Draw a model of the control circuit(s) required for

What properties are shared by all types of epithelia?

. In cool weather, jackrabbits sometimes flatten their ears against their body. What advantage and disadvantage do you think this body posture offers for survival?

Suppose you are standing at the edge of a cliff and suddenly slipyou barely manage to keep your balance and avoid falling. As your heart races, you feel a burst of energy, due in part to a surge of blood into dilated (widened) vessels in your muscles and an upward spike in the level of glucose in your blood. Why might you expect that this fight-or- flight response requires both the nervous and endocrine systems?

For a large animal, what challenges would a spherical shape pose for carrying out exchange with the environment?

Figure 8.21 (p. 160) illustrates feedback inhibition in an enzyme-catalyzed biosynthetic process. How does this type of negative feedback differ from that in thermoregulation?

If you were deciding where to put the thermostat in a house, what factors would govern your decision? How do these factors relate to the fact that many homeostatic control sensors in humans are located in the brain?

Like animals, cyanobacteria have a circadian rhythm. By analyzing the genes that maintain biological clocks, scientists were able to conclude that the 24-hour rhythms of humans and cyanobacteria reflect convergent evolution (see Concept 26.2, pp. 540541). What evidence would have supported this conclusion? Explain.

Is it accurate to define homeostasis as a constant internal environment? Explain.

What mode of heat exchange is involved in wind chill, when moving air feels colder than still air at the same temperature? Explain

Flowers differ in how much sunlight they absorb. Why might this matter to a hummingbird seeking nectar on a cool morning?

Suppose at the end of a hard run on a hot day you find that there are no drinks left in the cooler. If, out of desperation, you dunk your head into the cooler, how might the ice-cold water affect the rate at which your body temperature returns to normal?

Given that humans thermoregulate, explain why your skin is cooler than your body core.

If a mouse and a small lizard of the same mass (both at rest) were placed in experimental chambers under identical environmental conditions, which animal would consume oxygen at a higher rate? Explain.

Which animal must eat a larger proportion of its weight in food each day: a house cat or an African lion caged in a zoo? Explain.

If you monitored energy allocation in the penguin in Figure 40.20 for just a few months instead of an entire year, you might find the growth category to be a significant part of the pie chart. Given that adult penguins dont grow from year to year, how would you explain this finding?

Most hibernators are small. After reviewing Figure 40.19, suggest an explanation for this observation.

The body tissue that consists largely of material located outside of cells is a. epithelial tissue. b. connective tissue. c. skeletal muscle. d. smooth muscle. e. nervous tissue.

Which of the following would increase the rate of heat exchange between an animal and its environment? a. feathers or fur b. vasoconstriction c. wind blowing across the body surface d. countercurrent heat exchanger e. blubber or fat layer

Consider the energy budgets for a human, an elephant, a penguin, a mouse, and a snake. The __________ would have the highest total annual energy expenditure, and the __________ would have the highest energy expenditure per unit mass. a. elephant; mouse b. elephant; human c. human; penguin d. mouse; snake e. penguin; mouse

Compared with a smaller cell, a larger cell of the same shape has a. less surface area. b. less surface area per unit of volume. c. the same surface-to-volume ratio. d. a smaller average distance between its mitochondria and the external source of oxygen. e. a smaller cytoplasm-to-nucleus ratio.

An animals inputs of energy and materials would exceed its outputs a. if the animal is an endotherm, which must always take in more energy because of its high metabolic rate. b. if it is actively foraging for food. c. if it is hibernating. d. if it is growing and increasing its mass. e. never; homeostasis makes these energy and material budgets always balance.

You are studying a large tropical reptile that has a high and relatively stable body temperature. How would you determine whether this animal is an endotherm or an ectotherm? a. You know from its high and stable body temperature that it must be an endotherm. b. You know that it is an ectotherm because it is not a bird or mammal. c. You subject this reptile to various temperatures in the lab and find that its body temperature and metabolic rate change with the ambient temperature. You conclude that it is an ectotherm. d. You note that its environment has a high and stable temperature. Because its body temperature matches the environmental temperature, you conclude that it is an ectotherm. e. You measure the metabolic rate of the reptile, and because it is higher than that of a related species that lives in temperate forests, you conclude that this reptile is an endotherm and its relative is an ectotherm.

Which of the following animals uses the largest percentage of its energy budget for homeostatic regulation? a. a hydra b. a marine jelly (an invertebrate) c. a snake in a temperate forest d. a desert insect e. a desert bird

Draw a model of the control circuit(s) required for driving an automobile at a fairly constant speed over a hilly road. Indicate each feature that represents a sensor, stimulus, or response.

In 1847, the German biologist Christian Bergmann noted that mammals and birds living at higher latitudes (farther from the equator) are on average larger and bulkier than related species found at lower latitudes. Suggest an evolutionary hypothesis to explain this observation.

Eastern tent caterpillars (Malacosoma americanum) live in large groups in silk nests, or tents, which they build in trees. They are among the first insects to be active in early spring, when daily temperature fluctuates from freezing to very hot. Over the course of a day, they display striking differences in behavior: Early in the morning, they rest in a tightly packed group on the tents east-facing surface. In midafternoon, they are on its undersurface, each caterpillar hanging by a few of its legs. Propose a hypothesis to explain this behavior. How could you test it?

Medical researchers are investigating artificial substitutes for various human tissues. Why might artificial blood or skin be useful? What characteristics would these substitutes need in order to function well in the body? Why do real tissues work better? Why not use the real tissues if they work better? What other artificial tissues might be useful? What problems do you anticipate in developing and applying them?

In a short essay (about 100150 words) focusing on feedback control in thermoregulation, explain why shivering is likely during the onset of a fever.