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Option E Keegan Murphy, John Rubenchik, Enkhjin Myagmarsuren, Michal Tesfemariam, Define the terms stimulus, response and reflex in the context of animal behaviour Explain the role of receptors, sensory neurons, relay neurons, motor neurons, synapses and effectors in the response of animals to stimuli. Draw and label a diagram of a reflex arc for a pain withdrawal reflex. -The central nervous system includes the brain and the spinal cord. -The spinal cord acts independently from the brain during reflex actions. -The reflex is an automatic response to specific stimuli. -The reflex response is a fast involuntary reaction which increases the chance of an animal avoiding damage and therefore increasing chances of survival. Explain how animal responses can be affected by natural selection, using two examples. • Animal behaviour is more than a single reflex but a complicated series of responses to the environment. Some populations of organisms have changed their behaviour in response to a change in the environment. • Variations in behaviour can occur in populations in the same way as variation in the characteristic, such as colour, of the animals. The characteristic of an animal is determined by genes just as behaviour can be determined by genes. • Variations in behaviour can be selected by the environment. Since a genetically programmed behaviour can have variations, one behaviour can work better than another in a changing environment. The variation will allow one group of organisms to survive and reproduce better in the new environment. • The theory of natural selection states that the organism best fitted for the environment is more likely to survive to reproduce. Outline the diversity of stimuli that can be detected by human sensory receptors, including mechanoreceptors, chemoreceptors, thermoreceptors and photoreceptors mechanoreceptors: • membrane receptor proteins respond to mechanical deformation, • which results in membrane depolarization • leading to action potentials sent to brain, • which interprets the sensation, • e.g. Meissner’s corpuscle (light touch), Pacinian corpuscle (deep pressure), hair cells (hearing, balance), aortic baroreceptor (blood pressure) chemoreceptors: • membrane receptor proteins bind specific molecules • which results in membrane depolarization • leading to action potentials sent to brain, • which interprets the sensation, • e.g. olfactory neurons, gustatory cells of taste buds, aortic carotid bodies, hypothalamic glucoreceptors thermoreceptors: • membrane receptor proteins respond to temperature, • which results in membrane depolarization • leading to action potentials sent to brain, • which interprets the sensation, • e.g. free nerve endings in dermis detect warmth; hypothalamic thermostat detects internal temperature photoreceptors: • photopigments change when activated by specific wavelengths of light, • which results in membrane depolarization • leading to action potentials sent to brain, • which interprets the sensation, • e.g. rods and cones in the retina of the eye Label a diagram of the structure of the human eye. Annotate diagrams of the human retina to show the cell types and the direction in which light moves. Compare rod and cone cells Explain the processing of visual stimuli, including edge enhancement and contralateral processing. edge enhancement: • occurs within the retina – – two types of ganglion cell, each stimulated when light falls on a small circular area of retina called the receptive field on-center ganglion cells • • – off-center ganglion cells • • – ganglion is stimulated if light falls on the center of the receptive field but this stimulation is reduced if light also falls on the periphery light falling on the periphery of the receptive field stimulates the ganglion cell if light also fall on the center of the receptive field, stimulation is reduced both types of ganglion cell are therefore more stimulated if the edge of the light/dark is within the receptive field contralateral processing: • signal passes from photoreceptor to bipolar neuron to ganglion cell, • which leave the eye bundled in the optic nerve, • left and right optic nerves meet at the optic chiasm – – • neurons carrying impulses from the half of the retina nearest the nose cross over to the opposite optic nerve thus, left optic nerve carries information from the right half of the field of vision, and vice versa allows brain to deduce distances and sizes visual cortex: • receives point-by-point information about the visual field from optic nerves • and interprets it into meaningful images • by communicating with various areas of the brain, • comparing input with stored memories Label a diagram of the ear. E.2.7 Sound perception • How we perceive sound is a sequences of changes of energy from one form to another. Initially the incoming sound into the ear is in the form of a pressure wave in air which will ultimately be transformed into a nerve impulse, which as we know is a wave of sodium ions traveling down the axon. E.3.1 Distinguish between innate and learned behavior E.3.2 Design experiments to investigate innate behavior in invertibrates • Innate behaviors can be measured as the animals respond to environmental stimuli • Two basic kinds of movement are seen in invertebrate animals: – Taxis – Kinesis E.3.3 Analyse data from invertebrate behavior • Chemotaxis: response to chemicals in the environment; experiments involving variation in pH, dissolved drugs, food, pesticides • Phototaxis: response to light; experiments involving different wavelengths of light, intensities, and different types of bulb • Gravitaxis: response to gravity; experiments with organism in container that is turned upside down or on a turntable • Rheotaxis: response to water current; experiment involving animals with and against current • Thigmotaxis: response to touch; experiment involving different types of material to touch an organism E.3.4 Discuss how the process of learning can improve the chance of survival • Learning occurs most easily when it results in the animal’s survival • Imprinting – process by which young animals become attached to their mother within the first day or so after hatching or birth; assures that the young stay close to their mother for protection and as a source of food E.3.5 Outline Pavlov’s experiment • Classical conditioning can be used to modify a reflex response • Russian physiologist Ivan Pavlov designed experiments to illustrate classical conditioning • His subjects were dogs • Salivation is a reflex response to the presence of food in the mouth • Food is unconditional stimulus which elicits salivation which is unconditional response • Neutral stimulation that Pavlov employed was the ringing of a bell • He rang the bell (conditioned stimulus) just before the dog tasted the food • After training, the could ring the bell (CS) and the dog would salivate (conditioned result) • Dog had learned to salivate to the neutral stimulus E.3.6 Role of inheritance -birdsong • After hatching, there is a memorization phase in which the bird is silent but listening to the song of his species from adults (males) • He attempts to match his template to the full adult song • Phase if over within 100 days (sensitive period) • 2nd phase is motor phase in which he practices singing, continuing to listen to his own song and match it to his father’s • As he becomes sexually mature, his song will become perfected and he will begin to search for a mate • Crude template is innate; adult song is learned E.4.1 State the presynaptic neurons E.4.2 descision making in the CNS • Neurones form synaptic junctions with the cell body of other neurones. • A post synaptic neurone can have many pre-synaptic neurones forming synaptic junctions with it. • Pre synaptic neurones depolarise (excitatory) or hyperpolarise (inhibitory) the post synaptic membrane locally. • The sum of their effects takes place at the axon hillock E.4.4 List three examples of excitatory and three examples of inhibitory psychoactive drugs . excitatory psychoactive drugs: nicotine cocaine amphetamines inhibitatory psychoactive drugs: benzodiazepines alcohol tetrahydrocannabinol (THC) E.4.5 Explain the effects of THC and cocaine in terms of their action at synapses in the brain • THC is an inhibitory psychoactive drug that decreases synaptic transmission – cannabinoid synapses involve post-synaptic neuronal release of endocannabanoid NTs • endo-cannabanoids bind to cannabinoid receptors on pre-synaptic neurons • modifying the pre-synaptic neuronal release of NTs – THC binds to cannabinoid receptors • inhibiting the release of neurotransmitters from the pre-synaptic neurons such as GABA • the reduction in GABA frees dopaminergic synapses from inhibition • leading to increase in dopamine release in the pleasure pathway • cannabinoid receptors are found in various brain locations – cerebellum • THC thus impairs motor functions – hippocampus • THC thus impairs short-term memory functions – cerebral cortex • THC thus affects higher order thinking E.4.6 Discuss the causes of addiction, including genetic predisposition, social factors and dopamine secretion. • • • • • • • • • • genetic predisposition: the tendency toward addiction is variable, with studies indicating that genetic factors have some influence alcoholism, especially, tends to run in families social factors: a variety of social factors correlate positively with addiction: – cultural traditions – peer pressure – poverty – social deprivation – traumatic life experiences – mental health problems dopamine secretion many addictive drugs are excitatory at dopaminergic synapses, also known as the reward pathway addiction is a result of dopaminergic synapses responding to regular use – reduction in the number of dopamine receptors in post-synaptic neurons – reduction in the release of dopamine from pre-synaptic neurons tolerance to a drug – a result of decreased number of receptors – leading to increased dosage to produce the desired effect withdrawl – with reduction of receptors – normal level of dopamine fails to produce pleasure E.5.1 Label, on a diagram of the brain, the medulla oblongata, cerebellum, hypothalamus, pituitary gland and cerebral hemisphere E.5.2 Outline the functions for each of the parts of the human brain in. • medulla oblongata: controls automatic and homeostatic activities, such as: – – – – • cerebellum: coordinates unconscious functions, such as: – – • regulates, appetite, thirst, body temperature, and sleep secretes hormones of the posterior pituitary secretes hormone releasing factors regulating the anterior pituitary pituitary gland: – – • body movements posture and balance hypothalamus: maintains homeostasis, coordinating the nervous and endocrine systems: – – – • swallowing digestion & vomiting breathing heart activity posterior lobe stores and releases hypothalamic hormones anterior lobe produces, stores, and secretes many hormones regulating many body functions cerebral hemispheres: – – act as integrating center for high complex functions, such as: memory, learning, emotion, language, reasoning E.5.3 Explain how animal experiments, lesions and fMRI (functional magnetic resonance imaging) scanning can be used in the identification of the brain part involved in specific functions, providing one specific example of each. • • • • • • • • • • • • • animal experiments: surgical procedures allow access to brain experiments performed on live animals so that brain is functioning effects of experiments observed during and/or after experiment specific example: rats – research into visual impairments such as strabismus (‘cross eye’) – induced by covering the eye with material or stitching the eye shut – monitor visual development ethical issues related to suffering of animals, and sacrifice of animals lesions: damage to specific brain regions – injury by accident/war – stroke – tumor allow deduction of location of specific brain functions specific example: stroke – lesion in Broca's area in left cerebral hemisphere – causes dysphasia, inability to speak – but reading and writing are unaffected fMRI subject placed in scanning machine which measures blood flow to specific brain areas – 1st: high resolution – 2nd: series of low resolution while subject is given stimulus specific example: – subject view visual object moving across a screen and moves a cursor to track its movment – fMRI indicates strong activation in cerebellum – because cerebellum coordinates eye and hand movements E.5.4 Explain sympathetic and parasympathetic control of the heart, movements of the iris, and flow of blood to the gut. • autonomic nervous system: • sympathetic: – fight-flight-excercise • parasympathetic: – restorative, resting, digesting • heart • sympathetic: – heart rate accelerates, pumping more blood to muscles • parasympathetic: – heart rate slows, body relaxes, less blood needed to muscles • blood flow to gut • sympathetic: – blood vessels constricted, decreasing blood flow to gut • parasympathetic: – blood vessels dilated, increasing blood flow to gut 5.5 Explain the pupil reflex. • pupil reflex: when a bright light shines into one eye, the pupils of both eyes normally constrict – – – – – – – – – – retina detects light intensity impulses to brain in optic nerve brain stem/medulla controls the reflex sympathetic system causes dilation parasympathetic system causes constriction sympathetic neurons are in spinal nerve T1 parasympathetic neurons are in cranial nerve III pre- and postganglionic fibers of symp/parasymp neurotransmitters of symp/parasymp polysynaptic reflex Statement 5.6- Discuss the Use of the Pupil Reflex in Testing for Brain Death • If stimulation of the pupil with light fails to cause contraction then it is very likely that the CNS has sustained severe damage and brain death is possible. Statement 5.7- Outline How Pain is Sensed and How Endorphins and Enkephalins can Act as Painkillers. Pain receptors are located in the skin and on organs. Pain signals are sent along these nerve endings along nerve fibers on the spinal cord. The signals pass synapses to neurons that carry them up in an ascending tract to the stem or thalamus of the brain. The signals may pass on in other neurons to sensory areas of the cerebral cortex, causing conscious pain. --Endorphins and enkephalins act as painkillers by stopping the pain signal to the brain. Enkephalins block calcium channels in the membrane of the pre-synaptic neurons. They block the synaptic transmissions, so the message doesn’t reach the brain. Endorphins are released from the pituitary gland to control pain. They are carried to the brain and bind to pain receptors and block the release of the neurotransmitter that is used to transmit pain signals to the brain. Statement 6.1- Describe the Social Organization of Honey Bee Colonies There are three castes of honey bees which have different tasks. The single queen bee of a colony has to lay eggs. The worker bees do jobs that maintain the colony. The drones do nothing to help the colony to survive. However, if they successfully mate with virgin queens, they spread the genes of the colony to new colonies. Workers eject drones from the colony at the end of the season during which virgin queens are available. Statement 6.2- Outline How Natural Selection May Act at the Level of the Colony in the Case of Social Organisms. In the case of social animals, especially colonies, most of the individuals have very similar DNA so their genes are still getting passed down even if they aren't themselves reproducing. So these animals will sacrifice themselves for the greater good of their very close relatives. I.E. prairie dogs on the lookout for predators will make a loud noise warning everyone to get in their holes and by doing this he lets the predator know exactly where he is and will probably get eaten but he has saved a lot of the colony. Lions will give up trying to reproduce and just help their brother/nephew, whatever their relationship is to the dominant male, get as many ladies as possible and protect his young. From this evidence you can see that natural selection does not act on the population or the individual, rather the genes Statement 6.3- Discuss the Role of Altruistic Behavior in Social Organizations Using Two Examples • Wolves - In a pack of wolves, there is a dominant male and female which are the sole reproducers, and the other members of the pack hunt and bring back food for the breeding pair. • Naked Mole Rats - There exist breeding males and females, the diggers (who dig tunnels and provide food) and protectors who offer their lives when facing a predator. The concept is that the sacrifices will indirectly pass on their genes by protecting the mating pair. Statement 6.4- Outline Two Examples of How Foraging Behavior Optimizes Food Intake, Including Bluegill Fish Foraging for Daphnia Spirit Bear • Spirit bears are omnivores whose diet includes plants, insects, living animals and carcasses. During the salmon spawning season, spirit bears gorge themselves on salmon because the salmon provide the maximum calorie supply. When salmon are not available, 80% of their diet consists of plant material because meat is harder to find. • After catching a salmon spirit bears usually carry their fish away from the stream where they can feed in seclusion. If the fish is a female they begin feeding on the belly, which contains fat-rich eggs. They also feed on the brains and certain organs, which are also fat-rich. • The bear’s preference of feeding in seclusion reduces the chances of losing a meal to a rival bear or wasting time fighting the rival. And their preference for high-fat organs ensures that their bellies fill up with organs with the highest energy content. • The spirit bear’s food preferences match foraging theory. Over evolutionary time, natural selection has favored bears that prefer fatty meat because they were able to consume more calories than bears that ate less fatty meat. In bleak years, when competition for food was fierce, bears eating fatty foods would have survived better than individuals consuming lower energy food items. Statement 6.4- Outline Two Examples of How Foraging Behavior Optimizes Food Intake, Including Bluegill Fish Foraging for Daphnia (cont.) • When environmental conditions change, generalist feeders have an advantage over specialist feeders because they can adjust their feeding behavior to optimize their chances of survival. • A good example of this comes from studies on the bluegill sunfish, which feeds on small invertebrates like Daphnia. • When Daphnia is abundant the sunfish can afford to be choosy, and as such they feed exclusively on larger prey items. However, when prey is scarce they must eat whatever food items they can find. • The graphs indicate that average prey size increases as prey density increases. Statement 6.5- Explain How Mate Selection Can Lead to Exaggerated Traits. • • • • • • Evolutionary success means successfully passing on your genes to future generations. In some species evolutionary success has led to the evolution of differences between males and females, a phenomenon called sexual dimorphism. In some species, males have evolved conspicuous or exagerated traits that advertise their reproductive worth. The spectacularly colorful tail feathers of peacocks provide a good example of this. Some studies suggest that peahens choose to have sex with the most colorful peacocks available, and that males with parasites are less brightly colored. The researchers suggest that this color preference of peahens causes them to breed with the strongest, healthiest and least-parasitized males. However, more recent research has disputed a link between feather color and parasitism. These studies suggest that peacocks select males with the loudest vocalizations. So it’s possible that a peacock's color does not indicate health. If this is so then colorful peacock feathers could be an example ofrunaway evolution. In runaway evolution one female develops a whim for a particular male trait that she then passes on to future generations of females. These females start choosing males with the desired trait, which causes that trait to become exagerated in males over time. Thus runaway evolution can lead to to exaggerated traits that don’t really help the species as a whole. The peacock's tail, for example, requires a great deal of energy to grow and maintain, it reduces the bird's agility, and it increases the animal’s visibility to predators. Yet it has evolved, indicating that the advantage of having a longer tail, in terms of getting sex, outweighs the disadvantages. Statement 6.6- State That Animals Show Rhythmical Variations in Activity • Animals show a rhythmic variation in activity as the year passes. Many different animals show their rhythmic variation in the form of hibernation when, annually, the animals decrease in activity drastically during the winter months of the year Statement 6.7- Outline Two Examples Illustrating the Adaptive Value of Rhythmical Behavior Patterns. Krill • Krill are shrimp-like marine invertebrates. They are important sources of food for certain whales, sharks, seals and penguins. • Krill typically follow a diurnal vertical migration. They spend the day at greater depths and rise during the night towards the surface. The deeper they go, the darker the water becomes, and this makes it more difficult for predators to eat them. • The diurnal migrations of krill depend on accurate monitoring of daylight, which is achieved by their circadian system. Insect-eating Bats • The circadian "clock" in mammals is located in a part of the hypothalamus called the SCN. The SCN receives information about daylight from special photoreceptors in the retina. • The SCN sends a message to the pineal gland, a tiny structure in the brain, which secretes the hormone melatonin. Melatonin causes mammals to feel sleepy. In humans, secretion of melatonin peaks at night. • In bats, melatonin peaks in the daytime, which is why they are more active at night? Being active at night is a benefit to bats because they feed on moths, which mainly fly at night. Thus the circadian rhythm of bats helps them to hunt and feed when their prey is most abundant.