3.1.6.2 ecosystems + processes

• Biodiversity

  The variation of life forms within a given ecosystem, biome + entire earth. Used to measure the health of biological systems = more biodiverse = more resilient
• biomass

  mass of living biological organisms in a given area/ ecosystems at a given time
• species biomass

  mass of one / more species
• community biomass

  mass of all species in community
• biome

  major habitat category, based on distinct plant assemblages which depend on a particular climate i.e temp + precip

  such as tundra + temperate forest
• Climatic climax

  biological community of plants + animals = reached dynamic equilibrium with its climate + soils due to ecological succession. Such as temperate deciduous woodland climatic climax community in british isles with brown earth soils
• ecosystems

  system in which organism interact with eachother and environment, i.e abiotic and biotic factors
• net primary production

  rate at which an ecosystem accumulates energy/biomass, excluding the energy required for processes such as respiration + excretion

  gpp - resp = npp
• nutrient cycling

  movement of nutrients between three major stores, soil, biomass + litter
• litter

  dead organic matter, leaves + twigs + fruit seeds dead animals = food source for decomposers
• plagioclimax

  the plant community that exists when human interference prevents climatic climax veg being reached. i.e arresting factors. Such as heather moorlands in somerset + North Yorkshire
• seral stage

  individual stage within a sere i.e colonisation/ stabilisation
• sere

  entire sequence of stages in a plant succession, ie psammosere (sand) + halosere (salt)
• subclimax

  development of an ecological community to a stage short of expected climatic climax because of some other factor such as repeated fires im a forest which arrests normal succession
• succession

  series of changes in an ecological community that occurs over time
• trophic level

  organisms position in food chain
• Ecosystem


  A community of abiotic and biotic things that work together, they are dynamic
• Flow of energy in an ecosystem

  • Unidirectional
  • Open systems
  • Important to maintain at dynamic equilibrium
• Abiotic factors in aquatic ecosystems

  • Water depth
  • pH
  • Sunlight
  • Turbidity (water cloudiness)
  • Salinity
  • Nutrients
  • Dissolved oxygen
• Abiotic factors in terrestrial ecosystems

  • Wind
  • Temperature
  • Precipitation
  • Altitude
  • Soil
  • Sunlight
  • Topography (layout of lands, elevation, gradient, aspect)
• Aspect


  In the northern hemisphere, south facing slopes receive more sunlight
• Altitude


  Height above sea level
• Soils


  Rich ecosystems with dead organic matter, weathered rock, decomposers and detrivores
• Biotic components


  • Plants
  • Animals
  • Microorganisms
• Energy flow in an ecosystem

  1. Producers convert solar energy into chemical energy via photosynthesis

  2. Producers use energy for respiration and storage

  3. Producers release oxygen as a by-product

  4. Consumers depend on producers for food and cannot synthesise their own food
• Consumers- depend on producers for food + cant synthesise their own food, heterotrophs 


  • Primary consumers (herbivores)
  • Secondary consumers (primary carnivores)
  • Tertiary consumers (large carnivores)
  • Quaternary consumers (fed on by no one else)
• Decomposers- absorption via extra cellular enzymes 


  Bacteria and fungi that break down dead organic material, releasing simple inorganic and organic substances
• Detrivores

  Organisms that ingest dead organic material directly
• Biomass

  The mass of living organisms in a given ecosystem, expressed in g/m2 or J/m2
• Types of biomass

  • Mass of all living species
  • Mass of one species within an ecosystem
  • Mass of decaying material (e.g. leaf litter)
  • aquatic - Aquatic - phytoplankton + rooted plants + krill = disproportionate amount
  • Terrestrial - plants + change every season
• Gross primary production

  The total amount of energy producers get from photosynthesis
• Net primary production

  The energy available for plant growth, which is the gross primary production minus respiration
• Food chain

  A linear pathway showing how energy is transferred from producers to consumers
• Trophic level

  The position an organism occupies in a food chain
• Food web

  Shows multiple food chains and demonstrates different ways energy flows through an ecosystem
• As you go up trophic levels, the amount of energy and biomass decreases, with only about 10% transferred at each trophic level
• Nutrients

  The chemical elements and compounds needed for organisms to grow and function
• Nutrient stores

  • Soil
  • Litter (dead organic matter on top of soil)
  • Biomass (plants and animals)
• Temperate deciduous woodland ecosystem

  • Wet climate all year round with mild temperatures and distinct seasons
  • High productivity due to strong growing conditions
  • Soil is rich and fertile, generally well-drained, with nutrients provided by decomposed litter and weathered parent rock
• Vegetation in temperate deciduous woodlands

  • Ground layer of mosses, grasses, lichens and herbaceous species
  • Shrub layer of species like rowan and hawthorn
  • Canopy layer of tall deciduous trees like oak, elm and sycamore