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| Inquiry Questions Figure 52.4 The genetics of learning. Selection experiments in the laboratory established a genetic basis for differences in the ability to learn to run through a maze. What would happen if, after the seventh generation, rats were randomly assigned mates regardless of ability to learn the maze? Answer: Selection for learning ability would cease, and thus change from one generation to the next in maze learning ability; would only result from random genetic drift. FIGURE 52.6 Genetically caused defect in maternal care. (a) In mice, normal mothers take very good care of their offspring, retrieving them if they move away and crouching over them. (b) Mothers with the mutant fosB allele perform neither of these behaviors, leaving their pups exposed. (c) Amount of time female mice were observed crouching in a nursing posture over offspring. (d) Proportion of pups retrieved when they were experimentally moved. Why does the lack of fosB alleles lead to maternal inattentiveness? Answer: Normal fosB alleles produce a protein that in turn affects enzymes that affect the brain. Ultimately, these enzymes trigger maternal behavior. In the absence of the enzymes, normal maternal behavior does not occur. Figure 52.26 Optimal diet. The shore crab selects a diet of energetically profitable prey. The curve describes the net energy gain (equal to energy gained minus energy expended) derived from feeding on different sizes of mussels. The bar graph shows the numbers of mussels of each size in the diet. Shore crabs tend to feed on those mussels that provide the most energy. What factors might be responsible for the slight difference in peak prey length relative to the length optimal for maximum energy gain? Answer: Many factors affect the behavior of an animal other than its attempts to maximize energy intake. For example, avoiding predation is also important. Thus, it may be that larger prey take longer to subdue and ingest, thus making the crabs more vulnerable to predators. Hence, the crabs may trade off decreased energy gain for decreased vulnerability for predators. Many other similar explanations are possible. FIGURE 52.29 The advantage of male mate choice. Male mormon crickets choose heavier females as mates, and larger females have more eggs. Thus, male mate selection increases fitness. Is there a benefit to females for mating with large males? Answer: Yes, the larger the male, the larger the prenuptial gift, which provides energy that the female converts into egg production. FIGURE 52.30 Products of sexual selection. Attracting mates with long feathers is common in bird species such as (a) the African paradise whydah and (b) the peacock, which show pronounced sexual dimorphism. (c) Female peahens prefer to mate with males with greater numbers of eyespots in their tail feathers. Why do females prefer males with more spots? Answer: A question that is the subject of much current research. Ideas include the possibility that males with longer tails are in better condition (because males in poor condition couldn't survive the disadvantage imposed by the tail). The advantage to a female mating with a male in better condition might be either that the male is less likely to be parasitized, and thus less likely to pass that parasite on to the female, or the male may have better genes, which in turn would be passed on to the offspring. Another possibility is the visual system for some reason is better able to detect males with long tails, and thus long-tailed males are preferred by females simply because the longer tails are more easily detected and responded to. FIGURE 52.36 Flocking behavior decreases predation. As the size of a pigeon flock increases, hawks are less successful at capturing pigeons. Also, when more pigeons are present in the flock, they can detect hawks at greater distances, thus allowing more time for the pigeons to escape. Would living in a flock affect the time available for foraging in pigeons? Answer: Yes. If more birds are present, then each one can spend less time watching for predators, and thus have more time for foraging. Self Test 1). A male stickleback's display of aggression at a red object is an example of a). innate behavior. b). operant conditioning. c). associative learning. d). habituation. Answer: a 2). What type of behavior is associated with a "critical period" in which a stimulus must be detected to trigger the response? a). cognitive behavior b). taxis c). imprinting d). associative learning Answer: c 3). The study of song development in sparrows showed that a). the acquisition of a species-specific song is innate. b). there are two components to this behavior-a genetic template and learning. c). song acquisition is an example of associative learning. d). All of these are correct. Answer: b 4). The level of specificity in courtship signaling is often a). individual-specific. b). anonymous. c). species-specific. d). any of these. Answer: c 5). Which of the following is not a function of pheromones? a). sex attractants b). trigger alarm behaviors c). trail markers d). All of these are functions of pheromones. Answer: d 6). Behavioral ecology is the study of a). how natural selection shapes behaviors. b). how environmental conditions affect animal behaviors. c). how feeding opportunities affect animal behaviors. d). how interactions with other individuals of the same species affects behaviors. Answer: a 7). Which of the following would be most likely to occur according to the optimal foraging theory? a). Shore crabs eat the largest mussels even though they're harder to crack open. b). Columbian ground squirrels eat more because larger squirrels produce more offspring. c). Smaller yellow-eyed juncos eat larger prey, although they are harder to manage. d). An antelope will venture out on the open plain to feed even though lions are around. Answer: b 8). Which of the following statements about territories is true? a). Territories and home ranges describe the same area of land. b). The defense of a territory is always beneficial to the animal. c). A territory contains resources exclusively for the animal that defends it. d). Territories overlap in time or space with other territories. Answer: c 9). In the haplodiploidy system of sex determination, males are a). haploid. b). diploid. c). sterile. d). not present because bees exist as single-sex populations. Answer: a 10). According to kin selection, saving the life of your __________________ would do the least for increasing your inclusive fitness. a). mother b). brother c). sister-in-law d). niece Answer: c Test Your Visual Understanding 1). Can you predict what the graph in the seventh generation would look like if instead of mating the maze-bright rats with each other and the maze-dull rats with each other, you always mated maze-bright rats with maze-dull rats? Answer: After always mating the two extremes, maze-bright and maze-dull rats, with each other, the subsequent generations will tend to become more homogeneous and cluster around the middle of the graph. The bell-shaped curve in the graph will contain a higher peak in the center and the range of abilities on the x-axis will cluster closer to the center peak. Applying Your Knowledge 1). Imagine an animal society in which the individuals share an average of one-third of their alleles with one another. If the benefits to an individual of performing an altruistic act are twice the costs, does the kin selection model predict that these individuals are likely to be altruistic? Explain your reasoning. Answer: The animals in this society would be altruistic according to the kin selection model because when the benefit times the coefficient of relatedness are greater than the cost then the model predicts altruism: rb>c so in this case: r=0.333 b=(2c) so that: 0.333(2c) = 0.666c and 0.666c is greater than c 2). If a young animal exhibits a behavior immediately after being born or hatched, is it reasonable to conclude that the behavior is instinctive rather than learned? If not, what sorts of experiments might be performed to distinguish between these two possibilities? Answer: It is reasonable to conclude that the behavior is instinctual but because there could be some influence from the mother or siblings, an experiment should be performed that would separate the offspring from its parents and siblings prior to hatching or just after birth, in the case of a live birth. If the individual still exhibits the behavior after being isolated from parents and siblings, then it can be concluded with more confidence that the behavior is instinctual. 3). Swallows often hunt in groups, while hawks and other predatory birds usually are solitary hunters. What do you think is the basis for this difference? Answer: The swallows, being smaller birds, receive protection from predators when hunting with a flock, while hawks and other predatory birds have very few predators themselves to worry about. Swallows may also benefit from the flock by being able to obtain easier access to food by "news" spreading through the flock and by the sharing of large food sources. Birds of prey hunt what they need and don't usually require the assistance of another bird to capture their prey. |