Ecosystems Flashcards
Define term ‘ecosystem’
All interacting living organisms
+ non-living factors in an area
Define “biotic factors” –> Give examples
Living organisms affecting an ecosystem.
->Competition
->Predation
->Disease
Define “abiotic factors”
Non-living organisms affecting an ecosystem.
->O2 availability
->H2O availability
-> Temperature
-> Edaphic (soil) factors
What does ‘waterlogged soil’ refer to?
Soil that has water filling up all air spaces –> reducing oxygen availability to roots.
What dos trophic levels refer to?
Each stage in a food chain
Producers –> primary consumers –> Secondary consumers –> Tertiary consumers
Define biomass:
Mass of living material in an area/organism without H2O
Relates to energy content
How to measure biomass?
Calorimeter
Collect sample –> kill organism –> oven at 80 –> evaporate water
What are the units for biomass?
LAND -> gm-2
AQUATIC -> gm-3
What does ecological efficiency refer to?
Efficiency in which biomass/energy is transferred from 1 trophic level to the next (%)
Never 100%
–> Only small portion ingested = converted into new tissue.
What is the energy available at each trophic level measured in?
kJm-2yr-1 (kilojoules per metre squared per year)
–> Allows for changes in photosynthetic production and consumer feeding patterns throughout the year
Why is the % of ecological efficiency so low at consumer levels?
Majority of sunlight reflected (90%)
Some energy used up for photosynthesis to occur.
Other factors may limit photosynthesis –> water availability
Energy lost through respiration (heat)
Energy lost through excretion
Some parts of food not eaten
What does ‘useful’ energy refer to?
All energy needed to build biomass
How can the energy available to next trophic level be calculated?
Net production = gross production -respiratory loss
State some agricultural ways to increase ecological efficiency:
Keep animals indoors
Keep fences (reduce movement)
Feed then high energy content food
Vaccination
Genetic engineering/selective breeding
Define ‘primary production’
The generation of biomass in a producer
How can human activities manipulate biomass through ecosystems?
Agriculture involves manipulating environment to favour plant species/livestock.
Competition/threat of predation removed
Creases very simple food chain.
.:minimum energy lost –> fewer trophic levels
How to calculate ecological efficiency?
(Energy/biomass available after transfer ÷ by energy/biomass available before transfer) X 100
