Introduction Did you ever think a river could catch fire?

Introduction Did you ever think a river could catch fire?
In June, 1969, fire broke out on the Cuyahoga River in Cleveland, Ohio. For a century, oil refineries, steel mills, rubber factories, and other industries in Cleveland and Akron, 40 miles upstream, had dumped wastes directly into the river, along with raw sewage from both cities. The stretch of river between the two cities was devoid of fish, and the most heavily polluted sections lacked any signs of life. When the river caught fire, Clevelanders were not surprised—it had happened several times in the past!

Introduction Public outrage over the toxic conditions of the nation’s waterways, along with growing awareness of widespread environmental abuse, spurred a flurry of legislation, including the creation of the Environmental Protection Agency. Today, Cuyahoga Valley National Park surrounds a stretch of the river between Akron and Cleveland.

Figure Figure Unit Seven: Ecology

Figure Figure Why study ecology? (photo: Cuyahoga Valley National Park)

Chapter 34: Big Ideas The Biosphere Aquatic Biomes Terrestrial Biomes
Figure Chapter 34: Big Ideas The Biosphere Aquatic Biomes Figure Chapter 34: Big Ideas Terrestrial Biomes

Introduction Environmental concerns are among the most pressing issues we face today. How can we manage Earth’s resources in ways that meet the needs of people today without compromising the ability of future generations to meet theirs?

The Biosphere

34.1 Ecologists study how organisms interact with their environment at several levels
Ecology is the scientific study of the interactions of organisms with their environments. Organisms can potentially be affected by many different variables, grouped into two major types. Biotic factors include all of the organisms in an area, the living component of the environment. Abiotic factors are the environment’s nonliving component, the physical and chemical factors. An organism’s habitat includes the biotic and abiotic factors present in its surroundings. Student Misconceptions and Concerns  Students may confuse the terms ecology and environmentalism. The science of ecology and the environmental issues that it often raises are related but distinct processes. Teaching Tips  In the first chapter of the text, Module 1.2 introduces the levels of biological organization extending from an atom to the biosphere. Reviewing these with students will help them to place these ecology chapters in context.

Ecologists study environmental interactions at the levels of the organism, population, a group of individuals of the same species living in a particular geographic area, community, an assemblage of all the populations of organisms living close enough together for potential interaction, and ecosystem, both the abiotic and biotic components of the environment. Student Misconceptions and Concerns  Students may confuse the terms ecology and environmentalism. The science of ecology and the environmental issues that it often raises are related but distinct processes. Teaching Tips  In the first chapter of the text, Module 1.2 introduces the levels of biological organization extending from an atom to the biosphere. Reviewing these with students will help them to place these ecology chapters in context.

Figure 34.1a Figure 34.1a An organism

Figure 34.1b Figure 34.1b A population

Figure 34.1c Figure 34.1c A community

Figure 34.1d Figure 34.1d An ecosystem

Some ecologists take a wider perspective by studying landscapes, arrays of ecosystems usually visible from the air as distinctive patches. The biosphere extends from the atmosphere several kilometers above Earth to the depths of the oceans and is all of Earth that is inhabited by life. Student Misconceptions and Concerns  Students may confuse the terms ecology and environmentalism. The science of ecology and the environmental issues that it often raises are related but distinct processes. Teaching Tips  In the first chapter of the text, Module 1.2 introduces the levels of biological organization extending from an atom to the biosphere. Reviewing these with students will help them to place these ecology chapters in context.

34.2 SCIENTIFIC THINKING: The science of ecology provides insight into environmental problems
In the 1950s, the prevailing view of the environment was that “Nature” was a force to be tamed and controlled for human purposes, in the same way that livestock had been domesticated. Chemical pesticides were an innovation that was enthusiastically embraced. Student Misconceptions and Concerns  Students may confuse the terms ecology and environmentalism. The science of ecology and the environmental issues that it often raises are related but distinct processes. Teaching Tips  A website devoted to Rachel Carson can be viewed at

The most widely used chemical pesticide was DDT. DDT is an insecticide that was employed against crop pests and disease-carrying insects such as mosquitoes (which transmit malaria), body lice (typhus), and fleas (plague). But it was considered harmless to vertebrates, including people. Student Misconceptions and Concerns  Students may confuse the terms ecology and environmentalism. The science of ecology and the environmental issues that it often raises are related but distinct processes. Teaching Tips  A website devoted to Rachel Carson can be viewed at

Figure 34.2a Figure 34.2a Spraying DDT to control mosquitoes on Jones Beach, New York, in 1945

By the late 1950s, however, a heated debate was raging over the widespread use of chemical pesticides. Consumers raised questions about chemical residues in their food. Scientists also found that DDT remained in the soil or water long after application of the pesticide. Birds of prey seemed to be especially vulnerable. Student Misconceptions and Concerns  Students may confuse the terms ecology and environmentalism. The science of ecology and the environmental issues that it often raises are related but distinct processes. Teaching Tips  A website devoted to Rachel Carson can be viewed at

Figure 34.2b Figure 34.2b Peregrine falcon (Falco peregrinus)

The publication of a book called Silent Spring in brought widespread attention to the pesticide issue. Rachel Carson, a former marine biologist and writer with the U.S. Fish and Wildlife Service, compiled all of the available evidence about the consequences of widespread pesticide use. Awareness of the problems caused by pesticides quickly developed into concern for a host of environmental issues. Student Misconceptions and Concerns  Students may confuse the terms ecology and environmentalism. The science of ecology and the environmental issues that it often raises are related but distinct processes. Teaching Tips  A website devoted to Rachel Carson can be viewed at

Figure 34.2c Figure 34.2c Rachel Carson

34.3 Physical and chemical factors influence life in the biosphere
The most important abiotic factors that determine the biosphere’s structure and dynamics include the energy source, usually solar energy, temperature, abundance and type of water, inorganic nutrients, other aquatic factors such as availability of oxygen, and other terrestrial factors including wind and fire. Student Misconceptions and Concerns  Students may confuse the terms ecology and environmentalism. The science of ecology and the environmental issues that it often raises are related but distinct processes. Teaching Tips  In general, the sun is the primary source of energy input to ecosystems. Hydrothermal vent communities are a clear exception. Some students might enjoy researching additional details about these ecosystems and the roles they might have played in the early evolution of life on Earth. One excellent source of good information about hydrothermal vent communities is Active Lecture Tips  As a class focusing exercise, consider challenging students to work in pairs to make lists of all the abiotic components in a given ecosystem, perhaps in regards to the local area just outside your campus building. Alternately, students may work in small groups after class and turn in lists as a short homework assignment. The class might enjoy a bit of competition and a review of what groups thought of after the assignment is turned in.

Figure 34.3a Figure 34.3a The respiratory surface of a giant tube worm

Figure 34.3b Figure 34.3b A snowy owl

34.4 EVOLUTION CONNECTION: Organisms are adapted to abiotic and biotic factors by natural selection
One of the fundamental goals of ecology is to explain the distribution of organisms. The presence of a species in a particular place has two possible explanations. The species may have evolved from ancestors living in that location. It may have dispersed to that location and been able to survive once it arrived. Student Misconceptions and Concerns  Students may confuse the terms ecology and environmentalism. The science of ecology and the environmental issues that it often raises are related but distinct processes. Teaching Tips  Consider challenging your students to explain why organisms are typically limited to living in only certain parts of the biosphere. Module 34.4 notes that a species range may be limited by adaptations to particular environmental conditions. The same adaptations that permit survival under certain conditions may reduce survival rates under other conditions. Such trade-offs between specialization and generalization are a normal part of biology. If you want to emphasize the point with an analogy, you might note that choosing a particular major in college increases a student’s skills in that field, but comes at the cost of detailed study in other fields.

The pronghorn is a highly successful herbivorous running mammal of open country. It is a descendent of ancestors that roamed the open plains and shrub deserts of North America more than a million years ago. It is found nowhere else and is only distantly related to the many antelope species in Africa. Student Misconceptions and Concerns  Students may confuse the terms ecology and environmentalism. The science of ecology and the environmental issues that it often raises are related but distinct processes. Teaching Tips  Consider challenging your students to explain why organisms are typically limited to living in only certain parts of the biosphere. Module 34.4 notes that a species range may be limited by adaptations to particular environmental conditions. The same adaptations that permit survival under certain conditions may reduce survival rates under other conditions. Such trade-offs between specialization and generalization are a normal part of biology. If you want to emphasize the point with an analogy, you might note that choosing a particular major in college increases a student’s skills in that field, but comes at the cost of detailed study in other fields.

Figure 34.4 Figure 34.4 A pronghorn (Antilocapra americana)

A pronghorn’s habitat is arid, windswept, and subject to extreme temperature fluctuations. Individuals able to survive and reproduce under these conditions left offspring that carried their alleles into subsequent generations. Until around 12,000 years ago, one of their major predators was probably the now-extinct American cheetah, similar to African cheetahs alive today. Student Misconceptions and Concerns  Students may confuse the terms ecology and environmentalism. The science of ecology and the environmental issues that it often raises are related but distinct processes. Teaching Tips  Consider challenging your students to explain why organisms are typically limited to living in only certain parts of the biosphere. Module 34.4 notes that a species range may be limited by adaptations to particular environmental conditions. The same adaptations that permit survival under certain conditions may reduce survival rates under other conditions. Such trade-offs between specialization and generalization are a normal part of biology. If you want to emphasize the point with an analogy, you might note that choosing a particular major in college increases a student’s skills in that field, but comes at the cost of detailed study in other fields.

Ecologists hypothesize that the selection pressure of the cheetah’s pursuit led to the pronghorn’s blazing speed, which far exceeds that of its main present-day predator, the wolf. Like many large herbivores that live in open grasslands, the pronghorn also derives protection from living in herds. Populations of organisms are adapted to local environmental conditions, which may limit the distribution of organisms. Student Misconceptions and Concerns  Students may confuse the terms ecology and environmentalism. The science of ecology and the environmental issues that it often raises are related but distinct processes. Teaching Tips  Consider challenging your students to explain why organisms are typically limited to living in only certain parts of the biosphere. Module 34.4 notes that a species range may be limited by adaptations to particular environmental conditions. The same adaptations that permit survival under certain conditions may reduce survival rates under other conditions. Such trade-offs between specialization and generalization are a normal part of biology. If you want to emphasize the point with an analogy, you might note that choosing a particular major in college increases a student’s skills in that field, but comes at the cost of detailed study in other fields.

34.5 Regional climate influences the distribution of terrestrial communities
Climate often determines the distribution of communities. The Earth’s global climate patterns are largely determined by the input of radiant energy from the sun and the planet’s movement in space. Student Misconceptions and Concerns  Students may confuse the terms ecology and environmentalism. The science of ecology and the environmental issues that it often raises are related but distinct processes. Teaching Tips  Module 34.5 discusses the reasons why Earth’s tilt causes seasons. Consider challenging your students, perhaps as a short in-class activity, to explain why it is typically cooler (a) farther away from the equator and (b) during the winter months. Although you may not want to use class time on this activity every year, collecting student responses before your students read or learn about this in class can reveal misconceptions and areas of misunderstanding that will help direct your teaching for years to come.

Solar radiation varies with latitude. Equatorial regions receive sunlight more directly. Higher latitudes receive sunlight at more of a slant. Most climatic variations are due to the uneven heating of Earth’s surface. Student Misconceptions and Concerns  Students may confuse the terms ecology and environmentalism. The science of ecology and the environmental issues that it often raises are related but distinct processes. Teaching Tips  Module 34.5 discusses the reasons why Earth’s tilt causes seasons. Consider challenging your students, perhaps as a short in-class activity, to explain why it is typically cooler (a) farther away from the equator and (b) during the winter months. Although you may not want to use class time on this activity every year, collecting student responses before your students read or learn about this in class can reveal misconceptions and areas of misunderstanding that will help direct your teaching for years to come.

Arctic Circle Low angle of 60N incoming sunlight 30N Tropic of
Figure 34.5a Arctic Circle Low angle of incoming sunlight 60N 30N Tropic of Cancer Sunlight strikes most directly 0(equator) Tropic of Capricorn Figure 34.5a How solar radiation varies with latitude 30S Low angle of incoming sunlight 60S Antarctic Circle Atmosphere

The Earth’s permanent tilt causes the seasons. In June, the Northern Hemisphere of the Earth is tipped toward the sun. In December, the Northern Hemisphere of the Earth is tipped away from the sun. The reverse is true about the Southern Hemisphere, generating opposite seasons during the same time of year. Student Misconceptions and Concerns  Students may confuse the terms ecology and environmentalism. The science of ecology and the environmental issues that it often raises are related but distinct processes. Teaching Tips  Module 34.5 discusses the reasons why Earth’s tilt causes seasons. Consider challenging your students, perhaps as a short in-class activity, to explain why it is typically cooler (a) farther away from the equator and (b) during the winter months. Although you may not want to use class time on this activity every year, collecting student responses before your students read or learn about this in class can reveal misconceptions and areas of misunderstanding that will help direct your teaching for years to come.

March equinox (equator faces June solstice sun directly) (Northern
Figure 34.5b March equinox (equator faces sun directly) June solstice (Northern Hemisphere tilts toward sun) Constant tilt of 23.5 Figure 34.5b How Earth’s tilt causes the seasons December solstice (Northern Hemisphere tilts away from sun) September equinox

The tropics are the region surrounding the equator between latitudes 23.5° north and 23.5° south. Uneven heating of Earth causes rain and winds. The direct intense solar radiation in the tropics near the equator has an impact on the global patterns of rainfall and winds. The tropics experience the greatest annual input and least seasonal variation in solar radiation. Student Misconceptions and Concerns  Students may confuse the terms ecology and environmentalism. The science of ecology and the environmental issues that it often raises are related but distinct processes. Teaching Tips  Module 34.5 discusses the reasons why Earth’s tilt causes seasons. Consider challenging your students, perhaps as a short in-class activity, to explain why it is typically cooler (a) farther away from the equator and (b) during the winter months. Although you may not want to use class time on this activity every year, collecting student responses before your students read or learn about this in class can reveal misconceptions and areas of misunderstanding that will help direct your teaching for years to come.

As the air rises in the tropics, it cools and releases much of its water content, produces the abundant precipitation typical of most tropical regions, and creates an area of calm or very light winds known as the doldrums. Student Misconceptions and Concerns  Students may confuse the terms ecology and environmentalism. The science of ecology and the environmental issues that it often raises are related but distinct processes. Teaching Tips  Module 34.5 discusses the reasons why Earth’s tilt causes seasons. Consider challenging your students, perhaps as a short in-class activity, to explain why it is typically cooler (a) farther away from the equator and (b) during the winter months. Although you may not want to use class time on this activity every year, collecting student responses before your students read or learn about this in class can reveal misconceptions and areas of misunderstanding that will help direct your teaching for years to come.

Descending dry air absorbs moisture Descending dry air absorbs
Figure 34.5c Descending dry air absorbs moisture Descending dry air absorbs moisture Ascending moist air releases moisture Trade winds Trade winds Figure 34.5c How uneven heating causes rain and winds Doldrums 23.5 0 23.5 30 30 Temperate zone Tropics Temperate zone

After losing its moisture over equatorial zones, high-altitude air masses spread away from the equator until they cool and descend again at latitudes of about 30° north and south. This descending dry air absorbs moisture from the land. Thus, many of the world’s great deserts—the Sahara in North Africa and the Arabian on the Arabian Peninsula, for example—are centered at these latitudes. Student Misconceptions and Concerns  Students may confuse the terms ecology and environmentalism. The science of ecology and the environmental issues that it often raises are related but distinct processes. Teaching Tips  Module 34.5 discusses the reasons why Earth’s tilt causes seasons. Consider challenging your students, perhaps as a short in-class activity, to explain why it is typically cooler (a) farther away from the equator and (b) during the winter months. Although you may not want to use class time on this activity every year, collecting student responses before your students read or learn about this in class can reveal misconceptions and areas of misunderstanding that will help direct your teaching for years to come.

As the dry air descends, some of it spreads back toward the equator. This movement creates the cooling trade winds, which dominate the tropics. As the air moves back toward the equator, it warms and picks up moisture until it ascends again. Student Misconceptions and Concerns  Students may confuse the terms ecology and environmentalism. The science of ecology and the environmental issues that it often raises are related but distinct processes. Teaching Tips  Module 34.5 discusses the reasons why Earth’s tilt causes seasons. Consider challenging your students, perhaps as a short in-class activity, to explain why it is typically cooler (a) farther away from the equator and (b) during the winter months. Although you may not want to use class time on this activity every year, collecting student responses before your students read or learn about this in class can reveal misconceptions and areas of misunderstanding that will help direct your teaching for years to come.

The temperate zones are between the tropics and the Arctic Circle in the north and the Antarctic Circle in the south. The temperate zones have seasonal variations and more moderate temperatures than the tropics or the polar zones. Student Misconceptions and Concerns  Students may confuse the terms ecology and environmentalism. The science of ecology and the environmental issues that it often raises are related but distinct processes. Teaching Tips  Module 34.5 discusses the reasons why Earth’s tilt causes seasons. Consider challenging your students, perhaps as a short in-class activity, to explain why it is typically cooler (a) farther away from the equator and (b) during the winter months. Although you may not want to use class time on this activity every year, collecting student responses before your students read or learn about this in class can reveal misconceptions and areas of misunderstanding that will help direct your teaching for years to come.

Prevailing winds result from the combined effects of rising and falling air masses and Earth’s rotation. In the tropics, Earth’s rapidly moving surface deflects vertically circulating air, making the trade winds blow from east to west. In temperate zones, the slower-moving surface produces the westerlies, winds that blow from west to east. Student Misconceptions and Concerns  Students may confuse the terms ecology and environmentalism. The science of ecology and the environmental issues that it often raises are related but distinct processes. Teaching Tips  Module 34.5 discusses the reasons why Earth’s tilt causes seasons. Consider challenging your students, perhaps as a short in-class activity, to explain why it is typically cooler (a) farther away from the equator and (b) during the winter months. Although you may not want to use class time on this activity every year, collecting student responses before your students read or learn about this in class can reveal misconceptions and areas of misunderstanding that will help direct your teaching for years to come.

60N Westerlies 30N Trade winds Doldrums Trade winds Westerlies 30S
Figure 34.5d 60N Westerlies 30N Trade winds Doldrums Figure 34.5d Prevailing wind patterns Trade winds Westerlies 30S 60S

Ocean currents, river-like flow patterns in the oceans, result from a combination of prevailing winds, the planet’s rotation, unequal heating of surface waters, and the location and shapes of the continents. Ocean currents have a profound effect on regional climates. Student Misconceptions and Concerns  Students may confuse the terms ecology and environmentalism. The science of ecology and the environmental issues that it often raises are related but distinct processes. Teaching Tips  Module 34.5 discusses the reasons why Earth’s tilt causes seasons. Consider challenging your students, perhaps as a short in-class activity, to explain why it is typically cooler (a) farther away from the equator and (b) during the winter months. Although you may not want to use class time on this activity every year, collecting student responses before your students read or learn about this in class can reveal misconceptions and areas of misunderstanding that will help direct your teaching for years to come.

Greenland Europe North America Gulf Stream Africa ATLANTIC OCEAN
Figure 34.5e Greenland Europe North America Gulf Stream Africa ATLANTIC OCEAN Figure 34.5e Atlantic Ocean currents (red arrows indicate warming currents; blue arrows indicate cooling currents) South America PACIFIC OCEAN

Landforms can also affect local climate. For example, air temperature declines about 6°C with every 1,000-m increase in elevation. Rainfall is affected by the location of mountains and prevailing winds. Student Misconceptions and Concerns  Students may confuse the terms ecology and environmentalism. The science of ecology and the environmental issues that it often raises are related but distinct processes. Teaching Tips  Module 34.5 discusses the reasons why Earth’s tilt causes seasons. Consider challenging your students, perhaps as a short in-class activity, to explain why it is typically cooler (a) farther away from the equator and (b) during the winter months. Although you may not want to use class time on this activity every year, collecting student responses before your students read or learn about this in class can reveal misconceptions and areas of misunderstanding that will help direct your teaching for years to come.

Wind East direction Pacific Ocean Rain shadow Desert Sierra Nevada
Figure 34.5f Wind direction East Pacific Ocean Rain shadow Desert Sierra Nevada Figure 34.5f How mountains affect precipitation (California) Coast Range

Climate and other abiotic factors of the environment control the global distribution of organisms. The influence of these abiotic factors results in biomes, the major types of ecological associations that occupy broad geographic regions of land or water. Student Misconceptions and Concerns  Students may confuse the terms ecology and environmentalism. The science of ecology and the environmental issues that it often raises are related but distinct processes. Teaching Tips  Module 34.5 discusses the reasons why Earth’s tilt causes seasons. Consider challenging your students, perhaps as a short in-class activity, to explain why it is typically cooler (a) farther away from the equator and (b) during the winter months. Although you may not want to use class time on this activity every year, collecting student responses before your students read or learn about this in class can reveal misconceptions and areas of misunderstanding that will help direct your teaching for years to come.

Aquatic Biomes

34.6 Sunlight and substrate are key factors in the distribution of marine organisms
Aquatic biomes are shaped by the availability of sunlight and substrate. Student Misconceptions and Concerns  Students may benefit from a review of the general properties of water introduced in Modules 2.10–2.16, which provide insight into the abiotic properties of aquatic biomes. Teaching Tips  Before addressing aquatic biomes, consider asking your students to explain (a) why fog frequently forms over large bodies of water in the spring and fall and (b) how life would be different in aquatic environments if ice sank when it froze.  Consider exploring with your students the many ways that the Gulf of Mexico was impacted by the BP 2010 spill and the natural mechanisms in this biome that are helping it to recover. Active Lecture Tips  Before lecturing about rivers and streams, ask students to work in small groups and write down how the qualities of a stream change between its source and the point where it joins a larger body of water many kilometers downstream. In particular, how do water temperature, water clarity, water speed, and the types of fish inhabiting the water change as the water flows away from its source?  Challenge your students to work in small groups in class to write down the movements of water through your local community. You may want to have them consider all of the possible inputs of water into your community and the possible routes of exit. Students may not realize the possibility that the outflow of water from one community is connected to the inflow of water into another community downstream.

Video: Shark Eating a Seal

Video: Clownfish and Anemone

Video: Coral Reef

Video: Hydrothermal Vent

Video: Tubeworms

Within the oceans are the pelagic realm, which includes all open water, benthic realm, which consists of the seafloor, aphotic zone, where there is insufficient light for photosynthesis, and photic zone, where light penetration is sufficient for photosynthesis and phytoplankton can occur. Zooplankton are abundant in the pelagic photic zone. Coral reefs also occur in the photic zone. Student Misconceptions and Concerns  Students may benefit from a review of the general properties of water introduced in Modules 2.10–2.16, which provide insight into the abiotic properties of aquatic biomes. Teaching Tips  Before addressing aquatic biomes, consider asking your students to explain (a) why fog frequently forms over large bodies of water in the spring and fall and (b) how life would be different in aquatic environments if ice sank when it froze.  Consider exploring with your students the many ways that the Gulf of Mexico was impacted by the BP 2010 spill and the natural mechanisms in this biome that are helping it to recover. Active Lecture Tips  Before lecturing about rivers and streams, ask students to work in small groups and write down how the qualities of a stream change between its source and the point where it joins a larger body of water many kilometers downstream. In particular, how do water temperature, water clarity, water speed, and the types of fish inhabiting the water change as the water flows away from its source?  Challenge your students to work in small groups in class to write down the movements of water through your local community. You may want to have them consider all of the possible inputs of water into your community and the possible routes of exit. Students may not realize the possibility that the outflow of water from one community is connected to the inflow of water into another community downstream.

(seafloor from continental shelf to deep-sea bottom)
Figure 34.6a-0 High tide Low tide Pelagic realm (open water) Oarweed (to 2 m) Man-of-war (to 50 m long) Turtle (60–180 cm) Sea star (to 33 cm) Brain coral (to 1.8 m) Photic zone Phytoplankton Zooplankton Blue shark (to 2 m) 200 m Intertidal zone Continental shelf Sponges (1 cm–1 m) Sperm whale (10–20 m) “Twilight” Sea pen (to 45 cm) Octopus (to 10 m) Hatchet fish (2–60 cm) Aphotic zone Benthic realm (seafloor from continental shelf to deep-sea bottom) Sea spider (1–90 cm) Gulper eel (to 180 cm) 1,000 m Rat-tail fish (to 80 cm) Figure 34.6a-0 Ocean life (zone depths and organisms not drawn to scale) No light Brittle star (to 60 cm) Anglerfish (45 cm–2 m) Glass sponge (to 1.8 m) Sea cucumber (to 40 cm) Tripod fish (to 30 cm) 6,000– 10,000 m

(seafloor from continental shelf to deep-sea bottom)
Figure 34.6a-1 High tide Low tide Pelagic realm (open water) Oarweed (to 2 m) Sea star (to 33 cm) Brain coral (to 1.8 m) Photic zone Phytoplankton Zooplankton 200 m Intertidal zone Continental shelf Sponges (1 cm–1 m) Octopus (to 10 m) “Twilight” Sea pen (to 45 cm) Aphotic zone Benthic realm (seafloor from continental shelf to deep-sea bottom) Sea spider (1–90 cm) 1,000 m Figure 34.6a-1 Ocean life (zone depths and organisms not drawn to scale) (part 1) No light Brittle star (to 60 cm) 6,000– 10,000 m

Pelagic realm (open water)
Figure 34.6a-2 Pelagic realm (open water) Man-of-war (to 50 m long) Turtle (60–180 cm) Photic zone Zooplankton Blue shark (to 2 m) 200 m Sperm whale (10–20 m) “Twilight” Octopus (to 10 m) Hatchet fish (2–60 cm) Aphotic zone Gulper eel (to 180 cm) 1,000 m Figure 34.6a-2 Ocean life (zone depths and organisms not drawn to scale) (part 2) Brittle star (to 60 cm) Rat-tail fish (to 80 cm) Anglerfish (45 cm–2 m) No light Glass sponge (to 1.8 m) Sea cucumber (to 40 cm) Tripod fish (to 30 cm) 6,000– 10,000 m

Figure 34.6b Figure 34.6b A coral reef with its immense variety of invertebrates and fishes

Figure 34.6c Figure 34.6c An angler fish

The marine environment includes distinctive biomes where the ocean meets the land or fresh water. Intertidal zones are where the ocean meets the land and the shore is pounded by waves during high tide and exposed to the sun and drying winds during low tide. Estuaries are productive areas where rivers meet the ocean. Wetlands are transitional between aquatic and terrestrial ecosystems. Student Misconceptions and Concerns  Students may benefit from a review of the general properties of water introduced in Modules 2.10–2.16, which provide insight into the abiotic properties of aquatic biomes. Teaching Tips  Before addressing aquatic biomes, consider asking your students to explain (a) why fog frequently forms over large bodies of water in the spring and fall and (b) how life would be different in aquatic environments if ice sank when it froze.  Consider exploring with your students the many ways that the Gulf of Mexico was impacted by the BP 2010 spill and the natural mechanisms in this biome that are helping it to recover. Active Lecture Tips Before lecturing about rivers and streams, ask students to work in small groups and write down how the qualities of a stream change between its source and the point where it joins a larger body of water many kilometers downstream. In particular, how do water temperature, water clarity, water speed, and the types of fish inhabiting the water change as the water flows away from its source?  Challenge your students to work in small groups in class to write down the movements of water through your local community. You may want to have them consider all of the possible inputs of water into your community and the possible routes of exit. Students may not realize the possibility that the outflow of water from one community is connected to the inflow of water into another community downstream.

Figure 34.6d Figure 34.6d An estuary in Georgia

34.7 Current, sunlight, and nutrients are important abiotic factors in freshwater biomes
cover less than 1% of Earth’s surface, contain less than 0.01% of its water, harbor 6% of all described species, and include lakes, ponds, rivers, streams, and wetlands. Student Misconceptions and Concerns  Students may benefit from a review of the general properties of water introduced in Modules 2.10–2.16, which provide insight into the abiotic properties of aquatic biomes. Teaching Tips  The turnover of lakes and ponds in the fall often results in noticeable changes such as fish kills and alterations in water color and smell. If you are addressing this subject in the fall or early winter, you might instruct students to watch for this phenomenon.  The speed of water plays a key role in the removal and deposition of sediment in rivers and streams. Near the outer edge of a curve, a river or stream will erode the bank. However, in places where the river slows, such as along the inside of curves, sediment tends to be deposited, resulting in the winding shape of mature rivers. Satellite images of such rivers, such as the Mississippi, reveal the extensive curvature of these systems. Active Lecture Tips  Before lecturing about rivers and streams, ask students to work in small groups and write down how the qualities of a stream change between its source and the point where it joins a larger body of water many kilometers downstream. In particular, how do water temperature, water clarity, water speed, and the types of fish inhabiting the water change as the water flows away from its source?

Video: Flapping Geese

Video: Swans Taking Flight

34.7 Current, sunlight, and nutrients are important abiotic factors in freshwater biomes
Freshwater biomes fall into two broad groups: standing water biomes (lakes and ponds) and flowing water biomes (rivers and streams). Student Misconceptions and Concerns  Students may benefit from a review of the general properties of water introduced in Modules 2.10–2.16, which provide insight into the abiotic properties of aquatic biomes. Teaching Tips  The turnover of lakes and ponds in the fall often results in noticeable changes such as fish kills and alterations in water color and smell. If you are addressing this subject in the fall or early winter, you might instruct students to watch for this phenomenon.  The speed of water plays a key role in the removal and deposition of sediment in rivers and streams. Near the outer edge of a curve, a river or stream will erode the bank. However, in places where the river slows, such as along the inside of curves, sediment tends to be deposited, resulting in the winding shape of mature rivers. Satellite images of such rivers, such as the Mississippi, reveal the extensive curvature of these systems. Active Lecture Tips  Before lecturing about rivers and streams, ask students to work in small groups and write down how the qualities of a stream change between its source and the point where it joins a larger body of water many kilometers downstream. In particular, how do water temperature, water clarity, water speed, and the types of fish inhabiting the water change as the water flows away from its source?

Photic zone Benthic realm Aphotic zone Figure 34.7a
Figure 34.7a Zones in a lake

Figure 34.7b Figure 34.7b A stream in the Great Smoky Mountains, Tennessee

Figure 34.7c Figure 34.7c A marsh at Kent State University in Ohio

Terrestrial Biomes

34.8 Terrestrial biomes reflect regional variations in climate
Terrestrial ecosystems are grouped into nine major types of biomes, distinguished primarily by their predominant vegetation. The geographic distribution of plants and thus terrestrial biomes largely depends on climate. The key climate factors are temperature and precipitation The same type of biome may occur in geographically distant places if the climate is similar. Student Misconceptions and Concerns  Before addressing specific terrestrial biomes, consider providing some specific details about weather patterns with reference to the major factors that influence your local weather. Students may not understand the influences of mountains, large bodies of water, and latitude on the weather where they live, and will be engaged by an immediately observable, close-to-home example. Teaching Tips  The University of California Berkeley website on biomes is an excellent resource for Chapter 34.  Consider preparing a chart that will help your students compare the characteristics of the major terrestrial biomes. Students who are just beginning college may still need help learning the best ways to organize information.  Challenge your students to identify unpredictable natural disturbances in the terrestrial biomes examined. How is each biome adapted to recover? What components of each biome are dependent upon these natural disturbances? Exploring the role of disturbances in ecosystems may provide encouragement to students saddened by negative human impacts on biomes.

34.8 Terrestrial biomes reflect regional variations in climate
The current concern about global warming is generating intense interest in the effect of climate on vegetation patterns. Scientists are documenting shifts in latitudes of biome borders, changes in snow and ice coverage, and changes in length of the growing season. A high rate of biome alteration by humans is correlated with an unusually high rate of species loss throughout the globe. Student Misconceptions and Concerns  Before addressing specific terrestrial biomes, consider providing some specific details about weather patterns with reference to the major factors that influence your local weather. Students may not understand the influences of mountains, large bodies of water, and latitude on the weather where they live, and will be engaged by an immediately observable, close-to-home example. Teaching Tips  The University of California Berkeley website on biomes is an excellent resource for Chapter 34.  Consider preparing a chart that will help your students compare the characteristics of the major terrestrial biomes. Students who are just beginning college may still need help learning the best ways to organize information.  Challenge your students to identify unpredictable natural disturbances in the terrestrial biomes examined. How is each biome adapted to recover? What components of each biome are dependent upon these natural disturbances? Exploring the role of disturbances in ecosystems may provide encouragement to students saddened by negative human impacts on biomes.

30°N Equator 30°S Chaparral Coniferous forest High mountains
Figure 34.8 30°N Tropic of Cancer Equator Tropic of Capricorn 30°S Figure 34.8 Major terrestrial biomes Key Tropical forest Chaparral Coniferous forest High mountains (coniferous forest and alpine tundra) Savanna Temperate grassland Arctic tundra Desert Temperate broadleaf forest Polar ice

34.9 Tropical forests cluster near the equator
occur in equatorial areas, experience warm temperatures and days that are 11–12 hours long year-round, and have variable rainfall. Student Misconceptions and Concerns  Before addressing specific terrestrial biomes, consider providing some specific details about weather patterns with reference to the major factors that influence your local weather. Students may not understand the influences of mountains, large bodies of water, and latitude on the weather where they live, and will be engaged by an immediately observable, close-to-home example. Teaching Tips  The University of California Berkeley website on biomes is an excellent resource for Chapter 34.  Consider preparing a chart that will help your students compare the characteristics of the major terrestrial biomes. Students who are just beginning college may still need help learning the best ways to organize information.  Challenge your students to identify unpredictable natural disturbances in the terrestrial biomes examined. How is each biome adapted to recover? What components of each biome are dependent upon these natural disturbances? Exploring the role of disturbances in ecosystems may provide encouragement to students saddened by negative human impacts on biomes.

34.9 Tropical forests cluster near the equator
The tropical rain forest is among the most complex of all biomes. Tropical rain forests harbor enormous numbers of species. Large-scale human destruction of tropical rain forests continues to endanger many species. Student Misconceptions and Concerns  Before addressing specific terrestrial biomes, consider providing some specific details about weather patterns with reference to the major factors that influence your local weather. Students may not understand the influences of mountains, large bodies of water, and latitude on the weather where they live, and will be engaged by an immediately observable, close-to-home example. Teaching Tips  The University of California Berkeley website on biomes is an excellent resource for Chapter 34.  Consider preparing a chart that will help your students compare the characteristics of the major terrestrial biomes. Students who are just beginning college may still need help learning the best ways to organize information.  Challenge your students to identify unpredictable natural disturbances in the terrestrial biomes examined. How is each biome adapted to recover? What components of each biome are dependent upon these natural disturbances? Exploring the role of disturbances in ecosystems may provide encouragement to students saddened by negative human impacts on biomes.

Temperature range Precipitation
Figure 34.9 Temperature range Precipitation Figure 34.9 Tropical rain forest

34.10 Savannas are grasslands with scattered trees
are warm year-round, have 30–50 cm annual rainfall, experience dramatic seasonal variation, are dominated by grasses and scattered trees, and have insects as the dominant herbivores. Student Misconceptions and Concerns  Before addressing specific terrestrial biomes, consider providing some specific details about weather patterns with reference to the major factors that influence your local weather. Students may not understand the influences of mountains, large bodies of water, and latitude on the weather where they live, and will be engaged by an immediately observable, close-to-home example. Teaching Tips  The University of California Berkeley website on biomes is an excellent resource for Chapter 34.  Consider preparing a chart that will help your students compare the characteristics of the major terrestrial biomes. Students who are just beginning college may still need help learning the best ways to organize information.  Challenge your students to identify unpredictable natural disturbances in the terrestrial biomes examined. How is each biome adapted to recover? What components of each biome are dependent upon these natural disturbances? Exploring the role of disturbances in ecosystems may provide encouragement to students saddened by negative human impacts on biomes.

Figure 34.10 Temperature range Precipitation Fire Figure Savanna

34.11 Deserts are defined by their dryness
Deserts are the driest of all terrestrial biomes. They are characterized by low and unpredictable rainfall. The cycles of growth and reproduction in the desert are keyed to rainfall. Deserts can be very hot or very cold. Desertification, the conversion of semi-arid regions to desert, is a significant environmental problem. Student Misconceptions and Concerns  Before addressing specific terrestrial biomes, consider providing some specific details about weather patterns with reference to the major factors that influence your local weather. Students may not understand the influences of mountains, large bodies of water, and latitude on the weather where they live, and will be engaged by an immediately observable, close-to-home example. Teaching Tips  The University of California Berkeley website on biomes is an excellent resource for Chapter 34.  Consider preparing a chart that will help your students compare the characteristics of the major terrestrial biomes. Students who are just beginning college may still need help learning the best ways to organize information.  Challenge your students to identify unpredictable natural disturbances in the terrestrial biomes examined. How is each biome adapted to recover? What components of each biome are dependent upon these natural disturbances? Exploring the role of disturbances in ecosystems may provide encouragement to students saddened by negative human impacts on biomes.  In the 1960s and early 1970s, movies set in the American West were produced in portions of Europe with similar biomes. A Google search for “spaghetti westerns” will produce links to websites devoted to this genre of film.

Figure 34.11 Temperature range Precipitation Figure Desert

34.12 Spiny shrubs dominate the chaparral
The chaparral is a shrubland characterized by dense, spiny shrubs with tough, evergreen leaves. Chaparral experiences cool, rainy winters, hot, dry summers, and vegetation adapted to periodic fires. Firestorms that race through the densely populated canyons of Southern California can be devastating. Student Misconceptions and Concerns  Before addressing specific terrestrial biomes, consider providing some specific details about weather patterns with reference to the major factors that influence your local weather. Students may not understand the influences of mountains, large bodies of water, and latitude on the weather where they live, and will be engaged by an immediately observable, close-to-home example. Teaching Tips  The University of California Berkeley website on biomes is an excellent resource for Chapter 34.  Consider preparing a chart that will help your students compare the characteristics of the major terrestrial biomes. Students who are just beginning college may still need help learning the best ways to organize information.  Challenge your students to identify unpredictable natural disturbances in the terrestrial biomes examined. How is each biome adapted to recover? What components of each biome are dependent upon these natural disturbances? Exploring the role of disturbances in ecosystems may provide encouragement to students saddened by negative human impacts on biomes.  In the 1960s and early 1970s, movies set in the American West were produced in portions of Europe with similar biomes. A Google search for “spaghetti westerns” will produce links to websites devoted to this genre of film.

Figure 34.12 Temperature range Precipitation Fire Figure Chaparral

34.13 Temperate grasslands include the North American prairie
are mostly treeless, except along rivers or streams, are found in regions of relatively cold winter temperatures. experience precipitation of about 25–75 cm per year, with periodic droughts, and in North America have historically been grazed by large bison and pronghorn. Very productive farms have replaced most of North America’s temperate grasslands. Student Misconceptions and Concerns  Before addressing specific terrestrial biomes, consider providing some specific details about weather patterns with reference to the major factors that influence your local weather. Students may not understand the influences of mountains, large bodies of water, and latitude on the weather where they live, and will be engaged by an immediately observable, close-to-home example. Teaching Tips  The University of California Berkeley website on biomes is an excellent resource for Chapter 34.  Consider preparing a chart that will help your students compare the characteristics of the major terrestrial biomes. Students who are just beginning college may still need help learning the best ways to organize information.  Challenge your students to identify unpredictable natural disturbances in the terrestrial biomes examined. How is each biome adapted to recover? What components of each biome are dependent upon these natural disturbances? Exploring the role of disturbances in ecosystems may provide encouragement to students saddened by negative human impacts on biomes.

Figure 34.13 Temperature range Precipitation Fire Figure Temperate grassland

34.14 Broadleaf trees dominate temperate forests
Temperate broadleaf forests grow where there is sufficient moisture to support the growth of large trees and experience wide-ranging temperatures (–30°C to 30°C) and high annual precipitation (75–150 cm). Nearly all of the original broadleaf forests in North America have been drastically altered by agriculture and urban development. These forests typically have a growing season of 5 to 6 months and a distinct annual rhythm of leaf drop in the fall and the production of new leaves in the spring. Student Misconceptions and Concerns  Before addressing specific terrestrial biomes, consider providing some specific details about weather patterns with reference to the major factors that influence your local weather. Students may not understand the influences of mountains, large bodies of water, and latitude on the weather where they live, and will be engaged by an immediately observable, close-to-home example. Teaching Tips  The University of California Berkeley website on biomes is an excellent resource for Chapter 34.  Consider preparing a chart that will help your students compare the characteristics of the major terrestrial biomes. Students who are just beginning college may still need help learning the best ways to organize information.  Challenge your students to identify unpredictable natural disturbances in the terrestrial biomes examined. How is each biome adapted to recover? What components of each biome are dependent upon these natural disturbances? Exploring the role of disturbances in ecosystems may provide encouragement to students saddened by negative human impacts on biomes.

Figure 34.14 Temperature range Precipitation Figure Temperate broadleaf forest

34.15 Coniferous forests are often dominated by a few species of trees
Cone-bearing evergreen trees, such as spruce, pine, fir, and hemlock, dominate coniferous forests. The northern coniferous forest, or taiga, is the largest terrestrial biome on Earth. The taiga is characterized by long, cold winters and short, wet summers. Temperate rain forests of coastal North America are also coniferous forests. Student Misconceptions and Concerns  Before addressing specific terrestrial biomes, consider providing some specific details about weather patterns with reference to the major factors that influence your local weather. Students may not understand the influences of mountains, large bodies of water, and latitude on the weather where they live, and will be engaged by an immediately observable, close-to-home example. Teaching Tips  The University of California Berkeley website on biomes is an excellent resource for Chapter 34.  Consider preparing a chart that will help your students compare the characteristics of the major terrestrial biomes. Students who are just beginning college may still need help learning the best ways to organize information.  Challenge your students to identify unpredictable natural disturbances in the terrestrial biomes examined. How is each biome adapted to recover? What components of each biome are dependent upon these natural disturbances? Exploring the role of disturbances in ecosystems may provide encouragement to students saddened by negative human impacts on biomes.

Figure 34.15 Temperature range Precipitation Figure Coniferous forest

34.16 Long, bitter-cold winters characterize the tundra
The tundra covers expansive areas of the Arctic between the taiga and the permanently frozen polar ice. The treeless arctic tundra is characterized by permafrost, continuously frozen subsoil, and may receive as little precipitation as some deserts. Student Misconceptions and Concerns  Before addressing specific terrestrial biomes, consider providing some specific details about weather patterns with reference to the major factors that influence your local weather. Students may not understand the influences of mountains, large bodies of water, and latitude on the weather where they live, and will be engaged by an immediately observable, close-to-home example. Teaching Tips  The University of California Berkeley website on biomes is an excellent resource for Chapter 34.  Consider preparing a chart that will help your students compare the characteristics of the major terrestrial biomes. Students who are just beginning college may still need help learning the best ways to organize information.  Challenge your students to identify unpredictable natural disturbances in the terrestrial biomes examined. How is each biome adapted to recover? What components of each biome are dependent upon these natural disturbances? Exploring the role of disturbances in ecosystems may provide encouragement to students saddened by negative human impacts on biomes.

Figure 34.16 Temperature range Precipitation Figure Tundra

34.17 Polar ice covers the land at high latitudes
land north of the tundra, much of the Arctic Ocean, and the continent of Antarctica. Temperatures are extremely cold year-round and precipitation is very low. The terrestrial polar biome is closely intertwined with the neighboring marine biome. Student Misconceptions and Concerns  Before addressing specific terrestrial biomes, consider providing some specific details about weather patterns with reference to the major factors that influence your local weather. Students may not understand the influences of mountains, large bodies of water, and latitude on the weather where they live, and will be engaged by an immediately observable, close-to-home example. Teaching Tips  The University of California Berkeley website on biomes is an excellent resource for Chapter 34.  Consider preparing a chart that will help your students compare the characteristics of the major terrestrial biomes. Students who are just beginning college may still need help learning the best ways to organize information.  Challenge your students to identify unpredictable natural disturbances in the terrestrial biomes examined. How is each biome adapted to recover? What components of each biome are dependent upon these natural disturbances? Exploring the role of disturbances in ecosystems may provide encouragement to students saddened by negative human impacts on biomes.

Figure 34.17 Temperature range Precipitation Figure Polar ice

34.18 The global water cycle connects aquatic and terrestrial biomes
Ecological subdivisions such as biomes are linked by nutrient cycles and the water cycle. Water in the form of precipitation and evaporation moves between the land, oceans, and atmosphere. Over the oceans, evaporation exceeds precipitation. Over the land, precipitation exceeds evaporation and transpiration. Student Misconceptions and Concerns  Before addressing specific terrestrial biomes, consider providing some specific details about weather patterns with reference to the major factors that influence your local weather. Students may not understand the influences of mountains, large bodies of water, and latitude on the weather where they live, and will be engaged by an immediately observable, close-to-home example. Teaching Tips  The University of California Berkeley website on biomes is an excellent resource for Chapter 34.  Consider preparing a chart that will help your students compare the characteristics of the major terrestrial biomes. Students who are just beginning college may still need help learning the best ways to organize information.  Challenge your students to identify unpredictable natural disturbances in the terrestrial biomes examined. How is each biome adapted to recover? What components of each biome are dependent upon these natural disturbances? Exploring the role of disturbances in ecosystems may provide encouragement to students saddened by negative human impacts on biomes. Active Lecture Tips  Challenge your students to work in small groups in class to write down the movements of water through your local community. You may want to have them consider all of the possible inputs of water into your community and the possible routes of exit. Students may not realize the possibility that the outflow of water from one community is connected to the inflow of water into another community downstream.

34.18 The global water cycle connects aquatic and terrestrial biomes
Human activities affect the global water cycle. The destruction of tropical rain forests reduces the amount of water vapor in the air. Pumping large amounts of groundwater to the surface for irrigation can increase the rate of evaporation over land, resulting in higher humidity and depleting groundwater supplies. Student Misconceptions and Concerns  Before addressing specific terrestrial biomes, consider providing some specific details about weather patterns with reference to the major factors that influence your local weather. Students may not understand the influences of mountains, large bodies of water, and latitude on the weather where they live, and will be engaged by an immediately observable, close-to-home example. Teaching Tips  The University of California Berkeley website on biomes is an excellent resource for Chapter 34.  Consider preparing a chart that will help your students compare the characteristics of the major terrestrial biomes. Students who are just beginning college may still need help learning the best ways to organize information.  Challenge your students to identify unpredictable natural disturbances in the terrestrial biomes examined. How is each biome adapted to recover? What components of each biome are dependent upon these natural disturbances? Exploring the role of disturbances in ecosystems may provide encouragement to students saddened by negative human impacts on biomes. Active Lecture Tips  Challenge your students to work in small groups in class to write down the movements of water through your local community. You may want to have them consider all of the possible inputs of water into your community and the possible routes of exit. Students may not realize the possibility that the outflow of water from one community is connected to the inflow of water into another community downstream.

Solar heat Net movement of water vapor by wind Water vapor Water vapor
Figure 34.18 Solar heat Net movement of water vapor by wind Water vapor over the sea Water vapor over the land Precipitation over the land Precipitation over the sea Evaporation from the sea Evaporation and transpiration Oceans Figure The global water cycle Surface water and groundwater Flow of water from land to sea

You should now be able to
Define and distinguish between the different levels within ecosystems. Distinguish between the biotic and abiotic components of an ecosystem. Summarize the subject and impact of Rachel Carson’s influential book Silent Spring. Describe the abiotic factors that influence life in the biosphere. Describe the adaptations that enable pronghorns to survive in the open plains and shrub deserts of North America.

Explain how global climate patterns are influenced by solar energy input and the movement of Earth through space. Explain how landforms affect local climate. Explain why the seasons of the year, prevailing winds, and ocean currents exist. Describe the abiotic and biotic characteristics of the different ocean zones, adjacent aquatic biomes, and freshwater biomes. Describe the different types of freshwater biomes.

Explain how the properties of a river change between its source and its outlet. Explain why species in widely separated biomes may have similar features. Describe the characteristics used to define terrestrial biomes. Explain how all parts of the biosphere are linked by the global water cycle.

Organismal Population ecology ecology (individual) (group of
Figure 34.UN01 Organismal ecology (individual) Population ecology (group of individuals of a species) Community ecology (all organisms in a particular area) Ecosystem ecology (all organisms and abiotic factors) Figure 34.UN01 Reviewing the concepts, 34.1

Figure 34.UN02 Equator Figure 34.UN02 Reviewing the concepts, 34.8

Tropical forests cluster near the equator.
Figure 34.UN03-1 34.9 Tropical forests cluster near the equator. Savannas are grasslands with scattered trees. 34.10 34.11 Deserts are defined by their dryness. Figure 34.UN03-1 Reviewing the concepts, 34.9–34.11

Spiny shrubs dominate the chaparral.
Figure 34.UN03-2 34.12 Spiny shrubs dominate the chaparral. Temperate grasslands include the North American prairie. 34.13 Broadleaf trees dominate temperate forests. 34.14 Figure 34.UN03-2 Reviewing the concepts, 34.12–34.14

Coniferous forests are often dominated by a few species of trees.
Figure 34.UN03-3 Coniferous forests are often dominated by a few species of trees. 34.15 Long, bitter-cold winters characterize the tundra. 34.16 Polar ice covers the land at high latitudes. 34.17 Figure 34.UN03-3 Reviewing the concepts, 34.15–34.17

Figure 34.UN04 30N 0 30S Figure 34.UN04 Connecting the concepts, question 1a

March equinox June solstice Constant tilt of 23.5 December solstice
Figure 34.UN05 March equinox June solstice Constant tilt of 23.5 December solstice Figure 34.UN05 Connecting the concepts, question 1b September equinox

Temperate zone Tropics Temperate zone
Figure 34.UN06 Figure 34.UN06 Connecting the concepts, question 1c Temperate zone Tropics Temperate zone

Mean annual temperature (C) Mean annual precipitation (cm)
Figure 34.UN07 a. b. c. 30 d. 15 Mean annual temperature (C) e. f. Figure 34.UN07 Testing your knowledge, question 19 −15 100 200 300 400 Mean annual precipitation (cm)

Introduction Did you ever think a river could catch fire?

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Introduction Did you ever think a river could catch fire?

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