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CHAPTER

15 The Biosphere

Preview Key Concepts 15.1 Life in the Earth System

The biosphere is one of Earth’s four interconnected systems.

15.2 ClimateClimate is a key abiotic factor that affects the biosphere.

15.3 BiomesBiomes are land-based, global communities of organisms.

15.4 Marine EcosystemsMarine ecosystems are global.

15.5 Estuaries and Freshwater EcosystemsFreshwater ecosystems include estuaries as well as flowing and standing water.

Review Academic VocabularyWrite the correct word for each definition.

adaptation biome biomass ecosystem

1. : total amount, or dry mass, of organisms in an area

2. : global community of organisms characterized by plant communities and climate

3. : collection of living and nonliving things in an area

4. : trait that allows organisms to better survive in their environments

Preview Biology VocabularyTwo key terms from this chapter share the same word part. Read the definitions and guess what the word part means.

TERM DEFINITION WHAT I THINK PLANKTON MEANS

zooplanktontiny, free-floating animals that live in the water

phytoplanktontiny, free-floating, photo-synthetic organisms

GETTING READY TO LEARN

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SECTION

15.1The biosphere is the portion of Earth that is inhabited by life.

Everything that lives on Earth, and every place where those things live, is part of the biosphere. The biosphere includes all of the living and nonliving parts of all of Earth’s ecosystems. The living parts of the biosphere make up the biota.

The biosphere is one of four major systems on Earth. The other three Earth systems are

• the hydrosphere, all of Earth’s water, ice, and water vapor; • the atmosphere, the air that surrounds the entire planet;• and the geosphere, the physical features of Earth’s sur-

face—including the continents, rocks, the sea floor, and everything below Earth’s surface.

These four Earth systems are interconnected. A plant growing in the biosphere uses water from the hydrosphere, carbon dioxide from the atmosphere, and minerals in the soil that came from the geosphere. The four Earth systems all interact in Earth’s ecosystems.

Which Earth system includes all of the water on Earth?

Biotic and abiotic factors interact in the biosphere.

The four Earth systems include both living and nonliving—or biotic and abiotic—factors. Because they are all connected, a change in one sphere can affect the others. For example, when carbon dioxide levels increase in the atmosphere, plants can grow more quickly. As plants use more carbon dioxide, the levels of carbon dioxide in the atmosphere will drop. When the carbon dioxide levels drop, plant growth will slow. This is an example of a give-and-take, or a feedback loop, between the living and nonliving parts of Earth. New fields of science are investigating the relationships between the four Earth systems.

What do the words biotic and abiotic mean?

Life in the Earth SystemKEY CONCEPT The biosphere is one of Earth’s four interconnected systems.

The biosphere includes living organ-isms and the land, air, and water on Earth where living things reside.

VISUAL VOCAB

biosphere

biota

The collection of living things in the biosphere may also be called the biota.

Interactive Reader 255

B.4.1

What do the words biotic and abiotic mean?

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biosphere atmosphere

biota geosphere

hydrosphere

Fill in the blanks with the correct term from the list above.

1. the living part of the biosphere

2. the air that surrounds Earth

3. the water system on Earth

4. the features of Earth’s surface and below

5. the part of Earth where life exists

6. This drawing illustrates the interaction between the four main Earth systems. Label the part of the drawing that represents each system: biosphere, hydrosphere, atmosphere, and geosphere.

15.1 Vocabulary Check

Go back and highlight each sentence that has a vocabulary word in bold.

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15.1 The Big Picture

carbon dioxide

oxygen

minerals water

McDougal Littell Biology256

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SECTION

15.2Climate is the prevailing* weather of a region.

The weather may change from day to day. One day it might rain, and another day it might be sunny. In contrast, climate does not change from day to day. The climate is the long-term pattern of weather conditions in a region. Climate includes average temperature and precipitation, such as rain or snowfall. Climate also includes the changes that happen at different times of the year, like rainy seasons, dry seasons, winter, or summer.

A microclimate is the climate in a small, specific place within a larger area. For example, there may be many microclimates within a grassy meadow. The tops of the grasses might be dry and warm because they are exposed to sunlight. At the base of the grasses, near the ground, it may be shaded, damp, and cool. Different types of organisms may live in different microclimates within the same area. For example, frogs may live in the cool damp areas of the meadow and grasshoppers may live in the sunny dry tops of the grasses.

What is a microclimate?

Earth has three main climate zones.Earth can be divided into three main climate zones: polar, tropical, and temperate.

• The polar climate zone is found at the far northern and southern regions of Earth. Because Earth’s surface is curved, this area receives the least direct sunlight.

• The tropical climate zone is near the equator. This area receives the most direct sunlight.

• The temperate climate zone includes the area in between the tropical and polar zones.

The amount of direct sunlight that hits different parts of Earth is a main factor in the type of climate in that region. Other factors also influence climate. For example, the movement of air and water affects temperature and rainfall. Features such as mountains and oceans also affect climate.

ClimateKEY CONCEPT Climate is a key abiotic factor that affects the biosphere.

* ACADEMIC VOCABULARY

prevailing frequent, common


B.4.4

What is a microclimate?

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CLIMATE ZONES

The uneven heating of Earth by the Sun results in threePOLAR CLIMATE

The polar climate zone is located infar northern and far southern parts of the planet, where the temperatureis typically cold and often below freezing.

TROPICAL CLIMATE

The tropical climate zone, which sur-rounds the equator, is characterizedby warm, moist conditions.

TEMPERATE CLIMATE

The temperate climate zone is located in the broad area lying between thepolar and tropical climate zones. This zone has summer and winter seasonsof about equal length.

polar

temperate

tropical

temperate

polar

In which climate zone do you live?

climate microclimate

1. How is a microclimate different from a climate?

2. What are the three main climate zones?

3. What are two main factors that determine the type of climate in aregion?



Mark It Up15.2 Vocabulary Check


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15.2 The Big Picture15.2 The Big Picture


SECTION

15.3Earth has six major biomes.

A biome is a region that is defined by the climate and the plant commu-nities that live in the area. There are six major biomes:

• Tropical rain forest• Grassland• Desert• Temperate forest• Taiga• Tundra

These broad biomes can be divided into more specific zones. For example, there are different kinds of grasslands and different kinds of temperate forests.

WORLD BIOMES

A biome is defined by its climate and by the plant communities that live there.

Tropical Rain Forest Biome• This biome has warm temperatures and lots of rain. • Most organisms live in the uppermost branches of the forest,

which is called the canopy. • Very little sunlight makes it through the canopy.• Animals that live in the canopy use loud vocalizations to

communicate.

BiomesKEY CONCEPT Biomes are land-based, global communities of organisms.

Student text pages 462–467

See biomes in student text, pg. 463

Visual Connection


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Grassland Biome• A grassland is an area in which the main plant life

is grass.• There are both tropical and temperate grasslands.• In tropical grasslands, hoofed animals such as gazelles

and zebras are most common.• In temperate grasslands, many animals, such as prairie

dogs, live underground.

Desert Biome• A desert is very dry and gets little rain. • Plants and animals have adaptations to survive the

dry climate. • There are four types of deserts: hot, semi arid, coastal,

and cold.

Temperate Forest Biome• This biome has very different summer and winter seasons. • One type of temperate forest has deciduous trees, which drop

their leaves to survive cold winters. • Another type of temperate forest has many coniferous trees,

which keep their needles all year.

Taiga Biome• The taiga (TY-guh) is located in cooler climates. • Winters are long and cold and summers are short.• This biome has coniferous forests.

Tundra Biome• The tundra is located north of the taiga. • This biome has the coldest and longest winters.• The ground below the surface is always frozen.

In addition to the six major biomes, there are also some smaller biomes. One example is the chaparral (SHAP-uh-RAL), which has hot, dry summers and cool, moist winters. This biome is found along the southern coast of California and several other parts of the world. The main chaparral plants are small evergreen shrubs.

In the map of world biomes on page 259, circle the biome in which you live.

These are leaves of deciduous trees.

This conifer keeps its needles all year.


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Polar ice caps and mountains are not considered biomes.

Polar ice caps are ice-covered areas that have no soil and no specific plant community. In mountains, the climate and the plant and animal communities change at different altitudes.* Recall that biomes are defined partly by the plant community that lives in the region. Because polar ice caps do not have specific plant communities and mountains have different plant communities at different altitudes, these two regions are not considered biomes.

Why aren’t polar ice caps and mountains considered biomes?

altitude height above sea level


canopy coniferous

grassland taiga

desert tundra

deciduous chaparral


1. The two coldest biomes are .

2. Two types of trees are .

3. The top layer of rain forest trees is called the .

4. The driest biome is the .

5. Pick one of the six main biomes and describe it in the chart below.

Name of the biome

Location

Description



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SECTION

15.4The ocean can be divided into zones.

The ocean can be divided into zones according to distance from shore and water depth. The four major ocean zones are the intertidal zone, neritic zone, bathyal zone, and abyssal zone.

• The intertidal zone is the shore-line area between high and low tide lines. This zone contains tidal pools.

• The neritic zone (nuh-RIHT-ihk) is the next closest area to shore. This zone may be very shallow in some places and up to 200 meters deep in other places.

• The bathyal zone (BATH-ee-uhl) extends from the edge of the neritic zone to the ocean bottom. This zone ranges from about 200 to 2000 meters deep.

• The abyssal zone (uh-BIHS-uhl) is the deepest zone. No sunlight reaches this zone, so photosynthetic organisms do not live here. Instead, chemosynthetic organisms form the base of the food web.

Life in the Neritic ZoneThe neritic zone makes up only a small percentage of the total ocean area, but it contains a large percentage of ocean life. Huge quantities of tiny free-floating organisms called plankton live in the neritic zone. There are both animal plankton and photosynthesizing plankton. Ani-mal plankton are called zooplankton and photosynthesizing plankton are called phytoplankton.

Most of the photosynthesis that occurs on Earth is done by blue-green algae and other phytoplankton. Around 70 percent of the oxygen in each breath you take was produced by phytoplankton in the ocean. These organisms form the base of the food web in this zone.

What is the difference between zooplankton and phytoplankton?

Marine EcosystemsKEY CONCEPT Marine ecosystems are global.


OCEAN ZONES

The ocean is divided into four major zones.

abyssalzone

bathyalzone

neritic zoneintertidal zone


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Coastal waters are unique habitats.The neritic zone is nutrient-rich, and sunlight reaches through the water. This zone supports two main ocean habitats: coral reefs and kelp forests.

• Coral reefs are found mainly within the tropical climate zone. Water temperatures are warm all year. There may be hundreds of species of corals, fishes, sponges, and sea urchins in a single coral reef.

• Kelp forests are found in cold waters, such as California’s Monterey Bay. Thick communities of kelp, a type of seaweed, make up this habitat. A wide range of species lives here, from tiny invertebrates to large sea lions.

In which ocean zone are coral reefs and kelp forests found?

intertidal zone zooplankton

neritic zone phytoplankton

bathyal zone coral reef

abyssal zone kelp forest

plankton


1. List the four ocean zones, from closest to shore to farthest from shore.

2. Which term is a tiny, free-fl oating organism?

3. What organisms form the base of the food web in the neritic zone?

4. What organisms form the base of the food web in the abyssal zone?

5. What is one main difference between the coral reef and kelp forest habitats?



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Sponges and fi sh live in coral reefs.


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SECTION

15.5

Estuaries are dynamic* environments where rivers flow into the ocean.

The area where a river flows into an ocean is called an estuary. Estuaries include many different ecosystems, such as salt marshes, mud flats, open water, mangrove forests, and tidal pools. Estuaries are sometimes called nurseries of the sea. Just like a nursery center takes care of babies, estuar-ies are very important areas where many different species of ocean organisms raise their young.

Estuary Characteristics• Fresh water from the river mixes with the salt water from the ocean

in estuary environments.• Estuaries are rich in nutrients that wash in from land. • Estuaries have great biodiversity. • Migrating birds use estuaries as stops along their migration paths.• Estuaries provide a protected area where many different species lay

eggs and raise young.

Estuaries Protect CoastlinesEstuaries are located between the ocean and the coast. They help to protect shorelines from storms, winds, and flooding. In some coastal areas of the United States, over 80 percent of the estuaries have been destroyed by land development and human activities. The destruction of estuaries harms ocean life. Their destruction also leaves the coastline unprotected, and more likely to be damaged by storms.

Why are estuaries sometimes called “nurseries of the sea?”

Estuaries and Freshwater EcosystemsKEY CONCEPT Freshwater ecosystems include estuaries as well as flowing and standing water.



dynamic active, constantly changing

Recall from Chapter 13 that biodiversity is the variety of species in an area. Estuaries have a high biodiversity.

VOCABULARY


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Freshwater ecosystems include moving and standing water.

Rivers and streams are ecosystems with moving water. Lakes and ponds are ecosystems with standing water, or water that stays in the same place. The water that fills these freshwater ecosystems comes from rain, snow, and springs that drain into the rivers and lakes from the surrounding land. The region of land that drains into a freshwater ecosystem is called a watershed.

WetlandsIn addition to rivers, streams, lakes, and ponds, wetlands are also impor-tant freshwater ecosystems. A wetland is an area of land that stays soaked in water for at least part of the year. Wetlands include bogs, marshes, and swamps. These are important habitats for many different species. Wet-lands also help to filter water and maintain a clean water supply.

Adaptations of Freshwater OrganismsDifferent freshwater ecosystems can differ in water temperature, oxygen levels, pH, the speed of water flow, and many other conditions. Each type of freshwater ecosystem is home to species with adaptations for the particular conditions in that ecosystem.

What is a wetland?

Ponds and lakes share common features.Just like the ocean can be divided into zones, so can lakes and ponds. Lakes and ponds can be divided into three zones: littoral, limnetic, and benthic.

• The littoral zone is along the shoreline, between the high and low water marks where rooted plants can grow. Snails, water lilies, and other organisms live here.

• The limnetic zone is the open water further out from shore. Large amounts of plankton live here, and are food for populations of fish.


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• The benthic zone is the lake or pond bottom, where less sunlight reaches. Bacteria and other decomposers live in the mud and sand in the benthic zone.

In which zone do many plankton live?

estuary limnetic zone

watershed benthic zone

littoral zone

Match the correct term from the list above to each description below.

1. bottom zone of a lake that receives little sunlight

2. region of land that drains into a river or lake

3. area where a river meets the ocean

4. open water zone of a lake

5. edge of a lake where rooted plants can grow

6. Describe the estuary environment in a way that a younger student could understand.

7. List at least one freshwater ecosystem with moving water and one with standing water.

8. Decomposers live in the mud and sand on the bottom of lakes and ponds. In which zone do they live—littoral, limnetic, or benthic?



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Chapter 15 Review 1. Label Earth’s three main

climate zones at the right.

2. How do the three climate zones differ?

3. In which climate zone is the tundra biome located?

4. What is one way in which deciduous and coniferous trees differ?

5. Which ocean zone contains the greatest biodiversity and the most ocean life?

a. the intertidal zone

b. the neritic zone

c. the bathyal zone

d. the abyssal zone

6. What is one way in which oxygen moves between the biosphere and the atmosphere in an ecosystem?

a. through decomposition and nitrogen fi xation

b. through biotic adaptations

c. through photosynthesis and respiration

d. oxygen is abiotic, and does not cycle through the biosphere

7. How has human activity affected estuary ecosystems?

8. Give an example of how the biosphere, atmosphere, hydrosphere, and geosphere interact in Earth’s ecosystems.


B.4.4

B.4.4

B.4.4

B.4.4

B.4.1

B.3.4

B.4.2

B.4.1

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