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Compare rod and cone cells.(3)
- rod, cone
- sensitive to low light specialized (more bleached in bright;
- not as sensitive to bright light (color specialized)
- sensitive to all wavelengths (monochrome vision);
- three types cells sens to red, green, blue light = color vis
- groups rods send info to single nerve fibre in optive nerve;
- passage fr single cone cell to single nerve fibre (higher visual acuity)
- wider FOV absent in fovea;
- less inretina more in fovea = smaller FOV
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Explain the processing of visual stimuli,
- visual process stimuli begins in retina
- response o each point on retina infl by neighbouring regions
- each ganglion cell receives signals fr rods and cones in certain area retina = receptive / visual field
- visual fields = circular with round centre and surround
- when light falls on photoreceptor, responds by firing more freq and inhibits adjacent cells fr firing = lateral inhibition
- r
eceptive field on retina can be drawn representing excitatory ganglia in centre, inhibitory ganglia on peripheries (on centre off surround)draw pic / annotate - + in centre, - in surround
- off: ganglion decrease neural activity less freq firing with more light , more light = more inhibitory
- center: excitatory, increase with neural activity more freq firing with more light
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edge enhancement
- edge enhancement occurs within retina and can be demonstrated with hermann grid illusion
- purpose is to provide a greater contrast at the edges of objects
- lateral inhibition makes neighborhood dark objec appear lighter, vice versa
- retina uses contrast instead absolute light intensity to recog objects
- hermann grid = ganglion cells aimed at intersection has greater proportion inhibitory surround stimulated by white strips -> more inhibited than cells above and image = grey due to lower excitation
- in pathways: smaller prop inhibitory surround stimul by light, less lateral inhibition @ centre, area = white
- vice versa in centre of squares (eyes scanning)
- if stare on centre, visual fields in fovea smaller than other parts retina
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contralateral processing
- -way in which the brain collects and integrates information from the eyes to create the perception of seeing
- -Bipolar cells in retina combine the impulses fr rod or cone cells and pass them onto sensory neurons o optic nerve
- -Axons o ganglion cells form optic nerves tt carry sensations fr eyes to brain
- -Optic nerves fr two eyes meet at optic chiasma near centre o base o cerebral cortex
- -due to optic chiasma, right brain processes info fr left visual field vice versa
- -optic nerves form synapses in the lateral geniculate nucleus with neurones from the primary visual cortex
- -brain is able to integrate the 2 dimensional information of the retina back into a 3 dimensional perception
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Label a diagram of the ear.
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Explain how sound is perceived by the ear
incl roles eardrum, bones middle ear, oval and round windows, hair cells cochlea (4)
- Eardrum(tympanum): Sounds waves =vibrate, ear drum move rapidly toward and away fr middle ear; eardrum picks up sounds vibrations fr air and transmits them to middle ear
- Bones o middle ear: Series o 3 small bones (ossicles) in middle ear, each touches next, role= transmit sound waves fr eardrum to oval window; role in sound amplification, both tympanum + ossicles increase force at oval window
- Oval and round windows: OW =membranous structure tt transmits sound waves to fluid o cochlea; fluid is incompressible, a second membranous window is needed (round window), when oval window moves toward cochlea, round window moves away fr it, so fluid in cochlea can vibrate freely w/o changing volume
- Hair cells: Cochlear tube has membr w/ receptors =hair cells, have hair bundles attached, stretch fr one membrane to another-when sound waves pass through cochlea, hair bundles vibrate, resonating with particular frequency; allows for detection o diff freq o sound, when vibrate, hair cells send msgs across synapses and on to brain via auditory nerve
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Describe the social organization of honey bee colonies and one other non-human example.
- social animals live in groups, interaction behavior = social behviour
- live in colonies up to 60k bees, = super organism tt lives or die together, can reprod to form more colonies by swarming
- 3 castes
- queen: 1, fertile fem lays eggs, produces pheromone to control activ workers + attract drones, mates once perhaps w/ several drones and stores sperm
- drones: fee hundred short lived, fertile males who do nothing to help colony survive, main task = mating, near end season ejected fr colony so mate w/ other queens + spread colony's genes
- workers: infertile females who do all work, collect nectar / pollen, convert pollen = honey, secrete wax for comb, feed and tend larvae, guard hive
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need to know dance bees communication?
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social organization naked mole rat colonies
- live in colonies of up to 80 individuals, in burrow systems in parts of East Africa.
- One dominant female mole rat acts like a queen bee = only female in the community to reproduce, mating with one males
- 'Frequent workers' dig the tunnels and bring food.
- Infrequent workers' are larger and occasionally help with heavier tasks.
- 'Non-workers' live in the central nest, keeping the breeding female and her young offspring warm and defending the colony if it is attacked.
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Outline how natural selection may act at the level of the colony in the case of social organisms.
- natural selection: Individuals who survive to reproduce pass on their genes into the next generation = Successful genes = more frequent in the population.
- colony = super organism
- either colony as whole survives and reprod or entire colony dies, no genes passed on
- indiv cannot survive alone
- natural selec allows for survival and reproduction only at colony lvl
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Discuss the evolution of altruistic behaviour using two non-human examples.
- darwinian fitness = contribution indiv makes to gene pool o next gen relative to contribu o other indiv
- altruistic behav = when harmful to self , but helpful to another
- honeybees when worker dies while defending colony or feeding larva when it is not parent
- naked mole rats when workers dig food and bring back to feed queen + soldiers, defend colony against invading snake
- altruistic behav explained by fact tt indiv colony closely genetically related, so helping rear off or protect = ensures survival own genes
- parental care not considered alt b/c increases fitness indiv showing
- vamp bats regurgitat blood to feed bat tt hasn't fed
- reciprocal altruism = benefit group, might get back
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Outline two examples of how foraging behaviour optimizes food intake, including bluegill fish foraging for Daphnia. / starling
- Defn: animals search for food=foraging.
- Animals optimize food intake by foraging
- Bluegill sunfish live in ponds, prey on small invertebrates, incl Daphnia
- When low density of prey, bluegill sunfish consume all sizes of them.
- At medium prey densities, bluegill sunfish consume only prey of moderate or larger sizes.
- At high prey densities they mostly consume large prey, some medium size.
- Consuming small numbers of large prey takes less energy than otherwise, hence the preference for large prey.
- At low prey densities, smaller prey have to be eaten as well, to get enough food in total.
- Starlings birds feed young mainly with crane-fly larvae
- Obtain by probing into soil w/ beak= less efficient at probing for larvae, as number held in their beaks increases
- Fewer journeys back to the nest, the less time and energy is used in transporting the larvae to the offspring
- Optimum number larvae to catch and carry back to the nest depends on the distance between the foraging area and the nest
- As the distance increases, the optimum number (total number) of larvae increases.
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Explain how mate selection can lead to exaggerated traits.
- Exaggerated traits inclu peacock tails
- Some species of animal have characteristics or behaviour patterns that seem to be developed excessively
- The long and brightly coloured tail feathers of a peacock = only used during courtship, to try to attract a female
- Other times, the tail feathers = encumbrance, hindering rapid movement, especially during attacks by predators.
- may be the explanation for the evolution of an exaggerated trait: any individual that survives, despite the exaggerated trait, must be well-adapted in other so is a good mate to choose
- e.g. lion’s mane
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animals show
animals show rhythmical variations in activity
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Outline two examples illustrating the adaptive value of rhythmical behaviour patterns.
Many animals show rhythmical patterns, usually follow either a diurnal (daily) or an annual (yearly) cycle.
- 1. Moonrats = nocturnal. Live in Asia, lowland forests and mangroves.
- excellent sense of smell = forage at night when much of their prey is active
- -insects and other invertebrates
- Less vulnerable to predation at night, day they rest in holes among tree roots or in hollow logs, where unlikely discovered.
- 2. Red deer Reproduction follows annual cycle in red deer
- Males/females sexually active in fall (autumn)
- Males fight to establish dominance over groups of females
- Advantage is that if the females start gestation in the fall, the offspring are born in spring.
- Most food available in spring/ summer for feeding offspring
- Type of season breeding gives the offspring the greatest chance of survival.
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state that some presynaptic neurons
excite pos-synaptic transmission and others inhibit post-synaptic transmission
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Explain how decision-making in the CNS can result from the interaction between the activities of excitatory and inhibitory pre-synaptic neurones at synapses.
- Summation: effect produced by release o both excitatory and inhibitory neurotransmitters fr two or more presynaptic neurons into synapses associated w/ single postsynaptic neuron;
- at the postsynaptic membrane, production o action potential depends upon summative effect reaching threshold lvl for tt neuron.
- inhibitory neurotransmitters import. =prioritizing sensory information reaching brain, allowing background sensory information to be ignored
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Explain how psychoactive drugs affect the brain and personality by either increasing or decreasing post-synaptic transmission.
- post-synaptic membrane contains receptors for the normal neurotransmitters. Normally when the neuro transmitter attaches to these receptors it either:
- Depolarise the post synaptic neurone resulting in an action potential
- Hyperpolarise the post synaptic neurone resulting in no action potential
- drug can therefore change post synaptic output by:
- Blocking or enhancing the depolarising neurotransmitter
- Blocking or enhancing the hyperpolarise neurotransmitter
- Psychoactive drugs are those that alter the state of mind by changing (stopping or enhancing ) the activity at the post synaptic neurone.
- Psychoactive drugs characteristically create either calm or excite moods.
- excitatory psychoactive drugs: increase synaptic transmission by promoting synaptic transmission at excitatory synapses, or inhibiting transmission at inhibitory synapses
- Inhibitory psychoactive drugs: decrease synaptic transmission opp o above
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List three examples of excitatory and three examples of inhibitory psychoactive drugs.
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