The animals at higher levels are more competitive, so fewer animals survive. B.

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1 Energy Flow in Ecosystems 1. The diagram below shows an energy pyramid. Which of the following best explains why the number of organisms at each level decreases while moving up the energy pyramid? The animals at each level have more predators, so they produce more offspring. A. The animals at higher levels are more competitive, so fewer animals survive. B. C. The animals at each level use energy, so only a small amount of their energy is available to the next level. The animals at higher levels move more than animals at lower levels, so they require more energy. D.

2 2. Examine the energy pyramid below. Why is the first block containing the plants the widest block? A. This block represents the trophic level with the most stored energy. B. This block represents ten times the number of organisms of the next block. C. This block represents the most complex organisms in the pyramid. D. This block represents all the producers and herbivores in the ecosystem. 3. Which level in a food web contains the highest amount of total available energy? A. producer B. secondary consumer C. decomposer D. primary consumer 4. What does the following diagram illustrate? Algae Minnows Salmon Bear A. a food chain B. a trophic level C. a food web D. a food pyramid

3 5. The diagram below shows a food chain. Grass Rabbit Weasel Fox Fungi Which population would most likely increase if the weasel was removed from the food chain? A. fungi B. fox C. grass D. rabbit 6. Examine the food web below. If plants were removed from this ecosystem, which of the following organisms would be affected? A. wolves B. frogs C. hawks D. all of these 7. Technology Enhanced Questions are not available in Word format. 8. The food chain below shows an example of how energy flows through an ecosystem.

4 What is the ultimate source of all of the energy that flows through this food chain? A. the Sun B. bacteria C. plant life D. oxygen gas 9. Examine the following food chain and choose the organism that would best fill in the blank portion. Wheat Mouse [?] Hawk A. oak tree B. cow C. snake D. algae 10. Technology Enhanced Questions are not available in Word format. 11. Food chains show how living organisms obtain their food, while food webs show how multiple food chains are interrelated. Which of the following is a true statement regarding food webs? Ninety percent of the matter that is available at one trophic level is transferred to the next level. A. Matter and energy are conserved as they pass through a food web. B. Matter and energy are not conserved as they pass through a food web. C. Ninety percent of the energy that is available at one trophic level is transferred to the next level. D. 12. What does the following diagram illustrate?

5 A. a trophic level B. a food chain C. a food pyramid D. a food web 13. Technology Enhanced Questions are not available in Word format. 14. Producers are autotrophic. That is, they are able to feed themselves by converting carbon dioxide from the air and light energy from the Sun into food. Consumers and decomposers are heterotrophic. This means that these organisms must obtain their food by eating other organisms or organic matter. The relationships among producers, consumers, and decomposers carrying out either autotrophic or heterotrophic nutrition are identified through A. food webs. B. the periodic table. C. feedback mechanisms. D. Punnett squares. 15. What is the ultimate source of energy for all ecosystems? A. secondary consumers B. the Sun C. primary consumers D. plants

6 16. The diagram below shows a food web. Which of the following is true about the food web? A. Squirrels provide foxes and owls with energy. B. Spiders gain energy directly from plants. C. Rabbits and mice provide each other with energy. D. Snakes are a source of energy for toads.

7 17. The energy pyramid below shows a possible amount of energy, in kilocalories, available in the organisms at each trophic level in an ecosystem. According to the law of conservation of energy, energy can neither be created nor destroyed. If this is true, why is there less energy in the top of the energy pyramid than there is in the bottom of the energy pyramid? Energy is lost between each trophic level as heat. A. The extra energy in the bottom is slower to reach the top. B. Organisms in the top of the energy pyramid use up energy the fastest. C. The law of conservation of energy does not apply to ecosystems. D. 18. Technology Enhanced Questions are not available in Word format. 19. As energy flows through ecosystems, atoms and molecules cycle among A. only the living components of the biosphere. B. neither the living nor the nonliving components of the biosphere. C. only the nonliving components of the biosphere. D. both the living and nonliving components of the biosphere.

8 20. Green plants are the first living organism in a food chain. Where do plants get the energy that they pass along to the primary consumers in their food chains? A. from secondary consumers B. from the Sun C. from other plants D. from decomposers 21. The trophic levels of the energy pyramid above show that the same amount of energy is available at every level of the energy pyramid. A. there is a great amount of energy lost as it travels up the energy pyramid. B. energy is not transferred between organisms in an ecosystem. C. there is a great amount of energy gained as it travels up the energy pyramid. D.

9 22. What does the following diagram illustrate? A. an energy pyramid B. a food web C. a food chain D. a trophic level 23. Technology Enhanced Questions are not available in Word format. 24. Based on the food chain shown above, energy in this ecosystem flows from A. the snake to the mouse. B. the mouse to the plant. C. the mouse to the snake. D. the hawk to the snake. 25. What happens to the chemical elements that make up the molecules of living things as they pass through a food web? A. All of their energy is dissipated as heat. B. Some of their energy is stored in newly made structures. C. They are not transferred at all. D. They remain intact in their original structures. 26. An organism makes glucose using energy from the Sun. The organism is a. A. decomposer B. producer C. primary consumer D. secondary consumer

10 27. Which of the following living things would be found closest to the beginning of a food chain? A. coyote B. scorpion C. mushroom D. caterpillar 28. Which level in a food web contains the highest amount of total available energy? A. producer B. decomposer C. primary consumer D. secondary consumer

11 29. The energy pyramid for an ecosystem is pictured below. Which type of organism can be found in all levels of the energy pyramid except the first (bottom) level? A. producers B. herbivores C. consumers D. carnivores

12 30. The Antarctic food web is less complex than other food webs around the world. There are fewer different species that are part of it. However, there are more of each species. According to the food web shown, which organism is both a primary consumer and a secondary consumer? A. fish B. baleen whale C. krill D. other seals Answers 1. C 2. A 3. A 4. A 5. D 6. D A 9. C B 12. D A 15. B 16. A 17. A

13 19. D 20. B 21. B 22. A C 25. B 26. B 27. D 28. A 29. C 30. C Explanations 1. Each level in a food chain provides energy for the level above it. However, the organisms at each level also use some of the energy to survive. This means that only about ten percent of the energy produced at each level is available to the level above it. 2. The width of a energy pyramid's blocks is determined by the amount of energy stored in the organisms at that trophic level. Because the energy stored by the organisms at each trophic level is about one-tenth of the energy stored by the next level, the lowest level is the widest and the highest level is the smallest. 3. Energy first flows into a food web through primary producers. Moving up each of the trophic levels, the available energy reduces by around ten percent each time. Thus, the amount of energy available to consumers or decomposers is much less than that of the producers. 4. The path of energy through the trophic levels of an ecosystem is called a food chain. All food chains begin with a producer. 5. The number of organisms at each trophic level is dependent upon the number of organisms feeding on it. The rabbit numbers are limited because they are a food source for the weasel. If the weasel was removed from the food chain, the rabbit population would most likely increase. 6. If plants were removed from the food web, all of the organisms in the ecosystem would be affected, since plants form the basis of the food web. Consumers cannot survive without the existence of producers Food chains describe the eating relationships and energy flow between species within an ecosystem. The ultimate source of energy for almost all ecosystems on Earth is the Sun. Producers, such as plants, receive energy from the Sun and make their own food (i.e., glucose sugar) through the process of photosynthesis. Producers are at the beginning of food chains because all of the other organisms in food chains depend on the food energy that they make. 9. In a food chain, each subsequent organism consumes the previous organism and is consumed by the organism that follows. In this case, you are looking for an organism that would consume a mouse, but be consumed by a hawk. Hawks are carnivorous, but only consume animals equal to or smaller than they are. A snake is a favorite food of a hawk

14 11. According to the laws of conservation of matter and energy, neither matter nor energy can be created or destroyed. They can only change forms. Although it is true that only 10% of the energy that is available at one trophic level is transferred to the next level, the rest changes into heat energy, so the total amount of energy is still conserved. However, the heat energy is considered "lost" because it is not useful to the system. Likewise, even though only a portion of matter is transferred from trophic level to trophic level, the remaining "waste" is recycled through processes such as the carbon or nitrogen cycles. Thus, the total amount of matter is also conserved. 12. In most ecosystems, energy does not follow simple straight paths because individual animals often feed at several trophic levels. This creates a complicated, interconnected group of food chains called a food web Food webs provide visual representations that identify the relationships among producers, consumers, and decomposers carrying out either autotrophic or heterotrophic nutrition. In a food web, arrows are drawn between organisms to show the directions in which food energy is transferred. 15. Although plants and other producers make up the first trophic level of all food webs or food chains, the ultimate source of energy for all ecosystems is the Sun. A continuous input of energy from the Sun drives many natural processes found in all ecosystems such as photosynthesis and the water cycle. 16. A food web shows the connections between the living things in an environment. An arrow from one living thing to another indicates that the living thing is a source of energy for the living thing that the arrow is pointing to. In this case, the food web shows that squirrels are a source of energy for both foxes and owls. 17. The law of conservation of energy is universal. Energy cannot be created nor destroyed. There is less energy available in the top of the energy pyramid than there is in the bottom because organisms all along the energy pyramid are using the energy, and some of the energy is lost between each trophic level as heat. The heat energy is dispersed into the surrounding environment As energy flows through ecosystems, atoms and molecules cycle among both the living and nonliving components of the biosphere. The atoms and molecules on Earth cycle among organisms as well as the nonliving components of the biosphere, such as atmospheric gases. For example, atoms in carbon dioxide and water molecules that are used in photosynthesis to form energy-rich organic compounds are returned to the environment when cells break these compounds down to release the energy. 20. The energy in a food chain initially enters through the green plants at the beginning of the chain. The plants make food from the energy they absorb from the Sun. 21. As energy travels from one trophic level up to the next in an energy pyramid, there is a great amount of energy lost. An average of only 10% of the energy from the previous level moves to the next level. The rest is used up or lost as heat energy. 22. Ecologists often illustrate the flow of energy through ecosystems with an energy pyramid, a diagram in which trophic levels are represented by stacked blocks. The size of each block is determined by the amount of energy stored in the organisms at that trophic level

15 24. Food chains describe the eating relationships and energy flow between species within an ecosystem. The arrows in a food chain represent the direction of energy flow and point from the organism that is being consumed toward the organism that is receiving energy. Based on the food chain shown in the picture, energy in this ecosystem flows from the mouse to the snake. 25. The chemical elements that make up the molecules of living things (e.g., carbon, hydrogen, nitrogen, oxygen) pass through food webs and are combined and recombined in different ways. At each link in an ecosystem, some energy (approximately 10%) is stored in newly made structures, although most of the energy (approximately 90%) is dissipated into the environment as heat. 26. Organisms that absorb sunlight and use the energy to manufacture carbohydrates, such as glucose, are producers. 27. Primary producers (plants) typically occur at the beginning of all food chains. The next organisms are the primary consumers, or livings things that consume plants. A caterpillar is an example of a primary consumer. A scorpion is a secondary consumer, which feeds on other consumers. Mushrooms are decomposers; these organisms feed on dead plant and animal material throughout the food chain. 28. Energy first flows into a food web through primary producers. Moving up each of the trophic levels, the available energy reduces by around ten percent each time. Thus, the amount of energy available to consumers or decomposers is much less than that of the producers. 29. Consumers can be found in all levels of an energy pyramid except the first (bottom) level, which is made up only of producers. Consumers can be primary, secondary, or tertiary. Primary consumers use producers as their main food source. Secondary consumers eat primary consumers. Tertiary consumers are at the top of the food chain. They feed on secondary consumers. 30. According to the diagram of the Antarctic food web, krill are the only organisms that eat both the energy producers (phytoplankton) and an organism that also eats the phytoplankton (other herbivorous zooplankton). This makes krill both primary consumers and secondary consumers.