Lecture VI. Biogeochemical cycles

Question 1

chemicals are NOT lost they are ___

Answer 1

cycled within ecosystems

Question 2

What do biogeochemical cycles describe?

Answer 2

they describe the flux of atoms and molecules between biotic and abiotic reservoirs

Question 3

Inaccessible reservoir > Accessible reservoir > Organisms

Question 4

Look at the biogeochemical cycle chart showing the above cycle for carbon nitrogen and phosphorus

Question 5

N2 is converted for uptake by plants via ____ by ____

Answer 5

nitrogen fixation, rhizobia

Question 6

What is mycorrhizal fungi

Answer 6

increases plant phosphorus uptake, fungi that live within the plant root, help get plant the nutrients it needs to grow. [positive biomass impact]

Question 7

decomposers (detrivores) are important because

Answer 7

they play a key role in the general pattern of chemical cycling

Question 8

as mean annual temperature is rising what happens to the decomposition rate?

Answer 8

as temperature rises we see that decomposition increases as well.

Question 9

What is a trophic cascade

Answer 9

In top down control predators can initiate what is called a trophic cascade by suppressing their prey, which releases the next lower trophic level from predation/herbivory

Ex. Wolves impact on elk populations near streams/rivers (elk eating tons of plants but once wolves were introduced, there was less erosion because elk population decreased in size hiding from wolves and a rebound in plants and shift in ecosystem)

Question 10

Reservoir

Answer 10

Place where type of atoms ormolecules accumulate or are held for a relatively long period of time.

Question 11

Flux

Answer 11

Rate of movement between reservoirs

Question 12

What are the four main chemicals we will be working on for the biogeomemical cycles

Answer 12

Water, nitrogen, carbon, phosphor

Question 13

What are the four types of biogeochemical reservoirs

Answer 13

a) lithosphere b) hydrosphere c) atmosphere d) organisms

Question 14

Explain the nitrogen cycle

Answer 14

N2 found in atmosphere > bacteria in plants convert nitrogen gas to ammonia (NH3) > plants take in roots, assimilated, plants and cows die, decay, bacteria convert that nitrogen to ammonium

Nitrifying bacteria convert ammonium into nitrites then nitrates, compounds usable by plants

Question 15

Is earth a closed or open system for elements and nutrients

Answer 15

Earth is a closed system for elements and nutrients

Question 16

What is the primary physical phase in which water is used

Answer 16

Liquid water is the primary physical phase in which water is used, (97% water is oceans)

Question 17

Explain the process of the water cycle

Answer 17

Biotic parts, cow drinks water, for abiotic parts, evaporation from lakes and oceans, it is also undergoing evapotranspiration where it evaporates through the plant condensation, then it precipitates, runoff and the whole thing happens again

Question 18

Explain the process of the carbon cycle

Answer 18

Plants get carbon through photosynthesis and phytoplankton in the ocean, if biotic, cows simply eat plant or we eat the cow, goes back through cellular respiration as carbon dioxide. Can be buried as fossil fuels and can be extracted through wells

Question 19

Explain the process of the nitrogen cycle.

Answer 19

N2 > Nitrogen Fixation > NH3 Ammonia > Fertilizer > Plants take in through roots > we get nitrogen through the plant by eating it > plant/cow dies, > decay and bacteria/fungi make ammonium (can be used by plants) > nitrifying bacteria convert ammonium to nitrite to nitrate > (nitrate can also be used by plants) > leaching and eutrophication runoff of algae in streams > denitrifying bacteria sends back into the atmosphere.

Question 20

What is rhyzobia

Answer 20

Root nodules of nitrogen fixing bacteria that live on plant roots, the plant gives rhizobia sugars, rhizobia helps the plant get better nitrogen nutrients (mutualism - heavily reliant)

Question 21

What are some limiting nutrients in many marine and terrestrial ecosystems?

Answer 21

Nitrogen and Phosphorus are both limited nutrients in terrestrial ecosystems. Since both are limiting, it can lead to eutrophication

Question 22

In low nitrogen environments, why do insectivorous plants exist?

Answer 22

Through predation, plants can get the nitrogen they need to survive through other organisms by trapping insect prey.

Question 23

Explain the process of the phosphorus cycle?

Answer 23

Rock is uplifted, causing phosphorus to ruse, weathering and erosion leads to phosphorus moving into soil to the water supply, fertilizers add phosphorus and since its limiting, it can lead to eutrophication, assimilation, eat plants, eventually we die, through excretion and decomposition we return that phosphorus to the water supply, it becomes sediment, and will become phosphorus rock and eventually rise again.

Question 24

What are detritivores, what role do they play?

Answer 24

Decomposers, play a key role in general patterns of chemical cycling

Question 25

What is the rate of decomposition controlled by

Answer 25

Temperature, moisture, oxygen, and nutrient availability

Question 26

Hubbard Brook Experimental Forest, what is it?

Answer 26

They built dams and clear-cut watershed and measured how much nitrate was in the water that was clear cut vs was not clear cut. Deforested areas had higher nitrate than non-cut areas. FORESTS ARE SUPER IMPORTANT FOR KEEPING NITRATES SAFE IN WATER