bio chp 1-5,7,11-12,14-15 summaries.docx

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Chapter 3 Summary: 10. Although CO2 is scarce in the atmosphere, it is more abundant in aquatic systems, where it dissolves to form bicarbonate ions. The availability of carbon in aquatic systems is limited, however, by the rate of diffusion of CO2 gas and bicarbonate ions through water, especially through the boundary layers of still water that form at the surfaces of plants and algae. 11. Oxygen is abundant in the atmosphere, but is relatively scarce in water, where its solubility and rate of diffusion are low. Oxygen may be depleted by respiration (producing anoxic conditions), especially in environments where it cannot be replenished by photosynthesis. 12. The rates of most physiological processes increase by a factor of 2 to 4 for each 10C increase in temperature within the physiological range. This factor is known as the Q10 of a process. The generality of this temperature effect has been captured in the metabolic theory of ecology. 13. Higher temperatures generally accelerate physiological processes, but can also cause proteins and other biological molecules to unfold and lose their structure and function. Some extremophiles can tolerate very high temperatures because their proteins are chemically designed to generate strong forces of attraction to hold molecules together. 14. Organisms in cold environments withstand freezing temperatures by lowering the freezing point of their body fluids with glycerol or glycoproteins, or by supercooling their body fluids. 15. Most organisms function best within a narrow range of environmental conditions. This optimum is determined by characteristics, such as the structure, function, and quantity of its enzymes, that influence the organisms ability to function under various conditions. 16. The temperature of an organism is closely tied to its thermal environment, which influences gains and losses of heat through radiation, conduction, convection, and evaporation. Together with metabolically produced heat, these factors make up the heat budget of the organism. 17. Maintenance of constant internal conditions, called homeostasis, depends on negative feedback mechanisms. Organisms sense changes in their internal environment and respond in such a manner as to return those conditions to a set point. 18. Homeostasis requires energy when a gradient between internal and external conditions must be maintained. For example, endotherms must generate heat metabolically to balance loss of heat to their cooler surroundings. Chapter 4 Summary: 11. Global climatic patterns result from differential input of solar radiation at different latitudes and from the redistribution of heat energy by winds and ocean currents. 12. Periodic climatic cycles follow astronomical cycles, including the rotation of the earth on its axis (daily), revolution of the moon around the earth (roughly monthly), and revolution of the earth around the sun (annually). Variations in atmospheric and ocean circulation occur at longer periods of tens to many thousands of years. 13. Solar radiation and winds are responsible for the evaporation and circulation of water vapor in the atmosphere and thus for global and seasonal patterns of precipitation. The equilibrium vapor pressure of water increases with temperature. 14. Air is warmed and rises at the equator, where solar radiation is most intense, then cools and sinks at about 30 north and south, forming Hadley cells over the tropics. The sinking air of the Hadley cells drives secondary cells, called Ferrel cells, over the temperate zones, which in turn drive Polar cells at higher latitudes. This global pattern is known as Hadley circulation. 15. Variation in marine conditions is determined on a global scale by wind-driven ocean currents. These currents redistribute heat over the surface of the earth and greatly affect climates on land. Upwelling currents, caused by winds, ocean basin topography, and variations in water density related to temperature and salinity, bring cold, nutrient-rich water to the surface in some areas. 16. Thermohaline circulation, caused by differences in the density of water masses, moves water masses at great depth between ocean basins. This circulation pattern can be interrupted by climate changes that melt glacial or sea ice, changing the salinity of surface waters. 7. Seasonality in terrestrial environments is caused by the tilt of the earths axis of rotation in relation to the sun. In the tropics, the northward and southward movement of the intertropical convergence, which follows the movement of the solar equator, results in pronounced rainy and dry seasons. At higher latitudes, the seasons are expressed primarily as annual cycles of temperature. 8. Seasonal warming and cooling influence the characteristics of lakes in the temperate zone that experience surface freezing in winter. During summer, such lakes are stratified, with a warm surface layer (epilimnion) separated from a cold bottom layer (hypolimnion) by a sharp thermocline. In spring and fall, the temperature profile becomes more uniform, allowing vertical mixing. 9. Irregular and unpredictable variations in climate, such as El NioSouthern Oscillation events, may cause major changes in temperature and precipitation and disrupt biological communities on a global scale. 10. Topography and geology superimpose local variation in environmental conditions on more general climatic patterns. Mountains intercept rainfall, creating arid rain shadows on their leeward sides. At high latitudes, north- and south-facing slopes receive differing amounts of sunlight. Because temperature decreases about 6C for every 1,000 m of elevation, conditions at higher elevations resemble conditions at higher latitudes. 11. The characteristics of soil reflect the influences of the parent material from which it forms as well as climate and vegetation. Weathering of bedrock results in the breakdown of some of its minerals and their incorporation into clay particles, which mix with organic detritus entering the soil from the surface. These processes usually result in distinct soil horizons. 12. Clay particles have negative charges on their surfaces, which hold cations. The cation exchange capacity of a soil determines its fertility. 13. In acidic (podsolized) soils of cool, moist regions of the temperate zone, and in deeply weathered (lateritic) tropical soils, clay particles break down and the fertility of the soil is much reduced. Chapter 5 Summary: 1. The geographic distributions of plants are determined primarily by climate. Each climatic region has characteristic types of vegetation that differ in growth form. 2. Because plant growth form is directly related to climate, the major types of vegetation match temperature and precipitation closely. Major vegetation types can be used to classify ecosystems into categories called biomes. 3. Two ways of classifying biomes are represented by the climate zone approach of Walter and the vegetation approach exemplified by Whittaker. The first classifies regions on the basis of climate, within which a characteristic type of vegetation normally develops. The second classifies regions according to vegetation type, which generally reflects the local climate. 4. Climate zones and biomes are grouped within tropical, temperate, boreal, and polar latitudes. The adaptations of plants to different temperature ranges distinguish the vegetation types of each of these latitudinal bands. Within each of these latitudinal bands, annual precipitation, the seasonality of precipitation, and additional factors such as fire further differentiate terrestrial biomes.
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