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Planet
Earth
Ecosystems of the world (Biomes)
Energy in Ecosystems Productivity
Energy available to next level in food chain is:
GPP - R = NPP (Net primary productivity)
Plants also use energy in respiration (R)
Total primary productivity is known as Gross Primary Productivity (GPP)
Primary productivity is the amount of light energy fixed into chemical energy in a certain length of time.
Energy is fixed primarily by auto-trophs during photosynthesis.
Measuring productivity
Net primary productivity is the biomass after respiration energy is taken into account.
Gross primary productivity is the total yield of organicmatter from photosynthesis.
Primary productivity = the biomass of vegetation added to an ecosystem per unit area in a certain time (e.g. g/m2/year)
Factors affecting primary productivity
Aquatic ecosystemslight, inorganic nutrients
Terrestrial ecosystems precipitation, temperature, light, inorganic nutrients
Examples:
Seasonal changes
Type of ecosystem
Soil nutrients/water
Temperature, light intensity, supply of CO2
Energy Flow
primary, secondary and tertiary consumers
Herbivores, carnivores, omnivores, decomposers
Niche is an organisms role in an ecosystem.
Ecological niches
Food chains and food webs.
Feeding relationships
Range of efficiencies 5 - 20% depends on ecosystem
90% used by previous organism (heat energy, respiration, undigested waste, movement
each link in chain 10% energy available for next level
plants use 1% of light energy
Energy transfer - not efficient
Trophic levels - represent feeding levels in a food chain
Representations of productivity
Pyramids of
productivity
biomass
numbers
Pyramid of numbers
numbers of organisms counted and grouped into trophic levels
exceptions include when a tree is supporting many insects and birds
Pyramid of Biomass
total mass of organisms at each trophic level
exceptions occur when primary consumers outweigh primary producers e.g. aquatic ecosystems
Wet mass v dry mass
Pyramid of Productivity
Energy available at each level to be passed on to next level.
Energy is always less at each trophic level.
Measuring productivity
Net primary productivity is the biomass after respiration energy is taken into account.
Gross primary productivity is the total yield of organicmatter from photosynthesis.
Primary productivity = the biomass of vegetation added to an ecosystem per unit area in a certain time (e.g. g/m2/year)
Ultimate loss of energy is as heat from respiration, as organic materials are broken down by decomposers into inorganic materials to be reused
Decomposers