Biosphere Contents

1. Organic Matter

Conclusion

The nature and productivity of organic matter - the plants, animals and other organisms that make up the rich variety of life in the biosphere - has been characterised. Its role in the ecosphere's chemical and nutrient cycles has been explained. This includes its vital function in converting solar energy and assimilating carbon (as carbon dioxide) during photosynthesis. Respiration is the converse of that process. The assimilation of nitrogen and other nutrients by plants has been explained, and it has been noted that the products of assimilation are either ingested by herbivores or are broken down by micro-organisms.

Question and answers

1. What does the biosphere consist of?

question 1 answers

2. Give a one line definition of the lithosphere, atmosphere, hydrosphere and biosphere.

question 2 answers

3. Name the three most abundant elements in organic matter.

question 3 answers

4. Name four macronutrients and four micronutrients required by all plants.

question 4 answers

5. What are the definitions of standing crop, biomass and productivity?

question 5 answers

6. What is primary productivity?

question 6 answers

7. How is carbon i) incorporated into the biosphere, and ii) how is it removed?

question 7 answers

8. i) Which ecosystem contains the largest amount of plant biomass, and ii) Which ecosystem with approximately one thousand times lower primary producer biomass has a similar net primary productivity to i)?

question 8 answers

9. Give two examples of the amount of time that any one unit of carbon is stored as biomass in different components of the biosphere?

question 9 answers

10. What is a nutrient cycle?

question 10 answers

11. How does nutrient uptake differ between terrestrial higher plants (e.g. flowering plants, conifers, ferns) and lower plants (e.g. mosses)?

question 11 answers

12. Give one example of active nutrient uptake in the cells of algae and higher plants.

question 12 answers

Question 1 answers

The biosphere consists of all the plants and animals (organisms) which are present on Earth

Question 2 answers

Lithosphere - rocks and minerals of the earth's outer shell;
Atmosphere - surrounding envelope of gases;
Hydrosphere - water in seas, rivers, ice, snow and water in rocks and soil;
Biosphere - component of living material in each of these spheres.

Question 3 answers

Carbon, oxygen and hydrogen.

Question 4 answers

Macronutrients are elements required in large quantities by plants. These can include carbon (C), hydrogen, (H), oxygen (O), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg).

Micronutrients are elements required in smaller quantities by plants. These can include iron (Fe), sodium (Na), manganese (Mn), copper (Cu), zinc (Zn), molybdenum (Mo), boron (B) and chlorine (Cl).

Question 5 answers

Standing crop is the amount of 'crop' present at a point in time, i.e. standing crop per m2 ; per hectare; per km2 . 'Crop' could be, for example, plants, trees, fish, mammals or birds.

Biomass is the amount of organic material contained in living organisms in a given area. It is normally measured as dry weight per unit area or energy per unit area. 

Productivity is the rate at which biomass is produced. If plants are grazed or harvested, or if leaf fall occurs during the time period across which productivity is being measured, estimates of productivity must take this into account.

Question 6 answers

Primary productivity is the rate at which biomass is produced by primary producers (autotrophic organisms like green plants). This normally uses the sun's energy through photosynthesis.

Question 7 answers

i) Carbon gets into the biosphere by assimilation by green
plants in photosynthesis.
ii) It is released in respiration by plants, animals, and
bacteria.
Otherwise it is incorporated into sediments and released when,
for example, fossil fuel are burnt.

Question 8 answers

i) The largest amount of plant biomass is contained within the
tropical rainforests.
ii) The net productivity of the oceans is comparable to that of the
rain forests (20.4 x 1015 tonnes C yr-1 ).

Question 9 answers

Answers include:
- Phytoplankton = days / weeks
- Leaves on trees = one season
- Trunks of trees = tens to hundreds of years
- Fossil fuels = millions of years

Question 10 answers

Nutrient cycles represent the movement and exchange of chemical elements.

Cycles may involve the movement of elements through living organisms, the atmosphere, the hydrosphere, the soil and rocks.

Question 11 answers

Terrestrial higher plants (e.g. flowering plants, conifers and ferns) uptake nutrients from the soil through their roots.

Lower plants (e.g. mosses) uptake nutrients directly through the cell walls of their leaves and stems.

Question 12 answers

Potassium (K+) and chloride (Cl-) ions are actively taken up by plant roots. They can have concentrations inside roots 1000 times greater than their concentrations outside the medium.