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PRACTICE QUESTIONS

ANIMAL BEHAVIOR TEST I

(Answers are given below the questions)

FOR EVERY STATEMENT THAT FOLLOWS EACH OF THE QUESTIONS, INDICATE IF IT IS TRUE OR FALSE AND THEN JUSTIFY YOUR ANSWER. IF YOU THINK A STATEMENT IS FALSE, EXPLAIN WHAT YOU BE NECESSARY TO MAKE IT TRUE. BE SURE TO ADDRESS EACH POINT RAISED IN EACH STATEMENT. BE SURE TO REFER TO THE APPROPRIATE PARTS OF THE DIAGRAM OR WRITTEN INFORMATION ABOVE IN YOUR JUSTIFICATIONS. YOU MUST JUSTIFY EACH ANSWER, WHETHER TRUE OR FALSE. IT IS POSSIBLE FOR ALL ANSWERS TO BE TRUE OR FALSE.

1. The sea slug, Triatonia, is preyed upon by starfish. When detecting starfish odor, Triatonia performs an escape response. This consists of alternate contraction and relaxation of the muscles on either side of the body, which results in the slug swimming away. Only starfish odor triggers the escape response. Once this escape response is released, it can run to completion without sensory feedback.

The neural circuitry for the escape response is diagramed below. Sensory neurons (SN) in the skin respond only to starfish odor. These synapse onto the giant interneuron (GI), and have the indicated transmission ratio. The GI synapses onto a group of interneurons that once stimulated produce the entire escape response. The GI is capable of releasing the escape motor program alone, even if it is the only neuron firing. The group of interneurons will produce the entire escape response when stimulated, even if dissected out of the slug's body and receiving no other inputs. There are stretch receptors (SR) in the muscles that influence muscle contraction as diagramed (SRs occur in all muscles, but are shown for only the first pair.) The SRs fire only if there is extra contraction in the muscles, such as may occur if the animal needs to temporarily push harder against a sudden change in water current.

(link to diagram)

Based on this information, assess each of the following statements.

a. The 8:1 transmission ratio between the SNs and the GI serves no adaptive function.

b. There is no evidence that a command neuron is involved in the escape response of Triatonia.

c. There is evidence that a central pattern generator is involved in producing the rhythmical contractions that make up the escape response.

d. The escape response corresponds closely to the classical ethological model for the functioning of innate behaviors. (Whether you think this statement is true or false, list the three components of the classical model and indicate the neural components, if any, that correspond).

e. The rhythmical muscular activity in escape cannot be influenced by sensory feedback.

2. You are conducting a study of male mating behavior in house flies. You present males with 4 different pairs of models, as shown below. For all models, shaded indicates that the model is black, unshaded indicates it is white. In pair A, both models are the normal size of females and are coated with normal amounts of female sex pheromone. In pair B, the two models are normal in size and have normal amounts of pheromone, but differ in color. In pair C, both models are the same in color and have normal pheromone levels, but one is twice as big as the other. In pair D, both models are normal size and color, but one has the normal amount of pheromone (X) while the other has twice the amount (2X). You test 20 different males with each pair of models. The number of males that mount each model is presented above each model.

(link to diagram)

Based on these results, which of the following can you correctly conclude about male mating behavior (be sure to refer to the appropriate figures)?

a. Tests with pair A reveal that males possess a mental "photograph" of what a female should look and smell like.

b. Mating is regulated by sign stimuli. (If you think this is true, you must indicate the sign stimuli involved and the evidence for each; if you think it is false, you must clearly present the evidence for your conclusion).

c. The responses exhibited for pairs C and D are aberrant, and have no biological explanation.

d. A model that was twice normal size coated with 2X pheromone would elicit a stronger response than any of the models shown above.

3. A colony of honey bees is visiting two resources at 12 noon, a food source and a potential new nest site, as shown. Several of the bees visiting the nest site are performing marathon dances in the hive. Workers have been visiting the food site for several days and show up at the site at the same time each day. One day at 4 PM a violent thunderstorm suddenly hits and kills many of the bees out in the field, such that the colony experiences a drastic loss of most of its foraging force.

(link to diagram)

Based on this information, you can correctly predict that:

a. at 12 noon the waggle runs for the food site will be oriented straight up on the combs, while those for the nest site will be oriented 90 degrees to the left of vertical.

b. if the marathon dances continue for hours without the dancers leaving the hive, then at 3 PM their waggle runs will be oriented 90 degrees to the right of vertical. (If you think this is false, then what would the correct orientation be and how were the dancers able to achieve this orientation without leaving the nest?)

c. the ability of the foragers to keep track of time involves a biological clock, in which the Va1R gene produced ICER protein, which accumulates until it reaches a threshold concentration, which then triggers the for locus which activates a negative feedback loop.

d. if it becomes overcast before the storm and blocks the ability to see the sun, then the waggle runs for the food source will become disoriented.

e. the colony may starve to death because it will be unable to respond to the thunderstorm by rapidly generating new foragers (if false, explain the mechanism).

4. A honey bee colony reproduces by swarming, in which the laying queen and about half of the workers leave the old nest and relocate to a new nest site. Workers of all ages leave the old nest with the swarm. However, by the time the swarm finds a new nest cavity, constructs comb and the queen starts laying eggs, none of the workers are young enough to be nurse bees. By the time brood rearing starts in the new nest, all of the workers are either in "late middle age" or are of foraging age. Some of these older bees will undergo a behavioral reversion and become "overage nurses". Based on what was covered in lecture, hypothesize what would happen in these overage nurses with respect to gene expression associated with the following (give specific mechanisms where possible)?

a. circadian rhythms

b. waggle dance behavior

c. food collection behavior

ANSWERS

a. The 8:1 transmission ratio between the SNs and the GI serves no adaptive function.

False: This is a dividing ratio that helps to establish a high response threshold, so that lots of stimulation is needed to elicit escape. Some starfish odor may be present at low levels at all times. Only when the odor reaches a certain level, such as would occur when a starfish is in the immediate vicinity, would escape be necessary. It would be maladaptive to elicit the escape response to trace levels that do not accurately predict the presence of a predator.

b. There is no evidence that a command neuron is involved in the escape response of Triatonia.

False: The GI functions as the “decision maker”: it alone can trigger escape. Thus, it functions as a command neuron.

c. There is evidence that a central pattern generator is involved in producing the rhythmical contractions that make up the escape response.

True: the group of interneurons act as a CPG. They are contained entirely within the central nervous system and can generate the complete motor program for escape without feedback. This fits the definition of a CPG: a group of interneurons contained entirely within the CNS that, once stimulated, can generate a complete motor program without sensory feedback.

True: The 3 component are: -- sign stimulus: a specific stimulus that elicits one particular behavior pattern. Here, the sign stimulus is starfish odor, because the SNs are so constructed that that can detect and respond to only this stimulus.

-- innate releasing mechanism: an inborn neural devise that responds to one specific sign stimulus and triggers one particular behavior pattern. Here, the GI acts as an IRM. It receives all sensory input from the SNs and is the sole decision maker for triggering the escape response.

-- fixed action pattern: an inborn motor program that once released runs to completion regardless of feed back. Here, the group of interneurons (which is a CPG) produced the Fixed Action Pattern of escape, which once triggered runs to completion without feedback. This is shown by the fact that even if the slug’s central nervous system is dissected out of the body and stimulated, the complete program of firing is still produced.

e. The rhythmical muscular activity in escape cannot be influenced by sensory feedback.

False: As diagrammed, the stretch receptors in the muscles can temporarily inhibit the CPG and stimulate the motor neurons. This would allow the animal to override temporarily the endogenous rhythm of contraction and relaxation produced by the CPG and maintain contraction on one side of the body. This would help it to push against sudden gusts of current and maintain an escape route. If it could not modify the basic pattern with feedback, then it would not be able to steer the escape response.

a. Tests with pair A reveal that males possess a mental "photograph" of what a female should look and smell like.

True or False: If you look at only the results from pair A, they could be interpreted as a mental photograph for mate recognition, because the models look almost identical to a real female. However, if you examine the results from the other pairs, then it is clear that models that look nothing like a female can generate a response as strong or stronger than the black model in pair A.

True: Mating is regulated by at least three sign stimuli. Pair B shows that dark color is one sign stimulus, because when presented with two models of the same size and pheromone concentration, males prefer the dark one. Pair C shows that size is a second sign stimulus, because if models have the same color and pheromone concentration, but differ in size, males prefer the larger one. Pair D shows that the female sex pheromone is a third sign stimulus, because if models have the same size and color, but differ in pheromone concentration, males prefer the higher concentration.

c. The responses exhibited for pairs C and D are aberrant, and have no biological explanation.

False: C and D represent supernormal stimuli. In C, the second model is a supernormal stimulus for size, while in D the second model is a supernormal stimulus for pheromone. Because the male has sensory neurons that respond maximally to these different cues, then models that present more of the cue elicit a strong-than-normal response.

d. A model that was twice normal size coated with 2X pheromone would elicit a stronger response than any of the models shown above.

True: Such a model would present two supernormal stimuli simultaneously and release a stronger response than any of the models used previously.

a. at 12 noon the waggle runs for the food site will be oriented straight up on the combs, while those for the nest site will be oriented 90 degrees to the left of vertical.

False: (remember, bees indicated the location of a resource relative to the sun, not the position of the sun itself). At 12 noon, the food source is located 180^o away from the sun, so the waggle-runs will be oriented straight down on the combs. The nest site is located 90o to the right of the sun (you must look at this from the bee’s perspective when it is leaving the hive; as it faces the sun, the nest site is to the right). So, the waggle-runs at 12 noon would be oriented 90o to the right of vertical on the combs.

False: At 3 PM, the sun will have moved toward the west another 45^o (remember that the sun moves about 15^o an hour). Thus, at 3 PM, the nest site will be 45^o to the right of the sun. Because the bees have a well-developed circadian rhythm based on an internal clock that tracks time, they will innately know that 3 hours have elapsed and that the sun has moved 45^o, and thus will orient their waggle-runs 45^o to the right of vertical.

False: the biological clock of the bee is regulated by the per gene which produced PER protein, which accumulated in the cell of the optic lobes. When PER reaches a critical level, it activates two other genes: (1) dbt which produces a protein that degrades PER, and (2) tim which produces the protein TIM that complexes with PER and the TIM+PER complex enters the nucleus and inhibits the per gene. As a result, the activity of per cycles in a 24 hour periodicity. The Va1R gene is not found in honey bees but occurs in mammals such as voles and is associated with pair bond formation. ICER protein is produced by the CREM gene and is found only in mammals and birds and is part of their biological clocks; it is not found in honey bees. The for locus is not involved in the periodicity of the biological clock and is not what inhibits the per gene (the PER+TIM complex inhibits per). The for locus produces PKG which is associated with foraging behavior. PKG levels are low in preforaging age workers, but increases to high levels in foraging age bees and this protein helps to stimulate foraging activity.

d. if it becomes overcast before the storm and blocks the ability to see the sun, then the waggle runs for the food source will become disoriented.

False: patterns of polarized light will still be visible and bees can use polarized light to orient and will thus continue to perform their waggle runs correctly.

e. the colony may starve to death because it will be unable to respond to the thunderstorm by rapidly generating new foragers (if false, explain the mechanism).

False: The loss of foragers will remove many of the older bees from the colony. Thus, younger bees will have less contact with older workers and this will cause the rate of JH production to increase in some of the younger workers. The increased JH will result in their developing low response thresholds to foraging stimuli earlier than normal and they will become precocious foragers. Furthermore, the loss of foragers will influence the activity of the for locus. Normally in younger bees for is less active and produced lesser amounts of PKG. But, in foraging age bees for is active and they produce large amounts of PKG and this helps to stimulate foraging behavior. Thus, in the precocious foragers, the activity of for will increase at an earlier age.

a. circadian rhythms: although the overage nurses are of foraging age and have fully functioning circadian rhythms, nurse bees are arrhythmic and thus the circadian clocks of the overage nurses will regress. When foragers, the per gene is active, which produce PER protein that build up inside the cells of the optic lobes. Once PER reaches a critical level, it actives the dbt gene, which produces an enzyme that degrades PER. It also activates the tim gene, which produces TIM protein that complexes with PER and the PER+TIM complex moves into the nuclei and inhibits per. In this way, the activity of the per gene has a 24-hr. cycle. Young bees are arrhythmic and do not exhibit this cyclic periodicity of per. Thus, even though the per cycle was active in the foraging-age bees, when they reverted to brood care this system would have been deactivated and they would become arrhythmic and perform brood care at all times of the day.

b. waggle dance behavior: because the response thresholds of the overage nurses will have changed, they will no longer be able to perform or respond to waggle dances. This will involve large scale changes in gene expression in the brain, and the brain gene expression patterns of the overage nurses will be similar to young nurses, and unlike those of foragers who are the same age as the overage nurses. Waggle dance performance may be affected because in the overage nurses the activity of the per gene will decline, and thus they will not have the biological clock activity necessary to use the sun as a compass for dance orientation. The activity of the Amfor gene (and thus PKG levels) will also decline, which may reduce the positive phototaxis of the nurses, so that they remain in the darker regions of the nest where the brood is. This may also reduce waggle dancing, since the detection of light (the sun) is necessary for waggle dance orientation. Also, reduced Amfor activity will change response thresholds for foraging stimuli and responding to waggle dances. So, the overage nurses will not respond to waggle dances, partly because of reduced per and Amfor activity.

d. food collection behavior: As foragers, these bees will have increased activity of the for (Amfor) locus and increased production of PKG, which stimulates foraging activity. However, younger bees have reduced activity of for and lower levels of PKG. Thus, in the overaged nurses, the activity of for would decline and PKG production would decrease, thereby helping to turn off foraging behavior (see answer b).