Chapter 23- Ecosystems Flashcards
Define an ecosytem
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.
Biotic factors that affect an echo stem
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
Abiotic factors affecting ecosystem
The non living factors.
Abiotic factors
Light Temperature Water availability Oxygen availability Edaphic soil factors
Biotic factors
Food
Space
Breeding partners
How to calculate efficiency
Biomass transferred/biomass intake x100
Trophic levels
Produce
Consumers
Define biomass
Is the mass of living material present in a particular place or in particular organisms
How to measure biomass
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
How to calculate net production
Gross production- respiratory losses
Human activities that can affect biomass
Shorten the food changing meaning minimum energy is lost since there are fewer tropic levels present.
Role of decomposers
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
What are decomposers an example of
Saprotrophs because they obtain their energy from dead or waste organic material.
Nitrogen fixation
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
Where do the nitrogen fixing bacteria live
Inside root nodules
Mutualistic relationship between plant and bacteria
Plant gains amino acids
Bacteria gains carbohydrates
Nitrification
Process by which ammonium compounds in the soil are converted into nitrogen containing molecules that can be used by plants
Two steps of nitrification
- Nitrifying bacteria (such as nitrosomonas) oxidise ammonium compounds to NO2-
- Nitrobacter oxidise nitrites to NO3- nitrates
Denitrification
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
Ammonifcation
Is the name given to the process by which decomposers convert nitrogen containing molecules in dead organisms into ammonium compounding
Fluctuations of CO2 levels
Photosynthesis only occurs during day
Whereas respiration always occurs therefore atmospheric CO2 leves are higher at night
Why have CO2 levels increased significantly
Combustion of fossil fuels
Deforestation
Define succession
One proccess by which ecosystems change over time is called succession
Define primary 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
Define secondary succession
This occurs on areas of land where soil is present, but it contains no plant or animal species
Where does primary succession occur
Volcanoes erupt
Sand is blown by the wind
Slit and mud are deposited at river estuaries
Glaciers retreat
What is each stage in succession known as
Seral stage
Main seral stages
- Barren land
- Pioneer community
- Intermediate community
- Climax community
Pioneer community
The first species to arrive usually carried by the wind from nearly by land masses
How are pioneer species adapted
Able to produce large amounts of seeds or spires
Seeds that germinate fast
Ability to photosynthesise
Tolerance to extreme environments
Explain environment in climax community
In a stable state
Will show very little change over time
Often not the most biodiversity often mid succession is most diverse
Explain deflected succession
Human activities can halt the natural flow of succession and prevent the ecosystem from reaching a climax community. When succession is stopped the final stage is known as phagioclimax
Why does deflected succession occur
Grazing and trampling of vegetation
Removing existing vegetation
Burning
Measuring distribution
A line or belt transfer is used
A line transect involves laying a line or surveyors tape along the ground and taking samples at regular intervals.
A belt transfer provides more info- two parallel lines are marked, and samples are taken of the area between specified points
They are both forms of systematic sampling
Definition of abundance of organisms
Refers to the number of individuals of a species present in an area at any given time
Measuring plant abundance
Use quadrants
Estimated population= number of individuals in sample / area of sample
Measuring animal abundance
- Capture as many individuals in a given area as possible
- Mark or tag each individual
- Release the marked animals back into area
- Recapture as many individuals as possible
- Record the number of marked and unmarked individuals caught
- Use Lincoln’s index first sample x second sample / number of recaptured individuals
Define a producer
Convert light energy to chemical energy
Define a consumer
Which lives and feeds of other animals
Define a trophic level
A stage in a food web
Difference between conservation and preservation
Maintains ecosystems with active management
Whereas preservation leaves the ecosystems I disturbed
