Concept 1 Biogeochemical Cycles

biogeochemical cycles

represent the movement of a particular form of matter through the living and nonliving parts of an ecosystem

Why must essential nutrients be continuously cycled?

since matter can neither be created nor destroyed and Earth is a closed system

Where is water found?

• Earth’s surface (including oceans, lakes, rivers, etc)

  • 97% is in the ocean

  • 3% is freshwater, of that 2% is frozen in glaciers

• under Earth’s surfaces (groundwater, aquifers)

• in the atmosphere

• in living organisms

What drives the water cycle?

the sun, which causes evaporation from reservoirs and organisms

What are the main stages of the water cycle?

1. precipitation

2. infiltration

3. runoff

4. evaporation

5. transpiration

6. condensation

What is precipitation?

water falls to Earth as a liquid (usually rain, sleet, or snow)

What is infiltration?

some water seeps underground from the surface of the Earth

What is an aquifer?

an underground layer of permeable rock that can hold water

What is runoff?

liquid water that isn’t infiltrated runs along the surface and collects in bodies of water

What is evaporation?

sun heats liquid water to vapor and it rises to the atmosphere

What is transpiration?

water rises back into the atmosphere as water vapor from plants

What is condensation?

water vapor condenses to form clouds before precipitating again

What impact do living organisms have on the water cycle?

• all organisms take in water for nutrient transport, chemical reactions, diffusion, etc

  • means they have to eliminate water too (example: urine, feces)

• All organisms release water when breaking down food for energy (cellular respiration)

• plants take in water to make sugar (photosynthesis)

What impacts do humans have on the water cycle?

• deforestation: decreases transpiration

• paving/building/development: increases runoff and decreases infiltration

• pollution

• eutrophication

What is eutrophication?

when a body of water becomes overly enriched with nutrients, causing excessive algae growth

What is the carbon cycle?

• carbon is the basis of all organic molecules, and is found in a variety of chemical forms

• carbon changes chemical forms as it cycles (unlike water)

  • example: carbon is CO₂ in the atmosphere but C₆H₁₂O₆ as glucose in plants

Where is carbon found?

• macromolecules (proteins, carbohydrates, lipids, nucleic acids)

• our atmosphere

• minerals and rocks

• fossil fuels (coal, oil, natural gas)

• organic materials in soil or aquatic sediments

What are the main stages of the Carbon Cycle?

1. photosynthesis

2. cellular respiration

3. consumption

4. decomposition

5. fossilization

6. combustion

What is photosynthesis?

plants capture CO₂ from the atmosphere and use it to make sugar

What is cellular respiration?

CO₂ released into the atmosphere as waste from metabolism

What is consumption?

one organism eats another for carbon

What is decomposition?

decomposers break down carbon from dead organisms, recycling it in the soil

What is fossilization?

converts carbon from once-living organisms into fossil fuels through intense heat and compression

What is combustion?

CO₂ released into atmosphere from burning

What role do living organisms have in the carbon cycle?

• decomposers (like bacteria, earthworms, and fungi) break down dead materials and return nutrients (like carbon) to the soil

• photosynthetic organisms (like plants and algae) remove CO₂ from the atmosphere and convert it into simple sugars

• animals, plants, and fungi do cellular respiration in order to break down carbon-rich foods for energy

What impact to humans have on the carbon cycle?

when wood or fossil fuels, which contain carbon, are burned by humans, there is a major rise in CO₂ in the atmosphere

How is the nitrogen cycle similar to the carbon cycle?

it takes on a variety of chemical forms during the cycle

Where is nitrogen found?

• in the atmosphere in the form of a gas (N₂)

  • plants and animals cannot use nitrogen in this form

• macromolecules (proteins and nucleic acids)

• fossil fuels

• waste

• soil

What are the main stages of the nitrogen cycle?

1. nitrogen fixation

2. consumption

3. decomposition

4. ammonification

5. nitrification

6. denitrification

What is nitrogen fixation?

bacteria (or lightning) in the soil or water convert nitrogen (from the air or water) into forms that plants can use

What is consumption (nitrogen)?

one organism eats another and obtains the nitrogen in it

What is decomposition (nitrogen)?

decomposers, like bacteria, break down dead matter, returning nitrogen to the soil

What is ammonification?

bacteria convert nitrogen from waste (urine and feces) into ammonia

What is nitrification?

bacteria convert nitrogen in ammonia into nitrates and nitrites to be absorbed by plants in their roots (how nitrogen enters the food chain, and eventually reaches to us)

What is denitrification?

bacteria convert nitrogen in ammonia to N₂ so it can go back into the atmosphere

How do living organisms affect the nitrogen cycle?

• no step is completed without the help of living organisms

• bacteria is the most important living organism in converting nitrogen to different forms

• fungi and other decomposers break down nitrogen-rich waste and put it in the soil

How do humans impact the nitrogen cycle?

• fertilizers: the use of fertilizers adds way too much nitrogen to the soil, creating an imbalance

  • can runoff and cause eutrophication

• combustion: burning fossil fuels does release excess nitrogen into the atmosphere