Cycles in Ecosystems / Study Guide

Cycles in Ecosystems / Study Guide

There are always changes happening in an ecosystem. Organisms in an ecosystem are constantly producing waste. For example, plants lose leaves and branches, and animals leave behind their droppings.

All organisms in an ecosystem in an ecosystem eventually die, and their bodies take up space.

New organisms in an ecosystem are also constantly born. How is there room in the ecosystem for the new organisms when there are dead organisms and waste in an ecosystem. Decomposers are organisms that help to clean up the waste and dead organisms in an ecosystem so that there is room for new organisms to grow.

Multiple Choice

What are decomposers?

• organisms that get energy from eating other living organisms

• organisms that get energy from breaking down waste and dead organisms

• organisms that produce their own energy

Multiple Select

Fungi are decomposers that can break down dead trees in a forest ecosystem. What would happen in a forest without these decomposers.

Select all choices that are true.

• There would be no food for trees, so many trees would die.

• There would be no space for new trees and plants to grow.

• The forest would be crowded with dead trees and dead plant matter.

It may seem like waste and dead organisms disappear from an ecosystem, but these things are actually slowly broken down and recycled into an ecosystem by decomposers. To get energy, decomposers eat waste and dead plant and animal matter. They break this material into tiny bits, and the nutrients and minerals in the materials are added back into the soil.

There are many different kinds of decomposers. Most are microorganisms, like bacteria, tht you need a microscope to see. Earthworms are decomposers that you can see without a microscope. They live in the soil and break down dead plant matter. Many kinds of fungi can break down dead trees using a special chemical.

A food chain shows the flow of energy and nutrients through organisms. Animals get energy and nutrients from the food they eat. Living things need both energy and nutrients to be able to live and grow. Decomposers are very important in an ecosystem because they return nutrients and minerals to the soil when they break down dead organisms and waste. Producers can use these nutrients to live and grow.

Energy can flow to decomposers at all points in a food chain, since organisms are constantly dying or producing waste. Decomposers break waste and dead organisms down and return nutrients to the soil, so they keep nutrients flowing through the food chain. This flow of material through an ecosystem in a repeating pattern is called a cycle.

Multiple Choice

Where are the decomposers in this diagram?

• around the outside of this food chain diagram.

• in the center of this food chain diagram.

Multiple Choice

What is one way this diagram could be improved to show the role of decomposers in an ecosystem.

• The Sun could be removed from the chart, since it doesn't play a role in a food chain.

• There could be arrows pointing from the decomposers to the plants labeled nutrients

• All of the consumers could be removed from the chart since they are not helped by decomposers.

Nitrogen Cycle

One nutrient that most plants and animals need to live and grow is nitrogen. Just like energy and other nutrients, nitrogen cycles through ecosystems. However, there are a few special steps that have to happen before plants and animals are able to use nitrogen.

Nitrogen is a gas that makes up about 8/10 of Earth's atmosphere. Even though nitrogen makes up a large part of Earth's atmosphere, most plants and animals cannot use the gas form of nitrogen. It must be changed into a form that plants can absorb into their roots before it can cycle through plants and animals.

Plants can absorb nitrogen compounds through their roots. Nitrogen compounds are chemicals that contain nitrogen, which plants can take up through their roots and use to live and grow. How can nitrogen in the atmosphere be changed into a nitrogen compound? Read further to find out how.

When lightening strikes, it can burn the air and cause nitrogen in the atmosphere to combine with other chemicals that can be carried into the soil and water by rain.

Some kinds of special bacteria live on plant roots and special tropical plants called bromeliads. These bacteria can take in nitrogen from the air and make it into nitrogen compounds that plants can use.

When a plant or animal dies, decomposers break down these organisms and return nitrogen compounds to the soil. Some animals wast also contains nitrogen that decomposers break down and add back into the soil.

Multiple Choice

All plants can use the nitrogen that is in a gas form in Earth's atmosphere.

Multiple Choice

Which of the following is NOT a way that nitrogen compounds can be formed?

• Decomposers break down dead organisms and return nitrogen compounds to the soil.

• Some special kinds of bacteria can take in nitrogen from the air and turn it into nitrogen compounds

• Lightning can burn the air and cause nitrogen in the atmosphere to combine with other chemicals.

• Some animals create nitrogen compounds using energy from the Sun.

Multiple Choice

How does this elephant get the nitrogen it needs to live and grow?

• It gets nitrogen when it is struck by lightning.

• It gets nitrogen by eating plants.

• It gets nitrogen from the Sun warming its body.

Multiple Choice

A farmer notices that her crops are very unhealthy. What is one way she could help her plants?

• She could take all of the earthworms and decomposers out of the soil that might be eating the crops.

• Shc could cover the crops in plastic and pump in more nitrogen in the form of gas.

• She could add a fertilizer that contains nitrogen compounds to her crops.

• She could add more metal cages on top of her crops and hope that lightning will strike them

Farmers and gardeners sometimes add nitrogen compounds to the soil to help plants grow. Sometimes nitrogen compounds are in fertilizers that people can add to the soil. These nitrogen compounds are in a form that can soak into the water and be absorbed through the roots of plants.

Multiple Choice

A farmer adding nitrogen-rich fertilizer to her crops is most like which of the following scenarios?

• An injured person going through surgery.

• A person building a fence around his or her garden.

• A person putting on a warm coat in the winter.

• A person taking a vitamin.

Carbon dioxide and oxygen are also gases in the Earth's atmosphere. Oxygen makes up about 2/10 of the air, and carbon dioxide makes up less than 1/10 of the air in Earth's atmosphere. Just like energy and nutrients, these gases are constantly being created and used in a cycle by living things in ecosystems.

Multiple Choice

Is there more oxygen or carbon dioxide in Earth's atmosphere?

Plants use carbon dioxide, water, and energy from sunlight to make sugars for food during photosynthesis. They release oxygen during this process.

Plant and animal cells use cellular respiration to turn food into usable energy. This process uses oxygen and sugar and releases carbon dioxide.

Multiple Choice

What gas is released during the process of photosynthesis?

• oxygen

• carbon dioxide

Multiple Choice

What gas is released during the process of cellular respiration?

• oxygen

• carbon dioxide

Plankton and other microorganisms in the ocean also create food through photosynthesis. These organisms release a large amount of oxygen into Earth's atmosphere.

As dead organisms are decomposed, they release carbon dioxide into the atmosphere.

When volcanoes erupt, they release lava, ash, and large amounts of carbon dioxide.

Combustion is the process of burning a material. Combustion can cause large amounts of carbon dioxide to be released into the atmosphere.

Natural combusion can happen when forest fires start from natural causes, like lightening striking a tree. Natural and man-made forms of combustion release large amounts of carbon dioxide into the atmosphere. Carbon is stored in living things. When wood and other plants catch on fire, they release carbon dioxide. Fire also takes oxygen from the air as it burns.

Combustion is one way that people get machines and cars to run. People also burn materials like wood and coal to heat their homes. Carbon is stored in living things. Coal, oil, and other fuels contain the remains of dead organisms. When these fuels are burned to run machines and create, heat carbon dioxide is released into the environment.

Multiple Choice

Plants are the only organisms that produce food through photosynthesis and release oxygen into the atmosphere.

Multiple Select

Which of these natural processes release oxygen into the environment?

Multiple Select

A company clears away a large forest of trees to build a power plant that burns coal. How could this action impact the carbon dioxide and oxygen cycle in an ecosystem?

Select all choices that are true.

• There will be a large amount of oxygen in the ecosystem since it will not be used by the trees during photosynthesis

• There will be a large amount of carbon dixoide in the ecosystem since it is released during combustion in the power plant.

• There will be a large amount of oxygen in the ecosystem ince it is released during combustion in the power plant.

• There will be a large amount of carbon dioxide in the ecosystem since it will not be used by the trees during photosynthesis

Multiple Select

Cellular respiration is one way that living things release carbon dioxide into the atmosphere. Select the pictures that show other processes that release carbon dioxide into the environment.

Multiple Choice

What is a cycle?

• the process of burning a material

• a flow of materials through a system in a repeating pattern of process that happens over and over

• a gas that animals need to survive

• an organism that breaks down other organisms for energy

Multiple Choice

What is nitrogen?

• a gas that plants must have to complete photosynthesis

• a gas that animals must breathe to survive

• the process of burning a material

• a gas that makes up a majority of Earth's atmosphere.

Multiple Choice

What are nitrogen compounds?

• chemicals that contain oxygen that plants can take up through their roots

• chemicals that flow through a system in a repeating pattern or process that happens over and over

• chemicals that contain nitrogen that plants can take up through their roots

• chemicals that contain carbon dioxide that plats can take up through their roots

Multiple Choice

What is combustion?

• the process by which plants make sugars for food

• the process that animals and plants use to turn food into usable energy

• the process of burning a material

• the process by which decomposers break down dead plant and animal matter

Multiple Choice

Which organisms keep ecosystems "clean" by breaking down waste and dead organisms?

• producers

• consumers

• herbivores

• omnivores

• decomposers

Multiple Choice

The flow of materials through an ecosystem in a repeating pattern is called a _________.

• carbon cycle

• a cycle

• nutrients

• nitrogen

• combustion

Multiple Choice

Which of the following are materials that move through the ecosystem in a cycle?

• nitrogen

• carbon dioxide

• nutrients

• oxygen

• all choices are correct

Multiple Select

Which of these processes release carbon dioxide into the atmosphere?

Check all that are true.

• cellular respiration

• photosynthesis

• combustion

• a volcanic eruption