6.5 Ecosystems Flashcards
What are abiotic factors?
non-living components of an ecosystem that affect other living organisms
What are biotic factors?
environmental factors associated with living organisms in an ecosystem that affect each other. e.g. predation, disease
Define ecosystem
A community of animals, plants and bacteria interrelated with the physical and chemical environment
Examples of biotic factors
- producers
- consumers
- decomposers
Examples of abiotic factors
- pH
- relative humidity
- temperature
- concentration of pollutants
- weather, eg storms
Why do we refer to ecosystems as dynamic?
Because they change
Three types of changes in ecosystems that affect population size?
- cyclic changes (moving tides and changes in day)
- directional changes (erosion of coastline)
- unpredictable/ erratic changes (lighting and hurricanes)
What is biomass transfer?
transfer of biomass from one trophic level to another
What is a trophic level?
the level at which an organism feeds in a food chain
How is biomass lost from a food chain?
- lost as heat, CO2 and water
- dead organisms and waste material, only available to decomposers
What does the area if a pyramid of biomass represent?
Its proportional to the dry mass of the organisms at that trophic level
How do you calculate the dry mass of an organism?
-collect organisms
-oven at 80 degrees until all water has evaporated
(destructive so use wet mass and calculate dry mass on the basis of previously published data)
Equation to calculate the efficiency of biomass transfer between trophic levels?
Ecological efficiency = (Biomass at higher trophic level/biomass at lower trophic level) x 100
efficiency=(biomass/ biomass transferred) x 100
What is productivity?
The rate of production of new biomass by producers
What is gross primary productivity?
the rate at which plants convert light energy to chemical energy by photosynthesis
How can you increase gross primary productivity using light?
- light banks
- crops planted early to provide a longer growing season to harvest more light
Ways to increase gross primary productivity?
- light levels
- irrigating/ drought resistant crops
- increasing temp
- nutrients
- removing pests
- removing competition from weeds for light, water and nutrients (herbicides)
How can you increase gross primary productivity using temperature?
Greenhouses, increases photosynthesis and rate of production of biomass
-planting crops early to provide a longer growing season helps avoid effect of temperature on final yield
How can we increase gorss primary production using nutrients?
- crop rotation (growing a different crop in each field of rotational cycle)
- including nitrogen fixing crop, such as peas or beans replenishes nitrogen levels
- some crops bred to respond to high levels of fertiliser
How does crop rotation help conservation of biomass?
Stops reduction in soil levels of inorganic materials such as nitrate or potassium
How can we increase gross primary production that is reduced by pests and fungi?
- pesticides
- some plants have been bred to be pest resistant
- fungicides
How can you increase secondary productivity?
- harvesting animals before adulthood (no loss of energy for growth)
- selective breeding (fast growth rates)
- treating with antibiotics (no loss of energy to pathogens and parasites)
- constant temperatures
- supplying food
Steps of saprotrophic decomposition…
- saprotrophs secrete enzymes onto dead material
- enzymes digest material into small molecules which are absorbed
- molecules are stored or respired
Examples of fixed nitrogen
NH4+ or NO3-
