Option G Ecology and Conservation: G2 Ecosystems and Biomes

Define gross production, net production, and biomass.

• Gross production is the total amount of organic material produced by plants in an ecosystem.

• Net production of an ecosystem is gross production less the material expended by the plants in respiration.

• Both of these are measured in kJ per squared meter per year (Kj m-2 yr-1).

• Biomass is the dry weight of organic matter in organisms of an ecosystem.

Calculate values for gross production and net production and net production using the equation: gross

production – respiration = net respiration

• GP – R = NP

Discuss the difficulties of classifying organisms into trophic levels.

• It is difficult due to the fact that some organisms can be secondary, tertiary, and may be quaternary consumers at the same time, such as humans. It is difficult to place them on a certain level of the food pyramid.

Cont’d

• For this reason, an alternate method of classification - the food web - has been developed. The food web displays relationships not as a simple hierarchy but rather a complex network, with the various feeding relationships between species existing as connections and the animals themselves existing as the hubs.

Explain the small biomass and low number of organisms in higher trophic levels

• There is a decreasing biomass of organisms in the higher trophic levels because energy is lost between levels in the form of heat (respiration), waste, and dead material.

• Only around 10-15% of the energy proceeds on to the next trophic level.

• Often referred to as the 10% rule

Construct a pyramid of energy, given appropriate information

• The lowest bar of the pyramid of energy represents gross primary productivity, the next bar is the energy ingested as food by primary consumers, and so on. The arrows demonstrate the direction of energy flow. The units are energy per unit area per unit time

Distinguish between primary and secondary succession using an example for each

• 1o

• Ecological succession is the gradual change in the composition of a community with time in an ecosystem. If succession occurs in a lifeless area it is primary succession. It can start after things such as volcanoes, fire or flood.

• The process is usually goes: lichen, moss, ferns, flowerings plants, conifers.

• For example on the Volcan Osorno in south Chile after ash covers the ground: mosses spread over the ash. Small herbs and ferns arrive and through the activity of their roots, soil formation starts to occur. Shrubs and bushes grow and replace these. Then flowering trees grow, then conifers, and other larger trees producing a forest.

2o succession

Secondary succession is the series of community changes which take place on a previously colonized, but disturbed or damaged habitat.

Examples include areas which have been cleared of existing vegetation (such as after tree-felling in a woodland) and destructive events such as fires. Fallowed farm fields.

1o and 2o Succession images

Explain the effect of living organisms on the abiotic environment, with reference to the changes occurring

during primary succession• Help with soil development, as a plant grows,

their roots grow deeper down and break rock into small particles, helping soil formation.

• Plants enrich the soil with minerals as they die and decompose.

• The plant roots hold the soil particles together, preventing soil erosion and retain nutrients.

• The water that evaporates from many plant leaves condenses and comes down in the form of rain.

Distinguish between biomes and biosphere

Explain how rainfall and temperature effect the distribution of biomes

Outline the characteristics of the 6 major biomes

• HOMEWORK…. You should include precipitation averages, temp ranges, examples of flora and fauna that can be found in these biomes as well