Ecosystems and Interactions PDF

# ABIS® E-books ## Chapter 2: Ecosystems and Interactions ### Understand and Apply 1. Indicate if the following statements are true or false. Correct the false statements. * Water is an abiotic factor in an ecosystem. **True** * Acid rain is a consequence of water pollution. **True**...

# ABIS® E-books ## Chapter 2: Ecosystems and Interactions ### Understand and Apply 1. Indicate if the following statements are true or false. Correct the false statements. * Water is an abiotic factor in an ecosystem. **True** * Acid rain is a consequence of water pollution. **True** * Chlorophyll traps energy from plants. **False**: Chlorophyll traps energy from the sun. * Predactors eat only plant material. **False**: Predactors can be carnivores, omnivores, or scavengers. * Plants and animals are biotic factors of an ecosystem. **True** * Climate change may be caused by natural processes or humans. **True** * An ecosystem contains only living parts. **False**: An ecosystem contains both biotic and abiotic factors. 2. Which of the following does **NOT** result in fewer species? * Species extinction * Mutualism * Resource depletion * Pollution 3. Which of the following is **NOT** part of the carbon-oxygen cycle? * Carbon dioxide * Respiration * Photosynthesis * Nitrogen 4. Nitrogen is changed into a form that plants can use by: * Nitrogen-fixing bacteria. * The sun. * Decaying organisms. * Animals. 5. A relationship in which an organism is harmed is: * Parasitism. * Mutualism. * Commensalism. * Cooperation. 6. What level in an energy pyramid contains the most available energy? * The producer level. * The primary consumer level. * The secondary consumer level. * The tertiary consumer level 7. Which of the following is least likely to be affected if a tree is cut down? * Amount of sunlight reaching the ground. * Soil erosion. * Human activities. * The carbon-oxygen cycle. ### Organize Information | | Producer | Consumer | Decomposer | |---|---|---|---| | Apple tree | X | | | | Eagle | | X | | | Bacteria | | | X | | Fungi | | | X | | Human | | X | | | Mushroom | | | X | | Cow | | X | | | Grass | X | | | | Seaweed | X | | | ### Infer * **What might be three adaptations of a prey animal that help it escape from its predactors?** * **Camouflage**: Blending in with the surroundings * **Speed**: Running faster than the predator * **Defense Mechanisms**: Venomous bites, sharp claws, etc. ### Explain * **How might your local environment be affected by the building of a dam?** * The dam might change the natural flow of the river, impacting aquatic life. * The dam might change the surrounding areas due to flooding or changes in water levels. * The dam might impact the local ecosystem by changing the available habitat for animals and plants. ### Predict * **What might happen over thousands of years if the climate in a large tropical ecosystem got cold and snowy?** * The tropical ecosystem would struggle to adapt to the new climate. * Many species may not survive the colder temperatures and snowfall. * The ecosystem may shift towards a more temperate climate, with different plant and animal life. ### Take it Further 1. **Use Models:** Find pictures of various producers, consumers, and decomposers. Organize the pictures according to the feeding relationships that exist among the pictured species. Write a paragraph that explains the roles and feeding relationships of the organisms. 2. **Research:** Research the organisms that are active in a compost pile. Find out how they convert dead plant material to compost. If possible, build a compost pile on school grounds, a compost column in a plastic bottle, or a worm bin. Watch the organisms at work. Use the compost for starting seeds in the classroom or in a schoolyard garden. ## Chapter Review ### Chapter Summary * An ecosystem is composed of two parts: the biotic factors, or living parts, and the abiotic factors, or nonliving parts. The nonliving parts support the lives of the living parts. Members of the same species living in the same area at the same time form a population. All the populations in an ecosystem form the ecosystem's community. Water, carbon dioxide, oxygen, and nitrogen are abiotic factors that cycle through an ecosystem. These abiotic factors influence the sizes of populations. * All organisms need energy to fuel their life processes. This energy comes from food. Producers make their own food, using the energy from sunlight to convert carbon dioxide and water to sugars and oxygen. Consumers get energy by eating other organisms. Decomposers are organisms that get energy by absorbing nutrients from dead organisms and waste. They are important in recycling material in an ecosystem. Food chains and food webs are models that show how matter and energy flow through an ecosystem. An energy pyramid is a model that shows how the amount of available energy decreases in an ecosystem. * The ways organisms interact with each other affect their population growth. Many consumers are predators. They hunt and eat prey organisms. Many predators cooperate when hunting for food. Organisms compete for resources, especially if the amount of a resource is limited. Organisms of one species form symbiotic relationships with organisms of another species. Both species may benefit from the relationship (mutualism), one may benefit while the other is unaffected (commensalism), or one species may benefit while the other is harmed (parasitism). * Natural factors can cause changes in ecosystems. Humans are part of their ecosystem. As such, they also cause changes to the ecosystem. These changes affect both biotic and abiotic factors in the ecosystem. Ecosystems have changed throughout time in response to changes in abiotic factors, interactions among organisms, and the actions of humans. These changes have caused, and are still causing, climate change, species extinction, reduced numbers of species, resource depletion, and pollution of air, water, and land. ### Science Vocabulary 1. Fill in the blanks with the most appropriate terms from the box below. * **_Carnivore_** is an animal that eats only meat. * **_Herbivore_** is an animal that eats only plant material. * **_Consumer_** gets energy from food that it eats. * **_Producer_** uses the energy in sunlight to make food. * **_Omnivore_** eats both plants and animals. * **_Decomposer_** gets energy while recycling nutrients from dead material. * **_Population_** consists of only one species. * **_Community_** is all the living things in an ecosystem. * **_Symbiosis_** is a close relationship between organisms of different species. 2. Match the descriptions in Column B with the corresponding terms in Column A. | | Column A | Column B | |---|---|---| | 1 | Prey | d. is the organism captured and eaten | | 2 | Mutualism | f. both species benefit | | 3 | Commensalism | g. one species benefits, the other is not affected | | 4 | Parasitism | c. one species benefits, the other is harmed | | 5 | Competition | a. usually occurs if resources are limited | | 6 | Cooperation | e. organisms work together | | 7 | Food web | b. shows flow of energy and food in an ecosystem | ## Pollution * Pollution is the addition of harmful materials to the air, water, and land. Even materials that are not usually harmful can cause pollution if they build up in the environment. * The burning of fossil fuels is a major source of air pollution. Motor vehicles, factories, and power plants all burn coal and oil. The chemicals that form are released into the air. These chemicals can cause breathing problems. They are also the primary cause of acid rain. Acid rain occurs when gases produced by burning coal and oil dissolve in water vapor in the air. Drops of acid rain form and fall to Earth, killing trees and fish and damaging soil. * Water is polluted when chemicals are dumped into water either accidentally or on purpose. Fertilizers and animal waste wash into lakes and rivers from farmland. Oil pollutes oceans when tankers leak. Even soil can cause pollution when it washes into rivers. * Soil may become polluted when chemicals contained in precipitation to the ground or when polluted water flows through the soil. Plants that absorb the pollutants may die. Entire food webs can be affected as consumers lose their food sources. The result can be a decrease in the variety of species. * Land also may become polluted if people do not dispose of their waste properly. Landfills are areas designated for disposing of solid waste, such as old TVs, tires, and other garbage. Paint, batteries, and household chemicals must be disposed of in special places because they are hazardous to our health. ### Summary * Changes in ecosystems can be from natural causes. Humans also cause changes that affect both living and nonliving parts of an ecosystem. Natural and human-caused changes can cause climate change, species extinction, loss of species, resource depletion, and pollution of air, water, and land. ### Discussion 1. Identify a human activity that causes climate change. 2. Describe two changes that can result in fewer species. 3. Infer how water pollution can affect a food web in an ecosystem. 4. Predict what effect human overpopulation might have on resources. 5. Evaluate the following statement: Changing biotic factors in an ecosystem has no effect on abiotic factors. ## Species Extinction * When all individuals of a species die out, the species is extinct. Extinction can be a natural process. Most species that have ever lived are now extinct. Species die out because their environment changes and can no longer meet their needs. * Human activity also causes extinction. Humans need places to live and work. They need roads, schools, and stores. Humans clear land and change natural ecosystems to build the structures that meet their needs. They mine for resources that lie beneath Earth's surface. They clear land for agriculture. They build dams to provide electricity. They fill in wetlands to build on them. They introduce species that reproduce so fast that they take over an area. All these activities cause habitat destruction, which is the destruction of natural ecosystems that provide homes to organisms. * Habitat destruction is a significant cause of population decline in many species. For example, scientists estimate that half of the South American rain forest has been destroyed, as land is cleared for agriculture. No one knows for sure how many species may be lost, but some estimates predict the extinction of as many as 27,000 species per year. ## Resource Depletion * The human population on Earth is increasing rapidly. By the time you sit through one science class, 10,000 people have been born. All of the billions of people on Earth need and use Earth's resources. * Some resources cannot be replaced very quickly. For example, fossil fuels take billions of years to form. Metals are another resource that cannot be replaced. Others, such as trees, can be replaced by planting new ones. However, if trees are cut down faster than they can grow, they can become depleted, too. * Resources like water continually cycle through the environment from rivers to oceans, to the sky, and back again. However, fresh water can become a depleted resource if not used carefully. Many people pump fresh water from underground reservoirs to use for drinking and cooking. In some areas, underground water sources are disappearing because water cannot cycle back into the ground fast enough. There is no longer enough fresh water to support life in some of these areas. ### Try It at Home * Interview an older adult to find out what changes have occurred in the availability of resources such as food, water, trees, and wildlife since he or she was a child. Report your findings to your class. ## Natural Changes * Most ecosystems change over time. Change may be the result of a natural occurrence, such as a volcanic eruption. This kind of change is sudden and causes vast changes. Lava destroys everything in its path, leaving only bare rock. Soil must reform, which can take decades. Seeds blown into the area may sprout, and plants may grow. Eventually the area may support a diverse ecosystem again, but the ecosystem will probably be different from the original one, with different plants and animals. * Forest fires started by lightning strikes or floods are other examples of sudden natural changes. Thousands of square kilometers of forests or other ecosystems may be destroyed as a result of these natural disasters. * Other natural changes to ecosystems occur more slowly. Beavers cut down trees to dam streams. They use the cut trees to form large structures called lodges, where they live and raise their young. The solid stream gradually moves around the blockage, and a pond forms upstream from the dam. Fish that prefer deep, still water may move into the pond and then attract wading birds that feed on fish. ## Changes Caused by Humans * Like many other organisms, humans change their environment to meet their needs. Humans use resources and produce wastes. For example, logging a forest to use the wood changes the forest ecosystem. Birds and squirrels lose their homes. The amount of sunlight reaching the forest floor increases, which changes the kinds of plants that grow there. * Cutting down a forest is a change done on purpose. But some changes are done by accident. Humans may accidentally start a forest fire, or sewage may accidentally leak into a river. Both events kill organisms and disrupt food webs as a result. * Climate change includes changes in temperature and precipitation. The fossil record shows that climates have changed as part of Earth's natural processes. Some parts of Earth have become warmer, and other parts have become colder. However, today there is concern that using coal and oil is causing climate change at a much faster pace. Burning coal and oil causes carbon dioxide to accumulate in the air. Some carbon dioxide is needed because it warms Earth by trapping the sun's heat in Earth's atmosphere. However, too much carbon dioxide can raise temperatures on Earth and cause problems to ecosystems, such as the melting of glaciers and polar ice. ## Symbiosis: Commensalism * Not all relationships are two-way. The symbiotic relationship in which one species benefits while the other is not affected is called commensalism. Birds often form commensal relationships with larger animals. Cattle and other livestock that graze in fields usually stir up insects as they move. Cattle egrets follow the cattle to catch and feed on the insects. The egrets benefit because the livestock have helped them find food, while the livestock are not affected. * In rain forests, tropical vines form commensal relationships with trees. Not much light falls on the forest floor because the trees are so dense. Orchid vines climb up tree trunks to reach the light they need for photosynthesis. The vines also take in nutrients that run down the tree trunk. The trees do not benefit and are not harmed by the relationship as long as the vines do not become too large and heavy. * Barnacles are invertebrates whose adults cannot move. Barnacles hitch a ride on the backs of whales and sea turtles. The barnacle benefits by being transported to new sources of food in the ocean. The whale or turtle is unaffected by its passenger. ## Symbiosis: Parasitism * Parasitism is a symbiotic relationship in which one species benefits and the other, called the host, is harmed. Some parasites, such as ticks and lice, attach themselves to the host's skin and feed on the host's blood. Other parasites, such as tapeworms and the protist that causes malaria, live inside the host. They take nutrients from the host and reproduce inside the host's body. These activities cause harm to the host. ### Summary * Organisms interact with each other in different ways. These interactions affect population growth and keep populations under control. Organisms may cooperate or they may compete for resources. Many consumers are predators. They capture and eat prey organisms. Other organisms form symbiotic relationships with other species. Both species may benefit from the relationship, one may benefit while the other is unaffected, or one species may benefit while the other is harmed. ### Discussion 1. Identify the predator and prey organisms in the following food chain. * grass, caterpillar, bluebird 2. Give an example of mutualism. 3. Explain why better adapted organisms usually get more resources than poorly adapted organisms. 4. Infer how the members of a football team are like bees that live together in a colony. 5. Infer: What adaptations might help a predator survive? ## Competition * Under ideal conditions, each population in a community has plenty of food, water, space, and other resources. But conditions in an ecosystem are rarely ideal. Resources are limited, and organisms must compete for resources. Competition is the struggle between individuals or populations for a resource. The organism that is better adapted will get more of the resource. * Individuals of the same species, such as two oak trees, may compete for water, sunlight, or space. If one tree has a larger root system and takes in more water, that tree may grow faster. * Competition also occurs between members of different species. Both grey squirrels and red squirrels lived in Great Britain and competed for food. Because grey squirrels ate a more varied diet, more of them survived. Over time, the grey squirrel population increased, and the red squirrel population decreased. * As long as two species have different roles within an ecosystem, they will not compete. For example, one bird species might build nests in the top branches of a maple tree. Another bird species might build nests in the same maple tree, but in lower branches. These two species will not compete for space. ## Symbiosis: Mutualism * Another interaction between organisms of different species is symbiosis. Symbiosis is the interaction between members of different species that live together in a close relationship. The relationship is so close that at least one of the two species depends on the other for survival. Many symbiotic relationships help provide a resource to at least one of the species. Other symbiotic relationships help an organism reproduce. * There are three types of symbiosis: where both species benefit, where one species benefits and the other is not affected, and where one species benefits and the other is harmed. Mutualism is an interaction between two species in which both species benefit. * The ant-aphid relationship in the chapter opener is an example of mutualism. * Another example of mutualism is the relationship between cows and the bacteria that live in cow intestines. Cows eat grass but cannot digest its tough cell walls. Certain bacteria that live in cow intestines digest the grass, providing the animal with nutrients and energy. In exchange, the bacteria get a safe place to live with a ready source of nutrients. Neither species could survive without the other. ## Predators and Prey * Many interactions among organisms of different species involve hunting for food. A predator is an animal that captures and eats another animal. The animal eaten by a predator is the prey. * Recall that consumers make up most of a food chain. The consumers in a food chain can be both predators and prey. Each consumer eats another organism, and many consumers are eaten in turn. In the food chain, algae, snail, fish, heron, the fish is a predator of the snail but prey for the heron. * Predators keep the size of prey populations under control. Predators also improve prey populations over time. Because predators usually kill old, young, or sick animals, the strongest prey animals survive and reproduce. Prey populations also affect predators. Predators are found in an ecosystem only where their food is located. ## Cooperation * Many organisms cooperate to get resources. Cooperation is an interaction that occurs when organisms work together to help each other. Members of the same species that cooperate by hunting together for food use less energy and capture more food than when they hunt alone. A pack of coyotes can successfully capture a large prey animal such as an elk, whereas a single coyote could not. A pod of orca whales can circle a school of fish, bringing them closer together so they can be scooped up and eaten. A single orca might have to catch fish one at a time. * Bees and ants live in colonies. The insects in a colony are divided into different groups, with each group having a different job. Some groups gather food. Others protect the colony. Sharing responsibilities benefits the whole colony. * Members of different species also may cooperate. Coyotes and badgers often hunt together. Badgers dig for burrowing ground squirrels. Coyotes chase ground squirrels when they try to escape the badger. Because the two predators use different hunting methods, they can catch more prey.