26. Nutrient Cycles I

Question 1

flows/cycles

Answer 1

energy flows (one-way trip), nutrients cycle (round and around)

Question 2

reservoirs

Answer 2

stores of water or nutrients in a cycle

Question 3

macronutrients

Answer 3

essential elements required in

large concentrations in an organism: carbon, hydrogen, oxygen, nitrogen, phosphorus

Question 4

micronutrients

Answer 4

essential elements required only in small concentrations in an organism: iron, magnesium, iodine, selenium, zinc

Question 5

phosphorous cycle

Answer 5

1. Plants take up phosphate ions from soil or water and incorporate them directly into tissue
2. Animals gain phosphate by eating these tissues, or from the tissues of other organisms
3. Animals eliminate excess phosphorus through urine

Question 6

nitrogen cycle

Answer 6

1. The biggest reservoir of N is the atmosphere (as N2 gas).
2. Nitrogen can be fixed, through nitrogen fixation, by certain prokaryotes. It also can be fixed by lightning!
3. During nitrogen fixation, N2 gas is reduced to ammonia, NH3: N2 + 8 H+ → 2 NH3 + H2
4. After fixation, nitrogen it is available to primary producers and can be immobilized (assimilated into their tissue).
5. Consumers can gain nitrogen by eating these primary producers or other organisms.
6. Once an organism dies, nitrogen is released from its tissues by fungi and bacteria during decomposition.
7. Nitrogen released through mineralization, also called
   ammonification. During this process the organic nitrogen is converted into ammonium NH4+
8. This ammonium can then be converted into nitrate through nitrification (a two-step process)
9. Nitrogen re-enters the atmosphere reservoir through denitrification, when denitrifying bacteria convert nitrate into N2 gas

Question 7

carbon cycle

Answer 7

1. Some of the big carbon reservoirs are the atmosphere, terrestrial soils, all organisms, and the oceans.
2. Carbon moves between organisms and the atmosphere through respiration and photosynthesis.
3. Respiration moves carbon to the atmosphere
4. Photosynthesis removes carbon from the atmosphere
5. humans are messing up the balances in the carbon
   cycles, thus are creating global climate change by burning fossil fuels, vegetation, and peat

Question 8

decomposition

Answer 8

the breakdown of organic matter accompanied by the release of CO2

Question 9

factors that influence decomposition

Answer 9

1. Temperature
2. Moisture
3. Chemical composition of decaying matter
4. Chemical composition of the environment

Question 10

factors that influence decomposition: temperature

Answer 10

annual leaf mass loss in tropical forests is about three times that occurring in temperate forests

Question 11

factors that influence decomposition: moisture

Answer 11

increased precipitation = increased decomposition

Question 12

chemical composition of decaying matter

Answer 12

Higher the ratio of lignin to N, the longer it took to decompose

Question 13

chemical composition of the environment

Answer 13

the more N in the soil, the higher the decomposition rate

Question 14

nutrients

Answer 14

elements that are required for the development, maintenance, and reproduction of organisms

Question 15

phosphorous

Answer 15

• Essential to energetics, genetics and structure of living systems.
• main component of ATP, RNA, DNA, and phospholipid molecules
• Not very abundant in the biosphere
• Does not have an atmosphere reservoir
• Can be a limiting factor for aquatic primary production, not usually for terrestrial primary production

Question 16

nitrogen

Answer 16

• Important to structure and functioning of organisms.
• May limit rates of primary production in terrestrial and marine systems.
• One of the biggest reservoirs is the atmosphere (Earth’s atmosphere = 78% N)
• Microbes play a BIG role in the nitrogen cycle

Question 17

forms of nitrogen

Answer 17

Ammonia: NH3
Ammonium: NH4+
Nitrite: NO2-
Nitrate: NO3-
Nitrogen gas: N2
Nitric oxide: NO

Question 18

5 transformations of N

Answer 18

1. nitrogen fixation
2. immobilization
3. mineralization (ammonification)
4. nitrification
5. denitrification

Question 19

nitrogen fixation

Answer 19

the process of converting atmospheric nitrogen into forms primary producers can use

Question 20

immobilization

Answer 20

the conversion of mineral forms of nitrogen (ex. ammonia and nitrate) into organic forms (ex. proteins)

Question 21

mineralization (ammonification)

Answer 21

the conversion of organic forms of nitrogen (ex. proteins) into mineral forms (ex. ammonia and nitrate)

Question 22

nitrification

Answer 22

the conversion of ammonium(NH4+) to nitrite (NO2), and then nitrite (NO2) to nitrate (NO3-)

Question 23

denitrification

Answer 23

the process of converting nitrate

NO3-) into nitrogen gas (N2

Question 24

carbon

Answer 24

It makes organic molecules organic. We humans are messing up the balances in the carbon cycles, thus are creating global climate change

Question 25

carbon in aquatic ecosystems

Answer 25

1. In aquatic ecosystems CO2 has to be dissolved into the water before it is available to primary producers.
2. When dissolved in water, CO2 turn into two compounds (in equilibrium):
   - Bicarbonate HCO3-
   - Carbonate CO32-
3. CO32- can combine with dissolved calcium and precipitate out as calcium carbonate CaCO3

Question 26

factors that influence decomposition in aquatic ecosystems

Answer 26

– Temperature
– Nutrient content of the decaying matter
– Nutrient content of the water