ch3 A3

Question 1

Define biogeochemical cycle. Give examples (6).

Answer 1

describe the flow of essential elements from the environment through living organisms and back into the environment.

carbon cycle, nitrogen cycle, water cycle, phosphorus, calcium, magnesium, etc…

Question 2

Define the main three components of a biogeochemical cycle

Answer 2

Reservoir: A place where anything is kept in store

Assimilation: Absorption, the metabolic conversion of nutrients into tissue

Release: the release of chemicals back to the environment

Question 3

Briefly explain hydrological cycle

Answer 3

describes the continuous movement of water on, above and below the surface of the Earth.

(water cycle)

1. Reservoir – oceans, air (as water vapor), groundwater, lakes and glaciers; evaporation, wind and precipitation (rain) move water from oceans to land
2. Assimilation – plants absorb water from the ground, animals drink water or eat other organisms which are composed mostly of water
3. Release – plants transpire, animals breathe and expel liquid wastes

Question 4

Briefly explain Carbon cycle

Answer 4

the series of processes by which carbon compounds are interconverted in the environment, involving the incorporation of carbon dioxide into living tissue by photosynthesis and its return to the atmosphere through respiration, the decay of dead organisms, and the burning of fossil fuels.

(carbon is required for building organic compounds)

1. Reservoir – Oceans, atmosphere (as CO2), fossil fuels (oil, coal), durable organic materials (for example: cellulose).
2. Assimilation – plants use CO2 in photosynthesis; animals consume plants.
3. Release – plants and animals release CO2 through respiration and decomposition; CO2 is released as wood and fossil fuels are burned.

Question 5

Briefly explain Nitrogen cycle

Answer 5

the series of processes by which nitrogen and its compounds are interconverted in the environment and in living organisms, including nitrogen fixation and decomposition.

(Nitrogen is required for the manufacture of amino acids and nucleic acids)

1. Reservoir – atmosphere as N2 soil as NH4+ or ammonium, NH3 or ammonia, N02- or nitrite, N03- or nitrate
2. Assimilation – plants absorb nitrogen as either NH4+ or as N03-, animals obtain nitrogen by eating plants and other animals. The stages in the assimilation of nitrogen are as follows:

Nitrogen Fixation: N2 to NH4+ by nitrogen-fixing bacteria (prokaryotes in the soil and root nodules), N2 to N03- by lightning and UV radiation.

Nitrification: NH4+ to N02- and N02- to N03- by various nitrifying bacteria.

3. Release – Denitrifying bacteria convert N03- back to N2 (denitrification); detrivorous bacteria convert organic compounds back to NH4+ (ammonification); animals excrete NH4+ (or NH3) urea, or uric acid.

Question 6

Briefly explain Phosphorus cycle

Answer 6

The phosphorus cycle is the biogeochemical cycle that describes the movement of phosphorus through the lithosphere, hydrosphere, and biosphere.

Reservoir – erosion transfers phosphorus to water and soil; sediments and rocks that accumulate on ocean floors return to the surface as a result of uplifting by geological processes

Assimilation – plants absorb inorganic PO43- (phosphate) from soils; animals obtain organic phosphorus when they plants and other animals

Release – plants and animals release phosphorus when they decompose; animals excrete phosphorus in their waste products