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| Pregunta | Respuesta |
| Define Stimulus | A change in the environment (internal or external) that is detected by a receptor and evokes a response |
| Define Response | A change in an organism resulting from a stimulus |
| Define Reflex | A rapid, involuntary (unconscious) response to a stimulus |
| Draw a reflex arc (10 labels) |
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| How does a Reflex Arc work? (5 points) | 1. RECEPTORS - transform stimuli to electrical nerve impulses (sensory cells or nerve endings of sensory neurons) 2. SENSORY NEURONS - Receive messages across synapses from receptors and relay nerve impulse to CNS via dorsal root 3. RELAY NEURONS - Transmit nerve impulses within CNS (receiving from sensory neurons via synapses and passing to motor neurons) 4. MOTOR NEURONS - Receive nerve impulses from CNS via ventral root. Relays signal to effector 5. EFFECTOR - Produces a response to the stimulus and can be either muscles (contraction) or glands (secretion) |
| Draw the Stimulus - Response Model | |
| Responses through Natural Selection or Inherited Behaviours (2 Examples) | Changes have to be a result of external agents and will affect chances of survival and/or reproductions and the offspring will inherit the successful responses MIGRATION PATTERNS OF THE BLACKCAP (Germany - Spain or now UK (10%) study shows some sign of genetic inheritance) FEEDING OF HOUSE SPARROW Those fledglings chirping and gaping most will be fed most, alleles responsible for this will then be passed on increasing the prevalence of the behaviour |
| State 4 Types of Sensory Receptor, their stimulus and an example of where they work. Name another 2 | 1. Mechanoreceptors - Mechanical energy in forms of sound waves. E.G: Hair cells in the cochlea of the ear 2. Chemoreceptors - Chemical substances dissolved in water (on tongue) or in air (nose) 3. Thermoreceptors - Detect temperature, in nerve endings of skin 4. Photoreceptors - In form of electromagnetic radiation (visible light) in rod and cones cells of eye 5. Nocireceptors - Detect Pain 6. Proprioceptors - Detect position |
| Label a Picture of the Human Ear (10 labels) |
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| Describe how Humans perceive Sound (5 points) | 1. EARDRUM Sound waves push against ear drum and cause vibrations, the degree of which depends on frequency and amplitude. The vibration goes towards and away from bones of middle ear 2. OSSICLES Each of the 3 bones touches each other, the first is connected to the eardrum and last to oval window. They reduce the amplitude of the waves, but increase force to amplify sounds (20x) . This is also helped by the oval windows small size in comparison to the eardrum. The bones displace the fluid in the cochlea when against the oval window 3. OVAL WINDOW / ROUND WINDOW Membranous structure. Transmits sound waves to fluid. Works with the round window to keep fluid able to vibrate 4. HAIR CELLS IN COCHLEA Hair cells have bundles that stretch either side of membrane. Sound waves that move fluid causes bundles to vibrate, movement affects the cilia and the width and thicknesses of each hair resonates a different sound so the frequencies are distinguished. Nerve impulse is generated and transmitted across synapse to brain through auditory nerve |
| Label a Diagram of the Human Eye (15 labels) |
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| Label a picture of the Retina (8 labels) |
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| Similarities and Differences (4) of Rod and Cone Cells | SIMILARITIES - Both are photoreceptors, absorbing light and transmitting messages to the brain and are found in the retina DIFFERENCES - 1. SENSITIVITY - Rod cells more sensitive to light - work better in dim lights 2. VISION TYPE - Rod cells absorb all wavelengths of visible light so give monochrome vision. Cone cells see red, green and blue 3. NUMBERS - Groups of up to 200 rod cells to one sensory neurone. Only one cone per bipolar cell (Cone cells have greater visual acuity) 4. LOCATION - Rod cells more widely dispersed across retina- wider field of vision. Cone cells concentrate onto fovea, a single acute field of vision |
| Explain Convergence as a form of Visual Processing | Bipolar cells in Retina combine impulses form groups of rod and cone cells and pass them onto ganglion cells (the sensory neurons of the optic nerve) |
| Describe the process of Edge Enhancement in Visual Processing (Inc. 2 types of ganglion cell) | Each ganglion cell is stimulated when light falls on receptive field (small circular area of retina) In the first type of ganglion cell, if light falls on the centre of the receptive field the cell is stimulated and stimulation is reduced when light falls on peripheries In the other type the opposite occurs Both types are more stimulated if the edge of the light/ dark areas are within the receptive field (HERMAN GRID) |
| Explain Contralateral Processing as a form of Visual Processing | The left and right optic nerve meet at the optic chiasma This means stimuli is processed on the opposite side to which it is detected - Information from left side of visual field is detected by the right half of the retina in both eyes and processed by right hemisphere At optic chiasma information from both eyes may swap and can be processed together Impulses then go to the thalamus to be processed before forming the image in the visual cortex This allows brain to deduce size and distance |
| Define Innate Behaviour | An instinctive response that is developmentally fixed (independent of environmental context) and is genetically determined |
| Define Learned Behaviour | Behaviour that is modified and developed as a result of experience (normally through trial and error) |
| Define Taxis | A change in movement, towards or away from a directional stimulus |
| Define Kinesis | The change in activity rate to a non- directional stimulus |
| An example of a Taxis Experiment | Daphnea will move towards a light source |
| Kinesis Experiment Example | Woodlice move around more in dry conditions as will seek humid areas (as have gills) |
| Wh is Learned Behaviour important? | In a diverse and changeable environment, animals can use the information from past experiences to adapt to new situations and improve survival chances Offspring must have capacity to learn Is better than innate behaviour as will allows responses to change to environment, giving the survival advantage |
| Give an Example of how Learning helps to Avoid Danger | GOSLINGS Imprint on their mothers as they are the first thing they see when they hatch Follow her around they avoid predators and then have a better chance of survival Copy her feeding habits etc. |
| Give an example of Learning how to hunt/ obtain food | GRIZZLY BEAR The bears learn how to catch salmon via practice |
| Explain how Learnt Behaviour helps to find Food | HONEYBEES Members of the colony learn off others where to find highest yield nectar by using the "waggle dance" |
| Other examples of Learned Behaviour (3) | CHIMPS - Learn how to catch termites by poking sticks into termite mounds FOXES - Avoid touching electric fences after being shocked HEDGEHOGS - Now run across busy roads rather than curling into a ball |
| Explain the Conditioned Reflex (Pavlovs Dogs) | PAVLOV - A scientist who investigated the salivation reflex in dogs through experiments in classical conditioning, calling it the CONDITIONED REFLEX, where the stimulus causing the response had changed 1. Dogs usually salivate through an UNCONDITIONED RESPONSE when anticipating an UNCONDITIONED STIMULUS (food) 2. Pavlov used a NEUTRAL STIMULUS (bell) prior to feeding the dogs for a number of days 3. The dogs then started to salivate before the UNCONDITIONED STIMULUS arrived - this is the CONDITIONED RESPONSE to the CONDITIONED STIMULUS |
| Define Conditioning | An alteration in the behaviour of an animal in response to the association of an external stimuli |
| Describe the development of Birdsong | Male birds use birdsong to establish territories and signal attraction Most birds are born with a genetically inherited template song As fledglings they learn to expand their song by listening to others and mimicking the adult version - MOTOR LEARNING The innate template stops them from learning the wrong species song Birds raised in sound proof boxes lack the complexity developed through learning The birds are selective in what they learn and once learnt, the song id rarely modified |
| Development of Birdsong Example | White Crown Sparrow The adult birdsong begins around 250 days after hatching Song is a plaintive whistle followed by some trills Dialect means song id subject to geographical variations |
| Explain how Excitatory Synapses work | Neurotransmitters released by presynaptic neuron causes an influx of Na+ ions to enter the postsynaptic neuron This depolarises the synaptic membrane and causes an action potential (may or may not reach threshold) EG: ACETYLCHOLINE |
| Explain how Inhibitory Synapses work | Neurotransmitters released by the presynaptic neuron causes hyperpolarisation (Via and influx of Cl- or a loss of K+ ions) this makes it more difficult to depolarise the neuron sufficiently to cause an action potential, lowering the resting potential - making it difficult to reach the threshold Postsynaptic transmission is therefore inhibited EG: GLYCINE OR GAMMA-AMINOBUTIC ACID (GABA) |
| Describe how Decisions are made in the CNS (Reference the two ways) | A single release of neurotransmitter is unlikely to be enough to trigger an action potential, as threshold potential has not been reached to cause postsynaptic transmission To cause post synaptic transmission, either one neuron has to be repeatedly releasing the transmitter (Temporal) or more than one neuron releases neurotransmitter at the same time (Spatial) |
| Explain how Summation works to Make Decisions in the CNS | The sum of signals from both excitatory and inhibitory neurons determines whether a signal is generated in the post synaptic membrane E + I = 0 (An excitatory transmission at the same time as a inhibitory transmission will cancel out) This is the basis of decision making in the CNS Summation can lead to the selection of alternative neuron pathways in the frontal cortex of the brain |
| Define Drugs | Drugs are chemical substances that are either ingested, injected or put into the body to cause a change in function (of some synapses) Psychoactive drugs affect the brain and personality |
| Explain what Excitatory drugs (Stimulants) do and how they work 3 EXAMPLES | Excitatory drugs promote the transmission of excitatory synapses or inhibit the transmission at inhibitory synapses They increase postsynaptic transmission and produce psychomotor arousal and increase alertness They serve as a neurotransmitter precursor and stimulate neurotransmitter release. They can also directly stimulate postsynaptic receptors and block neurotransmitter reuptake NICOTINE COCAINE AMPHETAMINES |
| Explain what Inhibitory drugs (Depressants) do and how they work 3 EXAMPLES | Inhibitory drugs decrease the transmission in the postsynaptic neuron and promote inhibitory transmission at inhibitory synapses. They also inhibit transmitters at excitatory synapses and slow brain activity and relax muscles They inhibit neurotransmitter synthesis, block neurotransmitter release, block postsynaptic receptors and prevent neurotransmitter storage ALCOHOL THC BENZODIAZEPINES |
| Explain how Psychoactive Drugs Affect Synaptic Transmission | Some psychoactive drugs have a chemical structure similar to neurotransmitters in the postsynaptic membrane, blocking receptors and preventing neurotransmitters having normal effect Others have the similar chemical structures but unlike the neurotransmitter are not broken down, so when they bind to the receptors they are much loner lasting Some interfere with the breakdown of neurotransmitters in synapses or their reabsorption into the presynaptic neuron, prolonging the effect of neurotransmitters |
| Explain how Cocaine works | Cocaine is an excitatory drug It stimulates the transmission in the brain at synapses that use dopamine as the neurotransmitter Dopamine receptors are found in the post synaptic regions in membranes of neurons in the brain associated with pleasure (The "reward pathway") Cocaine acts indirectly on dopamine, by binding to membrane proteins that pump dopamine back into the presynaptic neuron This causes dopamine to build up, remaining active in the synaptic cleft and able to continue binding to receptors and causing constant stimulation and excitation of the post synaptic neuron |
| Give 3 examples of the Effects of Cocaine | Sense of euphoria and mellowness Suppression of appetite Enhancement of energy - more talkative, alert and energetic Long term use is associated with severe mental disorders |
| Explain how THC works | THC is the active part of Cannabis It affects transmission at an unusual type of synapse where the postsynaptic neuron can release a signalling chemical that binds to receptors in the membrane of the presynaptic membrane THC mimics the neurotransmitter anandomide by binding to presynaptic Cannaboid receptors, blocking the release of excitatory neurotransmitters THC is therefore an inhibitory drug, causing hyperpolarisation and preventing neurotransmitter release and therefore postsynaptic excitation |
| Give 3 Effects of THC | Increased intensity of perceived sensory data Sense of emotional wellbeing Reduced concentration and impaired judgement of time and space |
| Define Addiction | Addiction is the dependance of a substance resulting in repeated and compulsive use (It is a chronically relaxing disorder where there is a loss of control in limiting uptake) (Stopping is difficult and causes severe mental and physical reactions- withdrawal) |
| Name 3 Causes of Addiction | 1. Dopamine Secretion 2. Genetic Predisposition 3. Social Factors |
| Explain how dopamine secretion causes addiction | In addictive drugs, transmission is stimulated at synapses using dopamine as the neurotransmitter The dopamine secretion gives the feeling of wellbeing as is released in response as a reward Cocaine enhances dopamine activity, nicotine and alcohol induce the reward pathway via dopamine Abuse of the drug may lead to reduction in dopamine receptors, meaning higher doses are required to achieve the same effect (habituation) |
| Explain how genetic predisposition causes addiction | There is evidence that addiction runs on families and the predisposition may be determined by polygenic inheritance People with one or more copies of the A1 allele for the DRD2 gene coding for dopamine receptor proteins are more likely to become addicted than those with the D2 allele |
| Explain how social factors cause addiction | Cultural traditions such as Rastafarianism encourage the use of drugs Personal trauma/ neglect and mental health issues Peer pressure or parental influences Poverty and deprivation |
| Label a diagram of the Human Brain (5 labels) |
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| Explain the functions of the 5 parts of the Human Brain | 1. CEREBRAL HEMISPHERE - Receives impulses from the eyes, nose, ear and tongue. Acts as an interrogation centre for higher complex functions, such as memory, emotion, learning and consciousness 2. MEDULLA OBLONGATA - Controls automatic and homeostatic activities such as swallowing, vomiting, breathing and heart activity (rate) 3. CEREBELLUM - Coordinates unconscious functions such as movement and balance (hand/ eye coordination) 4. HYPOTHALAMUS - Maintains homeostasis by coordinating the nervous and endocrine systems. Produces the hormones that are secreted by the posterior pituitary glands, sending releasing factors to stimulate hormone secretion by the anterior pituitary gland 5. PITUITARY GLAND - Produces (anterior lobe) and stores/ secretes (posterior lobe) hormones regulating many body functions |
| State the 3 ways used to Investigate Brain Functions | 1. Animal Experiments 2. Lesions 3. Functional MRI (fMRI) |
| Explain how animal experiments have been used to investigate areas of the brain (Good and bad) | Many experiments are performed on animals, particually primates. Many procedures are surgical and involve removing parts of the skull to gain access to the brain The animal is kept alive, so that the brain continues to function Regions of the brain can be stimulated with electrode or removing an area (lobotomy) to asses affects The procedures can be highly invasive, so animal models are sometimes used GOOD: Animal experiments have been used to understand and help develop treatments for diseases such as MS BAD: Ethical objections- Some animals are sacrificed or experience some kind of suffering . Animal brines are not the same as human's, so valid comparisons can be hard to make |
| Explain how Lesions have been used to investigate areas of the brain | Lesions are abnormal or damaged areas of brain tissue and are either congenital or from accidents or disease The locations of particular functions can be deduced from the loss of an area Split Brian Patients - (from the early treatment of epilepsy treated be a severed corpus callosum) can and have shown the roles of the right and left hemispheres of the brain Stroke patients lose the ability to speak when one half of the brain is damaged The brain has also shown it can relearn skills by rerouting the function to another part of the brain BAD: Many functions involve multiple areas of the brain, so complex functions become more difficult to interpret |
| Explain how fMRI has been used to investigate areas of the brain | fMRI is a technique used for determining which parts of the brain are activated by a specific though process fMRI records the changes in blood flow and can indicate active regions of the brain - oxyhaemaglobin responds differently to a magnetic field than deoxyhaemaglobin - this is represented by different colours The subject is placed in a scanner and a high intensity scan of the brain is taken A series of lower resolution scans are taken while the subject is given a stimulus designed to stimulate specific brain activity The scan is used to localise the regions involved Temporal activities can also be recorded to allow for identification of sequential collaboration between parts It is non invasive, but not ALL brain activity can be detected in this way (Used to monitor stroke recovery and has also been used to identify ADHD and dyslexia) |
| Describe the components of the Nervous System | Split between the CNS and the peripheral nervous system (Sensory and motor neurons) Further splits form peripheral to the somatic (motor neurons to skeletal muscle, sensory neurons form receptor sense neurons) and Autonomic nervous systems (Used to control unconscious internal processes by antagonistic actions) These impulses are sent from the brain go through either two parts of the autonomic system - The sympathetic and parasympathetic |
| Describe the Sympathetic Nervous System | Involved in the processes that prepare the body for action - fight or flight Releases noradrenaline (adrenergenic) via sympathetic nerves |
| Describe the Parasympathetic Nervous System | Involved in processes that occur when the body is relaxed - rest and digest Releases acetylcholine (cholinergenic) via parasympathetic nerves |
| Explain how the Sympathetic and Parasympathetic Nervous Systems affect the Heart | Parasympathetic - Heart rate slows to reduce blood flow via the stimulation of the vagus nerve (body is relaxed) Sympathetic - Heart rate increases so more blood can be pumped to the muscles via the release of adrenaline |
| Explain how the Sympathetic and Parasympathetic Nervous Systems affect the Blood Flow to the Gut | Parasympathetic - Blood flow to gut increases to facilitate digestion due to vasodilation of blood vessels by the smooth muscle Sympathetic - Blood flow to gut decreases due to the vasoconstriction of blood vessels by smooth muscle |
| Explain how the Sympathetic and Parasympathetic Nervous Systems affect the Iris of the Eye | Parasympathetic - Circular muscle fibres contract so the pupil constricts, reducing light and potential retinal damage Sympathetic - Radial muscles contract so the pupil dilates, improving vision |
| Explain the Pupil Reflex | If bright light shines into one eye, both pupils constrict This happens when photoreceptors in the retina detect the light stimulus. Nerve impulses are sent via sensory neurons of the optic nerve to the brain The medulla oblongata processes the impulses and sends them to the circular muscles fibres in the iris - the parasympathetic nervous system stimulates this Circular muscle fibres contract and pupils constrict In dim light, the sympathetic nervous system is stimulated and radials muscles contract causing pupils to dilate |
| Explain how Brain Death is diagnosed with the help of the Pupil Reflex | Advances in medicine have meant that the body can be kept alive even when some of the organs don't work If a patient is in a coma (prolonged unconsciousness) because of damage to the Cerebral Hemisphere, recovery can be possible With damage to the Medulla Oblongata, recovery is slim Whole brain death is the permanent absence of measurable activity in both the cerebrum and the brain stem Individuals with a non- functioning brain, but a functioning stem can be kept alive in a vegetive state - if not homeostatic processes cannot function Failiture of the pupil to respond to light is indicative of brain stem death - thus the pupil reflex is used to test for whole brain death in unconscious patients |
| Define Whole Brain Death | Whole brain death is the permanent absence of measurable activity in both the cerebrum and the brain stem |
| Explain how Pain is Perceived and the role of Endorphins | Pain is perceived when impulses are sent from pain receptors in the skin and other parts of the body (NOT brain) to the sensory areas of the Cerebral Cortex, where pain is processed This is essential to help us identify danger Pain can sometimes be excessive so the production of endorphins in the pituitary gland are stimulated (in times of stress, injury and exercise) They then travel in the blood to the brain and bind to receptors in the membrane of the neurons that send pain signals, blocking the release of neurotransmitters that are used to transmit pain signals in the brain |
| Explain the term of Eusocial Behaviour in terms of Social Organisations | 1. Individuals in the same species cooperate in caring for the young 2. There is an overlap of at least 2 generations in which the offspring contribute to colony labour 3. There is reproductive division of labour with sterile individuals who work on behalf on the reproductive ones Either the colony as whole survives or it doesn't - Natural Selection therefore exists at the colony level |
| Explain how Honeybees show Eusocial behaviour (Inc. the caste system) | Honeybees show a division of labour, living in colonies of up to 60,000 individuals. They live and die together and can reproduce to form extra colonies by swarming Each type of bee is specialised to a particular task that helps the group as a whole; QUEEN - The fertile female. Produces and lays eggs, but also produces a pheromone to control worker activity DRONE BEES - Some reproductive males that fertilise eggs and mate with virgin females WORKER BEES - Infertile females that collect nectar and pollen then convert it into honey. Secrete wax to build the comb. Feed and look after larvae. Protect the hive. (There are further sub divisions - Foragers and soldiers etc.) |
| Explain how Naked Mole Rats show Eusocial behaviour | They live in colonies of up to 80 individuals in burrow systems in E.Africa One DOMINANT FEMALE acts like a queen bee - the only reproductive female that mates with a single male The other castes of mole rat help her; FREQUENT WORKERS - Dig tunnels and bring food INFREQUENT WORKERS- Larger and occasionally help with the heavier tasks "NON WORKERS" - Live in the central nest keeping the breeding female and her young offspring warm. Also defend the colony if it is attacked |
| Explain how colonies evolve through altruistic behaviours | Natural selection acts on the gene pool of a given population Beneficial allele become more frequent as they promote reproductive success Because colonies are usually comprised of related individuals, traits that benefit the colony will become more frequent, even if they don't benefit the individual Many organisms form social clusters to improve survival prospects Such characteristics are more likely to be passed across generations and hence be more frequent in the gene pool |
| Define Altruistic Behaviour | Actions that increase another individuals lifetime number of offspring at a cost to one's own survival or reproductive success. (Behaviour that benefits another individual at the cost of the one carrying out the behaviour) |
| Explain Altruistic Behaviour | Alturism is behaviour that benefits another individual at the cost of the one carrying other the behaviour It appears to be opposition to natural selection, as it reduces the possibility of the altruistic individual passing on their own genes If the individuals are closely related, altruistic genes will persist in the gene pool and be naturally selected Enhancing the reproductive success of relatives is called kin selection Alturism occurs in social animals and is more common in members of the same species who are closely related |
| Define Kin Selection | Enhancing the reproductive success of relatives |
| Give 2 examples of Altruistic Behaviour | 1. VAMPIRE BATS Vampire bats are not always successful at getting a blood meal especially if young and learning. If they go two days without one, they are likely to die. Other colony members commonly regurgitate blood to share with its unlucky/ sickly roost mates who are unlikely to gain independent sustenance This is RECIPROCAL ALTRUISM as the donating bat may receive blood itself in the future There is advantage to the whole group, because the benefit of receiving blood after starvation is greater than the cost of donating blood after feeding well 2. NON BREEDING MOLE RATS the non breeding mole rats work to allow the breeding male/ female to reproduce successfully Even though offspring are not their own, they help to ensure the survival of their own genes as are all related |
| Explain the idea of Foraging Behaviours | Foraging is the act of searching for and finding food Animals adopt strategies that 1. Minimise cost of foraging 2. Maximise the benefits to the consumer As the availability and abundance of food sources vary, animals adapt their feeding behaviours to account for changes |
| Give two examples of Foraging Behaviours | BLUEGILL FISH Bluegill fish feed on Daphnia, a small aquatic crustacean It changes its foraging behaviour if prey availability is altered As high density of daphnia, Bluegills will pick out the larger ones to eat At lower densities, Bluegills will eat a range of Daphnia sizes Bluegills will eat more D.Pulex than D.Lumholtzi when found together When found separately, the Bluegills will eat both types This is all about consumption energies vs. energy gained CROWS EATING SHELLFISH Crows have to fly up and drop shellfish to break their shells If they fly too high, they waste energy If there fly too low, the shells won't break Experiments have shown that they regularly fly to exactly the right height to optimise energy |
| Explain what is meant by an Exaggerated Trait and give examples | The success of an organism is measured by the number (and quality) of offspring left behind, particularly their capacity to then breed (reproductive fitness) Features that improve a males chances of successfully competing with other males for the best mate (mate selection) will become more prevalent within the gene pool via natural selection The exaggerated traits (ornaments) are more likely to attract female attention and so promote successful reproduction These traits will be selected for even though they may increase predator attention and diminish the survival prospects of the individual (Natural selection won't continue when the cost/benefit threshold is met and the organism must also be adapted in other ways in order to be a good mate) the evolution of these traits in a particular gender has led to the marked sexual dimorphism of certain species PLUMAGE FEATHERS in Peacocks PRONGS on the antlers of the male Deers become larger and more in numbers |
| Explain what is meant by Rhythmical Behaviours | Animals often show rhythmical behaviours that appear at certain times Diurnal (Daily) Cycles Lunar (Monthly) Cycles Annual (Yearly) Cycles Or seasonal changes |
| Give 2 examples of Rhythmical Behaviours | CORAL In many species, the male and females release their gametes at the exact same time of year (mass spawning) The advantage of such behaviour is that it increases the chances of the gametes undergoing successful fertilisation (and reduces the chances of individual gametes being eaten by fish if a few were released at once) Spawning may be triggered by a number of factors including temperature (Seasonal) and moonlight (Lunar) CICADAS Most of the lifecycle is spent underground as herbivorous nymph before emerging for just a few days to breed and then die In the Eastern US, there are 6 species, 3 of which emerge every 13 years, 3 every 17 years These prime number events seem to be very difficult for predators to coordinate with When cicadas emerge, it is an event that only covers a few days, but where millions of adults are present This would be a welcome feast for a predator, but their inability to coordinate their own cyclic behaviours to a prime number has meant they are unable to take advantage of this glut of food, so the adaptive value of the cicadas is very usef |
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