OPTION E: NEUROBIOLOGY AND BEHAVIOR

1. OPTION E: NEUROBIOLOGY AND BEHAVIOR Madeleine Kresin

2. Stimulus and Response E.1Definitions E.1.1 Stimulus: change in the environment (either internal or external) that is detected by a receptor and elicits a response Reflex: rapid, unconscious response Response: reaction to a stimulus

3. Stimulus and Response E.1.2Response of Animals to Pain Stimuli: The Pain Reflex Arc • pain receptors receive the stimulus of excessive heat, pressure or chemicals produced by injured tissues • receptors generate nerve impulse in sensory neurons • sensory neurons carry the impulse toward the spinal cord • the sensory neuron's axon enters the spinal cord in the dorsal root and send a chemical message across the synapse to a relay neuron in the gray matter of the spinal cord • the relay neuron then synapses with a motor neuron in the grey matter in the ventral root of the spinal cord, and carries the impulse to an effector - organ that performs the response • in addition, the animal exhibits physical changes (growling etc.), because the spinal cord nerves carry impulses to the brain, and as the brain becomes aware of what is happening, it coordinates physical manifestations (growling)

4. Reflex Arc Diagram E.1.3

5. Effects of Natural Selection E.1.4 • Moth Population Variation in Behavior • in environment with dark tree bark, the moth population is primarily darker colored - light moths are more easily spotted by birds; in environment with lighter tree bark (i.e. with large lichen population), the population is primarily lighter colored

6. Effect of Natural Selection E.1.4 • European Blackcaps Variation in Behavior • traditionally breed in Germany in spring and summer and winter in Spain; 50 years ago it was observed that UK blackcaps left 10 days earlier in winter to return to Germany than the Spanish blackcaps and the earlier the birds arrived in Germany, they had more choice of territory and laid more eggs; warm UK winters increase bird survival rate; change in migration patterns may eventually result in a new species - especially likely if small changes in courtship behavior occur • Experiment: UK eggs and Spanish eggs collected; all were reared but had no parents to teach young which direction to fly, but UK eggs and Spanish eggs still flew respectively -they are genetically programmed to fly in a certain direction

7. Effects of Natural Selection E.1.4 • Sockeye Salmon Variation in Behavior • introduced into Lake Washington and over 60 years there have been 13 generations; some migrated to Cedar River (flows into lake), and some stayed in the lake, which is deep and quiet; DNA evidence shows that lake and river salmon have stopped interbreeding • lake salmon spawn on beaches - females lay eggs in sand, and males have heavy bodies for hiding in the deep lake waters, but are thus less efficient at navigating fast currents • river salmon females bury eggs deep in sandy river bottom, males are thinner and narrower for better maneuverability in the current, but can't spawn on the beach

8. Perception of Stimuli E.2Sensory Receptors and Diversity of Stimuli: E.2.1 • Mechanoreceptors: stimulated by mechanical force or pressure; sense of touch due to pressure receptors, arterial pressure receptors detect change in blood pressure; lung stretch receptors respond to degree of lung inflation; proprioceptors in muscle fiber, tendons, joints and ligaments maintain posture and balance; inner ear pressure receptors are sensitive to waves of fluid moving over them - equilibrium • Chemoreceptors: stimulated by chemical substances - taste and smell; arterial chemoreceptors monitor pH changes, which signal the body to adjust breathing rate; pain receptors respond to chemicals released by damaged tissues, which protects us from danger - pain reflex • Thermoreceptors: stimulated by change in temperature; warmth receptors respond when temperature rises, cold receptors respond when temperature drops • Photoreceptors: stimulated by light energy; in eyes - sensitive to light; rod cells respond to dim light resulting in black and white vision, while cone cells respond to bright light and give color vision

9. Structure and Function of Human Eye E.2.2

11. The Retina E.2.3 • vision begins when light enters eye and is focuses on retina photoreceptors cells - rods and the cones; rods and cones synapse with their own bipolar neurons, each of which synapses with a ganglion cell - axons of ganglions make up optic nerve • Rod Cells: photoreceptor cells which are very sensitive to light; receive stimulus of light and synapse with bipolar neuron • Cone Cells: photoreceptor cells activated by bright light; receive stimulus and synapse with bipolar neuron • Bipolar Neurons: retina cells which carry impulses from rod or cone to ganglion cell of optic nerve; each have two processes extending from cell body • Ganglion Cells: cell bodies of optic nerve - synapse with bipolar neurons and send impulses to brain

12. Rod Cells v. Cone Cells E.2.4

13. Processing Visual Stimuli E.2.5 • light rays pass through pupil and are focused by cornea, lens, and humors; image focused on retina is upside-down and reversed left to right; once retina photoreceptors are stimulated, they send impulses to bipolar neurons and ganglion cells - ganglion cell axons travel to visual area of cerebral cortex, where the position of image is corrected and is coordinated for images coming from left and right eye

14. Processing Visual Stimuli E.2.5 Edge Enhancement • perception of grey blobs in white area between black squares vanishes when looked at directly because areas where perceived gray are in peripheral vision where there are fewer light-sensitive cells than in fovea - some cells present may even be 'turned-off', sending the message of gray rather than white, but when the gray blobs are looked at directly, the fovea, with a high concentration of light-sensitive cells, is being used, so that even if some are 'turned-off', it is still perceived white • figure 'fools' the eye because of extreme contrast between black and white edges - demonstrates that there is a special mechanism for seeing edges; light-sensitive receptors in eye switch off neighboring receptors, making edges look more distinct because of extreme contrast between dark and light

15. Processing Visual Stimuli E.2.5Contralateral Processing • nerve fibers bringing information from right half of each visual field converge at optic chiasma and pass to left side of the brain; nerve fibers bringing information from left half of each visual field converge at optic chiasma and pass to right half of brain; information eventually ends up in visual cortex, and since each visual area only gets half the information from each field, the areas must share information to form a complete visual image - image received by cortex is both inverted and reversed, and so brain must correct image; impulses relating to the other stimuli - color, form and motion are parcelled out to other visual association areas of brain, and eventually the cerebral cortex rebuilds all parts into a cohesive whole

16. Structure of the Human Ear E.2.6

17. Perception of Sound By Human Ear E.2.7 • Outer ear catches sound waves - successive vibrations of air molecules, which, when travelling down auditory canal, cause eardrum (tympanic membrane) to move back and forth slowly • Malleus, incus and stapes all receive vibrations from tympanic membrane and multiply them 20X; stapes strikes oval window, causing it to vibrate, which passes to the fluid in the cochlea, causing special cells - hair cells - to vibrate; hair cells release chemical message across a synapse to the sensory neuron of the auditory nerve, stimulating the sensory neuron, which is then carried by sensory neuron in auditory nerve to brain; wave in fluid of cochlea dissipates as it reaches round window • Loud noises cause fluid to vibrate to a higher degree and hair cells bend more - interpreted by brain as higher volume; pitch is a function of sound wave frequency - short, high-frequency waves produce high-pitched sounds while long, low-frequency waves produce produce low-pitched sounds; sound which is sensed by brain is processed in auditory area of cerebral cortex

18. Innate and Learned Behavior E.3Innate v. Learned Behavior E.3.1 • Innate Behavior: develops independently of environmental context; no trial-error learning; controlled by genes and inherited from parents; genetically programmed behaviors which ensure animal survival; some are performed in a certain order (i.e. mating behavior); example: male 3-spined stickleback does a zigzag dance when he sees the female, attracting her attention; she follows male as he leads her to the nest constructed in the bed of the river, where he backs out of the nest and she enters; he vibrates his body at nest entrance and female releases her eggs; she leaves nest and male enters; he releases sperm cells that fertilize eggs

19. Innate v. Learned Behavior E.3.1 • Learned Behavior: not genetically programmed; results in new knowledge not previously existent or new skill not originally possessed; process of gaining new knowledge or skills or modifying existing knowledge or skills; learning measured by performance - rat that learns by pressing a pedal, food is released, rate originally pressed pedal by accident during exploration of cage, and after pellet of food was released over and over again, rat learned to associate food with pedal, and later pushing pedal to get food becomes deliberate act

20. Innate v. Learned Behavior E.3.1

21. Innate Behavior in Invertebrates E.3.2 • Taxis: directed response to stimulus; positive response: animal's body is moved toward the stimulus; negative response: animal moves away from stimulus • Chemotaxis: response to chemicals in environment; organisms in water can move toward or away from food / other chemicals which are dissolved in their aquatic medium • Phototaxis: response to light - different wavelengths and intensities of light • Gravitaxis: response to gravity • Rheotaxis: response to water current • Thigmotaxis: response to touch • Planaria: flatworm in lakes; move by contraction of muscle fibers, simple nervous system at have 2 eyespots at anterior end which have photoreceptors and chemoreceptors; negatively phototaxic and positively chemotaxic - could be tested for response to temperature gradient • Euglena: protoctist; flagellum propels it through water, anterior eyespot; positively phototaxic (needs light for photosynthesis) - could be tested for wavelengths of light

22. Innate Behavior in Invertebrates; Kinesis E.3.2 • movement in response to non-directional stimulus; rate of animal movement depends on intensity, not direction, of stimulus; does not move toward or away from stimulus, if in an uncomfortable environment, it moves rapidly and randomly until in a more comfortable 'zone' • Orthokinesis: organism changes speed in response to stimulus but doesn't move toward stimulus • Klinokinesis: organism turns slowly or rapidly in response to stimulus but doesn't move toward stimulus • Isopods: live on land but breathe with gills, so live in damp places; when placed in damp environment, they move slowly, in dry environment, move rapidly; their exoskeleton lacks a waterproof waxy cuticle, so it is highly subject to desiccation - quick random movements enable isopod to find itself in a humid environment, ensuring survival and enhancing ability to reproduce; favored by natural selection

23. Learning Improves Chance of Survival E.3.4 • Imprinting: process by which young animals become attached to their mother within first day after birth - assures that young stay close to their mother for protection and food source • food hoarding • birdsong for reproduction and territorial claims • false learning through mimicry of prey (butterflies and snakes)

24. Pavlov and Conditioning E.3.5 • Classical conditioning: can be used to modify reflex response; subject responds to stimulus in a new way • blinking - waved hang experiment is the UCS because it unconditionally stimulates eye-blink response; possible to then elicit reflex response with neutral stimulus (musical note); eventually subject responds with eye-blink to musical note and note is the conditioned stimulus and the eye-blink is the conditioned response • Pavlov: UCS of food elicits UCR of salivation; Pavlov employed ringing of a bell as his neutral stimulus, and so that he could eventually ring the bell - the conditioned stimulus, and the dog would salivate - the conditioned response; dog learns to salivate to neutral stimulus alone

25. Birdsong in Young Birds E.3.6 • birds sing through syrinx - bony structure at bottom of trachea; air forces past membrane in syrinx causes syrinx to vibrate and results in sound - pitch controlled by altering tension in syrinx membrane; volume controlled by altering air flow • singing important for male - reproduction and warning • birds hatch with a crude template: template inherited, and all next steps of development are learned: • memorization phase: bird is silent but listens to adult songs of his species (modifying inherited template); over at about 100 days of age - the sensitive period • motor phase: bird practices singing, hears his own singing and begins to shape song to match what he has heard from his father - bird must hear his own song in order to sing accurate adult song; as he becomes sexually mature, his song will become perfected and he will begin to search for a mate

26. Synaptic Transmission E.4.1 • excitatory neurotransmitters stimulate next neuron by increasing permeability of postsynaptic membrane to positive ions • inhibitory transmitters cause positive ions to move out of postsynaptic cell; movement of positive ions back into cleft chemically depresses postsynaptic cell and makes it harder to excite the postsynaptic cell

27. Decision Making in the Central Nervous System E.4.2 • as action potential reaches terminal, calcium ions rush in, causing vesicles containing neurotransmitters to fuse with presynaptic membrane and exocytose into the synaptic cleft, where they then bind to specific receptors on postsynaptic membrane • Excitatory Neurotransmitters: e.g. acetylcholine; increase permeability of postsynaptic membrane to sodium ions in the cleft to diffuse into the postsynaptic neuron, locally depolarizing it by the influx of sodium, so that there is a net positive interior charge compared to the outside; depolarization continues along the axon; threshold must be met to continue • Inhibitory Neurotransmitters: e.g. Gaba; causes hyperpolarization of neuron - making inside more negative, so that it is more difficult to generate an action potential

28. Psychoactive Drugs Affect Brain and Personality E.4.3 • Acetylcholine, if left in synapse, would fire indefinitely; this is prevented by acetylcholinesterase - breaks down acetylcholine in synapse • Cholinergic Synapses: use acetylcholine; i.e. nicotine stimulating transmission in cholinergic synapses calms body and personality; parasympathetic • Adrenergic: use noradrenaline - depolarizes postsynaptic neuron; e.g. cocaine and amphetamines - increased alertness, energy and euphoria; sympathetic

29. Psychoactive Drugs Affect Brain and Personality E.4.3 • excitatory drugs (nicotine, cocaine, amphetamine), increase nerve transmission while inhibitory drugs (benzodiazepines, alcohol, THC) decrease likelihood of nerve transmission • block receptor for neurotransmitter (drug has similar structure to neurotransmitter) • block release of neurotransmitter from presynaptic membrane • enhance release of neurotransmitter • enhance neurotransmission by mimicking neurotransmitter (when drugs have same chemical structure as neurotransmitter, have same effect but aren't broken down as easily so effect is stronger because they stay longer in synapse) • block removal of neurotransmitter from synapse and prolong effect of neurotransmitter

30. Excitatory v. Inhibitory Drug Action E.4.4 EXCITATORY • Nicotine: mimics Ach; acts on cholinergic synapses of body and brain to cause calming effect; after Ach is received by receptors, it is broken down by acetylcholinesterase but it can't break down the nicotine molecules (because they bind to same receptors), exciting postsynaptic neuron, which begins to fire, releasing dopamine - molecule of reward pathway; addiction • Cocaine: stimulates transmission at adrenergic synapses, causing alertness, euphoria, and dopamine release; blocks dopamine removal from synapse leading to buildup of dopamine, leading to over-stimulation of postsynaptic neuron (since its the reward pathway, it leads to euphoria); addiction • Amphetamine: stimulates transmission at adrenergic synapses and gives increased energy and alertness; passes directly into nerve cells which carry dopamine and noradrenaline, directly into vesicles of presynaptic neuron and causes their release into the synaptic cleft; normally these neurotransmitters would be broken down in the synapse, but the amphetamines interfere with breakdown, so there's high concentrations of dopamine in the synapse, causing euphoria, and high noradrenaline concentrations may be responsible for alertness and high energy

31. Excitatory v. Inhibitory Drug Action E.4.4 INHIBITORY • Benzodiazepine: reduces anxiety and can be used against epileptic seizures; modulates GABA activity; when GABA binds to postsynaptic membrane, Benzodiazepine increases binding of GABA to receptor, causing postsynaptic neuron to become more hyperpolarized (release of chloride ions into neuron, resisting firing) • Alcohol: increases GABA binding to postsynaptic membrane to cause neuron to become hyperpolarized - sedative effect of alcohol; decreases glutamate (excitatory neurotransmitter) activity and increases dopamine release and stops enzyme activity of breaking down dopamine in synaptic cleft (more reward pathway) • Tetrahydrocannabinol: main psychoactive chemical in marijuana; mimics anandamide by binding to same receptor (cannabinoid receptor); THC is an inhibitory neurotransmitter and causes postsynaptic neuron to be hyperpolarized; disrupts short-term memory

32. Effects of THC and Cocaine on Synaptic Action E.4.5 • THC: dilates pupils, causing color perception to be more intense, sense enhancement (panic / paranoia); cannabinoid receptors affect learning, coordination, problem solving, and short-term memory; since it mimics anandamide, it inhibits neurons that anandamide inhibits but it has a much greater effect because there's no enzyme breaking down THC in the synapse; when THC binds to cannabinoid receptors in hippocampus, it interferes with short-term memory; when THC binds to cannabinoid receptors in cerebellum and basal ganglia, it affects coordination - motor impairment • Cocaine: euphoria, talkativeness, increase in mental alertness; temporary decrease in need for food and sleep, later erratic and violent behavior; synaptic effect of cocaine is from its ability to sustain dopamine level in synapse - the reward pathway

33. Causes of Addiction E.4.6 • Genetic Predisposition: found in twin studies (when one twin suffers alcohol / drug addiction, the other twin's rate of addiction is 50% greater among identical twins than fraternal twins) • Social Factors: family addiction, family parenting skills and mental health problems of family / child; peer pressure; cultural introductions • Dopamine Secretion: in drug addiction, dopamine receptors are constantly stimulated, and over-stimulation decreases receptor numbers and remaining receptors become less sensitive to dopamine (desensitization), so that exposure to drug causes less response so more and more is required; glutamate may 'oversee' learning and memories which lead to cocaine seeking

34. Structure and Function of Human Brain E.5.1 and E.5.2

35. Structure and Function of Human Brain E.5.1 and E.5.2 • Cerebral Hemispheres: act as integrating center for high complex functions (learning, memory, emotions), and are associated with intelligence, personality, sensory impulses, motor function, organization and problem solving • Hypothalamus: maintains homeostasis, coordinating nervous and endocrine systems, secreting hormones of posterior pituitary and releasing factors regulating the anterior pituitary • Cerebellum: has two hemispheres and highly folded surface; coordinates unconscious functions (movement and balance) • Medulla oblongata: controls automatic and homeostatic activities (swallowing, digestion, vomiting, breathing and heart activity) • Pituitary Gland: posterior lobe stores and releases hormones produced by hypothalamus and anterior lobe, produces and secretes hormones regulating body functions

36. Identification of Brain Parts Involved in Specific Functions E.5.3 • Brain Lesions: lesions in identifiable areas of brain tell indirectly about function of those areas; some lesions which have been studied occur in either right or left half and give information about difference between halves • Right and Left Hemispheres: connected by thick band of axons - corpus callosum; Left: contains areas important for communication; LH damage may result from stroke, and after damage there's difficulty in speaking or using complicated hand / arm movement; Right: specializes in receiving and analyzing information coming from senses; people with lesions in RH have problems identifying faces and locating an object correctly in space • Experiments: • mid 1800s - people with injuries on left side had speech and language problems; on right side no language problems; injury to Broca's area interferes with ability to vocalize words, injury to Wernicke's area affects ability to put words into sentences • 1960s - study of group with severed corpus callosums to relieve epilepsy; already knew that input from right visual field is received by LH and vise versa; projected picture of spoon onto right side of card with dot in middle; split-brain looking at dot and spoon picture is flashed up, visual information about spoon crosses optic chiasma and ends up on LH - can identify and say 'spoon'; if projected on left side of dot, information goes to RH - no language ability, so the person will say that nothing is seen, when asked to pick up spoon with left hand, they correctly pick it up and information travelled to RH understands what a 'spoon' is even if they can't verbalize it • use chimerical picture to test split brain patients - when focusing on dot, information about woman's face will travel to R cerebral H and the information about man's face will go to LcH; if asked to look at pictures of complete, normal faces and point to face they have just seen, they will choose picture of woman (information of 'woman' went to RH), but if asked whether it was a man or woman, they say it's a man (side of brain that dominates will depend on what patient is asked to do - facial recognition does not require speech, and so RcH dominates

37. Identification of Brain Parts Involved in Specific Functions E.5.3 • fMRI: uses radio waves and strong magnetic field to enable scientists to see blood flow in brain as it's occurring; can produce new image every second and can determine with some precision when regions of brain become active and how long they remain active - possible to determine if brain activity occurs in same region or different regions all at same time as patient responds to experimental conditions; PET scanner is slower but can identify areas of brain activated by neurotransmitters and drugs; fMRI can determine: plan for surgery, treatment for stroke, placement of radiation therapy for brain tumor, effects of degenerative brain disease (i.e. Alzheimer's), diagnosing how a diseased or injured brain is working • Animal Experiments: • animal trained to press lever to get reward • animal is given injection of addictive substance as it pushes lever (self-administration required) • two levers must be available - one which gives substance and one which doesn't • if substance is reinforcing, animal will seek to repeat experience by pushing lever more frequently - supports hypothesis that substance is addictive

38. Sympathetic v. Parasympathetic Control E.5.4 • Central Nervous System: brain and spinal cord • Peripheral Nervous System: somatic system (takes sensory information from sensory receptors to CNS and then sends back motor commands from CNS to muscles - pain reflex arc) and autonomic system (involuntary and regulates gland, smooth muscle and heart activity) divided into sympathetic and parasympathetic systems

40. The Pupil Reflex E.5.5 • after closing and suddenly re-opening eyes, the pupil closes in response to sudden input of light as eyes open - cranial reflex (sensory and motor neurons connect in brain rather than spinal cord) • in eye, iris surrounds pupil (opening over lens); iris has two sets of smooth muscle that open and close pupil; pupil closes by parasympathetic response caused by acetylcholine; atropine stops acetylcholine action; constriction of pupil due to motor neuron causing circular muscle to contract and radial muscle relaxes • Pupil Reflex: • optic nerve receives messages from retina in back of eye (retina contains photoreceptors which receive light stimulus; synapse with bipolar neurons and then with ganglion cells - nerve fibers of ganglion cells become optic nerve) • optic nerve connects with pretectal nucleus of brain stem • from pretectal nucleus, message is send to Edinger-Westphal nucleus, whose axons run along oculomotor nerves back to eye • oculomotor nerves synapse on ciliary ganglion • axons of ciliary ganglion stimulate circular muscle of iris so it contracts

41. Brain Death E.5.6 • "That time when a physician has determined that the brain and brainstem have irreversibly lost all neurological function" - artificial maintenance of body without impulses which normally come from brain • Examination for Brain Death: movement of extremities: if arms / legs are raised and let fall, there must be no other movement or hesitation in fall; eye movement: eyes must remain fixed showing lack of brain-to-motor-nerve reflex; corneal reflex: must be absent - when cotton swab is dragged over cornea, eye doesn't blink; pupil reflex: must be absent - pupils don't constrict in response to very bright light shone into both eyes; gag reflex: must be absent - insertion of small tube into throat of comatose patient causes gag reflex; respiration response: must be absent - if patient is removed from ventilator, brain gives no response; EEG - measures brain activity in microvolts - lack of electrical activity is the electrocerebral silence; CBF: radioactive isotope is injected into bloodstream, radioactive counter is then placed over head for 30 minutes - if no activity is detected, conclusive evidence of brain death • in brain dead person, there can still be spinal reflexes - knee jerk response, short reflex motion can still be exhibited if hand / foot is touched in certain manner

42. Perception of Pain and Effect of Endorphins E.5.7 • pain signals are carried by peripheral nerve fibers from all around body to spinal cord and relayed to brain sensory area, which connect with nocioreceptors - sense excess heat, pressure or chemicals from injured tissues, nerve impulses of pain travel to spinal cord - ascending tracts in spinal cord send messages up brain; message of pain travels to cerebral cortex - receives message of pain from spinal nerves and directs body to respond by: telling muscles to stop action which is causing pain stimulus, alert autonomic nervous system if pain requires change in heart rate / breathing, can direct other brain cells to release pain-suppressing endorphins • Endorphins are CNS neurotransmitters with pain-relieving properties; small peptides which bind to opiate receptors and block transmission of impulses at synapses involved in pain perception

43. Social Organization of Honey Bee Colonies E.6.1 • nest above ground inside hollow tree, make wax combs with individual compartments for storing honey and rearing young; each hive has queen who lays eggs, female workers are sterile and search for nectar / pollen, make wax / honey, and feed / protect the young; workers live for 6 weeks, queens live for 2 years, male drones develop from unfertilized eggs, and mating with the queen is their only function • queen lays eggs in cells of honeycomb; if eggs are unfertilized they develop into males no matter what they are fed, but if fertilized and female, type of food they are fed as larvae determines whether they will become a worker or a queen - eggs develop into larvae and are fed royal jelly (glandular secretions) for the first few days, workers then switch larvae destined to be workers to less nutritious diet of honey and pollen, but if queen is needed, larvae destined to be queen are fed royal jelly their whole development • queens control hive with pheromone secretion - inhibit ovarian development in workers (workers lick pheromone from queen's body and pass it onto other workers during food exchange) • chemical secreted from abdomen tip of one bee is used to identify source of nectar / water for others; some bees scout out source of nectar and waggle to indicate direction and distance of source, another chemical is released from mouth area when colony is in danger and signal is spread to others

44. Social Organization of Honey Bee Colonies E.6.1

45. Social Organization in Chimpanzees E.6.1 • highest order of society is the community - typically made up of 40-60 members; smaller group within community is the party - up to 5 members, party may be all male, family unit, or nursery unit (makeup of parties depends on food supply - the more food there is, the larger the groups which travel together) • highest ranking male is 20-26; dominance determined by physical fitness and fighting ability; dominance hierarchy in females linked with age (older females dominant over younger females); strong social bonds exist between males because they are related to each other - males stay in same community where they were born, while females may migrate to other communities • male bonding leads to cooperative behavior needed to keep out intruders, hunt together and share food; parental care is responsibility of mother and is crucial to infant survival; young chimpanzees receive food, warmth, protection and learn skills from their mothers • communication includes facial expressions and vocalizations

46. Social Organization in Chimpanzees E.6.1

47. Natural Selection at the Level of the Colony E.6.2 • natural selection in the case of social organisms is acting on colony as a whole; genes which are selected are those who promote social organization, for pheromones which control worker behavior, for behavior of finding nectar and making wax, for taking care of young all are selected; all females have these genes and it is just a matter of chance which female is fed the royal jelly to become the queen; workers, even though sterile, are ensuring survival of their own genes

48. Evolution of Altruistic Behavior E.6.3 • Belding's Ground Squirrel: when predator approaches, one of ground squirrels gives high-pitched call which alerts the rest of the population to nearby danger; alarm squirrel is more likely to be killed than the other squirrels in the population because the alarm call gives away the location of the caller to the predator; alarm calls are predominantly performed by females, which live closer (than the males) to their relatives - females sacrifice themselves so that their close relatives can reproduce; if all female's close relatives are dead, she doesn't sound alarm calls; altruistic behavior increasing representation of its genes in the next generation since it shares genes with its relatives • Naked Mole Rats: workers excavate and extend their burrows, and make nesting chambers and forage for food; worker bites off part of tuber and brings it to queen, larger workers stay near queen and her young, and queen suppresses sexual behavior of other females and of males except when she is ovulating; when snake attacks burrow, queen sends out workers to attack snake - workers are sacrificed so that queen and her young can live; developed this lifestyle because the soil is hard and dry and food is scarce - pair of naked mole rats couldn't survive on their own, but colony with altruistic behavior survives well; naked mole rats are almost genetically identical

49. Evolution of Altruistic Behavior E.6.3

50. Foraging Behavior Optimizes Food Intake E.6.4 • Smallmouth Bass: can forage for either minnows (more energy per unit) or crayfish (easier to catch); minnows are easier to digest than crayfish - exoskeleton; smallmouth bass switch from minnows to crayfish and back again in order to keep energy that they take in higher than the energy they expend; since no preference is shown for either minnows or crayfish, each may be optimal under different conditions • Bluegill Sunfish: eats Daphnia - small crustaceans which are found in varying sizes; bluegills forage for larger Daphnia - the most energy, but will select smaller Daphnia if larger ones are too far away; when density of Daphnia is low, bluegill won't be selective as to size when foraging, but when there's high density, they become more selective and choose larger Daphnia; young bluegill sunfish don't feed as efficiently as older sunfish, not clear it that's due to lack of ability to see size of Daphnia correctly or if it's due to learning that takes place as they mature