Topic 4 Ecology: Biochemical Cycles

Question 1

• There are multiple cycles showing the flow of essential elements from the environment, to living things, and then back to the environment.

Answer 1

Note

Question 2

• Are major storage locations for essential elements

Answer 2

Reservoirs

Question 3

• Is the process through which elements are incorporated by terrestrial plants and animals.

Answer 3

Assimilation

Question 4

• Is the process by which the element returns to the environment.

Answer 4

Release

Question 5

1. Hydrologic cycle (water cycle) - The reservoir are the oceans, air (water vapor), groundwater, and glaciers. Evaporation, wind, and precipitation moves water from the ocean to land. Assimilation is done by plants absorbing water from the soil, and by animals drinking and eating other organisms (which are mostly water). Release is done when plants transpire and when animals and plants decompose

Answer 5

Cycle part 1

Question 6

2. Carbon cycle - carbon is required for building organic materials. It is the basis for photosynthesis and respiration. The reservoirs are atmospheric CO2, fossil fuels (coal, oil), peat, and durable organic matter (e.g., cellulose). Assimilation is done by plants when they use CO2 in photosynthesis, and by animals when they consume plants (this is carbon fixing because the carbon is reduced from its inorganic form of CO2 to organic compounds). Release of CO2 occurs through respiration, decomposition, and when organic material is burned

Answer 6

Cycle part 2

Question 7

3. Nitrogen cycle - nitrogen is required for the manufacture of amino acids and nucleic acids. The reservoirs are atmospheric nitrogen (N2) and soil (NH4+, NH3, NO2, NO3). Assimilation occurs when plants absorb nitrogen as either NO3- or NH4+ and when animals obtain nitrogen by eating plants/ animals.
   i. Nitrogen fixation - this is when atmospheric nitrogen (N2) is converted into organic nitrogen (NH4+) through nitrogen-fixing bacteria in the soil. Nitrogen can also be fixed by lightning and be converted into nitrogen oxides (NOx)
   ii. Nitrification - this is when ammonium (NH4+) is converted to nitrite (NO2-) followed by the conversion of nitrite to nitrate (NO3-) by nitrifying bacteria
   - Release of nitrogen is done by denitrifying bacteria, which convert nitrate into atmospheric nitrogen. Detritivorous bacteria also release nitrogen by converting organic compounds back to ammonium (ammonification). Animals release nitrogen by excreting ammonium, urea, or uric acid, and through decay since nitrogen in the form of ammonia (NH3) is released from dead tissues

Answer 7

Cycle Part 3

Question 8

4. Phosphorus cycle - phosphorus is required for manufacturing ATP and all nucleic acids. Cycles for other minerals such as calcium and magnesium are similar to the phosphorous cycle. The reservoirs for phosphorous are rocks and ocean sediments because erosion transfers phosphorous to the water and soil. Assimilation occurs when plants absorb inorganic phosphate (PO43-) from the soil and when animals obtain organic phosphorus when they eat. Release of phosphorous occurs when plants and animals decompose, and when animals excrete phosphorous in waste products

Answer 8

Cycle Part 4