1. Chapter 3 Preview Section 1 The Earth System Section 2 Heat and Energy
Earth's Systems and Cycles
Preview
Section 1 The Earth System
Section 2 Heat and Energy
Section 3 The Cycling of Energy
Section 4 The Cycling of Matter
Concept Map

2. Chapter 3
Section 1 The Earth System
Bellringer
How does energy from the sun cause the movement of air in the atmosphere?
Write your answers in your science journal.

3. Chapter 3 What You Will Learn
Section 1 The Earth System
What You Will Learn
Energy and matter flow through Earth’s four spheres: the geosphere, atmosphere, hydrosphere, and biosphere.
Energy flows through the atmosphere and hydrosphere mostly by convection.

4. Chapter 3 Earth: An Overview
Section 1 The Earth System
Earth: An Overview
Earth is the only planet known to have abundant liquid water on its surface.
Water covers about 71% of Earth’s surface.
The water is called the global ocean.

5. Earth: An Overview, continued
Chapter 3
Section 1 The Earth System
Earth: An Overview, continued
The global ocean is part of Earth’s hydrosphere.
The hydrosphere is the portion of Earth that is water.
The biosphere is the portion of Earth where life exists.

6. Earth: An Overview, continued
Chapter 3
Section 1 The Earth System
Earth: An Overview, continued
The atmosphere is a mixture of gases that surround Earth.
The geosphere is the mostly solid, rocky part of Earth.
Energy and matter are cycled between these four spheres.

7. Chapter 3 The Geosphere The geosphere is divided into layers.
Section 1 The Earth System
The Geosphere
The geosphere is divided into layers.
Compositional layers are based on chemical composition.
Physical layers are based on physical properties.

8. The Geosphere, continued
Chapter 3
Section 1 The Earth System
The Geosphere, continued

9. Chapter 3 The Atmosphere
Section 1 The Earth System
The Atmosphere
The atmosphere is a mixture of invisible gases that surround Earth.
The atmosphere extends outward to about 500 km from the surface of Earth.
Most of the atmospheric gases lie within 8 to 12 km of Earth’s surface.

10. The Atmosphere, continued
Chapter 3
Section 1 The Earth System
The Atmosphere, continued
The troposphere is the atmospheric layer in which we live.
It extends outward to about 12 km from Earth’s surface.
Weather usually occurs in the troposphere.

11. The Atmosphere, continued
Chapter 3
Section 1 The Earth System
The Atmosphere, continued
The stratosphere is the layer directly above the troposphere.
Temperatures in the stratosphere increase with altitude.
The mesosphere is above the stratosphere.

12. The Atmosphere, continued
Chapter 3
Section 1 The Earth System
The Atmosphere, continued
The mesosphere is the coldest layer of the atmosphere.
The thermosphere is the uppermost layer of the atmosphere.
Temperatures in the thermosphere increase with altitude.

13. The Atmosphere, continued
Chapter 3
Section 1 The Earth System
The Atmosphere, continued
Energy Flow in the Atmosphere
Solar radiation heats Earth’s surface unevenly.
Uneven heating causes air in the atmosphere to move.
As cold air sinks, it forces warm, less-dense air upwards.

14. The Atmosphere, continued
Chapter 3
Section 1 The Earth System
The Atmosphere, continued
This movement of air distributes energy throughout the atmosphere.
The transfer of energy, especially heat, due to the movement of matter, such as air, is called convection.

15. Chapter 3 The Hydrosphere
Section 1 The Earth System
The Hydrosphere
All of Earth’s water is part of the hydrosphere.
More than 97% of the water on Earth is in the global ocean.
The global ocean covers a surface area of about 335 million square kilometers.

16. The Hydrosphere, continued
Chapter 3
Section 1 The Earth System
The Hydrosphere, continued
Energy Flow in the Hydrosphere
Solar radiation heats ocean water unevenly.
The temperature of ocean water varies from warm at the equator to near freezing at the poles.
The temperature of ocean water also decreases with depth.

17. The Hydrosphere, continued
Chapter 3
Section 1 The Earth System
The Hydrosphere, continued
Differences in density and the concentration of salts in the ocean affect the density of ocean water.
Differences in the density of ocean water causes movement called convection currents.
Convection currents distribute energy in the ocean.

18. Chapter 3 The Biosphere The biosphere contains all life on Earth.
Section 1 The Earth System
The Biosphere
The biosphere contains all life on Earth.
The biosphere includes Earth’s surface, the lower part of the atmosphere, and most of the hydrosphere.
The biosphere has certain factors that organisms need in order to live.

19. The Biosphere, continued
Chapter 3
Section 1 The Earth System
The Biosphere, continued
Liquid water, suitable habitat, and moderate temperatures are important to most organisms.
A stable source of energy is also important.
Plants and algae obtain energy from sunlight, other organisms obtain energy by eating other organisms.

20. The Biosphere, continued
Chapter 3
Section 1 The Earth System
The Biosphere, continued
Energy enters the biosphere as sunlight.
Plants and algae change this energy into chemical energy through the process of photosynthesis.
Then, the energy is passed to organisms that eat plants and algae.

21. The Biosphere, continued
Chapter 3
Section 1 The Earth System
The Biosphere, continued
Energy and matter is also passed to other organisms when they eat each other.
Dead organisms are consumed by decomposers, such as bacteria and fungi.
Materials broken down by decomposers, such as carbon dioxide, are used by plants to make food during photosynthesis.

22. Chapter 3
Section 2 Heat and Energy
Bellringer
How does heat flow in a glass of lemonade with ice cubes?
Write your ideas in your science journal.

23. Chapter 3 What You Will Learn
Section 2 Heat and Energy
What You Will Learn
Temperature is a measure of the average kinetic energy of particles in an object.
Heat is energy that is transferred between objects.
Heat flows by conduction, convection, and radiation.

24. Chapter 3 What Is Temperature?
Section 2 Heat and Energy
What Is Temperature?
Temperature is a measure of the average kinetic energy of the particles in an object.
All matter is made up of constantly moving particles, such as atoms or molecules.
When a particle is in motion, it has kinetic energy.

25. What Is Temperature?, continued
Chapter 3
Section 2 Heat and Energy
What Is Temperature?, continued
The faster particles move, the more kinetic energy they have.
The temperature of a substance depends on the kinetic energy of all of its particles.
The more kinetic energy the particles have, the higher the temperature of the substance.

26. What Is Temperature?, continued
Chapter 3
Section 2 Heat and Energy
What Is Temperature?, continued
The substance on the right has a higher temperature because its particles have a higher average kinetic energy.

27. What Is Temperature?, continued
Chapter 3
Section 2 Heat and Energy
What Is Temperature?, continued
Particles in a substance move at random and at different speeds.
The average of all these speeds is the average kinetic energy.
When you measure temperature, you are measuring average kinetic energy.

28. What Is Temperature?, continued
Chapter 3
Section 2 Heat and Energy
What Is Temperature?, continued
Temperature does not depend on the amount of particles in a substance.
A teapot holds more tea than a tea cup.
But if the atoms of tea in both containers have the same kinetic energy, then the tea in both containers has the same temperature.

29. Chapter 3 Thermal Expansion
Section 2 Heat and Energy
Thermal Expansion
When particles move faster, they move apart.
As the space between the particles increases, the substance expands.
Therefore, an increase in temperature leads to an increase in volume. This is called thermal expansion.

30. Chapter 3
Section 2 Heat and Energy
What is Heat?
Heat is the energy that is transferred between objects that are at different temperatures.
Heat energy is always passed from an object with a higher temperature to one with a lower temperature.
When you touch something hot, heat flows from the object to your finger.

31. Chapter 3
Earth's Systems and Cycles
Temperature and Heat

32. Chapter 3 What Is Heat?, continued
Section 2 Heat and Energy
What Is Heat?, continued
Thermal energy is the total kinetic energy of the particles that make up a substance.
Thermal energy, which is expressed in joules (J), depends partly on temperature.
Something at a high temperature has more thermal energy than something at a low temperature.

33. Chapter 3 What is Heat?, continued
Section 2 Heat and Energy
What is Heat?, continued
Thermal energy also depends on the amount of particles in a substance.
The more particles in a substance at a given temperature, the greater the thermal energy.

34. Chapter 3 What is Heat?, continued
Section 2 Heat and Energy
What is Heat?, continued
When things that have different temperatures come into contact, energy will always be transferred.
Energy will pass from the warmer to the cooler object until both have the same temperature.

35. How Is Heat Transferred?
Chapter 3
Section 2 Heat and Energy
How Is Heat Transferred?

36. How Is Heat Transferred?, continued
Chapter 3
Section 2 Heat and Energy
How Is Heat Transferred?, continued
The transfer of heat from one object to another through direct contact is called conduction.
Heat flows from the particles of hot soup to the part of the spoon that is in the soup.
Heat travels from particle to particle, from the soup all the way up the spoon’s handle.

37. How Is Heat Transferred?, continued
Chapter 3
Section 2 Heat and Energy
How Is Heat Transferred?, continued
The transfer of heat due to the movement of matter is called convection.
When you boil water, heat is passed from the burner to the pot and from the pot to the water by conduction.
As the water is heated, it becomes less dense.

38. How Is Heat Transferred?, continued
Chapter 3
Section 2 Heat and Energy
How Is Heat Transferred?, continued
Cooler, denser water at the top of the pot sinks.
This forces the warmer water to the surface.
Water continues to rise and fall in a circular pattern called a convection current.

39. How Is Heat Transferred?, continued
Chapter 3
Section 2 Heat and Energy
How Is Heat Transferred?, continued
The transfer of heat or other energy as electromagnetic waves, such as visible light or infrared waves, is called radiation.
Radiation can occur between objects that are not in direct contact with each other.
The sun transfers energy through space by radiation.

40. Chapter 3 States of Matter
Section 2 Heat and Energy
States of Matter
The states of matter are the physical forms in which a substance can exist.
The three states of matter are solid, liquid, and gas.
A substance’s state depends on the speed of its particles, the attraction between them, and the pressure around them.

41. States of Matter, continued
Chapter 3
Section 2 Heat and Energy
States of Matter, continued
A substance’s chemical composition also influences the state it is in at a given temperature.
For example, milk is a liquid at room temperature, but butter is a solid.
A change of state occurs when a substance changes from one state of matter to another.

42. States of Matter, continued
Chapter 3
Section 2 Heat and Energy
States of Matter, continued
Changes of state include:
condensing (gas to liquid)
freezing (liquid to solid)
melting (solid to liquid)
evaporating (liquid to gas)

43. States of Matter, continued
Chapter 3
Section 2 Heat and Energy
States of Matter, continued
A change of state involves a transfer of heat from one substance to another.
When a substance melts or boils, it gains energy.
When a substance condenses or freezes, it loses energy.

44. Chapter 3 Bellringer What is the source of 99% of the energy on Earth?
Section 3 The Cycling of Energy
Bellringer
What is the source of 99% of the energy on Earth?
How does this energy reach Earth?
Write your answers in your science journal.

45. Chapter 3 What You Will Learn
Section 3 The Cycling of Energy
What You Will Learn
Heat flow is the transfer of energy from a warmer object to a cooler object.
Energy from the sun, the major source of energy for phenomena on Earth’s surface, is transmitted to Earth by radiation.
Heat from Earth’s interior reaches the surface mostly by convection.

46. Chapter 3 The Flow of Energy
Section 3 The Cycling of Energy
The Flow of Energy
Energy can be carried from one place to another by heat flow, waves, or by moving objects.
Heat flow is the transfer of energy from a warmer object to a cooler object.
Waves—such as water wave, light waves, and sound waves—transfer energy through vibrations.

47. The Flow of Energy, continued
Chapter 3
Section 3 The Cycling of Energy
The Flow of Energy, continued
Waves move energy, but they do not move matter.
Objects carry energy while they are moving.
As they move, the objects pass energy to objects that they touch.

48. The Flow of Energy, continued
Chapter 3
Section 3 The Cycling of Energy
The Flow of Energy, continued
The sun is the major source of energy for the Earth system.
Heat from Earth’s interior supplies a much smaller amount of energy.
Energy moves through the processes of radiation, convection, and conduction.

49. Chapter 3
Section 3 The Cycling of Energy
Radiation
All energy from the sun travels to Earth in waves called electromagnetic radiation.
Electromagnetic radiation contains a wide range of wavelengths, collectively referred to as the electromagnetic spectrum.

50. Chapter 3 Radiation, continued
Section 3 The Cycling of Energy
Radiation, continued
Radio waves have the longest wavelengths, gamma rays have the shortest wavelengths.

51. Chapter 3 Radiation, continued
Section 3 The Cycling of Energy
Radiation, continued
All energy that Earth receives from the sun travels through space as electromagnetic radiation.
Wavelengths in or close to the visible light range make up most of the energy given off by the sun.
Some of this energy can pass through Earth’s atmosphere and reach Earth’s surface.

52. Chapter 3 Radiation, continued
Section 3 The Cycling of Energy
Radiation, continued
Energy from the sun drives the water cycle and makes life possible on Earth.
Energy from the sun is absorbed by Earth’s systems.
This energy is then converted to thermal energy and transferred by convection and conduction.

53. Chapter 3
Section 3 The Cycling of Energy
Convection
Most energy is moved through Earth’s systems by convection.
Most convection occurs in fluids, such as water and air.
Some convection can occur in solids that flow like putty.

54. Chapter 3 Convection, continued
Section 3 The Cycling of Energy
Convection, continued
The uneven heating of matter drives convection.
Matter that is heated becomes less dense and rises. Cooler, denser matter sinks.
The movement of matter that results from difference in density is called a convection current.

55. Chapter 3 Convection, continued
Section 3 The Cycling of Energy
Convection, continued
In the ocean, differences in temperature and salinity cause differences in density.
Salinity is the amount of salt in salt water.
Cold, salty water has a higher density than warm, less-salty water.

56. Chapter 3 Convection, continued
Section 3 The Cycling of Energy
Convection, continued
In the ocean, convection causes deep currents.
Deep currents are streamlike movements of water far below the ocean surface.
Deep currents take more than a thousand years to travel around the entire ocean.

57. Chapter 3
Section 3 The Cycling of Energy
Convection, continued

58. Chapter 3 Convection, continued
Section 3 The Cycling of Energy
Convection, continued
Convection currents in the atmosphere form when cold air sinks and forces warm air away from Earth’s surface.

59. Chapter 3 Convection, continued
Section 3 The Cycling of Energy
Convection, continued
Convection also occurs in the geosphere.
Energy produced deep inside Earth heats rock in the mantle.
The heated rock is under high pressure, so it becomes plastic without melting.

60. Chapter 3 Convection, continued The heated rock flows like putty.
Section 3 The Cycling of Energy
Convection, continued
The heated rock flows like putty.
As it becomes less dense, the heated rock rises toward Earth’s surface.
The cooler, denser rock surrounding the heated rock sinks.

61. Chapter 3 Convection, continued
Section 3 The Cycling of Energy
Convection, continued
In this way, heat inside Earth moves toward the cooler crust.
This movement of rock is a convection current.
Convection currents in the mantle cause the movement of tectonic plates.

62. Chapter 3
Section 3 The Cycling of Energy
Convection, continued

63. Chapter 3
Section 3 The Cycling of Energy
Conduction
When objects at different temperatures touch, their particles interact with each other.
Fast-moving particles in the warmer object transfer energy to slower moving particles in the cooler substance.
This causes the particles in the cooler substance to move faster and get warmer.

64. Chapter 3 Conduction, continued
Section 3 The Cycling of Energy
Conduction, continued
Energy can be transferred between the geosphere and the atmosphere by conduction.
When Earth’s surface is warmer than the atmosphere, the ground will transfer energy to the atmosphere.
When air comes into direct contact with the Earth, that energy is transferred by conduction.

65. Chapter 3 Earth’s Energy Budget
Section 3 The Cycling of Energy
Earth’s Energy Budget
Energy on Earth moves through and between four spheres.
These four spheres are open systems, which means they constantly exchange energy with each other.
Energy is neither created nor destroyed.

66. Earth’s Energy Budget, continued
Chapter 3
Section 3 The Cycling of Energy
Earth’s Energy Budget, continued
It is simply transferred between spheres and converted into another form of energy.
You can think of this movement of energy as part of an energy budget.
An addition of energy in one sphere means a subtraction of energy in another.

67. Chapter 3
Section 4 The Cycling of Matter
Bellringer
Matter is transferred over time from one organism to another in the food web and between organisms and their physical environment.
Imagine you are trying to explain this statement to a group of first graders. In your science journal, write an explanation of the statement that young students could understand. Be sure to include a definition of matter in your explanation.

68. Chapter 3 What You Will Learn
Section 4 The Cycling of Matter
What You Will Learn
The rock cycle is the series of processes in which rock changes from one form to another.
In the water cycle, water condenses, precipitates, and evaporates through the various spheres of Earth.
Nitrogen, carbon, and phosphorus cycle between Earth’s spheres.

69. Chapter 3 The Changing Earth
Section 4 The Cycling of Matter
The Changing Earth
As matter cycles through the Earth system, the matter changes.
Earth’s surface also changes.
Some of the processes that cause change may take millions of years.

70. The Changing Earth, continued
Chapter 3
Section 4 The Cycling of Matter
The Changing Earth, continued
Earth’s history spans 4,600 million (4.6 billion) years.

71. Chapter 3
Section 4 The Cycling of Matter
The Rock Cycle
One cycle that takes place over millions of years is the rock cycle.
The rock cycle consists of the processes by which rocks change from one form to another.
Processes that change rock include melting, cooling, cementation, heat, pressure, weathering, and erosion.

72. The Rock Cycle, continued
Chapter 3
Section 4 The Cycling of Matter
The Rock Cycle, continued
Weathering is the process by which rock is broken down by wind, water, and temperature changes.
Erosion is the process by which wind, water, ice, or gravity transport parts of the weathered rock from one location to another.

73. The Rock Cycle, continued
Chapter 3
Section 4 The Cycling of Matter
The Rock Cycle, continued

74. The Rock Cycle, continued
Chapter 3
Section 4 The Cycling of Matter
The Rock Cycle, continued
Rock may follow a number of pathways in the rock cycle.
The pathway that a rock follows in the rock cycle is determined by the forces that act on rock.
For example, if exposed to weathering and erosion, igneous rock may become sedimentary rock.

75. The Rock Cycle, continued
Chapter 3
Section 4 The Cycling of Matter
The Rock Cycle, continued
A rock’s location determines the forces that will act on the rock.
At Earth’s surface, rock is exposed to agents of weathering and erosion, such as wind and water.
Deep inside Earth, rock is exposed to high heat and pressure.

76. Chapter 3 Classes of Rocks
Section 4 The Cycling of Matter
Classes of Rocks
The three major classes of rocks are sedimentary, igneous, and metamorphic.
Sedimentary rocks form when rocks break into smaller pieces and those pieces become cemented together.

77. Classes of Rocks, continued
Chapter 3
Section 4 The Cycling of Matter
Classes of Rocks, continued
Igneous rocks form when hot, liquid rock—called magma—cools and becomes solid.
Metamorphic rocks form when rock is changed because of chemical processes or changes in temperature and pressure.

78. Classes of Rocks, continued
Chapter 3
Section 4 The Cycling of Matter
Classes of Rocks, continued
Sedimentary Rocks
Sedimentary rocks are divided into three types: clastic, chemical, and organic.
Clastic sedimentary rocks are made of fragments of rock or minerals.

79. Classes of Rocks, continued
Chapter 3
Section 4 The Cycling of Matter
Classes of Rocks, continued
Before they are cemented together, these fragments of rock or minerals are called sediment
Clastic sedimentary rocks form when sediments are buried, put under pressure, and cemented by minerals such as calcite and quartz.

80. Classes of Rocks, continued
Chapter 3
Section 4 The Cycling of Matter
Classes of Rocks, continued
Chemical sedimentary rocks form when minerals crystallize from a solution, such as ocean water.
The minerals are buried, put under pressure, and cemented together.
Organic sedimentary rocks form when the shells and skeletons of dead marine animals are buried and cemented by calcite or quartz.

81. Types of Sedimentary Rocks
Chapter 3
Earth's Systems and Cycles
Types of Sedimentary Rocks

82. Classes of Rocks, continued
Chapter 3
Section 4 The Cycling of Matter
Classes of Rocks, continued
Igneous Rocks
Igneous rocks are divided into groups based on texture of the rock or size of crystals.
Magma that slowly cools deep inside Earth forms coarse-grained rocks made of large crystals.

83. Classes of Rocks, continued
Chapter 3
Section 4 The Cycling of Matter
Classes of Rocks, continued
Lava that erupts and cools quickly at Earth’s surface forms fine-grained rocks made of very small crystals.
Igneous rock can also be classified by its chemical composition.

84. Classes of Rocks, continued
Chapter 3
Section 4 The Cycling of Matter
Classes of Rocks, continued
Chemical composition is determined by the type of rock that melts to form magma.
Magma from melted crustal material tends to form light-colored igneous rocks, such as granite.
Magma from Earth’s mantle forms dark-colored igneous rocks, such as basalt.

85. Classes of Rocks, continued
Chapter 3
Section 4 The Cycling of Matter
Classes of Rocks, continued
Metamorphic Rocks
Metamorphic rock forms from other rocks as a result of heat, pressure, or chemical processes.
Most metamorphic changes happen deep within Earth’s crust at depths greater than 2 km.
At these depths, pressure and temperature are much higher than at Earth’s surface

86. Classes of Rocks, continued
Chapter 3
Section 4 The Cycling of Matter
Classes of Rocks, continued
The two types of metamorphic rock are foliated and nonfoliated.
The minerals of foliated metamorphic rock, such as gneiss, are arranged in planes or bands.
The minerals of nonfoliated metamorphic rock, such as marble, are not arranged in planes or bands.

87. Chapter 3 The Water Cycle
Section 4 The Cycling of Matter
The Water Cycle
The water cycle is the continuous movement of water between the atmosphere, the land, and the oceans.

88. The Water Cycle, continued
Chapter 3
Section 4 The Cycling of Matter
The Water Cycle, continued
Evaporation is the process in which liquid water changes into gaseous water vapor.
Transpiration is the process in which plants release water vapor into the air through pores in their leaves.
Air that contains water vapor can cool and form clouds.

89. The Water Cycle, continued
Chapter 3
Section 4 The Cycling of Matter
The Water Cycle, continued
Clouds are made of liquid water droplets that form when condensation changes water vapor to liquid water.
When water droplets become large enough, they fall back to Earth as precipitation, such as rain.

90. The Water Cycle, continued
Chapter 3
Section 4 The Cycling of Matter
The Water Cycle, continued
Pathways of the Water Cycle
Most precipitation falls directly into the ocean.
Precipitation that reaches the land surface may fill lakes, streams, and rivers and eventually return to the ocean.

91. The Water Cycle, continued
Chapter 3
Section 4 The Cycling of Matter
The Water Cycle, continued
Water moving over the land surface is called runoff.
Gravity may move the water downward through spaces in rock or soil, where the water becomes groundwater.

92. Chapter 3 The Carbon Cycle
Section 4 The Cycling of Matter
The Carbon Cycle
Carbon is an important element that cycles through the Earth system.
Carbon is part of the proteins, fats, and carbohydrates of living things.
Carbon is also in the atmosphere, the water, the land, and the remains of living things.

93. The Carbon Cycle, continued
Chapter 3
Section 4 The Cycling of Matter
The Carbon Cycle, continued
The cycling of carbon between Earth’s spheres is called the carbon cycle.

94. The Carbon Cycle, continued
Chapter 3
Section 4 The Cycling of Matter
The Carbon Cycle, continued
Short-Term Processes
To build plant material, plants use carbon dioxide (CO2) from the air, water, and energy from the sun.
When animals eat plants, energy and matter are transferred to the animals.

95. The Carbon Cycle, continued
Chapter 3
Section 4 The Cycling of Matter
The Carbon Cycle, continued
When the animals break down the food, some carbon is returned to the air as CO2.
When the animals die, organisms break down the remains through decomposition.
Decomposition releases CO2 back into the carbon cycle.

96. The Carbon Cycle, continued
Chapter 3
Section 4 The Cycling of Matter
The Carbon Cycle, continued
Long-Term Processes
In some cases, dead organisms are buried before they decompose.
Their bodies chemically change as they are compacted for millions of years.

97. The Carbon Cycle, continued
Chapter 3
Section 4 The Cycling of Matter
The Carbon Cycle, continued
This process forms rock, such as limestone, or fossil fuels, such as coal, gas, and oil.
When humans burn these fuels, carbon returns to the atmosphere as carbon dioxide.
This process of burning fuel is called combustion.

98. Chapter 3
Earth's Systems and Cycles
The Carbon Cycle

99. Chapter 3 The Nitrogen Cycle
Section 4 The Cycling of Matter
The Nitrogen Cycle
The circulation of nitrogen among Earth’s spheres is called the nitrogen cycle.

100. The Nitrogen Cycle, continued
Chapter 3
Section 4 The Cycling of Matter
The Nitrogen Cycle, continued
Nitrogen is an important nutrient for all living things.
Certain bacteria in the soil change atmospheric nitrogen, N2, into forms of nitrogen that plants can use.
Other organisms get the nitrogen they need by eating plants.

101. The Nitrogen Cycle, continued
Chapter 3
Section 4 The Cycling of Matter
The Nitrogen Cycle, continued
When organisms die, decomposers release nitrogen from the dead organisms back into the soil.
Then, plants use some of this nitrogen.
Some bacteria in the soil change this nitrogen into atmospheric nitrogen, which returns to the air.

102. Chapter 3 The Phosphorus Cycle Phosphorus is found in living things.
Section 4 The Cycling of Matter
The Phosphorus Cycle
Phosphorus is found in living things.
It is also found in nonliving things, such as soil, rock, and water.
The roots of plants absorb phosphorus from the soil.

103. The Phosphorus Cycle, continued
Chapter 3
Section 4 The Cycling of Matter
The Phosphorus Cycle, continued
Animals obtain phosphorus when they eat plants.
When animals die, the phosphorus returns to the soil through decomposition.

104. Chapter 3 Other Cycles in Nature
Section 4 The Cycling of Matter
Other Cycles in Nature
Other forms of matter on Earth pass through cycles.
Many minerals, such as calcium, are cycled through the environment.
Every cycle is connected in many ways.

105. Other Cycles in Nature, continued
Chapter 3
Section 4 The Cycling of Matter
Other Cycles in Nature, continued
Some forms of nitrogen and carbon are carried through the environment by water.
Many nutrients pass from soil to plants to animals and back to soil.
Living things play an important role in each cycle and depend on each cycle for survival.

106. Chapter 3
Earth's Systems and Cycles
Concept Map
Use the terms below to complete the concept map on the next slide.
water cycle
rock cycle
condensation
metamorphic rock
precipitation
rock
sedimentary rock

107. Chapter 3
Earth's Systems and Cycles
Concept Map

108. Chapter 3
Earth's Systems and Cycles
Concept Map