Answers to Figure Legend Questions

FIGURE 4.4 The southern limit of aspen's range tends to be associated with survival of drought conditions, which are becoming more frequent in the center of the continent. As a result, the southern range limit of aspen may move to the north.

FIGURE 4.9 Cooling of leaves is important in any biome where leaf temperatures may rise to levels that are stressful, including many temperate and tropical biomes. However, a steady supply of water is needed to support transpirational cooling, which would be the case in tropical biomes and subtropical biomes during the rainy season.

FIGURE 4.10 Cooling mechanisms that do not use water, such as leaf pubescence or increasing convective heat loss, may be more important to cooling in deserts than in moister habitats such as the tropics, where the water supply is sufficient for transpirational cooling.

FIGURE 4.15 Moving between sun and shade influences the energy balance of the crocodile. The crocodile gains energy, particularly by solar radiation, when it moves to a sunny location. Moving into the shade results in net energy loss to the surrounding environment (losses > gains). If the riverbank on which the crocodile basks is warmer than its body, then it gains heat energy from the rock via conduction. A cooler rock in the shade will receive heat energy by conduction from the crocodile's body.

FIGURE 4.21 Closing stomates during midday lowers transpiration by increasing the resistance to water loss. Opening the stomates later in the afternoon when the air is cooler exposes the leaf to a concentration gradient of water from the plant to the air that is lower than at midday. As a result, transpirational water loss is less than it would be during the hotter part of the day.

FIGURE 4.25 The rate of water loss for each animal is given by slope of the line. If the external environment (light, temperature, humidity) is kept relatively constant, then the gradient of water potential from the animal to the air is the same, and the resistance modifies the actual water loss. Differences in the slopes therefore reflect differences in resistance to water loss.