Organisms and their environment
Energy flow and food chains
- Sun: principal energy sourceLight energyPhotosynthesis
- Energy flows, not cycledChemical energy in organismsHeat to environment
- Food chainTransfer of energyStarts with producerArrows: food to feeder
- Food webInterconnected food chains
- ConsumersPrimarySecondaryTertiaryQuaternary
- Herbivore, carnivore, decomposerEats plantsEats animalsFeeds on dead material
- Human impactOverharvestingIntroduced species
Trophic levels and pyramids
- Trophic levelPosition in food chainProducers are level 1
- Pyramid of numbersNumber of organismsCan be inverted
- Pyramid of biomassMass of living materialTakes size into account
- Pyramid of energySupplementkJ per m² per yearAlways pyramid-shaped
- Energy transfer is inefficientSupplementParts not eatenFaeces and urineRespiration: heat
- Food chains are shortSupplementFewer than five levelsToo little energy left
- Plants versus livestockSupplementFewer trophic levelsLess energy lost
Nutrient cycles
- Carbon cyclePhotosynthesis removes CO₂Respiration adds CO₂Feeding passes carbon onFossil fuels and combustion
- DecompositionBacteria and fungiRelease CO₂ by respiration
- Nitrogen cycleSupplementNitrate absorbed by plantsAmino acids and proteinsFeeding and digestionDeamination forms urea
- Bacteria and nitrogenSupplementDecomposition: ammonium ionsNitrification: nitratesNitrogen fixationDenitrification: nitrogen gas
- Fixation by lightningSupplementAir nitrogen to nitrates
Populations
- PopulationOne speciesSame areaSame time
- CommunityAll populationsDifferent species
- EcosystemCommunity plus environmentInteracting together
- Growth factorsFood supplyCompetitionPredationDisease
- Sigmoid curve phasesLagExponential (log)StationaryDeath
- Explaining the phasesSupplementLimiting factorsBirth rate and death rate