4.2 ENERGY FLOW Flashcards
ESSENTIAL IDEA
ecosystems require a continuous supply of energy to fuel life processes and to replace energy lost as heat
WHAT DO ECOSYSTEMS RELY ON?
light energy received from the sun
ALL PLANTS AND SOME PROKARYOTES ARE
photoautotrophs
they use pigments (chlorophyll) to trap light energy which is converted to chemical energy in carbon compounds
CHEMOAUTOTROPHS
volcanic vents on the ocean floor
producers which use energy from chemical processes
CONVERSION OF LIGHT ENERGY
the light energy from the sun is used to synthesis carbohydrates
the light energy is transferred into bonds (chemical energy) between the atoms in a carbohydrate M
CONSUMERS
ingest organic matter which is living or recently killed
FOOD CHAINS
show the flow of energy through the trophic levels of a feeding relationship
TROPHIC LEVELS
feeding position of an organism in a food chain
WHY DO ECOSYSTEMS REQUIRE A CONTINUOUS SUPPLY OF ENERGY?
no energy transfer is 100% efficient
waste: heat thermal energy is produced too
unlike light/ chemical energy organisms cannot convert heat energy into useful forms
PYRAMIDS OF ENERGY
show the flow of energy between trophic levels
PYRAMIDS OF ENERGY UNITS
kJ m^-2 y^-1
unit of energy per unit area per time
AROUND 90% OF ENERGY IS LOST BETWEEN TROPHIC LEVELS DUE TO (4)
not ingested foods
not digested or assimilated
excreted
lost as heat from respiration
AT HIGHER TROPHIC LEVELS PYRAMIDS OF ENERGY ALWAYS…
get smaller due to the loss of energy
BOTTOM LEVEL OF PYRAMIDS OF ENERGY =
producers
subsequent levels =
consumers (primary/secondary…)
AS THE TROPHIC LEVEL INCREASES
the biomass and energy available decreases
HIGHER TROPHIC LEVELS ARE OFTEN LESS EFFICIENT BECAUSE
more energy is spent on foraging more mobile prey
WHY IS BIOMASS INDIRECTLY USED AS A MEASURE OF ENERGY TRANSFER
chemical energy is held in molecular bonds
thus, as energy is lost between trophic levels it is natural for biomass to be lost too
FORAGE
searching widely for food
EVENTUALLY THE ENERGY REQUIRED TO FORAGE
exceeds the energy gained from foraging, making the trophic level unviable
BIOMASS IS USUALLY MEASURED AS
the total dry mass of organisms
ENERGY FLOWS
energy flows linearly
energy enters from sunlight
autotrophs capture sunlight
energy flows through the trophic levels
energy transfer is 10% from one level to the next
energy loss is due to material not consumed or assimilated/ egested/ excreted
energy passes to decomposers/ detritivores/ saprotrophs in dead organic matter
heat energy is lost through cell respiration = heat
NUTRIENT FLOW
nutrients are recycled
nutrients are recycle within ecosystems
nutrients from weathering rocks enter ecosystems
nutrients recycled from decomposition of dead organisms
nutrients move through food chain by digestion of other organisms
nutrients absorbed by producers/ plants/ roots
nutrients lost by leaching/ sedimentation
