5B3 Biogeochemical Cycles

Question 1

What is a biogeochemical cycle?

Answer 1

The cycling of elements through organisms and the environment.

Question 2

What is the water cycle also known as?

Answer 2

The hydrologic cycle.

Hydro- means water

Question 3

Define:

water cycle

Answer 3

The movement of water through Earth’s atmosphere.

Question 4

What are the seven components of the water cycle in order?

Answer 4

1. Evaporation
2. Condensation
3. Precipitation
4. Sublimation
5. Transpiration
6. Runoff
7. Infiltration

The stages of the water cycle do not need to go in order. Water can freely transition between a solid, liquid, and gas throughout cycle.

Question 5

What is the process by which liquid water is heated and changes state to gaseous water vapor?

Answer 5

Evaporation

As water boils in a pot, steam is released in the form of water vapor.

Question 6

What is the process through which gaseous water vapor becomes liquid water?

Answer 6

Condensation

Can occur through saturation or cooling to the dew point.

Question 7

What is the process by which water returns to Earth’s surface from the atmosphere?

Answer 7

Precipitation

Example: Rain, snow, sleet

Question 8

How does condensation occur through saturation?

Answer 8

Water vapor molecules collect within an air pocket and eventually become liquid water.

Question 9

How does condensation occur through cooling to the dew point?

Answer 9

Water vapor molecules are cooled down to the temperature at which they become liquid.

Question 10

How does sublimation differ from evaporation?

Answer 10

• Sublimation is the instantaneous change from frozen water, to water vapor.
• Evaporation is the change from liquid water to water vapor.

Question 11

What is transpiration in the context of the water cycle?

Answer 11

It’s the evaporation of liquid water from within plants through their leaves.

Question 12

What is runoff and how does it occur?

Answer 12

Occurs when precipitation collects on the surface of the Earth and gravity pulls it, creating a flow.

Question 13

What is the importance of infiltration in the water cycle?

Answer 13

It returns water to the ground by percolating down through the soil into the groundwater system.

Question 14

How much of the water on Earth is freshwater?

Answer 14

Roughly 3%.

Question 15

What are the two ways in which water changes phases from liquid to gas?

Answer 15

• Evaporation
• Transpiration

Question 16

What is the carbon cycle?

Answer 16

The movement of carbon through living organisms and the environment.

Can be split into the short term and long term carbon cycles.

Question 17

Describe the short term carbon cycle.

Answer 17

The pathways of carbon shared between living organisms, the atmosphere and the worlds oceans.

Question 18

What is the primary source of usable carbon for plants in the carbon cycle?

Answer 18

Carbon dioxide in the atmosphere.

Question 19

Describe the long term carbon cycle.

Answer 19

Carbon is removed from the atmosphere and stored.

Examples: Calcium carbonate skeletons of coral, oil and natural gas reservoirs under the ocean.

Question 20

Why is the percentage of Earth’s carbon that is actively being cycled very small?

Answer 20

Due to the long-term storage of carbon.

Only 1% of the worlds carbon is actively moved through the carbon cycle. The other 99% are found in carbon stores.

Question 21

What is the largest pool of carbon in the world?

Answer 21

Sediments of the deep ocean.

Question 22

What process takes the most carbon out of the short-term carbon cycle, on a net basis?

Answer 22

Formation of coral reefs.

Coral reefs achieve this by creating calcium carbonate exoskeletons that eventually form limestone, effectively storing carbon.

Question 23

What is the primary means of energy storage, transfer, and usage in plants and animals?

Answer 23

Carbohydrates

Question 24

What is the process by which autotrophs convert light energy into chemical energy?

Answer 24

Photosynthesis

Question 25

What happens to most of the *carbon dioxide fixed by autotrophs* through photosynthesis?

Answer 25

Returned to the atmosphere as a *result of cellular respiration*.

Question 26

What is the process in which oxygen is used to convert organic molecules to carbon dioxide and water and provide *energy* for the cell?

Answer 26

**Cellular respiration**

Question 27

Describe the **nitrogen cycle**.

Answer 27

The movement and transformation of nitrogen as it moves through the atmosphere and environment.

Question 28

What is the process called when some bacteria *add hydrogen atoms* to atmospheric nitrogen to create ammonia?

Answer 28

**Nitrogen Fixation** ## Footnote Ammonia created through nitrogen fixation is then released into the environment for other organisms to use.

Question 29

What is the process by which ammonia is converted to *nitrite* and then to *nitrate* called?

Answer 29

**Nitrification**

Question 30

In the nitrogen cycle, what process converts nitrate back into *atmospheric nitrogen*?

Answer 30

**Denitrification**

Question 31

What ecological process occurs when *excess nutrients* are added to a body of water?

Answer 31

**Eutrophication** ## Footnote Generally occurs when excess fertilizers, or untreated sewage runoff into local waterways.

Question 32

What are the **main pollutants** released into the atmosphere when fossil fuels and organic materials are burned?

Answer 32

* Carbon dioxide * Sulfur dioxide * Nitrogen oxides

Question 33

What is the major reason why coal is considered to be the *dirtiest fossil fuel*?

Answer 33

Burning coal releases much greater quantities of pollutants into the air than burning natural gas does.

Question 34

What is the result of the combustion of organic materials like fossil fuels, releasing carbon dioxide, sulfur dioxide, and nitrogen oxides into the atmosphere?

Answer 34

**Acid Rain**

Question 35

What are the consequences of acid rain in lakes and soils with little buffering capacity?

Answer 35

It can *significantly lower the pH of the water and soil*, leading to the death of sensitive aquatic animals and deforestation in some areas.

Question 36

What is the **phosphorus cycle**?

Answer 36

The flow of the essential element phosphorus from inorganic sources, through living organisms, and back into soils and rocks.

Question 37

What are the steps in the **phosphorus cycle**?

Answer 37

1. Weathering releases phosphates from rocks and sediments. 2. Plants absorb the phosphates from the soil. 3. Animals obtain phosphates by eating plants or other animals. 4. Decomposition of plants and animals returns phosphates back to the environment.

Question 38

Why is the phosphorus cycle *important*?

Answer 38

It enables plants and animals to access the essential element phosphorus, which is necessary for DNA, RNA, cell membrane structure, bone mineralization, enzyme and hormone activity, and neuromuscular function.

Question 39

**Where** does most of the phosphorus cycle take place?

Answer 39

A majority of phosphorus is bound to **soil, rocks, and sediments on Earth**, never found in the atmosphere as a gas.

Question 40

List some roles of phosphorus in *plants*.

Answer 40

* Essential for plant growth. * Facilitates reproduction. * Aids in cellular respiration for energy production.

Question 41

How is phosphorus *released* back into the environment?

Answer 41

Via waste excretion by animals, decomposition of plant and animal remains, and carried into waterways to be transported into soils.

Question 42

What is **artificial eutrophication**?

Answer 42

When excess nutrients like phosphates are carried into waterways, leading to algal blooms and oxygen depletion. ## Footnote Human activity has impacted the phosphorus cycle through phosphate mining for use in fertilizers for agricultural crops.