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How to Use This Presentation • To View the presentation as a slideshow with effects select “View” on the menu bar and click on “Slide Show.” • To advance through the presentation, click the right-arrow key or the space bar. • From the resources slide, click on any resource to see a presentation for that resource. • From the Chapter menu screen click on any lesson to go directly to that lesson’s presentation. • You may exit the slide show at any time by pressing the Esc key. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Resources Bellringers Chapter Presentation Transparencies Standardized Test Prep Visual Concepts Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 The Atmosphere Table of Contents Section 1 Characteristics of the Atmosphere Section 2 Water and Wind Section 3 Weather and Climate Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 1 Characteristics of the Atmosphere Objectives • Identify the primary layers of the atmosphere. • Describe how the atmosphere has evolved over time. • Describe how the oxygen-carbon dioxide cycle works, and explain its importance to living organisms. • Discuss the recent changes in Earth’s atmosphere. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 1 Characteristics of the Atmosphere Bellringer The phrase greenhouse effect refers to a process that keeps Earth warm. The greenhouse effect describes how Earth’s atmosphere traps energy from the sun. Write a paragraph describing what you think life on Earth would be like as a result of too much of the greenhouse effect and also not enough of the greenhouse effect. Include possible consequences for plant and animal life as well as for weather and Earth itself. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 1 Characteristics of the Atmosphere Layers of the Atmosphere • Earth’s atmosphere consists of a variety of gases. • The two main gases are nitrogen and oxygen. • Earth’s atmosphere has several layers. • • • • Troposphere Stratosphere Mesosphere Thermosphere Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 1 Characteristics of the Atmosphere Layers of the Atmosphere Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 1 Characteristics of the Atmosphere Layers of the Atmosphere, continued • Almost all weather occurs in the troposphere. • The troposphere is the atmospheric layer closest to Earth’s surface. • The troposphere is the densest layer. • Troposphere the lowest layer of the atmosphere, in which temperature drops at a constant rate as altitude increases Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 1 Characteristics of the Atmosphere Layers of the Atmosphere, continued • The troposphere gets cooler with increasing altitude. • The temperature decreases by 6° C for every kilometer of altitude. • At the top of the troposphere the temperature stops decreasing. • The boundary where this occurs is called the tropopause. • The temperature at the tropopause is -55° C. • The low temperature keeps water vapor from leaving the troposphere. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 1 Characteristics of the Atmosphere Layers of the Atmosphere, continued • Cold air can become trapped beneath warm air. • Temperature inversion the atmospheric condition in which warm air traps cooler air near Earth’s surface. • When a temperature inversion occurs, trapped air can become thick with pollution. • As long as a temperature inversion lasts, it is not healthy for people to exercise outside. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 1 Characteristics of the Atmosphere Temperature Inversion Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 1 Characteristics of the Atmosphere Layers of the Atmosphere, continued • The stratosphere gets warmer with increasing altitude. • Stratosphere the upper layer of the atmosphere, which lies immediately above the troposphere and extends from 10 km to about 50 km above Earth’s surface. • At about 25 km, the temperature begins to increase with altitude until it reaches about 0° C. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 1 Characteristics of the Atmosphere Layers of the Atmosphere, continued • The mesosphere and thermosphere exhibit extremes of temperature. • Mesosphere the coldest layer of the atmosphere, between the stratosphere and the mesopause • Temperatures in the mesosphere decrease with increasing altitude, to about -80º C. • Thermosphere the uppermost layer of the atmosphere, in which temperature increases as altitude increases • Temperatures in the thermosphere are extremely hot, absorbing intense solar radiation. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 1 Characteristics of the Atmosphere Layers of the Atmosphere, continued • The ionosphere is used in radio communication. • Solar energy absorbed in the lower thermosphere and upper mesosphere forms charged ions. • This layer is often called the ionosphere. • Electrons in the ionosphere reflect radio waves. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 1 Characteristics of the Atmosphere Layers of the Atmosphere, continued • The ionosphere is where auroras take place. • Auroras are colorful displays of light formed when energetic ions from the sun hit atoms and molecules in the ionosphere, causing photons to be emitted. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 1 Characteristics of the Atmosphere Changes in Earth’s Atmosphere • When Earth began to solidify, about 4.4 billion years ago, volcanic eruptions released gases. • The process of releasing gases during volcanic eruptions is called outgassing. • The gases released by volcanoes did not include oxygen. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 1 Characteristics of the Atmosphere Changes in Earth’s Atmosphere, continued • Photosynthetic plants contribute oxygen to the atmosphere. • Organisms evolved that used sunlight as an energy source in a process called photosynthesis. • Photosynthesis produces oxygen as a waste product. • Gradually the oxygen content increased to what it is today. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 1 Characteristics of the Atmosphere Changes in Earth’s Atmosphere, continued • Animals produce carbon dioxide necessary for photosynthesis. • Oxygen breathing organisms evolved and released carbon dioxide as a waste product. • The oxygen-carbon dioxide cycle maintains a balance of atmospheric gases on Earth. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 1 Characteristics of the Atmosphere Changes in Earth’s Atmosphere, continued • Man-made chemicals can deplete the ozone layer. • Ozone is formed when the sun’s ultraviolet radiation strikes oxygen molecules. • Ozone absorbs much of the sun’s harmful ultraviolet radiation. • Without the ozone layer, ultraviolet radiation would damage living cells. • Chlorofluorocarbons are chemicals that damage the ozone layer, but are now banned in most countries. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 1 Characteristics of the Atmosphere Ozone and Ecosystems Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 1 Characteristics of the Atmosphere Ozone and Ozone Holes Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 1 Characteristics of the Atmosphere Changes in Earth’s Atmosphere, continued • The greenhouse effect keeps Earth warm. • Greenhouse effect the warming of the surface and lower atmosphere of Earth that occur when carbon dioxide, water vapor, and other gases in the air absorb and reradiate infrared radiation • Greenhouse gases trap the sun’s heat and keep Earth’s surface warm. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 1 Characteristics of the Atmosphere Greenhouse Effect Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 1 Characteristics of the Atmosphere Greenhouse Effect Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 1 Characteristics of the Atmosphere Changes in Earth’s Atmosphere, continued • Increased levels of carbon dioxide may lead to global warming. • If too much heat is trapped the global temperature will rise. • Global warming is the gradual increase in temperature on Earth due to an increase in greenhouse gases • Global warming could cause problems, such as the melting of ice caps, rising of ocean levels, and drought in some areas. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind Objectives • Describe the three phases of the water cycle. • Explain how temperature and humidity are related. • Identify various cloud types by their appearance and the altitudes at which they typically occur. • Use the concept of pressure gradients to explain how winds are created, and explain how Earth’s rotation affects their direction. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind Bellringer Atmospheric pressure can be measured with a barometer. The simplest barometer, illustrated below, is a glass tube containing mercury with one end sealed and the other end open in a dish of mercury. The height of the mercury in the tube is a measure of how much the atmosphere is pressing on the mercury in the dish; the greater the amount of atmospheric pressure, the higher the mercury level reaches in the tube. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind Bellringer, continued 1. Which barometer is measuring the greater atmospheric pressure? Explain your answer. 2. Atmospheric pressure increases as the altitude at which the pressure is measured nears sea level. If all things are equal except atmospheric pressure, which barometer is more likely to be at the top of a mountain and which is more likely to be at sea level? 3. Explain how you decided which barometer is more likely to be at the top of a mountain. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind The Water Cycle • Water cycle the continuous movement of water from the ocean to the atmosphere to the land and back to the ocean • Water is continuously being moved, primarily between the oceans and the continents. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind The Water Cycle, continued • Evaporated water vapor condenses to form precipitation. • Evaporation occurs when solar energy heats water molecules, and they rise as gaseous water vapor • Transpiration the process by which plants release water vapor into the air through their leaves • Precipitation any form of water that falls to Earth’s surface from the clouds Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind Water Cycle Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind The Water Cycle, continued • Air contains varying quantities of water vapor. • Humidity the amount of water vapor in the air. • Relative humidity is the actual amount of vapor in the air compared to the maximum amount the air could hold at that temperature. • Air that has a relative humidity of 100% is said to be saturated. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind Humidity Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind The Water Cycle, continued • Warmer temperatures evaporate more water. • Warm air can hold more water vapor than cold air can, as illustrated in the graph. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind The Water Cycle, continued • Water vapor becomes liquid at dew point. • Dew point is the temperature at which air or a gas begins to condense to a liquid • When humidity is high, there are more molecules of water in the air and it is easier to form liquid. • The higher the humidity, the higher the dew point. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind Dew Point Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind The Water Cycle, continued • Clouds form as warm, moist air rises. • Clouds form when warm air rises and water vapor condenses into tiny droplets of liquid as it cools. • This process usually occurs in the troposphere. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind The Water Cycle, continued • Cloud names describe their shape and altitude. • Clouds are named with combinations of three root words: • cirrus • stratus • cumulus • Cirrus clouds are thin, wispy, and occur at high altitudes • Stratus clouds are sheetlike and layered • Cumulus clouds are white and fluffy with somewhat flat bottoms Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind The Water Cycle, continued Cloud names reflect combined characteristics. • Cirrostratus clouds are high, layered clouds that form a thin white veil. • Altostratus and altocumulus clouds are stratus and cumulus clouds that occur at middle altitudes. • Cumulonimbus clouds are towering rain clouds that often produce thunderstorms. • Nimbostratus clouds are large, gray clouds that often produce steady precipitation. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind Cloud Types Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind Formation of Clouds and Precipitation Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind Air Pressure • Barometric pressure the pressure due to the weight of the atmosphere; also called air pressure or atmospheric pressure • Changes in barometric pressure often accompany changes in the weather. • Falling pressure may indicate that a large air mass is leaving the area. • Rising air pressure may mean that an air mass is moving in. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind Atmospheric Pressure Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind Air Pressure, continued • Instruments used to measure air pressure are called barometers. • At sea level, the barometric pressure of air at 0 C is around 760 mm of mercury. • 760 mm of mercury is defined as 1 atmosphere (1 atm) of pressure Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind Wind • Differences in pressure create winds. • When air pressure varies from one place to another, a pressure gradient exists. • The air in a pressure gradient moves from areas of high pressure to areas of low pressure. • This movement of air from a high-pressure area to a low-pressure area is called wind. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind Wind Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind Wind, continued • Earth’s rotation affects the direction of winds. • Coriolis effect the curving of the path of a moving object from an otherwise straight path due to Earth’s rotation. • Points at different latitudes on Earth’s surface move at different speeds. • Earth goes through a full rotation in 24 hours. • Points on the equator travel the Earth’s full circumference in 24 hours. • Points closer to the poles do not travel as far. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind Coriolis Effect Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind Wind, continued • Predictable air circulation forms wind patterns. • Winds in the Northern Hemisphere curve clockwise. • Winds in the Southern Hemisphere curve counterclockwise. • The resulting patterns are very regular, and have been named by meteorologists. • Polar easterlies • Westerlies • Northeast trade winds • Southeast trade winds Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind Wind, continued • Global wind patterns form circulation cells. • Because temperatures closer to the equator tend to be warmer, air traveling toward the equator tends to rise. • Warm rising air tends to move toward the poles. • As air moves closer to the poles it cools and sinks. • Three loops of rising warm air and sinking cold are can be found in each hemisphere • These loops are called cells. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 2 Water and Wind Global Winds and Surface Currents Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 3 Weather and Climate Objectives • Describe the formation of cold fronts and warm fronts. • Describe various severe weather situations, including thunderstorms, tornadoes, and hurricanes. • Distinguish between climate and weather. • Identify factors that affect Earth’s climate. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 3 Weather and Climate Bellringer 1. The longest day of the year in the Northern Hemisphere occurs on June 21, when the Northern Hemisphere gets the most sunlight. Do you think this explains why the summer season contains the hottest months of the year in the Northern Hemisphere? Explain your answer. 2. Climate is the average weather of a location over a period of many years. Describe the climate of the area where you live by generalizing the weather of each season for the past 5 years. 3. Because of their size, mountains can have a profound effect on the climate of an area. Explain how you think mountains affect the weather. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 3 Weather and Climate Fronts and Severe Weather • Meteorologists predict weather by tracking the movement of air pockets called air masses. • Air mass a large body of air where temperature and moisture content are similar throughout • Interactions between air masses have predictable effects on the weather in a given location. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 3 Weather and Climate Fronts and Severe Weather, continued • Front the boundary between air masses of different densities and usually different temperatures • Clouds, rain, and sometime snow can occur at fronts. • The three types of fronts are: • warm front • cold front • stationary front Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 3 Weather and Climate Types of Fronts Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 3 Weather and Climate Fronts and Severe Weather, continued • Lightning is a discharge of atmospheric electrical energy. • Water droplets and ice crystals in thunderclouds build up electrical charges. • Sparks, called lightning, jump between clouds or between clouds and Earth to equalize the charge. • Lightning superheats the air so fast that the air expands faster than the speed of sound. The shockwave created is thunder. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 3 Weather and Climate Lightning and Thunder Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 3 Weather and Climate Fronts and Severe Weather, continued • Tornadoes are funnels of high-speed wind. • Tornado winds are the most violent winds on Earth, with speeds up to 500 km/h. • Tornadoes typically form along a front between cool, dry air and warm, humid air. • Tornadoes are fast moving and unpredictable. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 3 Weather and Climate Tornado Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 3 Weather and Climate Fronts and Severe Weather, continued • Hurricanes are large storm systems. • Hurricanes are large circulating masses of clouds, wind, and rain with diameters of about 600 km. • Hurricanes are powered by energy released as water vapor condenses to form clouds. • Hurricanes rotate around a center called the eye. • The most violent winds in a hurricane are those surrounding the eye. The eye is usually calm. • Hurricane winds can reach speeds greater than 250 km/h . • Hurricanes weaken and die as they move over land or cooler water. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 3 Weather and Climate Formation of a Hurricane Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 3 Weather and Climate Climate • Climate the average weather conditions in an area over a long period of time. • Temperatures tend to be higher close to the equator. • Sunlight strikes the earth more directly close to the equator. • The suns rays are less concentrated at the poles, and do not warm the atmosphere as much. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 3 Weather and Climate Climate, continued • Earth’s tilt and rotation account for our seasons. • When the North Pole is tilted toward the sun, the Northern Hemisphere experiences summer. • When the South Pole is tilted toward the sun, the Southern Hemisphere experience summer. • Summer solstice the longest day of the year • Winter solstice the shortest day of the year • Vernal equinox the point in the spring when the day and night are equal length • Autumnal equinox the point in the fall when the day and night are equal length Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 3 Weather and Climate Climate, continued • Earth’s surface features affect climate. • Topography the configuration of a land surface, including its relief • Variations in topography affect the climate of a region, for example: • Mountains can trap moisture on one side • Broad flat surfaces allow winds to reach great speeds Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 3 Weather and Climate Climate, continued • Global climate changes over time. • Many factors produce changes in Earth’s climate, such as: • movement of continents • slight changes in Earth’s tilt • volcanic eruptions • changes in the greenhouse effect • Earth’s climate is likely to continue changing over the millennia to come. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Section 3 Weather and Climate Concept Mapping Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Standardized Test Prep Understanding Concepts 1. During a temperature inversion, which of these can trap polluted air close to the ground? A. B. C. D. acid rain ocean breezes thunder clouds warm air layer Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Standardized Test Prep Understanding Concepts, continued 1. During a temperature inversion, which of these can trap polluted air close to the ground? A. B. C. D. acid rain ocean breezes thunder clouds warm air layer Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Standardized Test Prep Understanding Concepts, continued 2. What is the main substance added to the atmosphere by the combustion of fossil fuels that may contribute to global warming? F. G. H. I. carbon dioxide CFCs oxygen petroleum Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Standardized Test Prep Understanding Concepts, continued 2. What is the main substance added to the atmosphere by the combustion of fossil fuels that may contribute to global warming? F. G. H. I. carbon dioxide CFCs oxygen petroleum Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Standardized Test Prep Understanding Concepts, continued 3. What causes the seasonal variations in climate that occur on most of the Earth’s surface? A. the variations in distance from the sun B. the difference in the amount of solar energy striking the equator and the poles C. the variations in solar energy due to the tilt of Earth’s axis relative to the orbital plane D. the redistribution of energy around the surface of Earth by ocean currents and winds Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Standardized Test Prep Understanding Concepts, continued 3. What causes the seasonal variations in climate that occur on most of the Earth’s surface? A. the variations in distance from the sun B. the difference in the amount of solar energy striking the equator and the poles C. the variations in solar energy due to the tilt of Earth’s axis relative to the orbital plane D. the redistribution of energy around the surface of Earth by ocean currents and winds Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Standardized Test Prep Understanding Concepts, continued 4. Even though animals use oxygen in the atmosphere, the amount of oxygen available remains constant. Analyze how the carbon dioxide-oxygen cycle maintains the ratio of gases needed for life to exist on Earth. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Standardized Test Prep Understanding Concepts, continued 4. Even though animals use oxygen in the atmosphere, the amount of oxygen available remains constant. Analyze how the carbon dioxide-oxygen cycle maintains the ratio of gases needed for life to exist on Earth. Answer: Plants constantly remove carbon dioxide from the atmosphere and add oxygen to the atmosphere by photosynthesis. Animals remove oxygen and add carbon dioxide by respiration. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Standardized Test Prep Understanding Concepts, continued 5. In general, climates are cooler near the poles and warmer near the equator. Given this observation, why are some mountains near the equator covered with snow year-round? Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Standardized Test Prep Understanding Concepts, continued 5. In general, climates are cooler near the poles and warmer near the equator. Given this observation, why are some mountains near the equator covered with snow year-round? Answer: Higher altitudes are cooler, even at the equator, because the air is not as dense, so it does not hold as much heat. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Standardized Test Prep Reading Skills The climate and weather inside a city are often very different from that of surrounding rural areas. Buildings and pavement absorb more energy from the sun, and activities such as transportation and industry produce additional heat. The temperature in a city can be as much as 10°C higher than the temperature outside of the city. This heat contributes to increased smog and changes precipitation patterns. As people have become aware of these “heat islands,” they are taking measures to reduce the heat island effect, such as using light colored roofs to reflect heat, and planting trees and other plants to absorb solar energy. 6. How could planting gardens on the roofs of buildings in cities help reduce the effect of heat islands? Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Standardized Test Prep Reading Skills, continued 6. [See previous slide for question.] Answer: Roof plants can help reduce heat by decreasing the surfaces that absorb heat and by absorbing solar energy, converting it into plant growth. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Standardized Test Prep Interpreting Graphics 7. Which of the following results from the situation shown in the illustration? F. coastal rains as warm air rises G. inland rains as cool air descends H. rain on both sides of the mountain I. dry climate on both sides of the mountain Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 22 Standardized Test Prep Interpreting Graphics, continued 7. Which of the following results from the situation shown in the illustration? F. coastal rains as warm air rises G. inland rains as cool air descends H. rain on both sides of the mountain I. dry climate on both sides of the mountain Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.