Chapter 23- Ecosystems

Is made up of all the living organisms that interact with one another in a defined area, and also the physical factors present in that region.

The living factors. For example, in a forest ecosystem, the presence of shrews and hedgehogs are biotic factors, as is the size of their populations- the competition between these two animal populations for a food source is also a biotic factor

The non living factors.

Light Temperature Water availability Oxygen availability Edaphic soil factors

Food Space Breeding partners

Biomass transferred/biomass intake x100

Produce Consumers

Is the mass of living material present in a particular place or in particular organisms

Measure mass of fresh material present Organisms killed Then heated to 80 degrees until all water has been evaporated- this point is indicated by two identical mass readings

Gross production- respiratory losses

Shorten the food changing meaning minimum energy is lost since there are fewer tropic levels present.

Is an organism that feeds on and breaks down dead plant or animal matter, thus turning organic compounds into inorganic ones available to photosynthetic produces in the ecosystem

Saprotrophs because they obtain their energy from dead or waste organic material.

Bacteria such as rhizobium and azotobacter contain the enzyme nitrogenase, which combines with atmospheric nitrogen with hydrogen to produce ammonia. A form of nitrogen that can be absorbed and used by the plants

Inside root nodules

Plant gains amino acids Bacteria gains carbohydrates

Process by which ammonium compounds in the soil are converted into nitrogen containing molecules that can be used by plants

• Nitrifying bacteria (such as nitrosomonas) oxidise ammonium compounds to NO2- • Nitrobacter oxidise nitrites to NO3- nitrates

In the absence of oxygen, denitrifying bacteria converts nitrates in the soil back to nitrogen gas. Only happens under anaerobic conditions NO3- to N2 Bacteria use the nitrates as a source of energy for respiration

Is the name given to the process by which decomposers convert nitrogen containing molecules in dead organisms into ammonium compounding

Photosynthesis only occurs during day Whereas respiration always occurs therefore atmospheric CO2 leves are higher at night

Combustion of fossil fuels Deforestation

One proccess by which ecosystems change over time is called succession

Occurs on a area of land that has been newly formed or exposed such as bare rock. There is no soil or organic materials present to begin with