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Whether it's at the lunch table, over the telephone, on the playing field, or in the classroom, you spend much of your day speaking or being spoken to. Such conversations, or dialogues, are a central means of communication. Dialogue is a way to convey not only factual information, bur also thoughts and feelings. You express yourself through dialogue by the words you choose, the tone you use, and the way you speak.

Written dialogue does the same thing as spoken dialogue. When dialogue is written down, it's a way for a writer to create interactions between speakers or characters. In stories, plays, essays, or articles, writers use dialogue to make a story more realistic and to engage their readers. But they also use it to reveal more about the characters' personalities, show how the characters respond to different situations, indicate the dynamics of particular relationships, and present conflicting sides of an argument.

During a dialogue, energy is exchanged between speakers. Just think about a dialogue, between you and a family member. The energy of your emotions is expressed when you speak. Similarly, you are affected by the energy of the person with whom you are speaking. A reader would be able to determine the moods, location, and events that preceded and will follow the conversation by reading the dialogue exchanged between two people. You can study the interactions between characters in a written dialogue, then, much like ecologists study interactions between organisms.

In this activity, you will create various dialogues between organisms at different trophic levels. As you write, be sure to include a combination of dramatic dialogue, which is pure speech, and narrative dialogue, which consists of sentences of speech set in text.

1. To get comfortable with writing dialogues, write a paragraph describing a recent dialogue between you and a friend. You may have discussed a homework assignment, a television show, or even the lunch menu. Be sure to include all of the details of the conversation St) that anyone who reads the paragraph will feel as if he or she was present during the conversation. Give clues about the tone, mood, and setting in your descriptions. For example, you might write: Jeanie responded excitedly, "I'd be glad to go!" From this, the reader knows not only what Jeannie said but how she said it. You can also indicate what a person is doing during the dialogue. For example: As Vincent took off his glasses and slowly glanced up from his paperwork, he said "These numbers aren't adding up." In a similar way, you can describe the time of day, the weather, the location, and any other details that relate to the dialogue.

2. Now that you have had some experience writing a dialogue, use your textbook to choose two autotrophs and three heterotrophs (one herbivore, one carnivore, and either an omnivore or a parasite). The organisms you chose will be the "characters" in your next dialogues. In a sentence or two, describe the personalities of each organism. Are they strong and outgoing, or reserved and shy? Are they old or young? Your descriptions should be based on the information you learned in the chapter and your own creativity.

3. Set the stage for verbal encounters between organisms on the same trophic level. Where are they? Are they competing with each other? How are they similar and how are they different?

4. Now set the stage for verbal encounters between organisms on different tropic levels. Where do they meet? What is the relationship between these organisms? What conflicts might exist between them?

5. Begin a dialogue between organisms at the same trophic level that will reveal the characters as well as the situation. What types of comments might they make to one another as they obtain and use energy resources? Use distinctive vocabulary or sentence patterns to indicate the identity of the characters. Use the interchange of voices to show how the characters feel about one another and the situation. Do they argue with or console each other? Indicate whether they are optimistic or pessimistic. Tell how they speak. Do they murmur, shout, whine, or whisper?

6. Now try a dialogue between organism at different trophic levels. What is different about this situation and how can you show it through the characters' distinct voices? Do they shout at or interrupt each other?

7. So far you have written exchanges between two characters. But writers often like to involve more than two voices in order to explore multiple views on an important debate. In this chapter about energy and nutrients, you were introduced to some of the critical issues in ecology today. Imagine a round-table discussion at which your various characters are allowed to speak about a particular issue discussed in the chapter. Write a paragraph that develops this interchange of ideas through the characters' voices.

8. Technology has created numerous methods of conducting dialogues over long distances. Develop a conversation between organisms that might take place over the telephone, in a video conference, or on the Internet. How are these different from dialogues that occur in person?

Ecologists use three methods to study the interactions of living things with each other and with their environments. The three methods are observation, experimentation, and modeling. Each method has advantages and disadvantages. When choosing which method to use, an ecologist must consider which method is most likely to yield useful information as well as which one is most practical for the given situation. Sometimes an ecologist will combine two or even all three methods to investigate a complex situation.

Read the following descriptions of organisms and their environments. Identify which method(s) you would choose to study each ecological situation. Explain your choice.

1. Marisa is interested in the interaction between bees and flowers. She would like to investigate whether or not the flowers will produce seeds if bees are prevented from visiting them.

2. Ozone gas in the atmosphere absorbs ultraviolet radiation from the sun. Rafael is interested in the cause of the hole in the ozone layer of the Earth's atmosphere, and how this hole affects different forms of life.

3. Shauna wants to find out about old field succession on her family farm. This is the process that occurs when a farmer stops cultivating a field and allows it to return to its natural state. The process often takes fifty or more years to complete.

4. A new electricity-generating plant that will burn coal is being built near George's community. George is concerned that the sulfur-based emissions from the plant will cause acid rain which could harm the nearby forests.

5. Ramona has always heard the expression "The early bird gets the worm." She wants to find out if the blue jays that nest near her apartment really do eat worms. She also wants to know what other foods they eat.

6. Many oil tankers travel through the bay near Richard's home town. He is concerned about what affect an oil spill might have on the bay.

1. Ecology is defined as the scientific study of interactions between different kinds of _________________, and between living things and the ___________________________________________ in which they live.

2. Ecology is named after the Greek word oikos, which means ___________________________________

3. Scientists who study ecology are called _________________________________________________

Reviewing Concepts

____4. Ecology is the study of the solar system and all its living and nonliving parts.

____5. Ecologists use one or more of three basic research methods--observation, experimentation and modeling.

____6. Ecology cannot help us resolve such issues as flooding, decreasing fish populations, and the possible warming of Earth's atmosphere.

____7. The health of human society depends on the health of all other organisms.

____8. The study of ecology begins with the study of how different organisms obtain and use energy and nutrients.

Answer each of the following in the space provided. Use complete sentences as appropriate.

9. Why do you think the study of ecology is especially important today? (Drawing conclusions)

10. An ecologist wants to find the reasons why a coral reef is dying. Would studying the reef itself be sufficient to find an answer? Explain your answer. (Inferring)

11. State the two fundamental ecological truths. (Communicating)

12. Explain how the study of how different organisms obtain and use energy and nutrients is related to the definition of ecology. (Relating)

Primary producers generally form the foundation of ecological pyramids by capturing and using energy from the sun. As primary producers, plants and some bacteria use the sun's energy to form living tissue from nonliving nutrients such as water and carbon dioxide. However, you may be surprised to learn that not all primary producers use sunlight as an energy source. Some bacteria are able to produce their own food without the help of a single ray of sunlight.

In the late 1970s, an oceanographer named Dr. Robert Ballard discovered rich communities, or groups of species, living on the ocean floor deep in the Pacific Ocean. These communities lie 2500 meters underwater. Because sunlight does not penetrate to this depth, scientists were puzzled. What was the energy source for these underwater worlds? Scientists observed that the deep-sea organisms grew around thermal vents, or cracks, in the ocean floor. These vents release warm water that is rich in minerals from below the surface of the Earth. Scientists discovered bacteria called chemoautotrophs that use hydrogen sulfide (a chemical present in high concentrations in thermal waters) as an energy source. Chemoautotrophs are the primary producers of these deep-sea communities, producing their own food using chemicals, rather than the sun, as an energy source. These chemoautotrophic communities were an exciting new ecological discovery. Unfortunately, deep sea exploration is complicated and expensive. Thus, scientists have difficulty investigating the underwater communities any further.

In 1986, a Roman geologist, C. Lascu, discovered a chemoautotrophic community that was much easier to study. While digging a well in southeastern Romania, Lascu discovered a network of cave passages that are 240 meters long. Known as Movile Cave, the network is 20 meters underground and has been isolated from the surface of the Earth for several million years. Movile Cave is home to a chemoautotrophic community similar to those discovered on the deep ocean floor.

The upper level of Movile Cave is dry, but the lower level is partially flooded by waters rich in hydrogen sulfide. Because of the partial flooding, air pockets, or air-bells, form between the surface of the water and the roof of the cave. Mats of fungus and bacteria float in the water and grow on the walls of the air-bells. Three species of chemoautotrophic bacteria are found in the fungal mats. These chemoautotrophic bacteria are the primary producers of Movile Cave's underground community. The bacteria obtain their energy by breaking the chemical bonds in hydrogen sulfide. They then use this energy to form living tissue.

These unique primary producers support a rich variety of heterotrophic consumers, both aquatic (water-based), and terrestrial (landbased). In the aquatic communities, species of protists, worms, snails, and crustaceans make up the first level of consumers. Species of flatworms, leeches, and insects are the top level of consumers, the predators. In the terrestrial communities, insects, isopods, and millipedes are the first level of consumers. The top consumer, a predator, is a centipede. At least 46 species of aquatic and terrestrial invertebrates are found in Movile Cave. Over half of these invertebrates are newly discovered species found nowhere else in the world.

In Movile Cave, the organisms supported by chemoautotrophic producers are well adapted to their surroundings. These organisms have developed characteristics to help them survive underground. Since caves are dark, they do not need eyes to see or pigment for protective coloration. However, to make up for the loss of

____1. word that means self-feeding a. primary producer

____2. another term for consumers b. decomposer

____3. model created by the energy chain from primary c. autotroph

producers to herbivores to carnivores d. trophic level

____4. each step in the series of organisms eating other organisms e. consumer

____5. organisms that feed on the dead bodies of animals f. ecological pyramid

or plants or on their waste products g. heterotroph

____6. organisms that use energy from the sun and nutrients from their environment to create living tissue

____7. animals that feed on other organisms to acquire energy _

8. (Plants, Animals) use energy from the sun through the process of photosynthesis.

9. Plants are (primary producers, consumers).

10. A (herbivore, carnivore) is a heterotroph that obtains energy by eating other animals.

11. (Less, More) energy is available to consumers at higher trophic levels than was originally captured by the primary producers.

12. Approximately (10, 100) percent of the energy at one trophic level is available to consumers at the next trophic level.

13. The less energy available at any trophic level, the (less, more) living tissue that trophic level can have.

14. Where on the pyramid of biomass is each type of organism located? Write your answer in the space provided. (Classifying)

___________1. Nutrients that are available in limited quantities on Earth are cycled from one organism to another, and from one part of the biosphere to another.

___________2. Nitrogen fixation converts nitrogen in the atmosphere into a form that can be used by living things in the nitrogen cycle.

___________3. The water cycle consists of the processes of evaporation, condensation, and perspiration.

___________4. Heterotrophs use carbon dioxide from the atmosphere as a raw material for photosynthesis in the carbon cycle.

5. From what sources do primary producers get the energy and substances they need to manufacture carbohydrates, proteins, and fats?

6. How do heterotrophs get the nutrients they need?

7. Explain the following statement: Cycles are closed loops.

8. An ecosystem may suffer from low productivity despite the availability of energy from the sun. What is the probable cause of this low productivity?

9. Compare and contrast the movement of energy and nutrients through the biosphere. (Comparing)

10. Is it always beneficial when additional amounts of a limiting nutrient are added to an ecosystem? -Provide an example to support your answer. (Drawing conclusions)

1. food chain

2. food web

3. A sequence of living things showing a small fish eating algae and a larger fish eating the smaller one is called a __________________________

4. All __________________________ can be described in terms of primary producers, consumers, and decomposers.

5.Consumers and decomposers are classified as __________________________ because both obtain their energy by feeding on other organisms.

6.A typical pathway of energy and nutrient cycling in a terrestrial ecosystem is from primary producers to __________________________, to carnivores.

7. In a coastal salt marsh food web, the primary producers that are not eaten by herbivores die, decompose, and are converted into __________________________

8. The size of producers and consumers is restricted in parts of the open sea by the limited amount of __________________________ available.

10. Create an example of a food chain that consists of at least three organisms. Name each organism. (Comparing)

11. Draw an example of a food web consisting of at least eight organisms. (Sequencing)

You have probably had the unfortunate experience of opening a carbonated beverage only to watch the liquid bubble up and overflow. This is an example of the "explosive" force of carbon dioxide dissolved in liquid under pressure. What do you think would happen if a lake was carbonated like a beverage in a bottle?

In the middle of the night on August 21, 1986, over a thousand people and countless animals were killed in a village in Cameroon, West Africa. Nearby Lake Nyos, known locally as the "good lake," had released a deadly cloud of carbon dioxide in an eruption, or geyser, of gas and water that spouted for hours. Although carbon dioxide is not poisonous, it is heavier than air. As the dense cloud of carbon dioxide moved silently through the village, it displaced the air near the ground. The villagers, livestock, and wildlife were suffocated while they slept.

At first, scientists were unsure about the source of the geyser of carbon dioxide. Some scientists believed that the carbon dioxide came from biological pathways such as the decomposing organic matter in the lake. Others favored a geochemical explanation, such as volcanic activity. Because Lake Nyos lies in the crater of an old volcano, most scientists now believe the source was indeed geochemical. Carbon dioxide makes up about 12 percent of all gases released by volcanic eruptions. Volcanic carbon dioxide gas comes from deep within the Earth. When rocks that contain carbon are melted beneath the Earth's surface, the carbon is freed and forms carbon dioxide gas. Scientists believe that carbon dioxide slowly seeped into Lake Nyos from vents (cracks) in the volcanic crater. Due to the great depth of the lake, the carbon dioxide was not released immediately into the air, but dissolved into the water instead. This created a situation similar to an unopened carbonated beverage.

Once the scientists had formulated a theory about the source of the carbon dioxide, they were faced with the question of what triggered the eruption of the gas. Youxue Zhang, a scientist from the University of Michigan, created a mathematical model of the event. Based on his model, Zhang decided that the concentration of dissolved carbon dioxide in the lake had become very high after years of seepage from the vents in the volcanic crater.

Because of this high concentration, anything that upset the delicate balance of the lake at that point, such as an underwater landslide or even a rainstorm, could cause the carbon dioxide to bubble out of the water just as it would from an opened beverage. But how could a gentle rainstorm have caused a deadly eruption? Scientists believe that the cooler rainwater sank to the depths of the lake where the carbon dioxide concentration was very high. As this occurred, the cooler water forced the more highly carbonated water upward to release its carbon dioxide gas. This action started a chain reaction and caused the rapid release of the gas.

French engineers devised an experiment to test Zhang's model. They lowered a long pipe deep into Lake Nyos and then used a pump to start an upward flow of water and carbon dioxide into the pipe. When the pump was turned off, water and carbon dioxide continued to rush upward through the pipe. The engineers had created a miniature, self-sustaining geyser. You can demonstrate this same principle with a straw and a glass containing a carbonated beverage. If you place the straw in the beverage, you will see the liquid rise in the straw.

Scientists hope to use this research to prevent further eruptions in Lake Nyos. One plan calls for scientists to start geysers in the lake using the techniques devised by the French engineers. Scientists believe that this method would allow the lake to release carbon dioxide gradually and, thus, prevent another sudden eruption of the potentially deadly gas.

After the disaster in 1986, the scientists who originally investigated the eruption founded the Commission on Volcanic Lakes. This group hopes to cooperate with other scientists to do further research on the potential dangers of volcanic lakes. One goal of the commission is to identify other potentially dangerous volcanic lakes to prevent similar disasters in other parts of the world. Their immediate goal is to prevent another eruption at Lake Nyos. The carbon dioxide levels in the lake continue to rise at an alarming rate, and many scientists fear that another disaster will occur before a suitable method is found to release the gas.

1. Carbon dioxide is a greenhouse gas. Why would scientists want to release the carbon dioxide in Lake Nyos into the atmosphere instead of preventing its eruption? (Making inferences)

2. Do you think scientists should continue to try to change Lake Nyos to make it safe for nearby residents, or should they let nature control the lake? (Evaluating)

3. What can scientists do to protect people living near Lake Nyos if a method to safely release carbon dioxide from the lake cannot be found? (Making judgments)

Reviewing Concepts

Answer each of the following in the space provided. Use complete sentences as appropriate

1. According to the article by Revelle and Seuss, what is causing the return of organic carbon to the atmosphere and oceans?

2. What causes the air inside a glass greenhouse to be warmer than the air outside the greenhouse? Explain your answer.

3. Describe the greenhouse effect in the Earth's atmosphere.

4. What are the four kinds of pathways that occur in the carbon cycle?

5. What human activities are part of the carbon cycle?

6. Where is most of the carbon on Earth stored?

7. The flow of carbon due to human activities is one-way. Explain what this means in terms of the amount of carbon dioxide in our atmosphere.

8. What may happen if the insulating layer of carbon dioxide around the Earth gets thicker?

9. The flow of carbon due to human activities is one-way. How could humans change their activities to reduce the flow of carbon? Explain your answer. (Relating)

10. What do you think are some possible consequences of rising global temperatures? (Drawing conclusions)

1. The three basic methods of ecological research are <A>observations, connections, and models. <B>observations, experiments, and theories. <C>observations, experiments, and models. <D>intuitive insights, experiments, and models.

2. Organisms that can convert energy from the sun into living tissue are called <A>autotrophs. <B>heterotrophs. <C>consumers. <D>decomposers.

3. In the biosphere, energy flows through <A>decomposers to consumers to primary producers. <B>consumers to primary producers to decomposers. <C>primary producers to decomposers to consumers. <D>primary producers to consumers to decomposers.

4. The percentage of energy that can flow from one trophic level to the next is about <A>100 percent. <B>50 percent. <C>10 percent. <D>1 percent.

5. Water from the Earth returns to the atmosphere through water vapor released from plants and <A>condensation. <B>precipitation. <C>denitrification. <D>evaporation.

6. All of the organisms in an ecosystem are linked together into complex networks based on who eats whom, called <A>trophic levels. <B>food webs. <C>ecological pyramids. <D>food chains.