Practice Set 5.4 - Ecosystem Restoration

The figure below shows an ecosystem with different plants and animals. What statement can you make about the flow of energy in this ecosystem?

• a. On a cloudy day, no energy will flow in this ecosystem.

• b. Grass can use and store energy from the sun, which eventually flows to all of the other life-forms.

• c. Eagles eat snakes, rabbits, and frogs and are not affected by the energy in other parts of the ecosystem.

• d. If eagles are removed from the ecosystem, energy can no longer flow to any of the other animals.

Answer explanation

The sun is the ultimate source of energy in an ecosystem; plants use and

store energy from the sun, and all other life forms eat plants or other animals that

eat plants.

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This diagram shows the flow of matter and energy between producers, consumers, and decomposers. Decomposers can help your school garden grow. Which activity would make use of decomposers in the garden?

• collecting ripe fruit to eat in the school lunchroom

• raking up dead leaves to be picked up by city trucks

• adding plant food to the garden to ensure strong, healthy plants

• collecting food scraps from the lunchroom to add to the soil in the garden

Answer explanation

Food scraps will provide additional material that decomposers would use to

resupply nutrients to the garden.

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Each year, students carefully water the plants, add plant food, make sure the garden gets plenty of sunshine, and remove any dead leaves or stems. This year, students have decided to care for the garden in all the same ways, except they have stopped using plant food. Instead, they rely on the decomposition of the dead leaves and stems to supply nutrients to the plants. However, their garden does not grow this year. Which explanation supports this result?

• The dead leaves and stems are too big and need to be chopped up into smaller pieces.

• The plants have become accustomed to plant food, and now they cannot use the nutrients from the dead leaves and stems.

• The soil does not have enough nutrients because there is no longer enough matter for the decomposers to break down.

• The dead leaves and stems are preventing the sunshine from reaching the soil, which is keeping the plants from growing.

Answer explanation

Decomposers break down dead materials into nutrients in the soil. Since the

students have been removing dead stems and leaves, this indoor garden has not had

dead materials. As a result, the population of decomposers has decreased and the

organic material they would have produced does not exist.

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Which statement is true about changes that could be made to this food web?

• If producers are removed, consumers and decomposers will continue to maintain a cycle.

• If consumers are removed, producers and decomposers will continue to maintain a cycle.

• If decomposers are removed, producers and consumers will continue to maintain a cycle.

• If the sun is removed, producers, consumers, and decomposers will continue to maintain a cycle.

Answer explanation

Producers (plants) will die, and decomposers will break down this dead plant material into nutrients for the soil, allowing other producers to grow

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Study the food web. What belongs in the box?

• sun, because it supplies energy to the food web

• grass, because it can use and store energy from the sun

• consumer, because it can eat the mice

• bacteria, because it can take nutrients from decomposing materials

Answer explanation

Grass are producers, so they use and store energy from the sun; when eaten,

plants transfer energy to mice and grasshoppers.

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Students grew several healthy plants in their classroom. All of them were planted in healthy soil, placed in a sunny window, and watered once a week. After the plants grew, the students set up four experiments to see which conditions affected plant growth the most. For each experiment, students kept the same conditions for Plant A and changed the conditions for Plant B. The results of the experiment are below.

• Plants obtain most of the materials they need to grow from soil and sunlight.

• Plants obtain most of the materials they need to grow from water and plant food.

• Plants obtain most of the materials they need to grow from sunlight and water.

• Plants obtain most of the materials they need to grow from air and water.

Answer explanation

Although plants obtain nutrients from soil and use energy from the sun to

make food, most of the materials they need to grow are obtained from air and water.

Experiment #1 shows that plants cannot grow without any air, and Experiment #4

shows that plants cannot grow without water.

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White polar bears only eat fish and other types of meat. What is the source of their energy?

• Polar bears are white, which makes them able to use and store energy directly from the sun.

• The fish and meat that polar bears eat bring and store energy from warmer locations.

• Fish make their own energy and pass it on to polar bears and the other life-forms that eat fish.

• Ocean plants use and store energy from the sun and pass it on to the fish and other animals that the polar bears then eat.

Answer explanation

Energy from the sun is captured by plants and then transferred to all other

organisms in an ecosystem.

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Sonya builds a terrarium with different kinds of plants inside. She adds some crickets to the terrarium, too. Sonya wants to show how matter cycles within the terrarium. Which of the following actions could she take to show this? Select all that apply.

• Sonya could add worms and fungi to the terrarium. If a plant in the terrarium dies, these decomposers can recycle some materials back into the soil for the other plants to use.

• Sonya could remove all of the larger plants in the terrarium. She could plant them in a larger pot so that all the plants have enough space to grow.

• Sonya could add a lizard to the terrarium. The lizard may eat the crickets and leave droppings on the ground that will be absorbed back into the soil.

• Sonya could add plant food to the terrarium. The plant food will provide nutrients to the soil to help the plants grow taller faster.

Answer explanation

Matter cycles between the air and soil and among plants, animals, and

microbes as these organisms live and die. Adding decomposers that will feed on dead

matter will help recycle materials back into the soil.

Matter cycles between the air and soil and among plants, animals, and

microbes as these organisms live and die. Adding a lizard that will eat the crickets will

help recycle materials back into the soil.

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The matter in an ecosystem is constantly being used and reused by living organisms. Three of these statements describe matter flowing through an ecosystem. Which statement does not describe the flow of matter in an ecosystem?

• Humans release carbon dioxide when they breathe that plants then absorb from the air.

• Rainfall washes dirt to the bottom of a hillside.

• Decomposers break down dead animals into nutrients that plants can later use.

• Consumers eat smaller animals and then leave droppings on the ground.

Answer explanation

Rainfall washing dirt to the bottom of a hillside is not an example of the flow of matter in an ecosystem, it is simply the

flow of matter on Earth’s surface.

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An area has a large decrease in the deer population. How might this impact the ecosystem?

• The rabbit population could increase because the cougars now only eat rabbits.

• The population of mice could decrease, causing the snake population to decrease.

• There could be less food for cougars to eat, which would cause a decrease in their population.

• There could be an increase in both the cougar and snake populations because more grass will be available.

Answer explanation

Fewer deer would mean less food for the cougars and a likely decrease in the

cougar population.

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