Chapter 4 Ecosystems and the Physical Environment Chapter 5 Ecosystems and Living Organisms

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1 Lecture Outline: Chapter 4 Ecosystems and the Physical Environment Chapter 5 Ecosystems and Living Organisms I. Biogeochemical cycles A. The carbon cycle i. The global movement of carbon between organisms and the abiotic environment is known as the carbon cycle 1. Carbon is present in the atmosphere as carbon dioxide(co2), the ocean as carbonate and bicarbonate (CO3 2-, HCO3 - ) and sedimentary rock as calcium carbonate (CaCO3) 2. Proteins, carbohydrates, and other molecules essential to life contain carbon 3. Carbon makes up approximately 0.04% of the atmosphere as a gas ii. Carbon primarily cycles through both biotic and abiotic environments via photosynthesis, cellular respiration and combustion (CO2) 1. Photosynthesis incorporates carbon from the abiotic environment (CO2) into the biological compounds of producers (sugars) 2. Producers, consumers and decomposers use sugars as fuel and return CO2 to the atmosphere in a process called cellular respiration 3. Carbon present in wood and fossil fuels (coal, oil, natural gas) is returned to the atmosphere by the process of combustion (burning) 4. The carbon-silicate cycle (which occurs on a geological timescale involving millions of years) returns CO2 to the atmosphere through volcanic eruptions and both chemical and physical weathering processes B. The nitrogen cycle i. The global circulation of nitrogen between organisms and the abiotic environment is know as the nitrogen cycle 1. Atmospheric nitrogen (N2) is so stable that it must first be broken apart in a series of steps before it can combine with other elements to form biological molecules 2. Nitrogen is an essential part of proteins and nucleic acids (DNA) 3. The atmosphere is 78% nitrogen gas (N2) ii. Five steps of the nitrogen cycle 1. Nitrogen fixation 1

2 Chapter 5 a. Conversion of gaseous nitrogen (N2) to ammonia (NH3) b. Nitrogen-fixing bacteria (including cyanobacteria) fixes nitrogen in soil and aquatic environments (anaerobic process) c. Combustion, volcanic action, lightning discharges, and industrial processes also fix nitrogen 2. Nitrification a. Conversion of ammonia (NH3) or ammonioum (NH4 + ) to nitrate (NO3 - ) b. Soil bacteria perform nitrification in a two-step process (NH3 or NH4 + is converted to nitrite (NO2 - ) then to NO3 - ) c. Nitrifying bacteria is used in this process 3. Assimilation a. Plant roots absorb NO3 -, NO3 or NO4 + and assimilate the nitrogen of these molecules into plant proteins and nucleic acids b. Animals assimilate nitrogen by consuming plant tissues (conversion of aminio acids to proteins) c. This step does not involve bacteria 4. Ammonification a. Conversion of biological nitrogen compounds into NH3 and NH4 + b. NH3 is released into the abiotic environment through the decomposition of nitrogen-containing waste products such as urea and uric acid (birds), as well as the nitrogen compounds that occur in dead organisms c. Ammonifying bacteria is used in this process 5. Denitrification a. Reduction of NO3 - to N2 b. Anaerobic denitrifying bacteria reverse the action of nitrogen-fixing and nitrifying bacteria C. The phosphorus cycle i. Phosphorus cycles from land to sediments in the ocean and back to land 1. Phosphorus erodes from rock as inorganic phosphates and plants absorb it from the soil 2. Animals obtain phosphorus from their diets, and decomposers release inorganic phosphate into the environment ii. Once in cells, phosphates are incorporated into biological molecules such as nucleic acids and ATP (adenosine triphosphate) iii. This cycle has no biologically important gaseous compounds D. The sulfur cycle i. Most sulfur is underground in sedimentary rocks and minerals or dissolved in the ocean 2

3 Chapter 4 ii. Sulfur gases enter the atmosphere from natural sources in both ocean and land 1. Sea spray, forest fires and dust storms deliver sulfates (SO4 2- ) into the air 2. Volcanoes release both hydrogen sulfide (H2S) and sulfur oxides (Sox) iii. A tiny fraction of global sulfur is present in living organisms 1. Sulfur is an essential component of proteins 2. Plant roots absorb SO4 2- and assimilate it by incorporating the sulfur into plant proteins 3. Animals assimilate sulfur when they consume plant proteins and covert them to animal proteins iv. Bacteria drive the sulfur cycle E. The hydrologic cycle i. The hydrologic cycle is the global circulation of water for the environment to living organisms and back to the environment 1. It provides a renewable supply of purified water for terrestrial organisms 2. the hydrologic cylce results in a balance between water in the ocean, on the land, and in the atmosphere ii. Water moves from the atmosphere to the land and ocean in the form of precipitation iii. Water enters the atmosphere by evaporation and transpiration iv. The volume of water entering the atmosphere each year is about 389,500 km 3 II. Solar Radiation A. The sun powers biogeochemical cycles (i.e., hydrologic, carbon) and is the primary determinant of climate B. Most of our fuels (i.e., wood, oil, coal, and natural gas) represent solar energy captured by photosynthetic organisms C. Approximately one billionth of the total energy released by the sun strikes our atmosphere i. Clouds, snow, ice, and the ocean reflect about 31% of the solar radiation that falls on Earth ii. Albedo is the proportional reflectance of solar energy from the Earth s surface 1. Glaciers and ice sheets have a high albedo and reflect 80 to 90% of the sunlight hitting their surfaces 2. Asphalt pavement and buildings have a low albedo (10 to 15%) 3. Forests have a low albedo (about 5%) iii. 69% of the solar radiation that falls on the Earth is absorbed and runs the hydrologic cycle, drives winds and ocean currents, powers photosynthesis, and warms the planet D. Temperature changes with latitude i. Near the equator, the sun s rays hit vertically 1. Energy is more concentrated 3

4 Chapter 5 2. Produces higher temperatures 3. Rays of light pass through a shallower envelope of air ii. Near the poles, the sun s rays hit more obliquely 1. Energy is spread over a larger surface area (less concentrated) 2. Produces lower temperatures 3. Rays of light pass through a deeper envelope of air, causing the sun s energy to scatter and reflect back to space E. Temperature changes with season i. Season s are determined primarily by Earth s inclination on its axis ii. March 21 to September 22 the Northern Hemisphere tilts toward the sun (spring/summer) iii. September 22 to March 21 the Northern Hemisphere tilts away from the sun (fall/winter) III. The Atmosphere A. The atmosphere is an invisible layer of gases that envelops Earth and protects it s surface from lethal amounts of high energy radiation (i.e., UV rays, X rays and cosmic rays) i. 99% of dry air is composed of oxygen (21%) and nitrogen (78%) ii. Argon, carbon dioxide, neon, and helium make up the remaining 1% B. The interaction between atmosphere and solar energy is responsible for weather and climate C. Layers of the atmosphere vary in altitude and temperature with latitude and season i. Troposphere 1. Closest layer to Earth s surface 2. Temperature decreases with increasing altitude 3. Extends to a height of approximately 10 km 4. Weather, including turbulent wind, storms, and most clouds occurs in the troposphere ii. Stratosphere 1. Temperature is more or less uniform, but does increase with increasing altitude 2. Extends from 10 to 45 km above Earth's surface 3. Steady wind, but no turbulence (commercial jets fly here) 4. Contains ozone layer iii. Mesosphere 1. Temperatures drop steadily (to lowest temperature in atmosphere) 2. Extends from 45 to 80 km above Earth's surface iv. Thermosphere 1. Very hot (nearly 1000 C or more) 2. Extends from 80 to 500 km 3. Aurora borealis occurs in this level of the atmosphere v. Exosphere 1. The outermost layer of the atmosphere 2. Begins about 500 km above Earth's surface 4

5 Chapter 4 3. The exosphere continues to thin until it converges with interplanetary space D. Differences in temperature caused by variations in the amount of solar energy reaching different locations on Earth drive the circulation of the atmosphere i. Air is heated by warm surfaces near the equator cause it to rise and expand ii. Due to subsequent chilling, air tends to sink to the surface at about 30 degrees north and south latitudes iii. Similar upward movements of warm air and its subsequent flow toward the poles occur at higher latitudes, farther from the equator iv. This continuous turnover moderates temperatures over Earth's surface E. Surface winds i. Horizontal movements resulting from differences in atmospheric pressure and from the Earth's rotation are called winds ii. Winds tend to blow from areas of high atmospheric pressure to areas of low pressure (greater difference = stronger winds) ii. The influence of Earth's rotation, which tends to turn fluids (air and water) toward the right in the Northern Hemisphere and toward the left in the Southern Hemisphere is called the Coriolis effect iv. The atmosphere has three prevailing winds 1. Polar easterlies blow from the northeast near the North Pole or from the southeast near the South Pole 2. Westerlies generally blow in the midlatitudes from the southwest in the Northern Hemisphere or the northwest in the Southern Hemisphere 3. Trade winds (tropical winds) generally blow from the northeast in the Northern Hemisphere or the southeast in the Southern Hemisphere IV. The Global Ocean A. The global ocean is a single, continuous body of salt water that covers nearly ¾ of the Earth's surface B. Geographers divide it into four sections separated by continents (Pacific, Atlantic, Indian, and Arctic oceans) C. Prevailing winds blowing over the ocean's surface and the position of land masses influence patterns of circulation i. Currents are mass movements of surface-ocean water ii. Gyres are large, circular ocean current systems that often encompass an entire ocean basin iii. The Coriolis effect also influences the paths of surface-ocean currents B. The varying density of seawater affects deep-ocean currents and creates a vertical mixing of ocean water i. The ocean conveyor belt moves cold, salty deep-sea water from higher to lower latitudes ii. The ocean conveyor belt affects regional and possibly global climate and shifts from one equilibrium state to another in a relatively short period (years to decades) 5

6 Chapter 5 C. Ocean interactions with the atmosphere are partly responsible for climate variability i. El Niño-Southern Oscillation (ENSO) is a periodic, large scale warming of surface waters of the tropical eastern Pacific Ocean that temporarily alters both ocean and atmospheric circulation patterns 1. Most ENSOs last 1 to 2 years 2. ENSO has a devastating effect on fisheries off South America and alters global air currents (causing severe and unusual weather worldwide) ii. La Niña occurs when the surface water temperature in the eastern Pacific Ocean becomes unusually cool, and westbound trade winds become unusually strong 1. La Nina often occurs after an ENSO 2. La Nina also affects weather patterns around the world, but its effects are more difficult to predict V. Weather and Climate A. Weather i. Weather refers to the conditions in the atmosphere at a given place and time ii. Weather includes temperature, atmospheric pressure, precipitation, cloudiness, humidity, and wind iii. Weather is continuously changing (hour to hour, day to day) B. Climate i. The average weather conditions that occur in a place over a period of years is termed climate ii. Climate is determined by temperature and precipitation iii. Other climate factors include wind, humidity, fog, cloud cover, and occasionally lightning C. Precipitation i. Precipitation refers to any form of water that falls from the atmosphere ii. Examples of precipitation include rain, snow sleet and hail iii. Precipitation has a profound effect on the distribution and kinds of organisms present D. Rain shadows, tornadoes and tropical cyclones (hurricanes/typhoons) are extreme forms of weather that can have a significant impact on regional climate VI. Internal Planetary Processes A. Plate tectonics i. Plate tectonics is the study of the dynamics of Earth s lithosphere (outermost rigid rock layer) 1. The lithosphere is composed of seven large plates, plus a few smaller ones 2. The plates float on the asthenosphere (the region of the mantle where rocks become hot and soft) ii. Plate boundaries are typically sites of intense geologic activity earthquakes and volcanoes are common in such a region 6

7 Chapter 4 B. Earthquakes i. Forces inside Earth sometimes push and stretch rocks in the lithosphere 1. The energy is released as seismic waves causing earthquakes 2. Most earthquakes occur along fault zones 3. More than 1 million earthquakes are recorded each year ii. Landslides and tsunamis are some of the side effects of earthquakes E. Volcanoes i. When one plate slides under or away from an adjacent plate, magma may rise to the surface, forming a volcano ii. Volcanoes occur at subduction zones, spreading centers, and above hot spots 7

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12 Chapter 5 Answers to Thinking About the Environment End of Chapter Questions: 1. Scientists produce tentative conclusions based on a degree of uncertainty, whereas politicians and others making public policies prefer to deal in absolutes. How does this dichotomy relate to Hurricane Katrina and the restoration of New Orleans? Ans: Scientists cannot predict exactly how much New Orleans will continue to subside or how much sea level will continue to rise in the coming years. Nor can they predict the exact degree that rebuilt levees and canals will hold up to another storm of Hurricane Katrina s magnitude or greater. Furthermore, further loss of the surrounding wetlands could increase New Orleans vulnerability to hurricanes. Despite these uncertainties, city planners and representatives of local, state, and federal governments are developing longterm plans to rebuild New Orleans. These plans range from a complete rebuilding of all damaged areas to a scaled-back restoration of areas that are less vulnerable to future hurricane damage. If these plans do not take into account varying estimates of changing conditions the rebuilding of New Orleans may not be as successful as hoped. 2. What is a biogeochemical cycle? Why is the cycling of matter essential to the continuance of life? Ans: Biogeochemical cycles move matter from one organism to another and from living organisms to the abiotic environment and back again. The cycles of matter- carbon, nitrogen, phosphorus, sulfur and hydrologic- involve biological, geologic and chemical interactions. These five cycles are particularly important to organisms, because these materials make up the chemical compounds of cells. 3. Describe how organisms participate in each of these biogeochemical cycles: carbon, nitrogen, phosphorus, and sulfur. Ans: In the carbon cycle organisms fix, or incorporate, carbon from the atmosphere into chemical compounds through photosynthesis. Organisms also release carbon during cellular respiration. Other biological molecules that are not release during cellular respiration can be stored as fossil fuels for millions of years. Aquatic organisms incorporate Ca 2+ and HCO3 - into their shells. When these organisms die their shells sink to the ocean floor and become part of the sedimentary rock layer. The CO2 in these rock layers will later be released due to weathering or subduction. Atmospheric nitrogen is very stable and must be broken apart in order to combine with other elements. Bacteria are exclusively involved in all five steps of the nitrogen cycle, except assimilation. Nitrogen-fixing bacteria carry out biological nitrogen fixation in soil and aquatic environments. Soil bacteria perform nitrification, a two step process. First soil bacteria convert ammonia or ammonia to nitrite. Then other soil bacteria oxidize nitrite to nitrate. The process of nitrification furnishes these bacteria with energy. Ammonification begins when organisms produce nitrogen-containing waste products such as urea and uric acid. These substances, as well as the nitrogen compounds that 12

13 Chapter 4 occur in dead organisms, are decomposed, releasing nitrogen into the abiotic environment. Finally, denitrifying bacteria reverse the action of nitrogen-fixing and nitrifying bacteria by returning nitrogen to the atmosphere. In the phosphorus cycle plants roots absorb inorganic phosphates. Animals obtain most of their required phosphate from the foods they eat. Phosphorus is then release back into the soil when organisms die and decompose. In aquatic environments phosphorus is absorbed and assimilated by algae and plants, which are then consumed by plankton and larger organisms. A small portion of phosphate in the aquatic food web finds its way back to the land in the manure of sea birds. A tiny fraction of the global sulfur is present in living organisms. Plant roots absorb sulfate and assimilate it by incorporating the sulfur into plant proteins. Animals assimilate sulfur when they consume plant proteins and convert then to animal proteins. Sulfur is returned to the atmosphere by bacteria which convert sulfates to hydrogen sulfide gas. 4. How are photosynthesis and cellular respiration involved in the carbon cycle? Ans: During photosynthesis, plants, algae, and certain bacteria remove CO2 from the air and fix, or incorporate, it into chemical compounds such as sugar. Thus, photosynthesis incorporates carbon from the abiotic environment into the biological compounds of producers. Those compounds are used as fuel for cellular respiration by the producers that made them, by a consumer that eats the producer, or by a decomposer that breaks down the remains of the producer or consumer. Thus, cellular respiration returns CO2 to the atmosphere. 5. What is the basic flow path of the nitrogen cycle? Ans: There are five steps to the nitrogen cycle, in which nitrogen cycles between the abiotic environment and organisms: nitrogen fixation, nitrification, assimilation, ammonification and denitrification. Bacteria are exclusively involved in all of these steps except assimilation. 6. A geologist or physical geographer would describe the phosphorus cycle as a sedimentary pathway. Based on what you have learned about the phosphorus cycle in this chapter, what do you think that means? Ans: Phosphorus does not form compounds in the gaseous phase and does not appreciably enter the atmosphere. In the phosphorus cycle, phosphorus cycles from the land to sediments in the ocean and back to the land. Phosphorus in plants comes from weathered sedimentary rock layers and returns to the ocean floor to be incorporated back into rock. 13

14 Chapter 5 7. How have global air temperatures changed in the recent past? How is this change related to the carbon cycle? Ans: Global air temperatures have increased in the recent past. Since 1850, the advent of the Industrial Revolution, our society has used a lot of energy, which we have obtained by burning increasing amounts of fossil fuels. This has released CO2 into the atmosphere at a rate greater than the carbon cycle can handle. Numerous studies indicate that the rise of CO2 in the atmosphere is causing human-induced global warming. 8. Diagram the hydrologic cycle. Ans: Answers will vary. 9. What are the two lower layers of the atmosphere? Cite at least two differences between them. Ans: The layer of the atmosphere closest to the Earth is the troposphere. The troposphere extends to a height of approximately 10km (6.2mi). The temperature of the troposphere decreases with increasing altitude about -6 C (-11 o F) for every kilometer. Weather, including turbulent wind, storms and most clouds, occur in the troposphere. The layer directly above the troposphere is the stratosphere. The stratosphere extends from km (6.2 to 28 mi) above the Earth s surface and contains the ozone critical to life because it absorbs much of the sun s damaging ultraviolet radiation. There is a steady wind but no turbulence. There is little water, and temperature is more or less uniform (-45 C to - 75 C), however, the absorption of ultraviolet radiation by the ozone layer heats the air, and so temperature increases with increasing altitude in the stratosphere. 10. Describe the general directions of atmospheric circulation. Ans: Differences in temperature are caused by variations in the amount of solar energy reaching different locations on Earth and drive the circulation of the atmosphere. The warm surface near the equator heats the air in contact with it, causing this air to expand and rise. As the warm air rises, it cools and then sinks again. Much of it recirculates almost immediately to the same areas it has left, but the remainder of the heated air splits and flows in two directions, toward the poles. The air chills enough to sink to the surface at about 30 degrees north and south latitudes. This descending air splits and flows over the surface in two directions. Similar upward movements of warm air and its subsequent flow toward the poles occur at higher latitudes, farther from the equator. At the poles the cold polar air sinks and flows toward the lower latitudes, generally beneath the sheets of warm air that simultaneously flow toward the poles. The constant motion of air transfers heat from the equator toward the poles, and as the air returns, it cools the land over which it passes. This continuous turnover moderates temperatures over Earth s surface. 14

15 Chapter How do ocean currents affect climate on land? Ans: The persistent prevailing winds blowing over the ocean produce currents, mass movements of surface-ocean water. The prevailing winds generate gyres, circular ocean currents. Although surface-ocean currents and winds tend to move in the same direction, there are many variations on this general rule. The ocean and the atmosphere are strongly linked, with wind from the atmosphere affecting the ocean currents and heat from the ocean affecting atmospheric circulation. Ocean currents help establish consistent circulation patterns that moderate the climate. When currents are altered the climate is altered. One of the best examples of the interaction between ocean and atmosphere is the El Niño-Southern Oscillation (ENSO) event, which is responsible for much of Earth's interannual (from one year to the next) climate variability. ENSO alters global air currents, directing unusual weather to areas far from the tropical Pacific. 12. How do atmospheric and oceanic circulations transport heat toward the poles? Ans: The constant motion of air transfers heat from the equator toward the poles. The process of atmospheric circulation transfers the more concentrated solar energy found at the equator towards the poles. The warm surface near the equator heats the air in contact with it, causing this air to expand and rise. As the warm air rises, it cools and then sinks again. Much of it recirculates almost immediately to the same areas it has left, but the remainder of the heated air splits and flows in two directions, toward the poles. The constant motion of oceanic circulation also moves heat from the equator towards the poles. Surface currents transfer immense amount of heat from the tropics to the higher latitudes. As heat is transferred to the atmosphere water become colder and denser which causes it to sink. As it sinks it forms deep ocean currents. 13. Relate the locations of earthquakes to plate tectonics. Ans: Most earthquakes occur along faults, fractures where rock moves forward and backward, up and down, or from side to side. Fault zones are often found at plate boundaries- any area where two plates meet. Therefore, earthquakes are very common at plate boundaries. Understanding plate tectonics has increased our knowledge of earthquakes and predicting where they may occur. 14. Evaluate the area where you live with respect to natural dangers. Is there a threat of possible earthquakes, volcanic eruptions, hurricanes, tornadoes, or tsunamis? Ans: Answers will vary 15. The system encompassing Earth s global mean surface temperature can be diagrammed as follows: Solar radiation absorbed by surface Outgoing long-wave (infrared) heat energy Affected by albedo Affected by clouds and aerosols Earth s global mean surface temperature 15

16 Chapter 5 Please explain each part of this system. Ans: The sun releases energy into space in the form of electromagnetic radiation. A small fraction of this energy reaches the Earth s surface and is absorbed and runs the hydrologic cycle, drives winds and ocean currents, powers photosynthesis and warms the plant. The amount of energy absorbed is affected by albedo. Albedo is the proportional reflectance of solar energy from Earth s surface, commonly expressed as a percentage. Glaciers and ice sheets have high albedo, whereas ocean and forests have low albedo. The more energy that is absorbed the greater the Earth s global mean temperature will be. Aerosols are tiny particles of air pollution consisting mostly of sulfates, nitrates, carbon, mineral dusts, and smokestack ash once in the atmosphere, aerosols enhance the scattering and absorption of sunlight in the atmosphere and cause brighter clouds to form. Both the clouds and the light-scattering effect in the atmosphere cause a warming of the atmosphere and a threefold reduction in the amount of solar radiation reaching Earth's surface, including the ocean. Ultimately, all of this energy is lost by the continual radiation of long-wave infrared energy into space. 16. Examine the following changes that have been identified in the arctic hydrologic system in the past few decades. Predict the effect of these changes on the salinity in the North Atlantic Ocean. Increasing precipitation in arctic Melting arctic glaciers Decreasing extent & thickness of arctic sea ice Arctic hydrologic system Ans: Due to increased precipitation, melting of artic glaciers, and decreasing extent and thickness of artic sea ice the salinity in the North Atlantic Ocean is likely to decrease. Cold, salty warm is less dense than warm, less salty water. This physical property drives the deep ocean conveyor. Scientists are therefore concerned that this decrease in salinity could alter the ocean conveyor and the global climate. Answers to Review Questions Cycling of Materials within Ecosystems (page 97) 1. What roles do photosynthesis, cellular respiration, and combustion play in the carbon cycle? Ans: Photosynthesis removes carbon dioxide from the atmosphere and incorporates it into chemical compounds. Cellular respiration and combustion both return carbon dioxide to the atmosphere. 2. What are the five steps of the nitrogen cycle? Ans: The steps include nitrogen fixation, nitrification, assimilation, ammonification and denitrification. 16

17 Chapter 4 3. How does the phosphorus cycle differ from the carbon, nitrogen, and sulfur cycles? Ans: Unlike the carbon, nitrogen and sulfur cycles the phosphorus cycle does not form compounds in the gaseous phase and does not enter the atmosphere in appreciable amounts. 4. What sulfur-containing gases are found in the atmosphere? Ans: Sulfates (SO4 2- ), calcium sulfate (CaSO4), hydrogen sulfide (H2S), sulfur oxides (SOx) including sulfur dioxide (SO2), and sulfur trioxide (SO3). Solar Radiation (page 98) 1. How does the sun affect temperature at different latitudes? Why? Ans: The sun s energy does not reach all places uniformly due to the tilt of the Earth on its axis. The energy from the sun s rays that hit the equator are therefore more concentrated and produce higher temperatures. The solar energy that reaches the Polar Regions is less concentrated and temperatures are lower. 2. What is albedo? Ans: The proportional reflectance of solar energy from Earth s surface, commonly expressed as a percentage. The Atmosphere (page 103) 1. What is the innermost layer of the atmosphere? Which layer of the atmosphere contains ozone that absorbs much of the sun's ultraviolet radiation? Ans: The inner most layer of atmosphere is the troposphere. The stratosphere contains ozone that absorbs ultraviolet radiation. 2. What basic forces determine the circulation of the atmosphere? Ans: Warm surfaces near the equator heats the air causing it to expand and rise. As warm air rises it cools and then sinks again. Cold polar air sinks and moves towards the equator. This constant motion of air moderates earth s temperatures over its surface. In addition to these global circulation patterns, the atmosphere exhibits winds, complex horizontal movements that result in part from differences in atmospheric pressure and from the Coriolis Effect. 17

18 Chapter 5 The Global Ocean (page 106) 1. How are the sun's energy, prevailing winds, and surface ocean currents related? Ans: The sun s energy unevenly heats the Earth s surface and the air. This uneven heating results in air circulation and wind. The persistent prevailing winds blowing over the ocean produce currents. 2. What is the El Niño-Southern Oscillation (ENSO)? What are some of its global effects? Ans: ENSO is a periodic, large scale warming of the surface waters of the tropical eastern Pacific Ocean that temporarily alters both ocean and atmospheric circulation patterns. ENSO alters global air currents, directing unusual weather to areas far from the tropical Pacific. It is responsible for changing rain patterns that cause flooding and drought. Weather and Climate (page 110) 1. How do you distinguish between weather and climate? What are the two most important climate factors? Ans: Weather refers to the conditions of the atmosphere at a given place and time. These conditions may vary from hour to hour. Climate is the average weather conditions that occur in a place over a period of years. The two most important factors that determine climate are temperature and precipitation. 2. What are some of the environmental factors that produce areas of precipitation extremes, such as rain forests and deserts? Ans: The heavy rainfall of the tropics results mainly from the equatorial uplift of moisture-laden air. As warm moisture-laden air rises and cools its water holding capacity decreases. When it reaches the saturation point clouds form and it is released as precipitation. Mountains, which force air to rise, remove moisture from humid air. Precipitation occurs primarily on the windward slope of mountains creating rain forests. On the other side of the mountain the dry air results in desert conditions. 3. Distinguish between tornadoes and tropical cyclones. Ans: Tornadoes are powerful, rotating funnels of air associated with severe thunderstorms. They form when warm and cool air collide. Tropical cyclones are giant rotating tropical storms that form as strong winds pick up moisture over warm surface waters of the tropical ocean and start to spin as a result of Earth s rotation. One major distinction is the scale of the two types of storms, tornadoes are typically much more isolated events. 18

19 Chapter 4 Internal Planetary Processes (page 113) 1. What are tectonic plates and plate boundaries? Ans: Tectonic plates are the large pieces of the Earth s outermost rigid rock layer that float on the hot and soft mantle. Any area where two plates meet a plate boundary forms. These plate boundaries are site of intense geologic activity. 2. Where are earthquakes and volcanoes commonly located, and why? Ans: Earthquakes and volcanoes are common at plate boundaries, the area where two tectonic plates meet. When the two plates grind together, one of them sometimes descends under the other, in the process of subduction. When two plates move apart, a ridge of molten rock forms from the mantle wells up between them. 19