Biogeochemical Cycles Lesson

Biogeochemical Cycles

Multiple Choice

What does the "geo" part of biogeochemical cycle refer to?

• life

• earth

• matter

• all of the above

Multiple Choice

As plants and animals die, what do bacteria and other decomposers break them down into?

• proteins

• raw elements

• carbon dioxide

• ammonia

Multiple Choice

Which part of the environment includes aspects who have never been living?

• abiotic factors

• biotic factors

• organisms

• chemical cycles

Multiple Choice

Which type of factor would decaying organisms be considered?

• biotic factors

• abiotic factors

Multiple Choice

Which of these processes removes CO₂ from the atmosphere?

• Cellular Respiration

• Evaporation

• Combustion

• Photosynthesis

Multiple Choice

What do plants do with carbon dioxide (CO₂)?

• Plants use CO2 to make carbohydrates.

• Plants use CO2 to produce extra sunshne.

• Don't pick this answer.

Multiple Choice

How do animals get carbon into their bodies to build their cells?

• From the atmosphere

• From fossil fuels

• It just appears if we try hard enough

• By eating plants and/or other animals

Multiple Choice

How do living organisms return carbon dioxide into the atmosphere?

• respiration

• transpiration

• erosion

• combustion

​Nitrogen Fixation

Atmospheric Nitrogen exists as N₂, which is a very strongly bonded atom that is not usable by most living things.

Multiple Choice

The majority of the gas in the atmosphere is which element?

• Oxygen

• Nitrogen

• Hydrogen

• Helium

Multiple Choice

True or False: Atmospheric nitrogen is a very strongly bonded molecule.

• True

• False

Nitrogen Cycle

• About 78% of the earth's atmosphere is nitrogen gas.

• Plants and animals must have nitrogen to make proteins and nucleic acids.

• However, the nitrogen gas is not usable by plants or animals - so the nitrogen cycle must happen to change nitrogen into a usable form through a series of steps called nitrogen fixation

• Most of this is done using bacteria & decomposers; however, some nitrogen enters the soil via lightning.

Nitrogen Fixation

• Bacteria are the only organisms that can use nitrogen directly from the environment

• Bacteria "fix" nitrogen into a usable form by converting N₂ --> NH₃.

• Some plants have a symbiotic relationship with bacteria that can help fix nitrogen for them & the plant provides carbohydrates for the bacteria

Multiple Choice

Which of the following is NOT TRUE regarding nitrogen fixation?

• Plants can use elemental, atmospheric nitrogen directly from the air.

• Bacteria convert N₂ --> NH₃, the usable form that living things can absorb.

• Nitrogen fixation involves "fixing" the unusable atmospheric nitrogen into a usable form.

Multiple Choice

What is the only way that carbon (CO2) goes from the atmosphere to living organisms?

• photosynthesis

• respiration

• decomposition

• combustion

Phosphorus Cycle

• This is the only cycle without an atmospheric portion.

• Phosphate is released via the weathering of rocks.

• Plants & some fungi take up phosphorus.

• Phosphorus moves from producers to consumers via the food web.

• Phosphorus is released back into the soil when organisms die & decomposers break them down.

• Phosphorus gets into water via runoff and leaching from the groundwater.

• Mining and agricultural runoff add to the phosphorus in the environment.

Multiple Choice

There is no portion of the phosphorus cycle in the...

• atmosphere

• rocks

• water

• living organisms

Multiple Choice

Phosphorus is necessary to build which kind of molecules?

• carbohydrates

• DNA & RNA

• lipids

• proteins

Multiple Choice

Too much nitrogen in water can lead to eutrophication, which causes algae in ponds to do what?

• die

• grow uncontrollably

• become frozen

• combust

Fill in the Blanks

Dead Zones

An area that cannot support life because of its hypoxic (low oxygen concentration) state. There is little to no oxygen in the water. Dead zones are caused by too many nutrients in the water which over stimulate algae growth.

Multiple Choice

Which describes a dead zone?

• An area of low oxygen in water

• A single point where water drains to

• Where fresh water and salt water meet

Multiple Choice

The world's largest dead zone is located where, according to this lesson?

• your own backyard

• the Mississippi Delta

• The Baltic Sea

• none of the above

Open Ended

How do people contribute to eutrophication?