energy and food webs Flashcards
(21 cards)
ecosystem definition
biological community and abiotic environment
what is the standing crop?
the bodies of living organisms within a unit area
what is biomass?
the mass of organisms per unit area of ground or water
- expressed as units of energy (joules/m2) or dry matter
what is the first law of thermodynamics?
energy cannot be created or destroyed, can change from one form to another
what is the second law of thermodynamics?
when energy is converted from one form to another, some of it is lost in the form of heat or other waste
the entropy increases
what is primary productivity?
the rate at which light energy is converted by photosynthesis into biomass (chemical energy)
what is photosynthesis?
biological process where energy from the sun is transformed into chemical energy of glucose/sugar molecules
carbon dioxide + water = glucose + oxygen
what is chemosynthesis?
lithotrophs use inorganic substrates as energy
bacteria or archaea
important for soil formation and biogeochemical cycling
gross primary productivity (GPP)
the total rate of photosynthesis
total amount of energy that plants capture and assimilate in a given period of time
net primary productivity (NPP_
plant growth per unit area per time
represents the rate of production of new biomass, available as food to organisms
NPP = GPP - cellular respiration (R)
cellular respiration (R)
chemical energy is captured in photosynthesis and released within cells of plants and animals (ATP), used for biological work
creating new cells, reproduction, movement etc
what influences primary productivity?
water, temperature, nutrient availability, climate
primary productivity patterns
reflects global patterns of temp and precipitation, it is highest in warmest and wettest places
high NPP in equatorial zone and coastal regions
primary productivity in oceans
shallow coastal water are the most productive due to greater transport from bottom sediment to top water by wave action
human impact on NPP
- humans consume more of the earths resources than any other animal
- humans represent 0.5% of land based biomass, but use 32% of land based NPP
- contribute to loss of species/extinction
energy flow
energy moves through ecosystem in one direction:
- producers
- primary consumers
- secondary consumers
- decomposers
food chains
energy from food passes from one organisms to another
each link = trophic level
tropic levels
The energy ingested by organisms at each trophic level is reduced by
respiration and excretion, so that less energy is available for consumption
by the next trophic level.
only 10% of assimilated energy passed between levels
ecological pyramids
- show how much energy is present at each trophic level and how much is transferred
- shows number of organisms at each trophic level
- shows total biomass at each successive trophic level
food webs
links in food webs show feeding connections in an ecological community
they are dynamic
resources fluctuate in abundance - animals and plants
seasonal change can affect diet available to predator
connectance in food webs
connectance = actual number of inter-specific interactions
potential number of inter-specific interactions
If there are ‘n’ species / then the potential number of interactions is
= (n)(n-1)
2
(Assuming a species doesn’t exhibit cannibalism)
