Earth s Land and Water

Transcription

1 CHAPTER 2 Earth s Land and Water How do organisms survive in land and water ecosystems? 96

2 Lesson 1 Earth s Land Biomes PAGE 100 Lesson 2 Earth s Water Ecosystems PAGE 118 Lesson 3 Ecosystems in California PAGE LS 5. Organisms in ecosystems exchange energy and nutrients among themselves and with the environment. 97

3 Literature POEM ELA R Define how tone or meaning is conveyed in poetry through word choice, figurative language, sentence structure, line length, punctuation, rhythm, repetition, and rhyme. ELA W Write research reports. 98

4 MOJAVEfrom MOJAVE by Diane Siebert I am the desert. I am free Come walk the sweeping face of me. And as the desert seasons change, The hands of Nature rearrange My timeworn face with new designs Of colors, shadows, shapes and lines: In wintertime the north winds blow; My mountain peaks are capped with snow; But resting, waiting patiently Beneath the frost that covers me, I dream of spring, when I can wear The blossoms of the prickly pear, Along with flowers, wild and bright, And butterflies in joyful flight. Write About It Response to Literature This poem describes how a desert changes with the seasons. What happens when spring arrives? What causes the changes to occur? Write a research report about flowering plants that grow in the desert. Explain when they bloom and what causes them to do so. -Journal Write about it 99

5 Lesson 1 Earth s Land Biomes Although deserts receive little rainfall, many different organisms live there. In places such as Joshua Tree National Park in California, you can discover many secrets of the desert. What kinds of plants and animals live there? How do they survive? 100 ENGAGE 6 LS 5.d. Students know different kinds of organisms may play similar ecological roles in similar biomes.

6 What are Earth s biomes like? Make a Prediction A biome is a land region that has a particular climate. Earth s biomes include taiga, tundra, tropical rain forest, deciduous forest, desert, and grassland. Do all biomes have the same kinds of plants and animals? Write your answer as a prediction in the form If each biome has a particular climate, then plants and animals live in each. Test Your Prediction Work in groups of four or five. Each group should select one biome. Tape the paper to the walls of the classroom. Research the biome you selected. Find out about its location, climate, soil, and its plants and animals. Make a Model Draw a mural that represents your biome. Show at least two plants and two animals that live in the biome. Include a world map that shows the location of the biome. Communicate List the information you collected on the index cards, and attach them to your mural. Indicate where you obtained the information. Draw Conclusions Compare the plants and animals in the biomes. What similarities and differences do you see? Did your observations support your prediction? Explore More Compare food chains from the biomes. What are the main producers in each? What are the main consumers? Step Materials long piece of white butcher paper crayons and colored markers index cards 6 IE 7.d. Communicate the steps and results from an investigation in written reports and oral presentations. 101 EXPLORE

7 Main Idea 6 LS 5.d The environment defines the ecological roles of organisms. Vocabulary biome, p. 102 climate, p. 102 deciduous, p. 110 taiga, p. 112 What is a biome? Land on Earth can be classified into six major areas called biomes (BIGH ohmz). A biome is a region with a particular climate (KLIGH muht) that contains certain types of plants and animals. Climate is the average weather pattern of a region. It is mainly determined by temperature and precipitation. Differences in climate from place to place create different conditions for living things. tundra, p Reading Skill Cause and Effect California redwood forest 102

8 Earth s Biomes /@1B71 =13/< /B:/<B71 =13/< B`]^WQ ]T 1O\QS` >/17471 =13/< 3_cOb]` 7<27/< =13/< 7QS B`]^WQ ]T 1O^`WQ]`\ Bc\R`O BOWUO 2SQWRc]ca T]`Sab B`]^WQOZ `OW\ T]`Sab 5`OaaZO\R 2SaS`b Reading Maps Why are there different biomes around the world? Climate affects plant and animal life. All the organisms in a biome are adapted to live in the region s climate. That is why you will not find a penguin on a beach in Southern California or a cactus growing in the Arctic. Several factors help determine a region s climate. One factor is the amount of sunlight. Areas closer to the equator receive more direct sunlight than areas closer to the poles. Wind patterns, ocean currents, and barriers such as mountains also affect climate. Distance above sea level is another factor. Places at higher elevations tend to have cooler climates. A particular biome can be found in different parts of the world. For example, desert biomes exist in North Clue: Look at where different biomes are located in relation to the equator. America, South America, Africa, Asia, and Australia. However, most deserts lie at about latitude 30 N or 30 S. Tundra biomes exist in North America and Asia. At what latitude are they located? Quick Check Cause and Effect How does the amount of sunlight in a region affect its climate? Critical Thinking Why do you think some plants live only in biomes with cold climates? 103

9 What are tropical rain forests? Tropical rain forests are biomes located near the equator, where the Sun s rays strike Earth s surface most directly. The climate in tropical rain forests is hot and humid, with a lot of rainfall. This climate supports an enormous variety of plant and animal species more than those in all the other biomes combined. Vegetation grows in the rain forest in four levels. At the top is the emergent layer. This layer is made up of the tops of very tall trees that emerge from the forest below into the sunlight above. Many birds nest in this area to avoid predators. The next level, the canopy, shades the rain forest with a thick blanket of foliage. This foliage is so thick that very little sunlight passes through to the layers below. Plants such as orchids grow on the branches of trees, with their roots exposed to the air. Orchids absorb water and nutrients through their roots. Many animals, such as toucans, monkeys, snakes, owls, and insects, make their homes in the canopy. With an abundance of food available to them, some animals never leave this level. Tropical Rain Forest emergent layer scarlet macaw canopy emerald tree boa understory red-eyed tree frog forest floor Reading Diagrams Why do you think many animals live in the canopy layer? Clue: Where do animals find food? tapir 104

10 Tropical Rain Forest Location: Near the equator Climate: Hot year round, cm ( in.) of precipitation per year Soil: Poor in nutrients Plants: Greatest diversity of any biome; vines, orchids, ferns, and a wide variety of trees Animals: More species of insects, reptiles, and amphibians than any other biome; many tree-dwelling animals The Understory and the Forest Floor Beneath the canopy of the rain forest is the understory. This layer is made up of the trunks of the canopy trees as well as shrubs, vines, and small plants. Animals such as frogs, insects, snakes, and jaguars and other cats live in the understory. This part of the forest receives very little sunlight. The bottom level of the rain forest is the forest floor. Without sunlight very few plants can grow here. The soil is low in nutrients, because the shallow root systems of rain-forest trees quickly absorb nutrients. Rain also washes away some plant nutrients. Insects, snakes, frogs, and mice live on the forest floor. Plants here have large leaves to capture the limited amount of sunlight. Rain forests are found in Central America, South America, India, Africa, Southeast Asia, Australia, and many tropical islands. Although plant and animal species found in each rain-forest environment may differ, their roles remain the same. For example, squirrel monkeys live in large troops in the tropical rain forests of South America. The talapoin, another small monkey, lives in large troops in the rain forests of central Africa. Both types of monkeys eat fruit, seeds, insects, and eggs. Quick Check Cause and Effect Why does little sunlight reach the understory and the floor of a tropical rain forest? Critical Thinking Which layer of a tropical rain forest receives the most sunlight? Why? 105

11 What are deserts? Deserts are areas that receive less than 25 cm (about 10 in.) of rainfall per year. Plants and animals that live in deserts have special adaptations for surviving in such dry environments. There are four major types of deserts: hot and dry deserts, semideserts, coastal deserts, and cold deserts. The types are determined by their temperature ranges and the amount of rainfall they receive. Desert biomes are found on every continent, including Antarctica. Remember the definition of a desert. It is determined by the amount of rainfall, not the location. Hot and Dry Deserts As the name implies, these deserts are hot and dry year-round, especially in the summer. During the day the desert air contains little moisture to block the Sun s rays. At night the air can become very cool, because there is no cloud cover, and the dry air loses heat easily after dark. Hot and dry deserts receive little rainfall. When rain does fall, the water often evaporates before it reaches the ground. Occasionally, short periods of heavy rain occur and may cause flooding. Like other hot and dry deserts, the Mojave Desert in California has plants and animals that live in dry conditions. Plants that conserve water, such as yucca, prickly pear, and agave, can survive there. The animals tend to rest during the hot day and become active when the temperatures fall at night. They include insects, spiders, reptiles, birds, and burrowing animals. Animals in other desert regions play similar roles. For example, the jerboa of the Sahara in Africa also burrows in the sand during the day and comes out at night to search for food. Hot and Dry Desert Location: Middle latitudes Climate: Very hot days and cool nights, less than 25 cm (10 in.) of precipitation per year Soil: Poor in animal- and plantdecay products but often rich in minerals Plants: Cactuses, yucca, bunch grasses, shrubs, and a few trees Animals: Rodents, snakes, lizards, tortoises, insects, birds; in the Sahara in Africa, camels, gazelles, antelopes, small foxes, snakes, lizards, and gerbils 106 Arches National Park, Utah

12 Endangered Species Semideserts Semideserts are often located between a hot and dry desert and a grassland or a woodland. As in hot and dry deserts, summer temperatures are hot during the day and cooler at night. Semidesert plants include the creosote bush, bur sage, white thorn, catclaw, mesquite, and brittlebush. During the day, insects stay in shaded areas. Many animals remain in their burrows, where they are protected from the heat. The most common animal species include ground squirrels, jackrabbits, kangaroo mice, and kit foxes. Coastal Deserts and Cold Deserts collared lizard Coastal deserts are typically found on the western edges of continents. They have cool winters and warm summers. The Atacama Desert in Chile is a coastal desert near the Pacific Ocean. It is Earth s driest desert and sometimes receives no rain at all for several years. Cold deserts are found near the North and South poles, in places such as Antarctica, central Asia, and Greenland. These deserts have long, cold winters and short summers. Choose an endangered animal species to study. Use books, Web sites, and other sources to find information about this endangered species. Identify the species niche in its biome. Find out what it eats, where it lives, and how it interacts with plants and other animals in the biome. Draw a food web that shows the interactions between the endangered species and the plants and other animals in the biome. Show how they depend on each other for resources such as food and shelter. Infer What would happen if this animal became extinct? Quick Check Cause and Effect How does dry desert air contribute to the heat of a hot and dry desert? Critical Thinking How does resting during the day help desert animals survive? 107

13 What are grasslands and savannas? Grasslands are biomes in which grasses are the main plant life. Rainfall is irregular and usually not plentiful. Temperatures are cool in winter and warm in summer. Some of the world s most fertile soils are found in grasslands. For this reason grasslands are often used for farming. The roots of grassland plants hold soil in place. If the plants are removed, the soil can be blown away by winds. In the late 1800s, thousands of settlers in North America moved into the area known as the Great Plains. Grassland Location: Middle latitudes, interiors of continents Climate: Cool in winter and warm in summer, cm (10 30 in.) of precipitation per year Soil: Rich topsoil Plants: Mostly grasses and small shrubs, some trees growing near sources of water Animals: Prairie dogs, foxes, small mammals, snakes, insects, and various birds in American grasslands; elephants, lions, zebras, and giraffes in African grasslands Arriving in covered wagons called prairie schooners, they found prairies full of tall grasses as well as bison and other wildlife. Before long these tallgrass prairies were plowed under for farmland. Only about 1% of the original grasslands still exists. The plants and animals in grasslands vary from place to place. In North America, herbivores such as bison, gophers, ground squirrels, and prairie dogs live in the grasslands. Carnivores there include coyotes, badgers, and black-footed ferrets. The grasslands of central Russia, known as steppes, have different animals, such as Siberian chipmunks and wild boars. The grasslands of Argentina, known as the pampas, are home to pampas deer. A bison grazes in a grassland biome. 108

14 Savannas Savannas are a type of grassland. They stay warm year round. The soil is not as fertile as the soil of other grasslands. However, savannas receive more rainfall than other grasslands, although not enough to support a dense growth of trees. Savannas have long, dry winters and very wet summers. During the dry season, natural fires occur. These fires help clear out dead leaves and branches, prevent trees and shrubs from growing, and encourage the growth of grasses. Africa has large savannas dotted with acacia trees, which provide shade for animals. Animals in the African savannas include lions, giraffes, zebras, and antelope. In savannas and grasslands around the world, different organisms may play the same role. For example, the serval, a type of wildcat, lives in the savannas of Africa. It has the same feeding behavior as the maned wolf of the South American grasslands. Even though they live on different continents, both prey on rodents, lizards, and other small animals. Plants, such as the eucalyptus tree of the Australian savanna and Africa s acacia tree, also play similar roles. Quick Check Cause and Effect What happens when a natural fire occurs in a savanna? Critical Thinking What role do grasses play in a grassland biome? a family of lions in the African savanna 109

15 Deciduous Forest Location: Middle latitudes Climate: Relatively mild summers and cold winters, cm (30 50 in.) of precipitation per year Soil: Rich topsoil over clay Plants: Hardwoods such as oak, beech, hickory, and maple trees What are temperate deciduous forests? For a few months each year, the deciduous (di SIHJ uh wuhs) forests in some parts of North America are ablaze with color. This is when the leaves turn from green to the colors of autumn red, orange, yellow, and brown before falling to the ground. fungi on a tree trunk Animals: Wolves, deer, bears, and a wide variety of small mammals, birds, amphibians, reptiles, and insects Deciduous means tending to fall off during a particular season. Deciduous forests are those in which the leaves fall off many of the trees when winter comes. This enables the tree to conserve energy when sunlight is scarce. Deciduous trees include ash, oak, beech, hickory, and maple. When the leaves fall to the ground, they decay, making the soil very rich and fertile. Decomposers such as bacteria help break down the leaves. Deciduous forests also have species of evergreen trees. Most evergreen trees do not shed their leaves. Deciduous forests are found in eastern North America, northeastern Asia, and western and central Europe. In these forests, mosses, mushrooms, and ferns carpet the forest floor. 110

16 Animals in a Temperate Deciduous Forest You might observe birds such as cardinals, robins, crows, and hawks in deciduous forests. Under a rock you might find a salamander, a frog, or a garter snake. Chipmunks, squirrels, mice, and deer move through the forest looking for food. Some forest animals are herbivores that eat nuts, berries, and leaves. Other animals, such as cougars, coyotes, bears, owls, and raccoons, are predators. Great horned owls live in forests throughout the Americas. Owls are very efficient hunters. They usually become active at twilight, when the Sun has almost set. They have very good eyesight and can spot the small animals that run along the forest floor. Their specialized feathers allow them to fly almost noiselessly. Deer often live in forests. These animals will eat almost any plants. The spotted coat of a young deer helps it hide in the dappled light of a forest. The number of deer has increased dramatically in some areas. Ferns and mosses have adaptations that allow them to survive in the weak light that penetrates the tree leaves. Fungi do not need light to survive. They get their energy from breaking down dead organisms. The red salamander is often found in damp places under rocks or logs. Some salamanders can take in oxygen through their skin. In many places the number of these small creatures has declined dramatically. great horned owl deer red salamander Quick Check Cause and Effect How do fallen leaves affect the soil of the forest? Critical Thinking What is the main characteristic of a deciduous forest? 111

17 Taiga Location: Middle to high latitudes Climate: Very cold winters and cool summers, about 50 cm (20 in.) of precipitation per year Soil: Acidic and poor in minerals, decayed pine and spruce needles on surface Plants: Mostly spruces, firs, and other evergreens Animals: Birds (in summer), rodents, snowshoe hares, lynx, sables, ermines, caribou, bears, and wolves wolves in a taiga What are taigas and tundras? Taigas (TIGH guhs) and tundras are biomes found in far northern regions. The climates in these regions include very cold winters. For this reason tundras and taigas have fewer plant and animal species than other biomes. Taigas Taiga is the Russian word for forest. A taiga is a cool forest of cone-bearing evergreen trees. It is sometimes called a boreal forest. Trees in the taiga grow in clusters that provide some protection against winter s cold and wind. The taiga of the Northern Hemisphere, which stretches across Eurasia and North America, is the world s largest biome. Taiga winters are very cold, and summers are warm, rainy, and humid. These summer conditions encourage millions of insects to reproduce, which in turn attracts migrating birds. Taiga plant life is limited to the few species that can survive the rugged winters. These include trees such as pine, spruce, and hemlock as well as lowgrowing lichens and mosses. Taigas are also home to predators such as lynx, wolverines, and bobcats. These animals hunt herbivores such as snowshoe hares, red squirrels, and voles. 112

18 caribou in a tundra Tundra Location: High, northern latitudes Climate: Very cold, harsh, long winters and cool, short summers; cm (4 10 in.) of precipitation per year Soil: Poor in nutrients; permafrost layer a few centimeters (inches) down Plants: Grasses, wildflowers, mosses, and small shrubs Animals: Musk oxen, migrating caribou, arctic foxes, weasels, snowshoe hares, owls, hawks, various rodents, and occasional polar bears Tundras A tundra is a very cold, dry biome that includes a layer of permanently frozen soil. The frozen-soil layer is called permafrost. Tundras cover about 20% of Earth s surface. In the Northern Hemisphere, tundras circle the North Pole and spread south to the taigas. The cold, dry tundra conditions limit the types of plants and animals that can survive there. The permafrost prevents trees and large plants from rooting. However, mosses, grasses, lichens, flowers, and low shrubs can grow. They have adapted to resist the cold, harsh winds. Mammals such as snowshoe hares, caribou, and musk oxen feed on lichens and plants. Predators such as hawks, wolves, arctic foxes, and polar bears feed on these herbivores and other animals. As in the taigas, summer brings many different species of insects, which attract migratory birds. Quick Check Cause and Effect How does permafrost affect tundra plant life? Critical Thinking Why do plants such as grasses, mosses, and small shrubs grow in taigas? 113

19 What lives in Earth s coldest places? Freezing temperatures can be found at Earth s North and South poles. In these places the landscape is white, because snow or ice lasts the whole year. Cold winds and icy temperatures are a year-round feature. The Arctic regions, near the North Pole, and the Antarctic regions, near the South Pole, differ in one important way. There is no land near the North Pole. What appears to be snow- and ice-covered land is actually only snowand ice-covered water. In most winters the polar ice cap that covers the North Pole is solid. In the summer this polar ice cap breaks up into smaller pieces. Sometimes huge icebergs break off and drift south into the North Atlantic shipping lanes. The snow and ice near the South Pole, however, cover the huge continent of Antarctica. In the summer the vast continent remains covered with snow and ice. Glaciers near the ocean s edge produce icebergs. These icebergs float north on ocean waters toward the equator. Life in the Polar Regions Most life on Earth depends on energy from the Sun. This energy is trapped by plants and other producers and enters the food chain. In the cold polar regions, plants are not able to grow on land. All life in these regions ultimately depends upon life in the sea. Close to the North Pole, the polar bear, Earth s largest land carnivore, can be found. The diet of these bears consists mostly of seals and walruses, animals that live on fish and shellfish. In the winter polar bears move south into land areas, where they eat small animals, plants, and sometimes food scraps discarded by people. Antarctica has no land carnivores. One animal that does live there is the penguin. Like seals and walruses, penguins feed in the ocean. These birds often nest far from their ocean food source. They must walk many kilometers to feed on fish in the sea and then return to their nesting sites far inland. They are in danger when they return to the ocean to feed. Many penguins are eaten by leopard seals and sharks while they look for food. Quick Check Cause and Effect Why are penguins in danger when they go to the ocean to feed? polar bear Critical Thinking Plants are not part of the food chain in polar regions. Why is this so? 114

20 Summarize the Main Idea Make a Study Guide Make a trifold book (see pp ). Use the titles shown. In each column, list the causes and effects of changes to biomes. A biome is a region with a particular climate that contains certain types of plants and animals. (pp ) Tropical rain forests have more species of plants and animals than all the other biomes combined. (pp ) The tundra and taiga biomes are found in far northern regions and have cold climates. (pp ) Think, Talk, and Write Main Idea What defines the ecological roles of organisms? Vocabulary The average weather pattern of a region is its. Cause and Effect How do cool nighttime temperatures affect desert animals? Critical Thinking Explain why areas in the Arctic can be classified as deserts. Test Practice Which layer of the tropical rain forest contains a thick blanket of foliage? A emergent layer B canopy C understory D forest floor Test Practice Which biome has dry winters and wet summers? A taiga B savanna C tundra D desert Writing Link Write a Story Write a story about life in one of the biomes you have studied. In your story use information about the biome, such as its location, climate, soil, plants, and animals. Math Link Make a Bar Graph Using data from this lesson, find the average annual rainfall for each biome. Then make a bar graph to show your results. -Review Summaries and quizzes EVALUATE

21 Sequence Many things on Earth occur in a sequence. Think about it. You cannot be 13 years old before you are 12, and leaves do not fall off deciduous trees until the leaves have matured. The same is true about the layers of soil in a land biome. By digging down to lower layers, scientists can learn more about a biome and any changes that have taken place over time. In general, in a soil sequence, the lowest layers are the oldest. Learn It When you put things in sequence, you put one thing after another in a fixed order. When you sequence events, you put them in the order in which they happened. This order helps you see patterns. When scientists do experiments, they record their data in a time sequence showing what happened first, next, and last. Scientists need these data not only to verify what they discovered and when but also to be able to repeat the investigation or try it in a different way. A sequence chart is a useful tool for recording these kinds of data. Try It Suppose scientists wanted to verify the soil layers in a biome. They would make a plan to dig into the ground and examine it. Here is a sequence chart they might keep, but it is not in the correct order. Write a number in front of each box to show the order in which each layer would be found. Use number 1 for the topmost layer. Which level contained the newest soil materials? What did scientists find at the oldest level? How could knowing the sequence of soil and rock layers in a desert biome help scientists? 116 EXTEND

22 Apply It In this activity you will build a grassy environment. As you do this activity, make a sequence chart to show each step in your project and your observations. The overall growth of the plants will show whether you have built a healthy environment. You will need a 10-gallon fish tank, gravel, charcoal, sand, topsoil, grass seed, small seedlings, a plastic spoon, a mixing bowl, a watering can, plastic wrap, tape, a measuring cup, and a ruler. 1. Spread a 1-inch layer of gravel on the bottom of the tank with the spoon. Mix in a little charcoal, and then spread a 1-inch layer of sand over the gravel. 2. Measure 2 parts topsoil to 1 part sand in the bowl, and mix thoroughly. Spread a 2- to 3-inch layer of the mixture over the sand and gravel. 3. Sprinkle grass seed on half of the soil. Plant seedlings in the other half. Be sure to cover the roots and leave space between plants. Water the landscape gently until it is moist on top. 4. Cover the tank with plastic wrap. Use tape to secure the plastic tightly over the top. Place the tank in a sunny place. 5. Check the tank each day for a week, and record what you observe. Then answer the following questions. Do the layers in your environment appear to be in the same order as they were in the Try It activity? What did you observe in your environment? Using words and diagrams, describe the sequence that seeds go through as they germinate and grow. 6 IE 7.g. Interpret events by sequence and time from natural phenomena (e.g., the relative ages of rocks and intrusions). 117 EXTEND

23 Lesson 2 Earth s Water Ecosystems If you bend a light stick, it glows. The glow comes from a chemical reaction. Some squids use a similar chemical reaction, known as bioluminescence, to produce light. This squid lives in deep ocean water. Why do you think the squid produces its own light? 118 ENGAGE 6 LS 5.d. Students know different kinds of organisms may play similar ecological roles in similar biomes.

24 What are water ecosystems like? Materials Make a Prediction What will you observe when you compare samples of water from different sources? Will the contents be alike or different? Write your answer as a prediction in the form If water samples come from different sources, then... Test Your Prediction Obtain from your teacher samples of pond, lake, and ocean water. Place each sample in a different container. Label each container. Observe Note the appearance of each water sample, and record your observations. For each sample, place a drop of the water on a slide, and carefully place a coverslip over it. microscope slides with coverslips water samples from ponds, lakes, and the ocean Observe Examine the slide under a microscope at low power and at high power. Step Communicate Record what you see on each slide. Draw Conclusions Interpret Data Compare the samples. How are they alike and different? What do your observations tell you about water ecosystems? Did your results support your prediction? Step Explore More What organisms did you observe in the water samples? Where do the organisms fit in the food chain? Draw a possible food chain for each sample. 6 IE 7.b. Select and use appropriate tools and technology (including calculators, computers, balances, spring scales, microscopes, and binoculars) to perform tests, collect data, and display data. 6 IE 7.d. Communicate the steps and results from an investigation in written reports and oral presentations. 119 EXPLORE

25 Main Idea 6 LS 5.d Organisms in water ecosystems play roles similar to those of organisms in land biomes. Vocabulary intertidal zone, p. 121 nekton, p. 123 benthos, p. 123 estuary, p Reading Skill Summarize What are ocean ecosystems? Oceans cover about 75% of Earth s surface. The water in the oceans plays an important role in the water cycle. Energy from the Sun causes water to evaporate. The evaporated water rises and forms clouds. Eventually the water falls back to Earth as rain or snow. The oceans are divided into regions in much the same way that land is divided into biomes. The regions have different conditions that affect the plants and animals living in them. Factors that affect ocean organisms include temperature, salt content, water pressure, tides, and the amount of sunlight that penetrates the water. These lyretail anthias live near a coral reef. 120

26 Zones of Ocean Life The shallowest part of the ocean is the intertidal zone, the area between the high-tide line and the low-tide line. At high tide the intertidal zone is covered by water. At low tide it is exposed to sunlight and air. Some animals, such as crabs, burrow into the sand. From the low-tide line to the point where the ocean floor drops off is the neritic (nuhr I tik) zone. Sunlight penetrates the water here, allowing many photosynthetic organisms to grow. In addition, runoff from the land adds nutrients to the water. For these reasons, the neritic zone is richer in plant and animal life than any other part of the ocean. The oceanic zone is divided into two main areas. From about 200 m (656 ft) deep to about 2,000 m (6,562 ft) deep is the bathyal (BATH ee uhl) zone. Here you will find sharks, squid, octopuses, different species of fish, and many other organisms. Below the bathyal zone is the abyssal (uh BIS uhl) zone. At depths greater than 100 m (328 ft), there is no sunlight. The organisms that live at these depths have adapted to the cold, dark conditions. Reading Photos In what zone of ocean life do many plants grow? Clue: Look for the photosynthetic organisms. Quick Check Summarize What causes the abyssal zone to have few animals? Critical Thinking Why do many plants grow in the neritic zone? 121

27 Ocean Food Chain Reading Diagrams What are ocean food chains like? There are hydrothermal vents in some of the deepest parts of the ocean. Here jets of hot water rich in minerals come up through cracks in the ocean floor. No sunlight reaches the vents, so photosynthesis cannot occur. Bacteria live near the vents. These bacteria produce food through the process of chemosynthesis (kee moh SIN thuh sis), which is based on chemical reactions rather than light as an energy source. These bacteria form the bases of food chains that include microscopic animals, snails, shrimp, crabs, tube worms, octopuses, and fish. There are many possible food chains in the oceans. Like other food chains, those in the oceans include producers What role do phytoplankton play in an ocean food chain? Clue: What animals feed on phytoplankton? Watch an ocean food and different levels of consumers, ranging from small organisms to larger ones, as well as decomposers. Ocean food chains begin with plankton, microorganisms that live near the surface of the water. Phytoplankton (FIGH toh plank tuhn) are microscopic organisms that, like plants, use the Sun s energy to make food through photosynthesis. Other organisms eat phytoplankton and receive some of this energy. Zooplankton (ZOH uh plank tuhn) are microscopic animals that feed on phytoplankton. Small fish and other animals eat the zooplankton. 122

28 Ocean Food Web Larger fish eat the smaller fish and other animals, and mammals such as orcas eat the larger fish. Without plankton, other ocean organisms would not have the food they need to survive. Ocean food chains are not all the same. Some are short for example, blue whales feeding on plankton. In others, many organisms feed on one another in turn. The neritic zone has many complex food chains. Ocean Organisms Ocean organisms can be divided into three main categories. Plankton float near the surface of the water. Sometimes called floaters, they make up the largest group of organisms. Nekton (NEK tuhn) are animals, such as flounder, tuna, and squid, that swim through the water. Nekton come in many shapes and sizes and can be found in any ocean zone. Many nekton are predators, able to swim after their prey. Nekton are also prey for other animals. Benthos (BEN thahs) are organisms that live on or near the ocean floor. Benthos include seaweed and kelp as well as the tube worms that live near hydrothermal vents. Quick Check Summarize What would happen if an accident killed off the phytoplankton in an area of the ocean? Critical Thinking How does the ability to swim help nekton obtain food? 123

29 What are freshwater ecosystems? Freshwater ecosystems exist in and around bodies of water that contain little salt. These bodies of water include ponds, lakes, streams, rivers, and wetlands. Some of the same factors that affect ocean life such as sunlight, temperature, and the amount of food and oxygen present also affect freshwater ecosystems. In most ponds and lakes, the water is mostly still. You may see a covering of green algae. There may be plants such as cattails, bur reeds, and water lilies. Insects may glide over the water s surface. They may become food for the fish that swim below. Streams and rivers have moving water. Plants and animals there have developed adaptations to keep from being swept away. Reeds have roots that anchor them to the bottom. Some fish, such as trout, have streamlined bodies, while other animals have hooks and claws that help them cling to objects. Conserving Water As cities grow, people need more water. Water is piped into cities, where people and industries use it. However, the amount of fresh water available is not increasing. We can conserve water in three ways. The first and best way is to use less. The second way is to reuse water. Many cities reuse wastewater to water plants, trees, and grassy areas. The third way to conserve water is to clean it and recycle it, or use it again for the same purpose. young river otter in a freshwater ecosystem 124

30 Plants as Water Filters tricolored heron in a wetland Wetlands Wetlands are areas in which water is near the surface of the soil much of the time. In California, most wetlands are salt marshes, which help keep the shoreline from washing away. Birds that migrate from one place to another use salt marshes as rest stops. Wetlands serve as natural water filters, and they provide flood protection and erosion control. They can help remove pollutants released by industry and agriculture. You could also think of wetlands as the nurseries of the sea. Many kinds of fish and birds lay their eggs and raise their young in the wetlands. During the past 200 years, about half of all the wetlands in the United States were destroyed. Many were drained or filled in with soil for use as farms or places to build homes. In the 1970s, people began to protect and restore wetlands. Today more and more people recognize the value of these unique ecosystems. Set four small potted houseplants, with their pots, into the tops of four clear containers. Slowly pour clean water into one of the pots and watch it trickle through the pot into the container. Observe the liquid that comes out. Add about 1 g of soil to a cup of water and stir. Pour this mixture into a second pot. Observe the liquid that leaves the pot. Add some colored, powdered drink mix to a cup of water and stir. Slowly pour the mixture through a third pot. Note the color of the water that drains from the pot. Mix about 30 ml of liquid soap with a cup of water. Pour this mixture through the fourth pot. Does the soap flow through the soil? Observe Empty the containers under the third and fourth pots. Then pour some clean water over both plants. What drains out? Draw Conclusions Based on your results, what can you conclude about the role of plants in wetlands? Quick Check Summarize Explain why it is important to conserve water. Critical Thinking What is the advantage of strong roots to river reeds? 125

31 What happens when fresh water meets salt water? An estuary (ES choo eh ree) is the part of a river where fresh water meets the sea and is affected by tides. Bays, inlets, and harbors are also examples of estuaries. The water in an estuary contains less salt than the water in the ocean, but it is not as fresh as river water. As the tide flows in and out, the amount of salt in the water of an estuary changes. Sometimes the water at the surface is fresh, while denser salt water remains below. Organisms that live in estuaries, such as turtles, sea grasses, clams, and fish, adapt to the changing levels of salt and oxygen in the water. Estuaries filter the water and help prevent flooding. Estuaries are full of plant and animal life. The nutrients washed in by rivers help plants and animals thrive. Many kinds of birds and waterdwelling animals breed in estuaries. Tall grasses and their roots protect young fish and other animals. About three fourths of all the fish caught in the United States each year spent part of their lives in estuaries. Quick Check Summarize Why should people conserve estuaries? Critical Thinking Compare and contrast a wetland and an estuary. 126 Russian River, California

32 Summarize the Main Idea Ocean ecosystems cover about 75% of Earth s surface. (pp ) Ocean food chains begin with microorganisms called plankton. (pp ) Think, Talk, and Write Main Idea Organisms in play roles similar to those of organisms in land biomes. Vocabulary The area between the high-tide line and the low-tide line is the. Summarize What causes the amount of salt in the water of an estuary to change? Make a Study Guide Freshwater ecosystems include ponds, lakes, rivers, streams, and wetlands. (pp ) Make a layeredlook book (see pp ). Use the titles shown. On the inside of each fold, summarize how that topic can help you understand Earth s water ecosystems. Critical Thinking How would a streamlined body help a fish survive in an ecosystem with moving water? Test Practice What organisms form the base of an ocean food chain? A plankton B small fish C large fish D mammals Test Practice Which organisms live on or near the ocean floor? A plankton B nekton C bathyal D benthos Art Link Make a Poster Learn about a particular wetland. Draw all the living and nonliving things you can find in this wetland. How is it similar to and different from the community where you live? Math Link Make a Line Graph Research population growth in California for the past five years, and make a line graph of your data. Plot the years on the x-axis and the number of people on the y-axis. -Review Summaries and quizzes EVALUATE

33 Meet Eleanor Sterling Did you know that more animal species live on coral reefs than in rain forests? Like sprawling cities in the sea, reefs are home to thousands of species of marine organisms, from sea turtles and giant clams to tiny coral polyps. When reefs are damaged, the organisms that live there are in danger, too. Protecting coral reefs is a complicated business, and that s exactly what Eleanor Sterling and her colleagues are working to do. Eleanor is a scientist at the American Museum of Natural History. She travels to different ecosystems around the world to study and conserve the diversity of life. She and her colleagues recently visited a group of islands in the middle of the Pacific Ocean to study the coral reefs. Palmyra Atoll One of these islands is called the Palmyra Atoll. It is unusual because it is one of the most isolated places in the world, and only scientists are allowed to visit. The reefs at Palmyra are healthy. Eleanor is a conservation biologist. That s a scientist who studies endangered environments and organisms and works to ensure their conservation. 128 EXTEND ELA R Connect and clarify main ideas by identifying their relationships to other sources and related topics.

34 Meet a Scientist Unfortunately, though, many reefs around the world are being threatened by fishing practices, unusually warm water temperatures, deforestation, soil erosion, and tourism. In Palmyra Eleanor and her colleagues dive underwater and kayak around the islands to document the wildlife that lives in the reef. They are especially interested in the sea turtles. Nobody knows how many sea turtles live in Palmyra, so the scientists are trying to find out how large the population is, what parts of the reefs they use, and what they need to survive. The Eleanor Sterling studies the reefs near Palmyra Atoll. scientists use all this information to find ways to protect this habitat. From their work they learn lessons that can be used to protect marine ecosystems all over the world. Write About It Cause and Effect 1. What factors cause damage to coral reefs? 2. How does damage to coral reefs affect the organisms that live in them? Cause and Effect Think about factors that cause changes to occur. Consider the effects of each type of change. -Journal Write about it EXTEND

35 Materials plastic cups plastic spoons Inquiry Structured What is an estuary? Form a Hypothesis Fresh water and salt water have many similarities and differences. Both saltwater ecosytems and freshwater ecosystems have food webs that exist because of the Sun s energy. Both types of ecosystems have animals and plants that thrive in all types of temperatures. Estuaries are areas where fresh water flows into the ocean. This creates an area that has a different salt content and is a haven for many types of creatures. What are some unique characteristics of estuary waters? Write your answer as a hypothesis in the form If estuary water is different from salt water and fresh water, then buoyancy... Be Careful. Wash your hands with soap and water after the activity. salt water made from ocean mix waterproof markers eggs graduated cylinder Test Your Hypothesis Label three cups Fresh Water, Ocean Water, and Estuary Water. Measure Pour 200 milliliters of tap water into the cup labeled Fresh Water. Pour 200 milliliters of salt water into the cup labeled Ocean Water. Place an egg in the salt water. Record your observations in your journal, and mark the egg with a marker at the water level. Place the same egg in the fresh water, and mark the egg again. Record your observations in your journal. Remove 100 milliliters of water from each cup, and pour it slowly into the cup labeled Estuary Water. Record what happens to the water as you pour the two together. Place the egg in the estuary water, and record your observations. Step Step Step 130 EXTEND 6 IE 7.a. Develop a hypothesis. 6 IE 7.d. Communicate the steps and results from an investigation in written reports and oral presentations.

36 Draw Conclusions Explain What happened when you placed the egg in the salt water? In the fresh water? Analyze Based on your experiment, what can you determine about water found in estuaries? What can you determine about the animals and plants in estuaries? Inquiry Guided How do ocean salt levels affect living things? Form a Hypothesis What would happen to sea life if the ocean s salt levels changed? Write your answer as a hypothesis in the form If the ocean s salt levels change, then the organisms will... Test Your Hypothesis Design an experiment to investigate what effect salt levels have on organisms such as brine shrimp. Write out the materials you will need and the steps you will follow. As you follow your plan, record your results and observations. Draw Conclusions Did your results support your hypothesis? Why or why not? Present your results to your classmates. Inquiry Open What else can you learn about estuaries and their inhabitants? For example, what types of animal life can be found in estuaries? Think of a question to investigate. Then design an experiment or write out a research strategy to answer your question. Carry out your experiment or your research, and present your results to your classmates. Remember to follow the steps of the scientific process. Ask a Question Form a Hypothesis Test Your Hypothesis Draw Conclusions 131 EXTEND

37 Lesson 3 Ecosystems in California California sea lions, Farallon Islands, California California is home to many different kinds of plants and animals. Why do you think this is so? 132 ENGAGE 6 LS 5.e. Students know the number and types of organisms an ecosystem can support depends on the resources available and on abiotic factors, such as quantities of light and water, a range of temperatures, and soil composition.

38 What are California s ecosystems? Purpose What are California s ecosystems like? How are they similar or different? Write a prediction in the form If California s ecosystems have different, then they will have different. Procedure Work in groups of four or five. Find various ecosystems on the map provided. Make a Model Outline a map of California on a piece of cardboard. Using different colors of modeling clay, construct a state map showing the state s ecosystems. Include landforms and bodies of water. Observe Create an index card for each ecosystem. Use your clay map to find landforms and bodies of water that might affect plants and animals in the region. Record this information on the index cards. Think about the types of plants and animals you might find in each ecosystem. Draw Conclusions Analyze Using the information on your index cards, compare the ecosystems. How do the regions differ? Did your observations support your prediction? Explore More Choose one ecosystem on your state map. What adaptations do you think plants and animals in that region would need to survive? Step Materials modeling clay of different colors sturdy cardboard index cards 6 IE 7.f. Read a topographic map and a geologic map for evidence provided on the maps and construct and interpret a simple scale map. 133 EXPLORE

39 Main Idea What is a Mediterranean climate? 6 LS 5.e California has different ecosystems that are home to many native plant and animal species. Vocabulary chaparral, p Reading Skill Cause and Effect 1OcaS 3TTSQb The area around the Mediterranean Sea near Europe and Africa is one of the most fertile regions of the world. This area is located about halfway between the equator and the North Pole. Follow the same latitude around the globe, and you will find such a region in Central and Southern California. In the Southern Hemisphere, Chile, South Africa, and Australia have areas with the same characteristics. All of these regions have similar climates, known as Mediterranean climates, with hot, dry summers and mild, rainy winters. Areas with Mediterranean climates are usually found along the west coasts of continents. When the land near a coast heats up, the air over the land becomes warm and rises. Cooler air over the ocean flows in to replace the warm air. Mediterranean Climate Zones /B:/<B71 =13/< B`]^WQ ]T 1O\QS` 3_cOb]` >/17471 =13/< 7<27/< =13/< B`]^WQ ]T 1O^`WQ]`\ Reading Maps /`SOa ewbv ;SRWbS``O\SO\ QZW[ObSa What features are shared by regions with a Mediterranean climate? 134 Clue: Look at the map. How are the regions similar?

40 This process keeps temperatures from varying greatly. Sacramento, Fresno, and the Los Angeles area all enjoy the effects of a Mediterranean climate. Areas with Mediterranean climates are famous for food crops such as grapes, olives, figs, and citrus fruits. These crops grow in late winter and early spring, when temperatures are mild and rain is plentiful. To survive the hot, dry summer, plants in Mediterranean climates have adapted in several ways. Trees, such as evergreens, oaks, and olive trees, usually have thick bark to protect them from fire. Some trees, such as oaks, have deep roots. Others have tough, thick leaves that prevent water loss. Some plants become dormant, or less active, during the hotter months. Wildfires can be common in regions with a Mediterranean climate. These fires benefit the plant community in some ways. They clear out old growth and add nutrients to the soil, encouraging new plants to sprout. A Mediterranean climate makes Catalina Island in California a favorite place for boaters. Quick Check Cause and Effect Why do California, Chile, South Africa, and Australia all have Mediterranean climates? Critical Thinking What are two adaptations of plants that allow them to live in the Mediterranean climate? 135