Biomes Maddi
Biomes Maddi
Biomes Maddi
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Chapter 16
Biomes
In Chapter 6, you learned about seasons, wind, ocean currents, and weather patterns. All of these elements work together to produce different climates in different parts of the world. In this chapter, you will learn about climates and climate regions called biomes. Earth has six main biomes that have particular plants and animals. These biomes are deserts, grasslands, temperate deciduous forests, rainforests, taiga, and tundras. In which biome do you live? What types of plants and animals live where you live?
1. How do plants and animals survive in the desert? 2. In which biome would you find a moose? 3. What is your biome like?
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Climate
Factors that You learned about climates in Chapter 6. A climate is defined as affect climate the type of weather patterns that a place has, on average, over a
long period time. If you wanted to know about the climate in a place you were about to visit, you might ask questions like How hot and how cold does it usually get? Does it rain a lot? How often is the temperature below freezing? Climate depends on many factors, including latitude, precipitation, elevation, topography, and distance from large bodies of water. in terms of temperature, wind, and atmospheric pressure. Changes in these conditions cause weather patterns. The Sun is the major source of energy for weather and weather patterns.
Weather patterns Weather is a term that describes the condition of the atmosphere
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Characteristics of biomes
What is a biome? Scientists divide the planet into climate regions called biomes.
Earth has six main biomes: deserts, grasslands, temperate deciduous forests, rainforests, taiga, and tundras. These biomes generally differ in their latitude, weather and relative humidity, amount of sunlight, and topography. Each biome has a unique set of plants and animals that thrive in its climate. biomes - major climate regions
with particular plant and animal communities. Earth has six important biomes.
Latitude and Relative humidity is a measure of how much water vapor an air humidity mass contains (see full definition in Chapter 6). Humidity is related
to plant and animal diversity. From the poles to the equator, humidity and the diversity of plants and animals increases.
Sunlight at the Earth is hottest near the equator where the Sun is closest to being equator vs high directly overhead year round. At the north and south poles, latitudes temperatures are much colder. This effect is related to the fact that
light travels in straight parallel lines. To demonstrate what is happening, imagine shining a flashlight on a sheet of paper (Figure 16.1). The light makes a bright, small spot. By tilting the paper, you can make the light spot bigger and less intense.
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At the equator, sunlight is direct and intense. Earths north and south poles are tilted away from or toward the Sun depending on the time of year (review Chapter 6). The locations of the poles relative to the Sun and Earths spherical surface mean that sunlight reaching these areas is spread out and less intense. As a result, the average yearly temperature at the equator is 27 C (80 F), while at the North Pole it is -18 C (0 F). Generally, as latitude (or distance from the equator) increases, the amount of incoming solar radiation decreases.
on a piece of paper represents solar radiation reaching Earth. If you tilt the paper, the spot of light spreads out and becomes less intense.
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Water helps The differences in temperature between the two cities have to do regulate with water, which is an effective moderator of temperature. Water temperature warms up and cools down slowly. Land warms up and cools down
quickly. Therefore, regions near waterlike Portlanddo not have extremely hot or cold weather. Similarly, wet areas like marshes and swamps dont experience the temperature extremes found in desert regions.
Latitude versus Latitude is an important factor in defining a biome. However, altitude altitude is also a factor. The range of biomes that exist on Earth
from the equator to the poles also exists if one goes from the bottom of a mountain to the top of a mountain (Figure 16.3).
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Earths biomes
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Ecosystems Biomes are large geographic areas. Within a biome, there are
many interrelated ecosystems. An ecosystem is made up of the plants and animals that live there, plus nonliving things like soil, air, water, sunlight, and nutrients. The living and nonliving parts of an ecosystem work together, and each organism plays an important ecological role. On a baseball team, for example, important roles include coach, pitcher, catcher, outfielders, and infielders. Similarly, organisms play roles in their ecosystem.
Biodiversity
Answer the following questions. 1. What does the term diversity mean? 2. What does the term biodiversity mean? 3. Does this statement surprise you? Why or why not? The biodiversity of the desert is greater than for other biomes with the exception of the tropical rainforest. 4. Why is biodiversity in an ecosystem important?
How many roles? The number and types of organisms that an ecosystem can support
depends on the resources available (food sources) and on environmental factors, such as the amount of available sunlight, water, and the temperature. For plants, another important factor is soil composition. The roles within a biome ecosystem depend on the quantity and type of resources. Each ecosystem of a particular biome type has organisms that play similar roles. For example, both a rainforest in South America and a rainforest in Australia have predators, herbivores, and decomposers suited to surviving in the rainforest environment.
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Deserts
Desert regions A desert is a climate region that averages less than 35 centimeters
of rainfall per year. Most deserts are found between the latitudes of 30 N and 30 S. Because of the lack of cloud cover, deserts receive more than twice as much incoming solar radiation as humid regions. They also emit almost twice as much radiation at night. As a result, deserts have large variations in daily high and low temperatures.
How deserts form You may wonder why there is so little rain in the desert. The
answer depends on which desert you are talking about. The Sahara and Australian deserts are caused by regions of high atmospheric pressure found near 30 latitude lines (Figure 16.6). High pressure prevents air near the ground from rising and cooling. As a result, not much condensation takes place. When the condensation rate is lower than the evaporation rate, skies are usually clear and very little precipitation falls.
Australian deserts are caused by regions of high atmospheric pressure found near 30 latitude lines.
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Rainshadow Other deserts, such as one found in eastern Washington state, are deserts caused by the rainshadow effect. Prevailing westerly winds blow
moisture-filled air from the Pacific Ocean over the Washington coast. This air rises as it travels up the western slope of the Cascade mountain range and cools, causing condensation and lots of rain. By the time the air blows over the mountains to the eastern side, there is very little moisture left (Figure 16.7). Olympia, Washington, on the western side of the Cascades, receives an average of 201 centimeters of rain per year. This region has fertile, nutrient-rich land for growing trees. Yakima, on the eastern side, receives only 32 centimeters of rain per year and is a rainshadow desert (Figure 16.8).
Fog deserts A third type of desert is known as a fog desert. Fog deserts are
found on the west coasts of continents located between 20 and 30 latitude. Here the prevailing winds are easterly, so moisture-filled air does not blow in from the ocean. Cold water currents run along many of these coastlines. The cold water causes air to condense as fog over the ocean. The fog drifting over land causes a small amount of precipitation (rain). Fog deserts included the Baja desert of California and the Atacama desert in South America.
Figure 16.7: This graphic illustrates how the rainshadow effect works.
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Grasslands
Grasslands are found on every continent except Antarctica. There are two types of grasslands: tropical grasslands, known as savannas, and temperate grasslands. grasslands - climate regions with
too little rainfall to support a forest. Grasslands have grasses as the main vegetation.
Savannas Savannas are found in parts of the tropics where there is not
enough rainfall throughout the year to create a rainforest. Savannas are characterized by two seasons: rainy and dry. During the rainy season, which lasts for six to eight months, 50 to 127 centimeters of rain falls. This season is followed by a drought, which in many areas culminates with wildfires. The fires and the poor soil conditions prevent the growth of most trees. In fact, in some areas, trees grow only on termite mounds (Figure 16.9). The isolated trees found in savannas have cork-like bark or an outer coating that can withstand some fire damage.
Adaptations to Many large mammals of the savanna, including the wildebeest survive fires pictured at the right, have long legs that enable them to outrun
fires. Smaller mammals burrow under the ground and stay there until the fire has passed over them. Most birds fly away from the fire, but several species, including the Fork-tailed Drongos, actually fly toward the fires so that they can feast on the hordes of insects trying to escape the heat.
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Temperate Temperate grasslands grow in the middle latitude regions and grasslands receive most of their precipitation in late spring and early summer.
Most temperate grasslands are found in the interior of continents, far from large bodies of water. The average yearly rainfall is between 51 and 89 centimeters. Summer temperatures can reach over 38 C, while in the winter they can plummet below -40 C. The soil is rich in nutrients, and much of this biome has been cleared for farmland. Trees are uncommon except along river valleys.
Location Central Asia Southern Africa North America South America Australia
Name used for grasslands steppe savanna or veld prairie pampa outback
Grasslands have Around the world, grasslands go by different names (Figure 16.10). many names In central Asia a grassland is called a steppe. A grassland is called
a savanna or veld in southern Africa. In North America, a grassland is called a prairie. In South America, it is called a pampa. And in Australia, a grassland is called an outback.
Figure 16.10: Grasslands have different names in different parts of the world.
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deciduous trees lose their leaves in the fall, the end of the growing season.
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Tropical rainforests
Tropical Tropical rainforests are found near the equatorbetween the rainforests latitudes of 23.5 N and 23.5 S. They have an average rainfall of
tropical rainforests - climate
regions found near the equator that have a lot of rainfall and high biodiversity.
at least 200 centimeters per year. This large amount of precipitation occurs in the area where the northern and southern hemisphere trade winds meet. The intense Sun and warm ocean water cause this converging air to rise. As the air rises, it cools, condensing into clouds and rain. This cycle happens over and over, causing a period of thundershowers in the warmest part of the afternoon almost every day. Because the tropical rainforests are near the equator, the temperature varies little year round, averaging about 20 to 25 C.
Rainforest life Although tropical rainforests cover less than 6 percent of Earths
land, these biomes have extremely high biodiversity. Half of all of the animal and plant species in the world are found there. There can be as many as 100 different species of plants per hectare (2.47 acres). The most abundant type of plants are tall trees that form a dense canopy. Many foods we enjoy, including Brazil nuts, bananas, pineapple, cocoa, coffee, vanilla and cinnamon flavorings, and coconut originate in tropical rainforests (Figure 16.13).
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Trees and global According to NASA data, an area of tropical rainforest the size of climate North Carolina is destroyed every year. Land is cleared for crops,
grazing, lumber, or firewood. When clear-cutting occurs in this type of biome, the thin topsoil soon washes away, exposing thick clay that is almost useless for agriculture. This clay absorbs the Suns energy and then emits infrared radiation, which is absorbed by greenhouse gases. This process warms the atmosphere. Trees prevent some of this warming. Leaves appear green because they reflect green visible light. Light at this wavelength is not as readily absorbed by greenhouse gases as infrared radiation (Figure 16.14). In a forested area, more of the Suns energy is reflected directly back to space without first being absorbed by greenhouse gases. In this way, trees keep Earth cooler.
Figure 16.14: Recall from Chapter 6 that greenhouse gases describe certain gases in Earths atmosphere. Like the glass in a greenhouse, greenhouse gases can slow down Earths natural heat-loss processes. These gases are useful because they keep Earth warm.
Temperate Like temperate deciduous forests, temperate rainforests are found rainforests in the middle-latitude regions (Figure 16.15). For example,
temperate rainforests are found in coastal areas of the Pacific Northwest. Because these rainforests are in temperate areas, they may have temperate deciduous forest plants like oak trees. Like a tropical rainforest though, temperate rainforests experience a lot of rain (about 250 centimeters per year). Temperate rainforests are cool and periodically covered in fog which provides more moisture for the plants.
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The taiga
The largest land The taiga, otherwise known as a boreal or coniferous forest, is the biome largest land biome. The taiga can be found between the latitudes of
50 and 70 N in North America and Eurasia, including Canada and Russia. The average temperature in the taiga is below freezing for at least six months of the year. This makes it difficult for animals to stay year-round. Some do stay put, some hibernate, and some migrate (Figure 16.17). Annual precipitation averages 40 to 100 centimeters. Much of this falls during the short growing season (approximately 130 days). Summer temperatures rarely reach above 21C.
Figure 16.17: Taiga animals. Which of these animals might migrate during the freezing months?
16.4 TAIGAS AND TUNDRAS
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Taiga life Evergreen trees with needle-like leaves are the most common type
of vegetation found in the taiga, which is the Russian word for forest (Figure 16.18). These include pine, fir, and spruce trees. All of these trees are cone-shaped, which helps them shed snow so its weight doesnt break their branches. The needle shape of the leaves helps prevent moisture loss in the winter. This is important because trees cant take in water from frozen soil. The fact that they dont lose their needles in the fall means that they dont have to waste time in the early spring growing new ones, and can get started on photosynthesis as soon as it is warm enough. The roots of these trees are shallow and spread out wide. This makes it possible for them to take in surface water from melting snow and ice even though much of the ground underneath them is still frozen.
Snow keeps Did you know that snow is a great insulator? In the taiga biome, a things warm! thick layer of snow (often several meters deep) falls before the
coldest part of the winter. The air spaces between snow crystals prevent the ground underneath from losing more and more heat as the winter progresses (Figure 16.19).
Figure 16.18: Evergreen trees with needle-like leaves are the most common type of vegetation found in the taiga.
Surviving the While air temperatures may be well below 0 C for weeks on end, winter in the taiga the ground temperature will remain right around freezing. Mice
and other small mammals make tunnels in the snow that link their burrows and food stashes. The temperature in the burrows remains fairly constant, even when the outside air temperature plummets.
Figure 16.19: The air spaces between snow crystals prevent the
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Tundra
Tundra Tundra is the coldest biome on Earth. The word tundra comes from
a Finnish word for treeless land. There are two types of tundra Arctic tundra, found in a band around the Arctic Ocean, and alpine tundra, found high in mid-latitude mountains.
Arctic tundra Arctic tundra has a growing season of only 50 to 60 days. The
average winter temperature is -34 C. Summer temperatures rarely exceed 12 C. As a result of these cold temperatures, the ground is permanently frozen from 25 centimeters to about 100 centimeters below the surface. This frozen ground is called permafrost (Figure 16.20). There is a thin layer of soil above the permafrost that does thaw in summertime, but it is not deep enough to support the growth of trees. Lichens, mosses, grasses, and a few woody shrubs are the most common plants in the Arctic tundra.
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Permafrost Permafrost has a very important function on our planet: It stores stores carbon carbon dioxide. Heres how the process works. Usually, when dioxide plants die, they decompose into soil. This process releases carbon
dioxide into the air. However, when an Arctic tundra plant dies, the cold temperatures prevent it from rapidly decaying into soil. Instead, at least part of its structure remains intact until it is frozen in the permafrost. In fact, remains of plants 1,000 years old have been found in the permafrost. Since the plant structures dont completely decay, carbon that would have been released into the atmosphere as carbon dioxide stays in the ground. For this reason, permafrost is called a carbon sink (Figure 16.21). altitudes. Alpine tundra biomes occur in the Andes Mountains in South America, in the Rocky Mountains in North America, and in the Himalayan Mountains. Cold temperatures, windy conditions, and thin soil create an environment where only plants similar to those in the Arctic regions can survive. In rocky alpine regions, lichens and mosses are the dominant plants, but in alpine meadows, grasses and small woody shrubs can be found.
What is a carbon sink? Permafrost is known as a carbon sink. A sink is an area where more carbon is stored than is released into the atmosphere. Some scientists are concerned that if Earth warms up several degrees, the permafrost will begin to melt. If this happens, the frozen plants would decompose and release carbon dioxide into the air. The permafrost would no longer serve as a sink. It would become a source of carbon dioxide (a greenhouse gas) in the atmosphere.
Alpine tundra Alpine tundra occurs in middle-latitude regions, but at very high
carbon sink.
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6. What characteristics would you expect Arctic tundra plants to have? 7. Figure 16.22 shows an Arctic fox in the summer and then in the winter on the tundra. From these photographs, state one way that this animal is adapted to live in this biome. 8. Permafrost is known as a carbon sink. a. What is a carbon sink? b. Why is permafrost considered a carbon sink? c. How will global warming affect tundra biomes?
Figure 16.22: The Arctic fox in the summer (top) and in the winter (bottom).
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Chapter 16 Connection
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Fire is also important for maintaining the health of redwood trees. These giant trees have bark that is 2 to 4 feet thick. The bark insulates the tree from heat. After a fire, rich soil is formed and Sequoia seeds sprout new plants. Fires thin out the forest, letting in sunlight to help the seedlings grow. A healthy and vibrant forest ecosystem benefits from fire, which clears debris, allows new plants to grow, provides food for animals, kills diseases, and creates rich soil. Wildfires will always be part of the cycle of life in the forest.
Chapter 16 Connection
Questions:
1. Why is a fire policy that stops all fires not a good policy? 2. How is fire beneficial to a forest? 3. Describe several fire-resistant or fire-adapted trees.
UNIT 5 ECOLOGY
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Biome Expedition
Each individual biome is a region of Earth that has a unique set of plants and animals that thrive in its particular climate. In this chapter you have studied the desert, tundra, taiga, temperate deciduous forest, tropical rainforest, and grassland. Each biome is equipped with a unique set characteristics and harsh conditions, which you have studied. For instance, the desert is extraordinarily dry, and creatures that live there must have special adaptations to deal with a lack of water. Could you survive for three days with one suitcase worth of equipment and no shelter? You must plan carefully because it is likely that you would need different equipment to survive in the tundra than to survive in the tropical rainforest. Your challenge is to survive in one of these biomes for three days and two nights. The most important thing you can do to survive is to pack the proper equipment. Good luck on your expedition! 5. Now, you and your group mates will share the contents of your biome expedition suitcase with your class. Do not tell your classmates why you are bringing each item, simply tell them what you are bringing. 6. When you are done with your presentation, allow your classmate to guess for which biome and season you packed. How did your classmates do? Did they guess correctly?
Chapter 16 Activity
Reflection
Write a paragraph reflecting on the items you chose for your trip. Are there any items you would exchange or add to your suitcase? Are there any items you would remove?
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Vocabulary
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Read the following paragraph and explain the role Earth and the Sun are playing in this phenomenon: In the northern hemisphere, we often associate going south with getting warm. Birds, for example, fly south for the winter. States in the American South and Southwest are known as the sunbelt states. But in the southern hemisphere, the opposite is true. Birds fly north for the winter. The warmest part of Australia is the northern section. If you live near a coastline, would you expect your weather to be milder or more extreme than if you lived far away from the coast? Explain your answer. You can expect to find tundra in the high northern latitudes of the northern hemisphere. Where would you expect to find a tundra ecosystem on a mountain? Explain why plants and animals that are unique to a particular continent can play extremely similar roles as other kinds of plants and animals in similar environments elsewhere. A plant that lives in the desert most likely has the following characteristics. a. b. c. d. A deep root system to get groundwater deep within the ground. A shallow, sprawling root system to collect any/all of the rain that falls to the ground. Thick leaves to help the plant deal with dry conditions. All of the above
1. 2. 3. 4. 5. 6.
_____ are characterized by a cover of various grasses, and a dry climate. An area can only be considered a _____ if it receives less than 35 cm of rain a year. A _____ is a large region of Earth that has a unique set of plants and animals that thrive in its climate. _____ are found in middle-latitude regions and have four distinct seasons. Another name for a boreal or coniferous forest is _____. Although _____ cover less than 6 percent of Earths land, half of all of the animal and plant species in the world live in this biome. Permafrost is found in this extremely cold biome: _____
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Concepts
Section 16.1
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The _____ in a region depends on latitude, precipitation, elevation, topography and the distance from large bodies of water. Explain how latitude, humidity and sunlight play a role in defining a biome.
Section 16.2
8. 9.
2.
Why do deserts have large variations in daily high and low temperatures? Why does Yakima, Washington have relatively little rainfall each year? CHAPTER 16 BIOMES
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23. Describe the difference in the length of days during the summer compared to the winter in the arctic tundra. What accounts for this difference?
12. How many seasons are there in temperate deciduous forests? 13. If you were to visit a tropical rainforest, what could you expect to happen each afternoon? Why? 14. Why doesnt the temperature of a tropical rainforest change very much? 15. Why is so much area of the tropical rainforest destroyed each year? 16. Where are temperate rainforests found?
Section 16.4
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Explain why the average yearly temperature at the North Pole is -18C while the average yearly temperature at the equator is 27C. Study the following map showing population density and the Earths biomes map from the chapter (Section 16.1).
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17. Contrast a deciduous (broad-leaf) tree of a temperate deciduous forest with an evergreen tree in a taiga. 18. List the adaptations that evergreen trees have to help them survive the extreme conditions of the winter in the taiga. 19. In the chapter you learned that snow can keep the ground warm. Explain how this cold-weather stuff keeps things warm! 20. _____ is ground that is permanently frozen from 25 cm to about 100 cm below the surface in the tundra. 21. Arctic tundra has a growing season of _________________ a. b. c. d. 6 months 50-60 days 20-30 days 4 months a. b. Which biomes have the most densely populated areas according to the maps? Which biomes have the least densely populated areas according to the maps?
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CHAPTER 16 ASSESSMENT
7.
Use this table to answer the questions below. Temperature range Biome
Tropical rainforest Tundra
d. 3. a. b. c. d. e.
Section 16.2
a. b. c. d.
4.
Pick one of the types of grasslands listed in Figure 16.10 and research it using the Internet or your library. a. b. c. What is the main type of vegetation in this grassland? What kinds of animals live in this grassland? List one or more adaptations that animals have to live in this biome? 8.
Which biome has the biggest range of temperature? Which biome gets the warmest? Which biome gets the coldest? Using the data above, construct a bar graph that shows the average high temperatures and the average low temperatures for the rainforest compared to the tundra.
Antarctica is a special place on Earth. It is the coldest place and gets little or no rainfall making it a very cold desert! Research Antarctica and describe this unique biome in terms of its rainfall, temperature, and plant and animal life.
Section 16.3
5.
Writing from a point of view: a. People that inhabit the tropical rainforest are destroying it at an extremely fast rate. Write a paragraph that justifies why this is being done. Cutting down the rain forest has ecological consequences. What are these consequences? Write a paragraph that explains why the tropical rainforest should not be cut down.
b.
6.
Explain the connection between tropical rainforests, and greenhouse gases and global warming?
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