating or not being vigilant, someone else is doing that. Vigilance can be an important trait when looking for mates and the position within a flock can influence the time spent being vigilant vs. doing other tasks.
293
What is another type of vigilance which is different from anti-predator vigilance?
Social vigilance, which is for ensuring nobody else is cheating.
294
What is the dilution effect?
It is the idea that when you are in a large group, all individuals are less likely to be caught by a predator, or effected by a parasite.
295
What does the predator confusion theory predict?
It predicts that predators should find it harder to pick out one target from a group, so the attack-to-kill ratio should drop as group size increases.
296
What is the selfish herd theory?
The theory that all individuals head for the centre of the flock.
297
How can group living impact foraging?
- can enhance individual foraging success
- can enable the capture of larger/difficult prey items
- allows for specialisation or roles within the group
- can be a problem with sharing.
298
What is the me-too-effect seen in herons?
When a bird returns with lots of food, individuals will catch on and head out in the direction that the full heron returned from.
299
Why is sharing body heat within a confined space effection?
Because the microclimate becomes warmer and more moist which reduces head and water loss from individuals.
300
What is a problem relating to conspicuousness with a large group?
They are less conspicuous so have more predator attacks. There are also increased intraspecific predation and the ill/weak individuals are very easy to pick out in a group.
301
What is kleptoparasitism?
It is where food may be stolen by another individual, with the threat of theft rising with group sizes.
302
What is shadow-interferece?
It is where individuals upstream will reduce food availability for those downstream.
303
What are the main principles of self-organisation?
- simple, local interactions
- no global control
- no sophisticated decision-making necessary
- no signalling necessary
- no individual recognition necessary.
304
What is the impact of decentralised control?
It means that the group is robust to perturbations.
305
What simple rules does positioning within a flock rely on?
It relies on the simple rules of attraction, alignment and collision avoidance in response to neighbours only.
306
What is the "many wrongs" hypothesis?
That the accuracy of collective decision is a function of group size.
307
What are the 2 types of flocking?
- V formations
- cluster formations.
308
What are the main functions of flocking?
- Navigation, following a leader or adult
- Information, share foraging spots, roosts and mates
- Energy, saving energy by flying aerodynamically
- Predation, dilution effect and hoping its not you that gets eaten.
309
Where do you find upwash and downwash?
Upwash comes off the tips of the wings while downwash comes off behind the centre of the body.
310
Why can't V formations be utilised in planes?
It can't be used as the planes are too far apart t capture the upwash, and instead the V formations are used for navigation and to allow for gun use without damaging neighbours.
311
How do you reintroduce birds into a wild population?
You use imprinting, and then these imprinted foster parents show them the historic migratory routes.
312
What does the positioning of birds in a V formation fit?
It fits the fixed-wing aerodynamic theory.
313
How does the aerodynamics work?
There is significant spatial phasing of wingbeats, which creates wing-tip path coherence.
314
What are animal cultures?
Group-typical behaviour patterns shared by members of a community that rely on socially learned an transmitted information.
315
What does animal culture allow for?
It allows arbitrary or even maladaptive behaviour to spread.
316
What are some examples of animal cultures?
- salmon hats in orcas
- hydroplaning in dolphins
- beaching in orcas for seal capture
- dolphins using sponges as tools
- human tool use and boat stealing in orangutans
- onion anointing in monkeys
- grass in ears in chimpanzees.
317
How long can it take for animal culture to spread?
After 90 years, so 12 or 13 generations, for 50% of descendants, translocated individuals showed the animal culture.
318
What is surfing knowledge?
The difference between peak vegetation and migrator's arrival.
319
What can cultural transmission allow for?
It can allow for complex behaviours to be spread very quickly through a population.
320
What is an example of cultural transmission?
An example is chimps using sticks for ant dipping.
321
What are the criteria for a behaviour to be classed as cultural?
- social learners; juveniles observe adults
- ecology is not plausible explanation
- genetic transmission is not plausible.
322
What is vertical transmission?
Transmission across generations from parents to offpring.
323
What is horizontal transmission?
Transmission from peer to peer.
324
What is oblique transmission?
Transmission across generations, but not via parent'/offspring interactions.
325
What is the ethnographic method?
Behavioural variants in different areas/groups are documented, and possible alternative explanations are excluded.
326
What are translocation experiments?
An experiment where individuals are moved between groups, or whole groups are swapped, then behavioural changes are looked for.
327
What is the social network diffusion method?
Where new behaviours are monitored as they diffuse through the social system.
328
What is the criteria for the ethnographic method?
- socially transmission
- exclusion of genetic influences
- exclusion of ecological factors.
329
What are the criticisms of the ethnographic method?
- determines culture based on other factors that can never be absolutely excluded
- relies on circumstantial evidence
- correlations between behaviours and environment/genetics to be expected if culture is an adaptive behaviour
- genetic explanations ignored
- simply missing some behaviours.
330
What does the ethnographic method suggest happens as geographical distance increases?
Cultural differences increase, which suggests that there is possible exchange of migrants drives the exchange of knowledge.
331
What are the uses of the social network method in ecology?
- disease transmission
- group foraging
- predation risk
- mixed species interactions
- social information use
- conservation of social species.
332
What are the uses of the social network method in evolution?
- hereditability of social behaviour
- health and stress
- fitness outcomes
- cooperation and social evolution.
333
What is learning?
An inferred change in the organism's mental state which results from experience, and which influences in a relatively permanent fashion the organism's potential for subsequent adaptive behaviour.
334
What is social learning?
Learning that is influenced by observation of, or interaction with, another animal or its products.
335
Why is social learning important?
- cognitively interesting
- taxonomically widespread
- can be used to think about culture and human evolution.
336
When and where should social learning evolve?
- when environments vary too fast for genetic change but slow enough that social information is still relevant
- when asocial learning is risky, costly, or hard to obtain
- when social information out performs personal information
- in social species, and when juveniles are social with experience adults.
337
Why might social learning not always adaptive?
As social information may be wrong, inappropriate, or outdated.
338
Where is the best quality information likely to have been obtained through?
The best quality information is likely obtained through trial and error learning.
339
What can social learning involve?
- how to eat
- what to eat
- where to go
- where to stay
- what to fear
- what to sing and signal
- who to mate with.
340
What are the social learning mechanisms?
- social facilitation
- local enhancement
- stimulus enhancement
- imitation
- emulation
- teaching.
341
What are social learning strategies?
- un-biased transmission
- state-based, copy if uncertain, dissatisfied or seasonally
- model-based, copy if familiars, kin, dominants, prestige-based, age-based, and success-based
- frequency-dependent, copy the majority or the rare behaviour.
342
What is conformity?
It is the tendency to change behaviour to match the majority.
343
What are the minimum criteria for teaching?
- the teacher must modify its behaviour only in the presence of a naiive pupil
- the teacher must pay a cost or at least gain no immediate benefit as a result of the behavioural modification
- as a result of the teacher's behaviour, the pupil must acquire knowledge or learn a skill faster than it would have otherwise have done.
344
What is social facilitation?
The presence of one or more models draws in an observer.
345
What is copying?
It is when an observer repeats what a model has done.
346
What is the difference between imitation and copying?
Copying does not have to be a new, novel behaviour and does not have to involve some new topographical action whereas imitation does.
347
What does social learning not necessarily rely on?
It does not necessarily rely on species-specific social information.
348
Can social learning be observed in non-social species?
Yes.
349
What can social learning emerge in?
- different species
- non-social animals
- "simple" small-brained animals.
350
How are airborne pressure waves sensed in insects?
They are sensed by measuring pressure differences across and elastic membrane called a tympanum (ear drum).
351
How many times have tympanum ears evolved?
They have evolved at least 18 times independently.
352
What is the shared common structure of a tympanum ear?
There is a path of thin cuticle forming the tympanal membrane, backed by an air-filled tracheal sac, providing an internal pressure reference and it is instrumented with a stretch receptor called a chordotonal organ.
353
What can the plimose antennae of male mosquitos be used for?
It can be used in species recognition and sex recognition.
354
Why is the tympanum ear of mammals more complex than insects?
Because the tympanum between the air-filled outer and middle ears is mechanically coupled to a fluid-filled inner ear.
355
How do the tympanum ears of mammals work?
Water has a higher impedance than air and the middle ear provides impedance conversion by applying the force communicated from the tympanum to the smaller area of the oval window, via the level mechanism of the ear ossicles. This sets the basilar membrane in motion, to which are attached the sense cells responsible for mechano-transduction.
356
What do the mechanical properties of the basilar membrane varying along its length result in?
Sound impinging upon the ear sets up a travelling wave on the basilar membrane.
357
What is tonotopic representation of sound and what does it provide?
It is where the properties of the basilar membrane are tuned so that different frequency sounds excite the greatest motion at different points along the basilar membrane. It provides a mechanical decomposition of its frequency content.
358
What is ionotropic transduction?
Where the ion channels are gated directly by the stimulus, and this gating is extremely fast.
359
What is sensory transduction of the vibration of the basilar membrane performed by and how?
It is performed by inner hair cells, with difference cells at different points being stimulated by different frequencies of sound, and this is done through ionotropic transduction.
360
What do the katydids have for sound pereception?
They have evolved a more advanced tympanic ear than other insects that is mechanically convergent with mammalian ears. In addition to have a tympanum, it has impedance conversion and tonotopic frequency analysis along the membrane.
361
What do insects use to make sense of the motion in their typanum?
They use a fast ionotropic transduction mechanism.
362
How do humans and other mammals localise sound?
They localise sound in the horizontal plane by measuring the inter-aural differences in timing and intensity.
363
How can mammals localise sound vertically, even with one ear?
They learn the spectral filtering of the ears, head and shoulders reducing the energy of the sound at some frequencies more than others and their match their responses accordingly.
364
How is the maximum inter-aural delay measured?
It is measured by comparing the action potential from the far ear with the action potential from the near ear, which is carried along a delay line.
365
How do female crickets localise male crickets?
By using morphological computation.
Pressure waves arrive at the tympanum from different sources, via the outer surface of the two tympanum, and via the inner surface via the inner surface of the two tympana. Phase delays introduced by a elastic membrane called the acoustic septum mean that ipsilateral sounds at the frequencies at which the males sing produce constructive interference at the tympanum, whereas contralateral sounds produce destructive interference.
366
What has echolocation evolved multiple times in?
It has evolved multiple times in bats, shrews, toothed whales, oilbirds, and swiftlets.
367
What is the principle of echo-ranging?
To measure the time delay between the emission of a call and the receipt of its echo to estimate the distance to a surface.
368
When is the strength of a target echo maximal?
When the wavelength is smaller than the target.
369
Why is echolocation only useful over short distances?
Because higher frequency sounds attenuate faster than lower frequency sounds.
370
What is the measurement of the delay between pules and echo done by?
It is done by interneurons in the auditory cortex, whose spiking rate depends on the echo delay. Different interneurons are matched to different delays and to different frequencies, which enables fast parallel processing to identify the echo delay ay a given frequency call.
371
What are broadband calls well suited to and why?
They are well suited to accurate localisation at short ranges with strong calls as rapid changes in call frequency allow for the precise matching of a call and its echo.
372
What are narrowband calls suited to and why?
They excite the same auditory neurons over a longer period, so are well suited to detecting weak echoes over an extended distance range. They are also well suited to detecting acoustic glints.
373
What does making a constant frequency call allow bats to do?
It allows them to compensate for the Doppler shift in frequency that is from their own motion in forward flight.
374
What does ecological variation appear to predict in echolocation?
It does appear to predict echolocation signal time, both within and between species.
375
How have echolocation calls evolved in bat families?
Different families use different types of echolocation call, and different call types have evolved convergently in different families of bats occupying similar habitats or using similar behaviours.
376
How have moths evolved to avoid bats when they are echolocating?
Thoracic scales of some moths have recently been shown to act as porous sound absorbers, which greatly attenuate the reflection of high-frequency sound.
377
How do noctuid moths respond to hearing high frequency sound?
When hearing a bat at distance, it flies away, and at close range, it enters an erratic evasive dive manouver.
378
Why have some bats sacrificed echolocation range due to using quieter calls?
It is thought to be due to the evolutionary arms race between bats and moths.
379
What is an example of acoustic aposematism in tiger moths?
Tiger moths have evolved a sound-producing structure called a tymbal which can produce a very high frequency sound. Many species of tiger moth are toxic, and the high-frequency sounds that they produce are thought to be used as a form of acoustic aposematism.
380
What is the most information-rich sensory modalitiy?
Vision.
381
What are parallel processing pathways used for?
- feature detection
- colour vision
- polarisation vision
- sensing self-motion
- tracking targets.
382
What is visible light?
It is a form of EM radiation, describable both as a wave and as a particle.
383
What are the 3 fundamental properties of visible light?
- frequency
- intensity
- polarisation.
384
What is the basis of spatial vision?
The basis is knowing which direction the light has arrived from.
385
What are 3 mechanisms used to identify which direction the light is arriving from?
- using a very small aperture
- using a refractive lens
- using a reflective mirror.
386
What is the most important constraint in eye design?
The inevitable trade-off between sensitivity and resolution of a photoreceptor array.
387
What does sensitivity of eyes improve in proportion to?
- the area of the aperture through which light enters
- the solid angle sampled by each photoreceptor
- the absorption efficiency of the photoreceptors.
388
What is resolution of an eye limited by?
The sampling resolution of adjacent photoreceptors or the optical resolution.
389
What can sampling resolution be improved by?
It can be improved by making the photoreceptors smaller.
390
Why does sensitivity limit resolution directly in very dim light?
Because low photon catch rate introduces shot noise that makes resolving fine detail impossible.
391
What have deep-sea animals evolved to match their sensitivity to the downwelling light?
They have evolved blue-shifted visual pigments.
392
How are spookfish eyes adapted to spot silhouettes and bioluminescence of predators and prey in the downwelling light?
To spot the silhouettes, they have tubular eyes which are adapted to provide high sensitivity and high resolution over a narrow view.
To see bioluminescence, they have evolved a pair of laterally-directed accessory eyes with their own accessory retina. They use a concave mirror formed by shiny guanine crystals to form an image.
393
What are the 2 types of compound eye seen in insects?
- Superposition eyes
- Apposition eyes.
394
What are superposition eyes, and what are the limitations?
Nocturnal insects possess superposition eyes, where each photoreceptive rhabdomere gathers light from multiple facets. Optical cross-talk between adjacent rhabdomeres degrades resolution. It constrains eyes to have a regular spherical arrangement which leaves no possibility of specialising different regions of the eye for different tasks.
395
What are apposition eyes and what are the limitations and adaptability?
Diurnal insects usually possess apposition eyes, in which each photoreceptive rhabdomere only gathers light from its own facet, and adjacent ommatidia are optically isolated from one another by screening pigments. This optical arrangement has low sensitivity because of the very small aperture. This allows for different regions of the eye to be specialised for different tasks.
396
What is colour?
It is a psychological percept, which is established by comparing the responses of at least two photoreceptors with differing spectral sensitivity.
397
When can colour perception be made independent of the spectrum of the ambient white light?
When three or four different photoreceptors are being compared.
398
What does spectral sensitivity depend on?
Partly on the identity of the chromophore, and partly on the amino acid sequence in the region and around it.
399
What are visual pigments and what are they comprised of and bound to?
Visual pigments are G-protein coupled receptors, comprising an opsin protein with the seven membrane helices characteristic of GPCRs, but permanently bound to the inactive form of the chromophore molecule, forming its signal ligand.
400
What is the most common chromophore?
It is retinaldehyde, which is usually called retinal.
401
What is one of the best-understood examples of a metabotropic mechanism?
The molecular basis of phototransduction.
Absorption of a single photon of light by 11-cis retinal causes it to transition to the all-trans state. This photoisomerization causes a conformational change in the opsin, converting it to its active form.
402
How have opsins with differing spectral sensitivities arisen?
They have arisen through multiple gene duplication events.
403
When did the loss of several visual pigments in mammals occur?
It is thought to have occurred during a nocturnal phase in their evolution between 200 and 150 Mya.
404
What does primate colour vision reflect?
Their genetics, ecology and evolutionary history.
405
How does colour vision in New World monkeys work?
They a complex sex-linked polymorphism in which heterozygous females are trichromatic, and males and homozygous females are dichromatic.
406
What colour vision do Old World monkeys, apes, and New World howler monkeys have?
They are trichromatic.
407
What do animals use polarised light for?
- to detect water bodies
- to identify the axis on which the sun or moon lies from the polarisation pattern of the sky
- to increase contrast in a visual scene.
408
How do dung beetles utilise the polarisation pattern of the sky?
They use it to roll balls of dung in straight lines over long distances on moonlit nights, and when there is no moon, they use the milky way as a guide instead.
409
When does photoisomerization occur most readily?
When the electrical field vector of the incoming light oscillates parallel to the chromophores long axis.
410
How is the degree and direction of polarisation computed in invertebrates?
By comparing the output across different rhabdomeres.
411
How do insects sense the polarisation pattern of the sky?
By using specialized photoreceptors located in the dorsal rim area of the eye, where the microvilli of the rhabdoms are arranged orthogonally.
412
What are retinal polarisation analysers and what do they do?
They are interneurons and they identify the local direction and degree of polarization at different points in the dorsal visual field, by comparing the output of the different rhabdoms.
413
What do medullar POL interneurons do?
They integrate input from across these retinal polarization analyzers, responding to the average direction and degree of polarization over the entire dorsal rim area.
414
What do the optic lobes of the insect brain preserve and what does that mean?
They preserve a retinotopic organisation at each level. This means that the neurons in each neutrophil form a map of the visual field, which is preserved on down through each of the layers in a parallel processing architecture.
415
What did the multi-layered processing involved in the visual system of mammals inspire?
The layer structure of the deep network architectures that have recently come to dominate image classification and other applications of AI.
416
What has our understanding of the underlying neurophysiology been greatly advanced by?
Calcium imaging of neuronal response properties and by studies combining electron microscopy with machine learning to analyse the connectome of the medulla, lobula, and lobula plate.
417
What did Hassenstein and Reichardt’s model correctly identify?
That local motion is detected by comparing the output of one photoreceptor with the output of another with a delay.
418
What is a common principle that underpins all levels of animal visual systems?
The use of separate ON/OFF channels in processing local motion.
419
What is the best example of a simple neuronal circuit in all of biology and how does it work?
The elementary motion detectors (EMDs) of insects.
Local motion is processed by eight EMD circuits in parallel at each ommatidial unit. Their output is encoded by a set of four T4 cells signalling ON contrast (i.e. brightness increments) and by a set of four T5 cells signalling OFF contrast (i.e. brightness decrements). Each set of cells encodes the four cardinal directions of motion. The next layer of the motion vision system integrates input from across the visual field. This is done by lobula plate tangential cells (LPTCs), some of whose response fields resemble the optical flow fields that the motion vision system is set up to detect.
