Ecosystems UNIT 5. How do organisms interact in different ecosystems? How do human activities affect ecosystems?

Transcription

1 UNIT 5 Ecosystems How do organisms interact in different ecosystems? Essential Questions Lesson 1 How does energy flow between organisms in a food chain? Lesson 2 How does energy flow between organisms in a food web? Lesson 3 How do adaptations help living things survive in their environments? Lesson 4 What are the characteristics of different land and aquatic ecosystems? Lesson 5 LS.23, LS.24, LS.28 LS.25, SE.48 LS.27, LS.29 LS.26, LS.27 SE.49, SE.50 How do human activities affect ecosystems? 220 Katmai National Park, Alaska

2 Big Idea Vocabulary ecosystem all the living and nonliving things in an environment, including their interactions with each other (p. 224) predator an organism that hunts and kills other organisms for food (p. 228) food web the overlapping food chains in an ecosystem (p. 238) adaptation a characteristic that helps an organism survive in its environment (p. 250) estuary the boundary where freshwater feeds into salt water (p. 26 9) pollution addition of harmful substances to soil, air, or water (p. 276) Visit for online resources. 221 (c) Marty Snyderman/Visuals Unlimited, (bc) Joseph L. Fontenot/Visuals Unlimited

3 Lesson 1 Food Chains A cheetah chasing prey can run 110 kilometers per hour (70 miles per hour). That takes a lot of energy! How do organisms depend on one another for energy? 222 ENGAGE LS.23 Construct food chains that could be found in ponds, marshes, oceans, forests, or meadows (LS-M-C2) LS.24 Describe the roles of producers, consumers, and decomposers in a food chain (LS-M-C2) LS.28 Explain and give examples of predator/prey relationships (LS-M-C4)

4 How can you model a food chain? Materials Purpose A food chain shows how food energy transfers from organism to organism. Producers make their own food. Herbivores eat producers. Carnivores eat herbivores. Create food chains to model how food energy transfers from one organism to another. Producers Herbivores Carnivores Procedure algae grasshopper wolf berries, flowering plants deer otter shrubs chipmunk hawk seeds, grass squirrel robin acorn, oak tree fish owl blank note cards construction paper glue stick magazines markers scissors Make note cards for each of the organisms listed in the chart above. Draw or glue a picture of an organism on each card. Step Create a chart on the construction paper. Label the columns as shown. Use your organism cards to make five food chains. Place the organism cards on your chart under the correct columns. Draw Conclusions Communicate Explain how your food chains compare with a classmate s. Infer If one organism is removed from a food chain, what might happen to the other organisms? Explore More Research one of your food chains. What ecosystem is it part of? What other organisms are part of this ecosystem? How are these organisms connected to your food chain? SI.19 Communicate ideas in a variety of ways (e.g., symbols, illustrations, graphs, charts, spreadsheets, concept maps, oral and written reports, equations) (SI-M-A7) 223 EXPLORE

5 Essential Question How does energy flow between organisms in a food chain? LS.23, LS.24, LS.28 Vocabulary ecosystem, 224 food chain, p. 224 producer, p. 225 consumer, p. 225 decomposer, p. 225 predator, p. 228 prey, p. 228 Reading Skill Sequence What are food chains? You are hiking in Kisatchie National Forest in Louisiana. What do you see? You see plants, such as wildflowers and grasses, and maybe a raccoon or a pileated woodpecker. You also see nonliving things, such as water, rocks, and soil. The living and nonliving things in an area make up an ecosystem. Living things depend on their environment and each other for survival. For example, all living things need energy to live and grow. Where do living things get energy? They get energy from food. Some organisms can make their own food. Other organisms must eat other living things to get energy. A food chain is a model that shows the path of energy and nutrients in an ecosystem. Water Food Chain First Next Last Technology e-glossary, e-review, and animations online at producer secondary consumer primary consumer decomposer 224

6 How do you read a food chain? The arrows in a food chain represent the energy flow from one organism to another. An arrow pointing to an organism shows the living thing that the organism eats. An arrow pointing away from an organism shows the animal that eats that organism. Energy flows in only one direction in a food chain. The energy in a food chain starts with the Sun. It is the energy source for almost all organisms on Earth. Producers are organisms, such as plants and algae, that use the Sun s energy to make their own food. A consumer is any animal that eats plants or other animals. Consumers cannot make their own food. An ecosystem also has decomposers. A decomposer breaks down dead or decaying plant and animal material. Decomposers include fungi, bacteria, termites, and many worm species. Quick Check Sequence What general pattern do all food chains follow? Critical Thinking What is the fewest number of links a food chain could have? The greatest number? Land Food Chain producer Read a Diagram Which organism in this land food chain eats the berries? Clue: Follow the arrow that leads from the berries. primary consumer secondary consumer decomposer 225

7 What are herbivores? Most food chains are similar in a few ways. Sunlight provides the initial energy source for nearly all food chains. A plant or other type of producer uses the Sun s energy to make food. Recall that producers make food by making sugar molecules out of carbon dioxide and water. They use some of this food energy and store the rest. Producers are at the beginning of every food chain. When other organisms eat producers, they get energy from the food that the producers have made and stored. Herbivores (UR buh vorz) are animals that eat only plants. These consumers include animals such as squirrels, deer, grasshoppers, giraffes, cows, and gorillas. Herbivores are also known as primary consumers because they are the first consumers in a food chain. Herbivore Diversity Herbivores can be found in every environment where plants grow. This includes most environments on Earth. They are found in deserts, forests, grasslands, and even arctic environments near the North Pole and the South Pole. They can even be found in aquatic environments. Many fish species are herbivores that consume aquatic plants and algae. Herbivores vary in size. The African elephant, Earth s largest land animal, is an herbivore that eats mainly grasses. Some of the smallest herbivores include many species of insects. koala gorilla elephant manatee There are herbivores in every type of ecosystem. 226

8 Carnivores Some food chains end with an herbivore. For example, the West Indian manatee eats plants and other vegetation, but it is generally not eaten by any other animal. However, in many food chains, herbivores are food for other animals. Animals that eat only other animals are called carnivores (KAR nuh vorz). Carnivores are consumers, and bobcats, lions, owls, and hawks are a few examples. Carnivores that eat primary consumers are called secondary consumers. These carnivores eat herbivores. In some cases, though, carnivores eat other carnivores. These carnivores that eat secondary consumers are called tertiary (TUR shee er ee) consumers. For example, hawks often eat snakes. Herons eat fish, and lizards eat spiders. These consumers are at the top of most food chains. Bald eagles are carnivores. If they spot a fish near the water s surface, they can dive down and catch it with their sharp talons. Carnivores have special adaptations for catching and eating other organisms. For example, some carnivores, such as eagles and hawks, have sharp claws. Other carnivores, such as lions and tigers, not only have sharp claws, they also have sharp teeth. Quick Check Sequence What eats a primary consumer in a food chain? Critical Thinking If all the producers are removed from an ecosystem, what would happen to the herbivores? Leopards are carnivores. After they catch their prey, they will often hide it in a tree and return later to eat it. 227

9 What are omnivores? Some animals, such as raccoons, seem to eat everything! They eat fish, berries, insects, and small mammals. Are raccoons considered carnivores or are they herbivores? Raccoons are actually called omnivores (AHM nih vorz). An animal that eats both plants and animals is called an omnivore. There are several examples of omnivores in the animal kingdom. Omnivores include bears, woodpeckers, mice, chickens, and some crabs. Most people are omnivores too. Sometimes it is difficult to classify an organism as an herbivore, a carnivore, or an omnivore. For example, hippos are known as herbivores because they mainly graze on grass. However, hippos will occasionally eat meat. Predator and Prey Relationships Omnivores can be both predators and prey. A predator (Pre duh tur) is an organism that hunts and kills other organisms for food. Prey (PRAY) are organisms that are eaten by predators. Both predators and prey are consumers because they must eat other organisms to get energy. Most animals, at one time or another, can be both predators and prey. For example, a snake may eat a mouse one day but then be prey for a hawk the following day. A raccoon is an omnivore. Clownfish are omnivores. They will eat small invertebrates and also algae. 228

10 Predators are an important part of every food chain. They limit the size of prey populations. A population includes all members of a single species in an area at a given time. When the number of prey animals is reduced, producers and other resources in an ecosystem are less likely to run out. Prey are also an important part of food chains. They control the populations of producers and some primary consumers by consuming them. They also support predator populations because they are their food source. A predator population cannot get any larger than the prey populations can support. Predator and prey populations often cycle together. An increase in size of a prey population is often followed by an increase in the predator population. Quick Check Sequence How is energy from the Sun used by predators? Critical Thinking Can an omnivore and a carnivore be in the same food chain? Explain. Louisiana QL_AH Field Guide SI.3, SI.19 Observe QL_NL*. Take a QL_NL*. walk with a partner around the QL_NL*. schoolyard. Make <QL_RIH> a list of the plants QL_NL*. and animals that you see. QL_NL*. When you return to the classroom, use reference materials, such as books and magazines, to find out more about the organisms you observed. Are the organisms producers, herbivores, carnivores, or omnivores? Classify Make a field guide that includes the animals that you identified. Draw or cut out pictures of your organisms and place them in your field guide. Your guide should also include information about what the organisms eat. Communicate Did your classmates see the same type of organisms? Exchange your field guide with a classmate s to find out. Predator Prey Relationship In this example, the hawk is the predator. The snake is both a predator and prey. The mouse is prey. mouse snake hawk 229

11 Vultures eat rotting animal matter and get rid of it as waste. This helps decomposers break down matter faster. What are decomposers? Each fall and winter, thousands of leaves fall to the floor of some forests. Some trees also fall down. However, much of this plant material is gone by the following spring. There are fewer dead leaves on the ground, and the fallen trees are rotting away. Who or what is responsible for this cleanup? Decomposers do this important job for an environment. Decomposers break down organisms that are no longer living. They break them down into nutrients. Some nutrients become part of the soil. Organisms, such as plants, take in these nutrients. Animals then get the nutrients when they eat these plants. When plants and animals die, decomposers break down their bodies, and the food chain starts all over again. 230

12 Coyotes are scavengers. They will eat animals they did not hunt and kill. Special Jobs for Decomposers There are many types of decomposers. Each breaks down a different type of organism. Some decomposers, such as earthworms, break down plants. Some fungi break down rotting wood. Still other decomposers break down the remains of dead animals. Decomposers work together to break down organisms completely. They are essential components of all ecosystems. Scavengers also help remove dead organisms from an ecosystem. Scavengers are animals that feed on the remains of dead animals that they did not hunt or kill. Common scavengers include jackals, vultures, raccoons, and some crabs. Quick Check Sequence Why does a food chain start again after a decomposer does its job? Critical Thinking How do decomposers help an ecosystem? Fungi, such as these mushrooms, are decomposers. They slowly break down dead organisms. Earthworms return nutrients to the soil by breaking down dead plants. 231

13 Louisiana Food Chain What are some examples of food chains? heron Sun algae stone fly sunfish Louisiana has many different habitats. Within these habitats are a variety of food chains. However, the basic parts are the same in each. Below are some examples of food chains found in Louisiana. Can you identify which organisms are the producers and which are the consumers in each food chain? A pond food chain might start with algae. These algae float in the water, collecting sunlight and making food. Stone flies swarm near the surface of the water so they can eat the algae. The stone flies close to the water are then food for fish, such as sunfish. The sunfish are then eaten by birds, such as blue herons. After the herons die, decomposers break them down. Algae are also part of an ocean food chain. Shrimp eat the algae. Large predators, such as bottlenose dolphins, eat the shrimp. When the dolphins die, decomposers break down their bodies. A forest food chain may begin with trees. Mice eat the seeds and fruit from the trees. Predators, such as the barred owl, eat the mice. Decomposers break down the barred owls after they die. Read a Diagram Where does the fish in this diagram get its energy? Clue: Look for where the arrow that points to the fish comes from. Watch how organisms interact in food chains at Quick Check Sequence Describe the flow of energy through a Louisiana food chain. Critical Thinking Can one environment have more than one food chain? 232

14 Visual Summary A food chain is made of producers, consumers, and decomposers. Producers can make their own food. Consumers eat other organisms to get energy. They can be herbivores, carnivores, or omnivores. Think, Talk, and Write Vocabulary An animal that eats both plants and animals is called a(n). Sequence Describe the events that take place as energy from the Sun travels through a food chain. First Next Decomposers break down organisms that are no longer living. Last Critical Thinking What is your role in a food chain? Explain your answer. Make a Study Guide Make a layeredlook book. Use it to summarize what you learned about food chains. Test Prep Which type of organism makes its own food? A primary consumer B secondary consumer C producer D decomposer Essential Question How does energy flow between organisms in a food chain? Writing Link Predator-Prey Relationships Research examples of predator-prey relationships that are common to environments in Louisiana. Write a report to explain each relationship. Present your report to the class. Art Link Create a Lou isiana Food Chain Louisiana has a variety of different environments, such as ponds, marshes, oceans, forests, and meadows. Choose an environment, and research organisms found there. Use art supplies and other materials to construct a food chain. -Review Summaries and quizzes online at EVALUATE

15 Inquiry Skills: Observe and Infer Scientists can observe what happens when the population of one organism in a food web changes by studying populations in the wild. As an alternate method, scientists can conduct simulations and study the results. Then they infer what might happen in a real-world situation. Learn It When you observe, you use your senses to learn about something. It is important to record your observations, as well as any measurements you take. When you infer, you form an idea from your observations. You may then make more observations to determine if your inference was correct. In this activity you will observe changes in the sizes of a predator and a prey population over time. Then you will infer how the population sizes will continue to change. Try It Materials masking tape, eight 7.5-cm cardboard squares, one hundred 2.5-cm construction paper squares, graph paper Use tape to mark off a 60-cm by 60-cm square. This square represents a meadow. Distribute 10 of the 2.5-cm paper deer squares in the meadow. Toss the 7.5-cm cardboard wolf square into the meadow. Remove any deer that touch the wolf. In order to survive, the wolf must catch, or touch, three deer. If the wolf survives, it will produce one offspring. If the wolf does not catch any deer, it will starve. In the next trial, you will add or remove squares accordingly. Record your results in a data table like the one shown on the next page. What happened to the wolf and the deer in this trial? 234 EXTEND

16 At the start of the next trial, double the deer remaining from the first trial to represent new deer offspring. Scatter these new deer in the meadow. If the entire deer population was caught by the wolf in the previous trial, then add three new deer to the meadow. In each additional trial, toss a wolf square onto the meadow once for each wolf. This includes any surviving wolves from previous trials and any of the offspring produced in previous trials. Record your results in your data table. Repeat steps 2 through 5 for a total of 14 trials. Apply It Infer how the populations will change for six more trials. Base your inference on the pattern you observed during the first 14 trials. Then carry out trials Was your inference correct? If not, explain what might have caused your inference to be incorrect. Graph the data for your 20 trials. Place the deer and wolf data on the same graph so you can easily observe the predator-prey relationship. Label the vertical axis Number of Animals and the horizontal axis Trials. Use one color for the deer data and another for the wolf data. SI.16 Use evidence to make inferences and predict trends (SI-M-A5) SI.21 Distinguish between observations and inferences (SI-M-A7) SI.26 Use and describe alternate methods for investigating different types of testable questions (SI-M-B1) 235 EXTEND