cycles of matter

the element carbon

Carbon is an element. By itself, its a black solid. You can see a lump of carbon in Figure 18.10. Carbon is incredibly important because of what it makes when it combines with many other elements. Carbon can form a wide variety of substances. For example, in the air, carbon combines with oxygen to form the gas carbon dioxide. In living things, carbon combines with several other elements. For example, it may combine with nitrogen and

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the nitrogen cycle

Living things also need nitrogen. Nitrogen is a key element in proteins. Like carbon, nitrogen cycles through ecosystems. You can see the nitrogen cycle in Figure 18.13.

how carbon cycles through nonliving things

Carbon from decaying organisms enters the ground. Some carbon is stored in the soil. Some carbon may be stored underground for millions of years. This will form fossil fuels. When volcanoes erupt, carbon from the mantle is released as carbon dioxide into the air. Producers take in the carbon dioxide to make food. Then the cycle repeats. The oceans also play an important role in the carbon cycle. Ocean water absorbs carbon dioxide from the air. In fact, the oceans contain 50 times more carbon than the atmosphere. Much of the carbon sinks to the bottom of the oceans, where it may stay for hundreds of years.

human actions and the carbon cycle

Human actions are influencing the carbon cycle. Burning of fossil fuels releases the carbon dioxide that was stored in ancient plants. Carbon dioxide is a greenhouse gas and is a cause of global warming. Forests are also being destroyed. Trees may be cut down for their wood, or they may be burned to clear the land for farming. Burning wood releases more carbon dioxide into the atmosphere. You can see how a tropical rainforest was cleared for farming in Figure 18.12. With forests shrinking, there are fewer trees to remove carbon dioxide from the air. This makes the greenhouse effect even worse.

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human actions and the nitrogen cycle

Nitrogen is one of the most important nutrients needed by plants. Thats why most plant fertilizers contain nitrogen. Adding fertilizer to soil allows more plants to grow. As a result, a given amount of land can produce more food. So far, so good. But what happens next? Rain dissolves fertilizer in the soil. Runoff carries it away. The fertilizer ends up in bodies of water, from ponds to oceans. The nitrogen is a fertilizer in the water bodies. Since there is a lot of nitrogen it causes algae to grow out of control. Figure 18.14 shows a pond covered with algae. Algae may use up so much oxygen in the water that nothing else can grow. Soon, even the algae die out. Decomposers break down the dead tissue and use up all the oxygen in the water. This creates a dead zone. A dead zone is an area in a body of water where nothing grows because there is too little oxygen. There is a large dead zone in the Gulf of Mexico. You can see it Figure 18.14.

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fixing nitrogen

Air is about 78 percent nitrogen. Decomposers release nitrogen into the air from dead organisms and their wastes. However, producers such as plants cant use these forms of nitrogen. Nitrogen must combine with other elements before producers can use it. This is done by certain bacteria in the soil. Its called fixing nitrogen.

how carbon cycles through living things

Producers such as plants or algae use carbon dioxide in the air to make food. The organisms combine carbon dioxide with water to make sugar. They store the sugar as starch. Both sugar and starch are carbohydrates. Consumers get carbon when they eat producers or other consumers. Carbon doesnt stop there. Living things get energy from food in a process called respiration. This releases carbon dioxide back into the atmosphere. The cycle then repeats.

the carbon cycle

In the carbon cycle, carbon moves through living and nonliving things. Carbon actually moves through two cycles that overlap. One cycle is mainly biotic; the other cycle is mainly abiotic. Both cycles are shown in Figure 18.11.

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instructional diagrams

description_image

This is a diagram of the nitrogen cycle. Nitrogen is present in the earth's soil, atmoshpere, and biosphere. The amount of nitrogen on the earth is fixed, and it can't be created or destroyed. It can only change the forms it takes in chemical compounds. Nitrogen gas in the atmosphere enters the soil and ocean through t the action of nitrogen fixing bacteria. These bacterial convert nitrogen gas to ammonium, nitrites, and then to nitrates. Once in the soil, these nitrates can enter the terrestrial food web, or return to the atmosphere by the action of denitrifying bacteria. Nitrates in the ocean can the marine ecosystem, or can be converted back to nitrogen gas by denitrifying bacteria. Humans add nitrogen to the soil when they use fertiizers. These fertilizers can enter the marine food web as runoff.

description_image

The element carbon is the basis of all life on Earth. Biochemical compounds consist of chains of carbon atoms and just a few other elements. Like water, carbon is constantly recycled through the biotic and abiotic factors of ecosystems. The carbon cycle includes carbon in sedimentary rocks and fossil fuels under the ground, the ocean, the atmosphere, and living things. The diagram represents the carbon cycle. It shows some ways that carbon moves between the different parts of the cycle.

description_image

This is a diagram of the carbon cycle. Carbon is found in all living things on Earth. Carbon is cycled between the living (biotic) and nonliving (abiotic) parts of the ecosystem. Carbon is found in sedimentary rocks and fossil fuels, the atmosphere and in living things. Animals and plants release carbon in the form of carbon dioxide during the process of respiration. Carbon dioxide in the air is taken up by plants during photosynthesis. Photosynthesis produces glucose, a carbohydrate. Glucose is broken down by animals for energy.

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This diagram shows the carbon cycle. Here are examples of how carbon moves through human, animal, and plant activity. All living things contain carbon, as do the ocean, air, rocks, and underground fossil fuels, which are made in a process that takes millions of years. Plants take in sunlight and carbon dioxide, and create energy through photosynthesis. When they decay, and are buried underground, plants and other organisms turn into fossil fuel. When we burn fossil fuels, carbon dioxide is quickly released into the air. Plants can also release carbon dioxide just like animals do, through respiration.

description_image

This is an illustration of the nitrogen cycle. Nitrogen exists in several forms in the earth's soil, atmoshpere, and organisms. The earth has a fixed amount of nitrogen, and is endlessly cycled through these forms in the nitrogen cycle. Animals get their nitrogen directly by eating plants, or indirectly by eating organisms that have eaten plants. Plants can't use the form of nitrogen gas in the air. Plants can only use nitrogen in chemical compounds called nitrates. Plants absorb nitrates from the soil through their roots in a process called assimilation. Most plants use nitrates that are produced by bacteria that live in soil. A certain type of plants called legumes have nitrogen-fixing bacterial living in their roots, and don't need the bacteria in the soil. Bacteria that can change nitrogen gas in the atmosphere to nitrates are called Nitrogen-fixing bacteria. The nitrates in the detritus of organisms have their nitrogen returned to the soil as ammonium by the decomposition action of detrivores. Nitrifying bacteria change some ammonium in the soil into nitrates that can be used by plants. The rest of the ammonium is changed into nitrogen gas by denitrifying bacteria. Denitrifying bacteria convert ammonium to nitrogen gas that is released into the atmoshpere.

questions

process in which living things obtain energy from food

a. carbohydrate

-->  b. respiration

c. carbon

d. decomposition

e. nitrogen

f. nitrogen fixing

g. carbon dioxide

What happens during respiration?

a. producers create food energy from solar energy

b. consumers use solar energy to create food energy

-->  c. living things release energy from food

d. carbon dioxide is converted into oxygen

carbon compound used by plants to make sugar

a. carbohydrate

b. respiration

c. carbon

d. decomposition

e. nitrogen

f. nitrogen fixing

-->  g. carbon dioxide

What is nitrogen fixing?

-->  a. Soil bacteria make nitrogen useful for producers.

b. Producers make nitrogen useful for consumers.

c. Nitrogen gas in the atmosphere creates complex compounds.

d. Nitrogen combines with oxygen to make a useful gas.

key element in proteins

a. carbohydrate

b. respiration

c. carbon

d. decomposition

-->  e. nitrogen

f. nitrogen fixing

g. carbon dioxide

Greenhouse gases

a. absorb incoming solar radiation in the atmosphere.

-->  b. trap infrared radiation radiating from Earths surface.

c. scatter sunlight from one molecule to another.

d. All of these.

Carbon is

a. stored in the mantle

b. released into the atmosphere at volcanoes

c. stored in the oceans

-->  d. all of these

process that releases nitrogen from organic remains

a. carbohydrate

b. respiration

c. carbon

-->  d. decomposition

e. nitrogen

f. nitrogen fixing

g. carbon dioxide

process that changes nitrogen to a form that plants can use

a. carbohydrate

b. respiration

c. carbon

d. decomposition

e. nitrogen

-->  f. nitrogen fixing

g. carbon dioxide

Destroying forests changes the carbon cycle because

a. plants take carbon out of the atmosphere

b. burning plants releases stored carbon into the atmosphere

c. more carbon is in the atmosphere

-->  d. all of these

element that is the basis of all life on Earth

a. carbohydrate

b. respiration

-->  c. carbon

d. decomposition

e. nitrogen

f. nitrogen fixing

g. carbon dioxide

type of carbon compound that includes sugars and starches

-->  a. carbohydrate

b. respiration

c. carbon

d. decomposition

e. nitrogen

f. nitrogen fixing

g. carbon dioxide

Carbon is an important part of organic material.

-->  a. true

b. false

When an organism decomposes, its carbon is released back into the environment.

-->  a. true

b. false

Carbon is only found in organic material.

a. true

-->  b. false

Nitrogen is a nutrient so more is always better.

a. true

-->  b. false

Algae create food energy from sunlight.

-->  a. true

b. false

Carbon dioxide enters the atmosphere during

a. photosynthesis.

-->  b. burning.

c. decay.

d. all of the above

Which of the following compounds in living things contain carbon?

a. sugars

b. starches

c. proteins

-->  d. all of the above

Consumers get carbon by

a. photosynthesis.

b. respiration.

c. breathing.

-->  d. eating.

Human beings affect the carbon cycle by

a. burning wood.

b. using fossil fuels.

c. cutting down forests.

-->  d. all of the above

Which process releases nitrogen into the air?

-->  a. breaking down waste

b. fixing nitrogen

c. using fertilizer

d. making sugar

Without certain organisms that live in soil, plants would not be able to use

a. carbon.

b. oxygen.

-->  c. nitrogen.

d. carbon dioxide.

The underlying cause of dead zones is

a. not enough carbon in the water.

-->  b. too much nitrogen in the water.

c. too few organisms in the water.

d. none of the above

The carbon cycle includes both living and nonliving things.

-->  a. true

b. false

Carbon changes form as it moves through the carbon cycle.

-->  a. true

b. false

Volcanic eruptions release carbon dioxide into the air.

-->  a. true

b. false

The atmosphere contains more carbon than the oceans.

a. true

-->  b. false

Carbon cycles very quickly through ocean water.

a. true

-->  b. false

Nitrogen is one of the most important nutrients needed by plants.

-->  a. true

b. false

Plants obtain nitrogen directly from the atmosphere.

a. true

-->  b. false

Nitrogen in runoff that enters ponds kills algae and water plants.

a. true

-->  b. false

When algae use food for energy, they release oxygen into the water.

a. true

-->  b. false

There is a large dead zone in the Gulf of Mexico.

-->  a. true

b. false

diagram questions

question_image

Which gas is represented by letter F?

a. CARBON DIOXIDE

b. NITROGEN

c. CARBON MONOXIDE

-->  d. METAN

question_image

Identify photosynthesis in this picture

a. E

-->  b. R

c. C

d. F

question_image

Which process is represented in label R?

a. MITOSIS

b. PHOTOKINESIS

c. CARBON EMISSION

-->  d. PHYTOSYNTHESIS

question_image

Where does plant respiration take place?

a. U

b. R

-->  c. X

d. E

question_image

Which gas is represented by letter F?

a. NITROGEN

b. CARBON DIOXIDE

-->  c. METANE

d. CARBON MONOXIDE

question_image

Which represents photosynthesis?

a. F

-->  b. R

c. E

d. V

question_image

Which label identifies emissions from factories?

a. S

b. C

-->  c. E

d. X

question_image

Where does CO2 go after it is in the air?

a. R DEAD ORGANISMS AND WASTE

b. E FACTORY AND VEHICLE EMISSIONS

c. C ANIMAL RESPIRATION

-->  d. J PHOTOSYNTHESIS

question_image

What is leaked into the air from a volcano?

-->  a. AMMONIA

b. UPTAKE BY PLANTS

c. NITRATES

d. LIGHTNING

question_image

Identify the protein in this picture

a. V

b. D

-->  c. U

d. M

question_image

Which label refers to atmospheric nitrogen?

-->  a. A

b. V

c. P

d. H

question_image

Sunlight fuels what?

a. Plant respiration

b. Animal respiration

-->  c. Photosynthesis

d. Auto and factory emissions

question_image

Which of the following does NOT contribute to the CO2 cycle?

a. root respiration

-->  b. Auto and factory emissions

c. plant respiration

d. animal respiration

question_image

How many trees are depicted on the image?

-->  a. 2

b. 3

c. 1

d. 4

question_image

Through what process do plants remove carbon dioxide from the atmosphere?

a. organic decay

b. animal respiration

c. plant respiration

-->  d. photosynthesis

question_image

How many trees are depicted in the image?

-->  a. 2

b. 3

c. 1

d. 4

question_image

Where do the fertilizers go?

a. To the atmosphere

b. To the sky

c. To the water

-->  d. To the soil

question_image

What breaks down nitrates in the soil into nitrogen in the atmosphere?

-->  a. Denitrifying bacteria

b. Fertilizer

c. Nitrifying bacteria

d. Nitrogen-fixing bacteria

question_image

What releases nitrogen back to the atmosphere?

-->  a. Dinitrifying bacteria

b. Nitrogen-fixing bacteria

c. Fertilizers

d. Plant

question_image

How many types of fixation are shown in the diagram?

a. 4

b. 1

c. 3

-->  d. 2

question_image

What would happen to the reservoir of nitrogen if there were more factories?

a. It would be the same

b. It would disappear

c. It would be lesser

-->  d. It would be greater

question_image

When bacteria decays, what is the result?

a. Fixation by nitrogen-fixing bacteria

b. Industrial fixation

-->  c. Ammonia (NH3)

d. Denitrifying bacteria

question_image

What gas is removed from the atmosphere during photosynthesis?

a. Nitrogen

b. Oxygen

-->  c. Carbon

d. Carbon dioxide

question_image

Which label shows a process that removes Carbon Dioxide from the environment?

a. Burning

b. Fespiration

-->  c. Photosynthesis

d. Respiration

question_image

How many ways is carbon found in the carbon cycle?

a. 3

b. 2

-->  c. 4

d. 1

question_image

How do fossilized plants turn into atmospheric carbon dioxide?

-->  a. Through combustion

b. Through respiration

c. Through photosynthesis

d. Through decay

question_image

What converts plant material into animal tissue?

-->  a. Animals

b. Photosynthesis

c. Decay

d. Respiration

question_image

How many processes are involved in the carbon cycle?

-->  a. 5

b. 6

c. 4

d. 3

question_image

How many ways do green plants give off carbon?

a. 6

b. 2

c. 1

-->  d. 4

question_image

What compound do green plants absorb?

a. Oxygen

b. Carbon Dioxide

-->  c. Carbon

d. Carbon Monoxide

question_image

What happens to the CO2 emitted by combustion and animal respiration?

a. cows absorb it

b. decomposing matter absorbs it

-->  c. Green plants absorb it

d. clouds absorbs it

question_image

How many steps there are in the CO2 cycle?

a. 3

b. 2

c. 5

-->  d. 4

question_image

What would happen to the Carbon Dioxide in the atmosphere if there were fewer cows?

a. Stay the same

-->  b. Reduce

c. Disappear

d. Increase

question_image

Which of the following will reduce the level of CO2 in the atmosphere?

-->  a. Plant more trees

b. Cut more trees

c. Build more houses and factories

d. Breed more animals

question_image

What does CO2 in atmosphere and dissolved in water turns into?

a. decay

b. fuel

c. combustion

-->  d. photosynthesis

question_image

What phase does fuel go through before carbon dioxide is released in the atmosphere?

a. Death

-->  b. Combustion

c. Respiration and Metabolism

d. Photosynthesis

question_image

Which process does not release CO2 to the atmosphere?

a. Respiration and Metabolism

-->  b. Photosynthesis

c. Combustion

d. Decay

question_image

What is the process where green plants get carbon dioxide in the atmosphere and in water?

a. combustion

b. metabolism

c. respiration

-->  d. photosynthesis

question_image

How many direct sources of carbon dioxide are shown in the diagram?

a. 6

b. 5

c. 3

-->  d. 4

question_image

Which cycle is shown in the diagram?

-->  a. Carbon Cycle

b. Nitrogen Cycle

c. Oxygen Cycle

d. Helium Cycle

question_image

How is carbon dioxide removed from atmosphere?

a. Plant respiration

b. Animal respiration

-->  c. Photosynthesis

d. Factory emissions

question_image

According to the diagram, how many things contribute to CO2 in the atmosphere?

a. 4

b. 1

-->  c. 3

d. 2

question_image

Where can you find carbon?

a. water

-->  b. All of the above

c. dead organisms

d. fossils and fossil fuels

question_image

Which of the following constitutes an abiotic contribution to the carbon cycle?

a. Plant Respiration

b. Root Respiration

-->  c. Factory Emissions

d. Animal Respiration

question_image

What provides energy necessary for photosynthesis to occur?

a. Minaral Carbon

-->  b. The Sun

c. Carbon Dioxide

d. Plant Respiration

question_image

Which contributes directly to atmospheric carbon dioxide?

a. Photosynthesis

b. Dead organisms and waste products

-->  c. Factory Emissions

d. Mineral carbon

question_image

How many items in this diagram emit carbon into the atmosphere?

a. One

b. Two

c. Four

-->  d. Three

question_image

Living things consists mainly of what?

a. water

b. oxygen

-->  c. carbon

d. respiration

question_image

What does organic carbon transform into?

a. Factory emissions

b. photosynthesis

c. Plant respiration

-->  d. Mineral carbon

question_image

Organic matter undergoes materialization to form what chemical?

a. Nitrites

b. Gasseous Losses

c. Nitrates

-->  d. Ammonium

question_image

What does Fossil Fuel Emissions go towards?

a. Organic Matter

b. Gaseous Losses

-->  c. Precipitation

d. Bacteria Fixation

question_image

What would happen if the fossil fuel emissions were lowered significantly?

a. The process would be much slower.

-->  b. The air would be cleaner during the process.

c. There would be less precipitation.

d. it would not be affected at all.

question_image

What do you call the microorganisms that convert nitrates in soil into free atmospheric nitrogen?

a. Elk

b. Nitrogen Fixing Bacteria

-->  c. Denitrifying bacteria

d. Plant matter

question_image

What would happen to the amount of nitrogen in the atmosphere if the denitrifying bacteria population decreased?

a. The reservoir of nitrogen in atmosphere would increase

-->  b. The reservoir of nitrogen in atmosphere would decrease

c. The amount of animal waste would decrease

d. The amount of plant matter would decrease

question_image

Where does animal waste go to?

a. Fertilizers

-->  b. Decomposers bacteria

c. Resevoir of nitrogen

d. Atmospheric fixation

question_image

Which process does nitrous oxide go through to become atmospheric nitrogen?

a. uptake

-->  b. dentrification

c. spreading

d. fixation

question_image

Which label shows a process of biological oxidation of ammonium to nitrite followed by the oxidation of the nitrite to nitrate?

-->  a. Nitrification

b. Nitrogen Fixation

c. Eutrophication

d. Mineralization

question_image

How many arrows point to the water?

-->  a. 2

b. 5

c. 1

d. 4

question_image

What type of biochemical cycle is shown in the diagram?

-->  a. Nitrogen Cycle

b. Water Cycle

c. Carbon Cycle

d. Bicycle

question_image

Which process leads to a decrease in soil fertility?

a. Mineralization

-->  b. Leaching

c. Lightning fixation

d. Gaseous losses

question_image

Identify the process where plants absorb nitrates through their roots.

-->  a. Assimilation

b. Nitrification

c. Ammonififcation

d. Denitrifying Bacteria

question_image

What is the only form of nitrogen that plants can use?

a. Ammonium

b. Fungi

-->  c. Nitrates

d. Bacteria

question_image

How many steps there are in the Nitrogen cycle?

a. 3

b. 6

c. 7

-->  d. 5

question_image

How many types of nitrates are produced in the process below?

-->  a. 3

b. 1

c. 4

d. 2

question_image

How can animals get nitrogen based on the nitrogen cycle?

a. by decomposing

b. by absorbing nitrates

-->  c. by eating plants or other organisms that eat plants

d. through assimilation

question_image

Which process brings nitrogen from the atmosphere to the soil?

a. denitrifying bacteria

b. fertilizers

c. bacterial decay

-->  d. Fixation by nitrogen-fixing bacteria

question_image

Which two places do the nitrates in the soil go to?

a. Fertilizers and ammonia

b. The reservoir of nitrogen in the atmosphere and atmospheric fixation

-->  c. The reservoir of nitrogen in the atmosphere and plants

d. The reservoir of nitrogen in the atmosphere and industrial fixation

question_image

What does bacterial decay turn plant and animal waste and remains into?

a. Fertilizers

b. Nothing

c. Nitrates

-->  d. Ammonia

question_image

Where does ammonia go in this diagram?

-->  a. To nitrates in the soil

b. Denitrifying bacteria

c. Atmorpheric fixation

d. Industrial fixation

question_image

What does nitrification by bacteria produce?

a. Nitrogen oxides

b. Animal protiein

-->  c. Nitrates and nitrites

d. Amino Acids

question_image

How many factors directly affect growth of plants/plant protein?

-->  a. 3

b. 2

c. 4

d. 1

question_image

In this process, what happens after Immobilization?

a. Animal Protein

-->  b. Organic Residues Decay

c. Bacterial Fixation in Legumes

d. Fixation by Lightning

question_image

Which compound kills fish?

a. Nitrogen gas

-->  b. Ammonia

c. Nitrate

d. Nitrite

question_image

What does the Sun do with ammonia?

a. Kills fish

-->  b. Algae growth

c. Dinitrification

d. Nitrification

question_image

How many fish are in the picture?

a. 6

-->  b. 2

c. 4

d. 5

question_image

What process does nitrite go through to become nitrate?

a. dintrification

b. algae growth

c. photosynthesis

-->  d. nitrification

question_image

What is the function of the Denitrifying prokaryotes?

a. Convert Nitrates to No3

b. Convert Nitrates to NOH3

c. Convert Nitrates to N3

-->  d. Convert Nitrates to N2

question_image

Which prokaryotes convert N2 to ammonia?

-->  a. Nitrogen-fixing prokaryotes

b. Nitrifying prokaryotes

c. Denitrifying prokaryotes and Nitrifying prokaryotes

d. Denitrifying prokaryotes

question_image

How many kinds of prokaryotes are present in the nitrogen cycle?

a. 4

b. 2

-->  c. 3

d. 5

question_image

How many nitrates does nitrifying prokaryotes convert?

-->  a. 2

b. 7

c. 6

d. 4

question_image

What happens if there are no denitrifying prokaryotes?

-->  a. There would be no atmospheric nitrogen.

b. Nitrites will not be converted to nitrates.

c. Nitrates will not be converted to nitrites.

d. Nitrogen will not be converted to ammonia.

question_image

How do animals get the nitrogen they need?

a. By breathing in atmospheric nitrogen

-->  b. By eating plants

c. By getting hit by lightning

d. By eating soil

question_image

What compound turns into nitrates in the soil?

a. Ammonia

-->  b. Nitrates

c. Ammonium

d. Organic matter

question_image

What compounds are included when the soil is leaching?

-->  a. Nitrates and Nitrites.

b. Fossil Fuels.

c. Ammonia.

d. Nitrogen Oxide.

question_image

Which mineral does the plant absorb from the soil?

a. Ammonia

-->  b. Nitrates

c. Lightning

d. The cow

question_image

What process brings nitrogen from plants and animals?

a. nitrogen-fixing by bacteria

b. lightning

c. denitrifying of nitries by bacteria

-->  d. decaying of organic matter

question_image

In this diagram of cycles of matter, what happens after Nitrogen-fixing bacteria?

a. Plant Protein Eaten

b. Nitrogen in Atmosphere

c. Denitrifying bacteria

-->  d. Free nitrates, nitrites, and ammonia

question_image

What happens when organisms die and decompose?

a. They are broken down into proteins.

b. Nitrogen is released to the atmosphere.

c. Nitrogen is oxidized.

-->  d. Nitrogen is returned to the soil as ammonium ions.

question_image

What is absorbed by plants?

a. none

-->  b. amonia and nitrates

c. egestion

d. urine

question_image

What step is shown in the diagram?

a. 4

-->  b. 3

c. 1

d. 2

question_image

Which one absorbs ammonia and nitrates in soil?

a. cow

b. egestion

-->  c. plant roots

d. clouds

question_image

Identify condensation

a. D

b. M

-->  c. K

d. C

question_image

Where does the co2 in the air dissolve?

a. plants

-->  b. ocean

c. animals

d. air

question_image

What produces organic matter?

a. fertilizers

-->  b. plants and animals

c. farms and runoff

d. Fossil fuel emissions

question_image

Identify photosynthesis

-->  a. R

b. X

c. F

d. E