13.1 Ecologists Study Relationships Ecology is the study of the relationships among organisms and their environments.

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1 GETTING READY TO LEARN Preview Key Concepts 13.1 Ecologists Study Relationships Ecology is the study of the relationships among organisms and their environments Biotic and Abiotic Factors Every ecosystem includes both living and nonliving factors Energy in Ecosystems Life in an ecosystem requires a source of energy Food Chains and Food Webs Food chains and food webs model the flow of energy in an ecosystem Cycling of Matter Matter cycles in and out of an ecosystem Pyramid Models Pyramids model the distribution of energy and matter in an ecosystem. Review Biology Vocabulary Write the correct word for each definition. experiment organism observation population 1. : hypothesis is tested under controlled conditions 2. : using the senses to study the world 3. : all individuals of one species living in a certain area 4. : any individual living thing Preview Biology Vocabulary 'See how many key terms from this chapter you already know. Rewrite each phrase, using a different word or words for the words in bold. PHRASE 1. Rocks and air are examples of abiotic factors. REWRITTEN WITH DIFFERENT WORDS Rocks and air are examples of. 2. A plant is a producer. A plant 3. A rabbit is an herbivore. A rabbit is

2 13.1 SECTION Ecologists Study Relationships KEY CONCEPT Ecology is the study of the relationships among organisms and their environment. Student text pages Ecologists study relationships at different levels of organization. Eadogy is the study of the interactions among living things, and between living things and their surroundings. Ecologists study nature on different levels, from a local to a global scale. Organism An organism is one individual living thing. Population A population is a group of the same species that lives in one area. Community A community is a group of different species that live together in one area. Ecosystem An ecosystem includes all of the organisms as well as the climate, soil, water, rocks, and other nonliving things in an area. An entire ecosystem may live within a single decaying log. But the log may be part of a larger ecosystem, such as a forest. Biome A biome (BY-OHM) is a major regional or 'global community of organisms. A biome is usually defined by the climate and by the plant communities that live in an area...i.ut. :. Organism 7. _ r "'AW-411. Community... _ A, Ecosystem The Florida Everglades is an example of the subtropical savanna biome. Many organisms live in this aquatic ecosystem. Interactive Reader 221

3 Ecologists study relationships within and between each level of organization. For example, one ecologist might study a single population of Pacific salmon. Another ecologist might study how the current loss of Pacific salmon affects other species. Yet another ecologist might study the effects of this loss on a global scale.,is7r, tv What are five different levels of organization at which an ecologist might study biological relationships? Ecological research methods include observation, experimentation, and modeling. Ecological research involves many different methods and tools. Three main components of ecological research are observation, experimentation, and modeling. Observation Observation is the act of carefully watching something over time. Observation may be part of short-term or long-term studies. Long-term studies are important because many environmental changes happen slowly over time. Observation can involve directly watching populations of organisms. It can also involve indirectly observing populations by tracing signs of the organism's presence, such as tracks. Scientists also use radio collars to follow the movements of some animals. These collars allow scientists to track organisms that move long distances, such as coyotes. Experimentation Scientists may perform experiments in a lab or in the natural area where the organisms live. There are benefits and drawbacks to each type of experiment. A lab experiment allows for more control of variables. But at the same time, it does not include the complex interactions that happen in nature. An experiment in a natural setting gives a better picture of how organisms really interact. However, a natural setting also makes it difficult to identify the effects of individual variables. Observation involves carefully watching something over a certain period of time. 222 McDougal Littell Biology

4 Modeling Some questions cannot be easily investigated through observations or experiments. Models can be used to explore organisms and whole ecosystems in ways that would not be possible in a natural setting. One way of thinking about modeling is that it can be used to answer questions that start with "What would happen if...?" Models use real data to predict outcomes for different situations. For example, a wide variety of data was combined into a model of Yellowstone National Park. This model was then used to decide how best to reintroduce grey wolves into the park. utsa What are three components of ecological research? 4141' ecology community ecosystem biome Go back and highlight each sentence that has a vocabulary word in bold. Fill in the blanks with the correct term from the list above. 1. is the study of interactions among living things, and between living things and their surroundings. 2. A major regional or global community of organisms is a(n) 3. A(n) is all of the living things as well as the,nonliving things in an area. 4. A group of different species that all live together in one area is a(n) 5. Put the following in order from largest to smallest level of organization: community, biome, population, individual, ecosystem. 6. Describe the benefits and drawbacks of experiments in a laboratory compared with experiments in a natural setting. Interactive Reader 223

5 13,2 SECTION Biotic and Abiotic Factors KEY CONCEPT Every, ecosystem includes both living and nonliving factors. Student text pages An ecosystem includes both biotic and abiotic factors. All ecosystems are made up of living and nonliving components.* These parts are called biotic and abiotic factors. Biotic (by-aht-ihk) factors are living things, such as plants, animals, fungi, and bacteria. Abiotic (AY-by-AHT-ihk) factors are nonliving things, such as temperature, moisture, wind, rocks, and sunlight. In an ecosystem, biotic and abiotic factors work together in a complex web. t /iir ots. ir Give one example of a biotic factor and one example of an abiotic factor. Changing one factor in an ecosystem can affect many other factors. Every organism depends on a combination of biotic and abiotic resources to live. All species including humans are affected by changes to the biotic and abiotic factors in an ecosystem. Bickliversity (BY-oh-dih-VUR-sih-tee) is the variety of living things in an ecosystem. Some areas of Earth, including tropical rain forests, have very high biodiversity. Tropical rain forests cover less than 7 percent of Earth's ground surface, but contain over 50 percent of Earth's plant and animal species. A single change in an ecosystem can have a variety of effects. Some changes may have very little effect. But in.some cases, the loss of one species can have a very large effect on an entire ecosystem. A keystone species is a species that has an unusually large effect on its ecosystem. VISUAL VOCAB Like a keystone that holds up an arch, a keystone.species holds together a dynamic ecosystem. *ACADEMIC VOCABULARY component part 224 McDougal Littell Biology

6 One example of a keystone species is the beaver. Beavers cut down trees and build dams on rivers. This changes the ecosystem by turning a river into areas of ponds and marshes. Many different species can live in the pond and marsh environments that are made by beavers s tivr 4 What do beavers make that results in a wetland ecosystem? biotic abiotic biodiversity keystone species Go back and highlight each sentence that has a vocabulary word in bold. Circle the correct term from each pair to complete the sentences below. 1. Wind and rocks are two examples of biotic / abiotic factors. 2. Fungi and plants are two examples of biotic / abiotic factors. 3. A keystone species has a large / small effect on an ecosystem. 4. Biodiversity is the quantity / variety of organisms in an area. 5. What are two categories of factors that make up an ecosystem? Interactive Reader 225

7 13.3 SECTION Energy in Ecosystems KEY CONCEPT Life in an ecosystem requires a source of energy. Student text pages Producers provide energy for other organisms in an ecosystem. In Section 13.2 you read that ecosystems are made up of both biotic and abiotic factors. Another important part of an ecosystem is the flow of energy. All organisms need a source of energy in order to survive. Producers are organisms that make their own food. Plants and other photosynthesizing organisms are producers. Producers are also called autotropbs. Consumers are organisms that get their energy by eating other organisms, including plants and animals. Consumers are also called heterotrophs. Producers provide the basis for an ecosystem's energy. Some consumers eat producers. For example, moose and elk eat plants. Some consumers eat other consumers. For example, the grey wolf eats moose and elk. But all consumers depend on producers. Without producers, moose and elk could not survive and without moose and elk, the wolf could not survive. The suffix troph comes from a Greek word meaning "nourishment," or food. The prefix auto means "self." The prefix heteromeans "different." Plants are producers, or autotrophs. Animals are consumers, or heterotrophs. «c.2..y1 Epi Circle the names of three consumers in the paragraph above. 226 McDougal Littell Biology

8 Almost all producers obtain energy from sunlight. Most producers on Earth use sunlight as their energy source. Photosynthesis is the process by which plants and some protists, such as green algae, use energy from the Sun to make sugars. Plants use these sugars as energy for cellular respiration. Not all producers rely on the Sun for energy. In 1977 scientists first visited deep-sea vents on the floor of the ocean. They were very surprised to find many different organisms living in an ocean floor ecosystem, far from the reach of sunlight. The producers in this ocean floor ecosystem are prokaryotes that make their own food, using chemicals as an energy source, not the Sun. This process is called chemosynthesis (KEE-moh-SIHN-thih-sihs). Chemosynthetic organisms also live in hot springs. v.121., sof Underline two places that chemosynthetic organisms live. producer autotroph consumer heterotroph chemosynthesis Go back and highlight each sentence that has a vocabulary word in bold. Fill in the blanks with the correct term from the list above. 1. Which two words describe an organism that eats other organisms as food? 2. Which two words describe an organism that makes its own food? 3. List two different energy sources for producers. Circle the one that is the source for most producers. Interactive Reader 227