Option E - Neurobiology and behaviour Flashcards
(102 cards)
1
Q
What is a stimulus?
A
A change in the environment (internal or external) that is detected by a receptor and elicits a response
2
Q
What is a response?
A
A change in an organism due to a stimulus
3
Q
What is a reflex?
A
A rapid unconscious response to a stimulus
4
Q
What is the role of receptors in response to stimuli?
A
They detect the stimuli directly
5
Q
What is the role of sensory neurons in response to stimuli?
A
Carry the nerve impulse from the receptors toward the central nervous system
6
Q
What is the role of relay neurons in response to stimuli?
A
Synapses with a motor neurone in the grey matter of the spinal cord and transfers the impulse chemically across the synapse from sensory neurons to motor neurons
7
Q
What is the role of motor neurons in response to stimuli?
A
Carry the impulses from a relay neuron to an effector
8
Q
What is an effector?
A
An organ that performes the response
(muscles, glands etc.)
9
Q
What is the role of synapses in response to stimuli?
A
Carries the nerve impulse from neuron to neuron with the help of chemicals
10
Q
Draw the reflex arc for a pain withdrawal reflex
A
11
Q
Explain how animal responses can be affected by natural selection (blackcap)
A
- Sylvia atricapilla breeds in the early summer in central and northern Europe and migrates to warmer areas before winter
- Populations in Germany migrated to Spain and other Mediterranean areas
- Recently 10% of the birds have started migrating to the UK
- Direction of migration is genetically programmed and inherited
- Offspring of UK blackcaps tend to fly west whereas the others tend to fly southwest
12
Q
Explain how animal responses can be affected by natural selection (sockeye salmon)
A
- Species was introduced into Lake Washington
- Some of them migrated to the Cedar River
- The river flows quickly, but the lake is deep and quiet
- DNA evidence has shown that river salmon and lake salmon have stopped interbreeding
- The lake salmon have one breeding method and the river salmon have another
- The lake salmon lay their eggs in the sand of the beaches
- The lake males have heavy bodies perfect for hiding in the deep waters of the lake
- The river males have thin and narrow bodies for easier swimming in the river
- The river females bury their eggs deep in the sand of the river bottom so that they won’t be washed away
- The lake conditions favour one set of traits and the river conditions favour another set of traits
- The salmon are now split into two genetically distinct populations
13
Q
What is the role of chemoreceptors?
A
- Respond to chemical substances
- Allows tasting and smelling
- Give information about internal body environment
- Monitor pH changes
- Pain receptors of chemoreceptors respond to chemicals released by damaged tissues
14
Q
What is the role of mechanoreceptors?
A
- Stimulated by mechanical force or pressure
- Touch is due to pressure receptors
- In arteries pressure receptors can detect a change in blood pressure
- In lungs, strecth receptors respond to the degree of lung inflation
- Proprioceptors in muscle fibre, tendons, joints, and ligaments help maintain posture and balance
- In the inner ear, pressure receptors are sensitive to waves of fluid moving over them
15
Q
What is the role of thermoreceptors?
A
- Respond to a change in temperature
- Warmth receptors respond when the temperature rises
- Cold receptors respond when the temperature drops
16
Q
What is the role of photoreceptors?
A
- Respond to light energy
- Give vision
- Rod cells repond to dim light (black&white)
- Cone cells respond to bright light (colour)
17
Q
Label a diagram of the structure of the human eye
A
18
Q
Label a diagram of the retina to show the cell types and the direction in which light moves
A
19
Q
Compare rod and cone cells
A
Rods VS cones
- use dim light VS bright light
- one type sensitive to all wavelengths VS three types sensitive to red, blue, and green light
- passage of impulses from a group of rod cells to a single nerve fibre VS passage from a single cone to a single nerve fibre
20
Q
How are visual stimuli processed?
A
- Light rays pass through the pupil and are focused by the cornea, lens, and the humours
- An upside down image is focused on the retina and reversed from left to right
- Photoreceptors of the retina are stimulated
- Photoreceptors send impulses to the bipolar neurons and the ganglion cells
- The axons from the ganglion cells travel to the visual area of the cerebral cortex of the brain
- The brain corrects the position of the image so that it’s right side up and not reversed. It also coordinates the images coming from the left and right eye
21
Q
What is edge enhancement?
A
- The Hermann grid illusion
- The areas where grey is seen are in peripheral vision, where there are fewer light-sensitive receptors than in the fovea
- When looked directly at a grey spot using the fovea, which has a high concentration of these receptors, the grey vanishes
- Special mechanism for seeing edges
- Light-sensitive receptors switch off their neighbouring receptors (peripheral)
- This makes the edge look more distinct due to the extreme contrast between dark and light
22
Q
What is contralateral processing?
A
- The left and right optic nerves meet at a structure called the optic chiasma
- Nerves cross over to the opposite optic nerve
- Left optic nerve carries information from the right eye vision and vice versa
- This allows the brain to deduce distances and sizes (depth perception)
23
Q
How is the two sides of the brain working together illustrated by the abnormal perceptions of patients with brain lesions?
A
- Patients with lesions in the right side do not recognise the object they’re seeing and deny that it is the claimed object
- Patients with lesions in the left brain can describe the function of the object in question but cannot come up with the name for the object
24
Q
What are ganglion cells?
A
The cell bodies of the optic nerve. They synapse with the bipolar neurons and send the impulses to the brain
25
What are bipolar neurons?
Cells in the retina which carry impulses from a rod or a cone cell to a ganglion cell of the optic nerve
26
Label a diagram of the ear
27
Explain how sound is perceived
1. The outer ear catches sound waves
2. The soundwaves cause the eardrum to vibrate
3. The bones of the ear receive vibrations from the eardrum and multiply them approximately 20 times
4. The stapes strikes the oval window causing it to vibrate
5. The vibe is passed to the fluid of the cochlea
6. The fluid causes hair cells to vibrate in the cochlea
7. The hair cells (chemical receptors) release a chemical message across a synapse to the sensory neuron of the auditory nerve
8. The chemical mesage stimulates the sensory neuron
9. The message is carried by the sensory neuron in the auditory nerve to the brain
10. The wave in the fluid of cochlea dissipates as it reaches the round window
28
What is the difference between innate and learned behaviour?
Innate behaviour develops independently of the environmental context, whereas learned behaviour develops as a result of experience
29
Describe innate behaviour
- Develops independently
- Controlled by genes
- Inherited from parents
- Developed by natural selection
- Increases chance of survival and reproduction
30
Describe learned behaviour
- Dependent on the environmental context
- Not controlled by genes
- Not inherited from parents
- Develops by response to an environmental stimulus
- May or may not increase chance of survival and reproduction
31
What is taxis?
A movement towards (positive) or away (negative) from a directional stimulus, a directed response
32
What is kinesis?
A response to a non-directional stimulus, such as humidity. The rate of movement or the rate of turning depends on the level of the stimulus, but the direction of movement is not affected
33
What are the different types of taxes?
1. Chemotaxis: response to chemicals in the environment
2. Phototaxis: response to light
3. Gravitaxis: response to gravity
4. Rheotaxis: response to water current
5. Thigmotaxis: response to touch
34
How could the innate behaviour of Planaria be investigated with the help of a taxis?
- Flatworm which lives in lakes and ponds
- Eyes which contain photoreceptors
- Anterior which contains chemoreceptors
- Negatively phototaxic
- Positively chemotaxic to food
- Investigation could include Planaria's response to different wavelengths of light, how fast it moves towards different food substances, or its response to temperature gradient
35
How could the innate behaviour of Euglena be investigated with the help of a taxis?
- Single-celled protoctist
- Eyespot that is stimulated by light
- Positively phototaxic
- Investigation could include testing if it respons to different wavelengths of light
36
What are the different types of kinesis?
1. Orthokinesis: when an organism moves slowly or rapidly in response to the stimulus (not towards the stimulus)
2. Klinokinesis: when an organism turns slowly or rapidly in response to the stimulus (not towards the stimulus)
37
How could the innate behaviour of woodlice be investigated with the help of a kinesis?
- Woodlice show kinesis to humidity
- Damp environment → move slowly
- Dry environment → move quickly
- Moving quickly makes it more likely to get out of the dry air
- The minute is senses a damp environment its random movement slows down
- Investigation in humid air, normal air, and dry air
38
What are examples of learned behaviour improving the chance of survival?
1. Some chimpanzees learn to catch termites by poking sticks into termite mounds
2. Birds learn to avoid eating orange and black striped cinnabar moth caterpillars after associating their colouration and bad taste
3. Many bird species learn to take avoiding action when they hear alarm calls warning them of a predator
4. Foxes learn to avoid touching electric fences after receiving an electric shock
5. In the UK, hedgehogs have learned to run across busy roads instead of rolling up into a ball
6. Some grizzly bears have learned to catch slippery salmon in rushing river waters
39
Describe birdsong and why it is important to learn
- Partly innate and partly learned
- The song varies a little between males, allowing identification of individuals
- Used to keep other males out of their territory and to attract females
- Birds that do not learn their birdsong will not be able to attract females and reproduce
Birds in isolation:
- The song had some features of the normal song, correct length and number of songs → innate
- There was narrower range of frequencies and fewer distinctive phases → learned
40
Outline Pavlov's experiments about conditioning in dogs
1. Dogs secreted saliva when they saw or tasted food. The sight or taste of meat is called the **unconditioned stimulus** and the secretion of saliva is the **unconditioned response**
2. Pavlov gave the dogs a neutral stimulus, a ringing bell, before he gave the unconditioned stimulus
3. After repeating this procedure for a while, the dogs started to secrete saliva before they had received the unconditioned stimulus → the sound of the bell is the **conditioned stimulus** and the secretion of saliva is the **conditioned response**
4. The dogs had learned to associate two external stimuli
41
What is conditioning?
An alteration in the behaviour of an animal as a result of the association of external stimuli
42
What can you say about presynaptic neurons and postsynaptic transmission?
Some presynaptic neurons are excitatory and excite postsynaptic transmission.
Some presynaptic neurons are inhibitory and inhibit postsynaptic transmission.
43
What is the difference between sympathetic and parasympathetic systems?
Sympathetic is the fight or flight mode of a body whereas parasympathetic is the relaxed mode
44
How does the interaction between excitatory and inhibitory presynaptic neurons affect decision-making in the CNS?
- One pulse of excitatory neurotransmitter is unlikely to be enough to cause postsynaptic transmission (a rapid sequence of pulses of neurotransmitter is needed)
- Postsynaptic neurons have synapses with multiple presynaptic neurons
- The effect of excitatory neurotransmitters may be cancelled out if an inhibitory neurotransmitter is also being released
- Whether an action potential is initiated in the postsynaptic neuron is decided by the summation of messages from all of these synapses
45
How do excitatory neurotransmitters function?
e. g. acetylcholine
- Generates an action potential
1. Neurotransmitters increase the permeability of the postsynaptic membrane to positive ions
2. Sodium ions diffuse into the postsynaptic neuron
3. The postsynaptic neuron is depolarised locally by the influx of positive sodium ions
4. The inside of the neuron develops a net positive charge
5. The neuron is locally depolarised and the depolarisation continues as sodium ions diffuse to the adjacent area of the neuron (wave motion)
- An action potential is formed as the membrane depolarisation is raised above the threshold
- If the threshold is not met, the neuron does not carry the impulse to the next neuron
46
How do inhibitory neurotransmitters function?
e. g. GABA
- Inhibit action potentials
- Causes hyperpolarisation of the neuron (= the inside of the neuron becomes more negative) making it even more difficult for an action potential to be generated
- The neurotransmitter binds to its specific receptor
- This causes negative chloride ions to move across the postsynaptic membrane into the postsynaptic cell or can cause positive potassium ions to move out of the neuron
- Thsi movement of Cl– into the neuron or K+ out of the neuron is what causes the hyperpolarisation
47
What happens when excitatory and inhibitory stimuli meet?
- A neuron is on the receiving end of many opposite stimuli
- The neuron sums up the signals
- If the sum of the signals is inhibitory, the axon does not fire
- If the sum is excitatory, the axon fires
- The summation of messages is the way that decisions are made by the CNS
48
What are psychoactive drugs?
Drugs that affect the brain and personality
49
What are cholinergic synapses?
Synapses that use acetylcholine and cause relaxation (parasympathetic system)
50
What are adrenergic synapses?
Synapses that use noradrenaline and causes fight or flight reaction in the body (sympathetic system)
51
What are three excitatory psychoactive drugs?
1. Nicotine
2. Cocaine
3. Amphetamines
52
What are three inhibitory psychoactive drugs?
1. Benzodiazepines
2. Alcohol
3. Tetrahydrocannabinol (THC)
53
In what ways can psychoactive drugs change synaptic transmission?
1. Block a receptor for a neurotransmitter
(drug has structure similar to neurotransmitter)
2. Block release of a neurotransmitter from the presynaptic membrane
3. Enhance release of a neurotransmitter
4. Enhance neurotransmission by mimicking a neurotransmitter
(drugs have the same chemical structure as the neurotransmitter but are not broken down)
5. Block removal of a neurotransmitter from the synapse and prolong the effect of the neurotransmitter
54
How do excitatory drugs function?
Either by:
1. Promoting transmission at excitatory synapses
2. Inhibiting transmission at inhibitory synapses
55
How do inhibitory drugs function?
Either by:
1. Promoting transmission at inhibitory synapses
2. Inhibiting transmission at excitatory synapses
56
How does cocaine carry out its effect on the body?
- Excitatory
- Stimulates adrenergic synapses and causes alertness and euphoria
- Also dopamine release
- Blocks the removal of dopamine from the synapse so that it builds up
- This leads to overstimulation of the postsynaptic neuron → leads to euphoria
- Highly addictive
57
How does THC carry out its effect on the body?
- Inhibitory
- Main psychoactive chemical in marijuana
- Mimics the excitatory neurotransmitter anadamide
- Binds to the same receptor as anandamide (blocks it)
- Causes the postsynaptic neuron to be hyperpolarised
- Disrupts short-term memory in humans
58
What are the effects of THC?
- Relaxing and mellow
- Lightheaded and hazy
- Dilation of pupils cause colour perception to be more intense
- Some experience panic and paranoia
- Loss of coordination and short-term memory
- Stimulation of appetite
59
What are the effects of cocaine?
- Euphoria
- Increased energy, talkativeness and mental alertness
- Temporary decrease in the need for food and sleep
- Large amounts can cause erratic and violent behaviour
60
What is crack?
A form of cocaine that forms a vapour when heated. Can be inhaled and absorbed very rapidly and gives intense effects. Causes greater addiction and overdose problems than usual cocaine
61
What are three factors that increase the levels of addiction?
1. Genetic predisposition
2. Social factors
3. Dopamine secretion
62
How is genetic predisposition relevant in causing addiction?
- Addictions are much more common in some families than others
- This suggests that genes can make some people predisposed
- Evidence found in studies of twins
63
How are social factors relevant in causing addiction?
- Cultural traditions
- Peer pressure
- Poverty
- Social deprivation
- Traumatic life experiences
- Mental health problems
All increase the chances of an addiction developing
64
How is dopamine secretion relevant in causing addiction?
- Some drugs are addictive and some are not
- Transmission is stimulated at the synapses using dopamine as the neurotransmitter → dopamine builds up
- Gives feeling of pleasure
- People become dependent on the feelings that dopamine promotes
- Over-stimulation makes receptors less sensitive to dopamine → more of the drug is needed to reach the euphoric state
65
Label on a diagram of the brain, the medulla oblongata, cerebellum, hypothalamus, pituitary gland, and cerebral hemispheres (HL)
66
What is the role of the medulla oblongata? (HL)
Controls automatic and homeostatic activities, such as swallowing, digestion, vomiting, breathing, and heart activity
67
What is the role of cerebellum? (HL)
Coordinates unconscious functions, such as movement and balance, including hand-eye coordination
68
What is the role of hypothalamus? (HL)
Maintains homeostasis, coordinating the nervous and endocrine systems, secreting hormones of the posterior pituitary, and releasing factors regulating the anterior pituitary gland
69
What is the role of pituitary gland? (HL)
The posterior lobe stores and releases hormones produced by the hypothalamus and the anterior lobe, and produces and secretes hormones regulating many body functions
70
What is the role of cerebral hemispheres? (HL)
Receives impulses from the eye, ear, nose, and tongue. Act as the integrating centre for high complex functions such as learning, memory, consciousness and emotions
71
What is meant by the pupil reflex? (HL)
- If a bright light shines into one eye, the pupils of both eyes constrict
- Photoreceptor cells in the retina detect the light stimulus
- Nerve impulses are sent in the sensory neurons of the optic nerve to the brain
- The medulla oblongata processes the impulses and then sends impulses to circular muscle fibres in the iris of the eye
- These muscle fibres contract, causing the pupil to constrict
72
How can the pupil reflex be used in testing brain death? (HL)
- Damage to the medulla oblongata can be detected by testing the pupil reflex
- If an unconscious patient's pupils do not constrict when a light is shone into the eye, this suggests that they have injuries in the medulla serious enough to have caused brain death
73
How does the autonomic nervous system control heart rate? (HL)
Parasympathetic:
- Heart rate is slowed as the body is relaxed and less blood flow is needed
Sympathetic:
- Heart rate speeds up so that more blood can be pumped to the muscles
74
How does the autonomic nervous system control the blood flow to the gut? (HL)
Parasympathetic:
- Blood vessels are dilated, increasing blood flow to the gut
Sympathetic:
- Blood vessels are constricted, decreasing blood flow to the gut
75
How does the autonomic nervous system control the iris of the eye? (HL)
Parasympathetic:
- Circular muscle fibres contract, so the pupil constricts to protect the retina
Sympathetic:
- Radial muscles contract, dilating the pupil to give a better image
76
What is brain death and how is it tested? (HL)
"That time when a physician has determined that the brain and brain stem have irreversibly lost all neurological function"
External stimuli are tried:
1. Movement of extremities: if limbs are raised and let fall, there must be no other movement or hesitation in the fall
2. Eye movement: eyes must remain fixed showing lack of brain to motor nerve reflex (there is no rolling motion of the eyes when the head is turned)
3. Corneal reflex: when a cotton swab is dragged over the cornea, the eye doesn't blink
4. Pupil reflex: pupils do not constrict in response to a very bright light
5. Gag reflex: insertion of a small tube into the throat will not cause a gag reflex
6. Respiration response: the patient cannot breathe without a ventilator
NB: spinal reflexes may still occur as they do not involve the brain (knee jerk)
77
What are the two nervous systems? (HL)
1. Central nervous system (CNS)
2. Peripheral nervous system (PNS)
78
What does the CNS consist of? (HL)
The brain and the spinal cord
79
What does the PNS consist of? (HL)
1. Somatic system (voluntary)
- information received by the senses and messages sent to the skeletal muscles
2. Autonomic system (involuntary)
- controls cardiac muscle of the heart
- Two antagonistic systems:
- sympathetic system
- parasympathetic system
80
What can be used in the identification of the brain part involved in specific functions? (HL)
1. Animal experiments
2. Lesions
3. Functional magnetic resonance imaging (FMRI)
81
How can brain lesions be used in identifying brain part functions? (HL)
- Injuries to particular areas of the brain help to understand the functions of each part
- Damage to the left hemisphere causes difficulties in speaking or doing complicated movements of the hands or arms (deaf people could not use sign language after a stroke), speech and language problems
- Damage to the right hemisphere causes difficulties in identifying faces, locating objects correctly in space, and identifying melodies
82
What are the functions of the left and right hemispheres of the brain? (HL)
Left hemisphere
- Controls communication (language) and motion
Right hemisphere
- Receives and analyses information to understand words
- Helps to understand what we hear and see
83
How can animal experiments be used in identifying the functions of brain parts? (HL)
- Experimental procedures directly to the brain
- Exposing animals to addictive substances. Animals respond in similar ways to humans when addicted:
- want more and more of the substance
- spend lots of time and energy getting it
- keep taking it despite adverse conditions
- have withdrawal symptoms
- go back to the substance when stressed§
84
How can FMRI be used in identifying functions of different parts of the brain? (HL)
- Uses strong radio waves and a strong magnetic field
- Enables seeing the blood flow in the brain as it is occurring
- Helps to determine with some precision when regions of the brain become active and how long they remain active
- Possible to determine if brain activity occurs in the same region or different regions at the same time as the patient responds to different stimuli
Used by doctors to determine:
- a plan for surgery,
- treatment for a stroke,
- placement of radiation therapy for brain tumour,
- effects of degenerative brain disease such as Alzheimer's,
- diagnosing how a diseased or injured brain is functioning
85
How is pain perceived? (HL)
- Pain signals are carried by peripheral nerve fibres to the spinal cord and relayed to the sensory area of the brain
- Fibres connect with pain receptors called nocioreceptors
- Nocioreceptors can sense heat, pressure, or chemicals from tissue. Located in the skin and the muscle, bones, joints, and membranes
1. The nerve impulses of pain travel to the spinal cord
2. The spinal cord sends the messages up to the brain
3. The message travels to the cerebral cortex
4. The cerebral cortex receives the message and directs the body to respond in one or more ways:
- it can tell the muscles to stop the action which is causing the pain stimulus,
- it can alert the autonomic nervous system if the pain requires change in heart rate or breathing,
- it can direct other brain cells to release pain-suppressing endorphins
86
What are endorphins? (HL)
- CNS neurotransmitters with pain-relieving properties
- Small peptides which bind to opiate receptors and block the transmission of impulses at synapses involved in pain perception
87
Outline the social organisation of honey bee colonies (HL)
1. Queen: fertile female that lays eggs and produces a pheromone to control the activities of workers
2. Workers: infertile females that collect nectar and pollen, convert pollen into honey, secrete wax to build the comb, feed and look after the larvae, guard the hive
3. Drones: fertile males that mate with virgin females (queens)
88
What is the waggle dance of honey bees? (HL)
- Some bees look for a source of nectar
- When they find one they do a waggle dance to indicate the direction and distance of the source
89
What determines whether a honey bee egg will become a drone, a worker, or a queen? (HL)
- If the eggs are unfertilised they will develop into male drones
- If the eggs are fertilised and fed with less nutritious diet of honey and pollen they will become infertile female workers
- If the eggs are fertilised and fed with "royal jelly" they will become queens
90
Outline the social organisation of naked mole rats (HL)
1. Queen: only female in the community to reproduce, mating with one of the males in the colony
2. Frequent workers: dig tunnels and bring food
3. Infrequent workers: larger and occasionally help with heavier tasks
4. Non-workers: live in the central nest, keeping the breeding female and her young offspring warm and defending the colony in case of an attack
91
How does natural selection affect a social colony in honey bees? (HL)
- Worker bee behaviour is not promoted by natural selection
- Natural selection in the case os social organisms acts on the colony as a whole
- Genes which are selected are ones that promote social organisation
- Genes for pheromones which control the behaviour of workers are selected
- Genes for finding nectar and making wax are selected
- Genes for taking care of babies are selected
- All females have the same genes and only the egg that gets fed royal jelly becomes the queen
- The worker gene present in the queen keeps the colony functioning well
92
What is meant by altruism? (HL)
Actions that increase another individual's lifetime number of offspring at a cost to one's own survival and reproduction
93
What is kin selection? (HL)
Behaviour which results in a decrease inthe fitness of the altruist and an increase in the fitness of a close relative
94
How is altruistic behaviour present in naked mole rats? (HL)
- Some of the rats are non-breeding
- The tasks they do allow the breeding male and female to reproduce successfully
- Since the rats in a colony are all genetically related, helping to produce offspring that are not their own is helping to ensure the survival of their own genes
95
How is altruistic behaviour present in vampire bats? (HL)
- If one of the bats fails to feed for more than two consecutive nights it may die of starvation
- Other bats regurgitate blood for a bat that has failed to feed
- This is done whether the two bats are genetically related or not (reciprocal altruism)
- Reciprocal because the bat that donates blood may in the future receive blood when it is hungry itself
- Advantageous for the group because the benefit of receiving food when starving is greater than the cost of donating blood after feeding well
96
What is meant by foraging behaviour? (HL)
Optimising animals' food intake by changing their way of feeding when necessary
97
How does foraging behaviour optimise food intake in bluegill sunfish? (HL)
- When the density of prey is low, the fish consume all sizes of them
- At medium prey dnesities, the fish only consume moderate or large sizes
- At high prey densities, the fish mainly consume large prey
- Consuming small numbers of large prey takes less energy than large numbers of small prey
98
How does foraging behaviour optimise food intake in starlings? (HL)
- Birds that feed their offspring mainly on larvae, which they obtain by probing into soil with their beak
- Become less efficient at probing for larvae as the number of larvae they are holding in their beaks increases
- The fewer journeys back to the nest, the less time and energy is used in transporting the larvae
- The optimum number of larvae depends on the distance between the foraging area and the nest
- As the distance increases, the optimum no of larvae increases
- When birds have been observed, the number of larvae actually caught has been found to be very close to the theoretical optimum
99
How does mate selection lead to exaggerated traits (peacocks)? (HL)
- The largest tail signifies the healthies bird with the best change for healthy offspring
- Originally, the tail size and number of eyespots may have had an actual advantage but not it is just a sign of the best male
- When females choose the male with the largest tail, these traits wil be carried on to their offspring, resulting in an even larger tail
- Eventually they may become a disadvantage (attracting a new predator etc)
100
Do animals show rhythmical variations in activity? (HL)
Yes
101
How do corals show rhythmical behaviour patterns? (HL)
- Once a year the corals release millions of gametes in a synchronised mass spawning ritual
- Releasing the gametes at the same time increases the chances of fertilisation
- Predators are overwhelmed with more food than they can consume
- The cue for releasing all the gametes is not known
102
How do red deer show rhythmical behaviour? (HL)
- Reproduction follows an annual cycle
- Males and females are only sexually active in the autumn
- Males fight to establish dominance over groups of femalse
- If the females start gestation in the autumn, the offspring are born in the spring
- Most food is available during the spring and the summer
