Planet Earth

Ecosystems of the world (Biomes)

Energy in Ecosystems Productivity Energy is fixed primarily by auto-trophs during photosynthesis. Primary productivity is the amount of light energy fixed into chemical energy in a certain length of time. Total primary productivity is known as Gross Primary Productivity (GPP) Plants also use energy in respiration (R) Energy available to next level in food chain is: GPP - R = NPP (Net primary productivity)

Measuring productivity Primary productivity = the biomass of vegetation added to an ecosystem per unit area in a certain time (e.g. g/m2/year) Gross primary productivity is the total yield of organic matter from photosynthesis. Net primary productivity is the biomass after respiration energy is taken into account.

Factors affecting primary productivity Temperature, light intensity, supply of CO2 Soil nutrients/water Type of ecosystem Seasonal changes Examples: Terrestrial ecosystems precipitation, temperature, light, inorganic nutrients Aquatic ecosystems light, inorganic nutrients

Energy Flow Food chains and food webs. Ecological niches Niche is an organisms role in an ecosystem. Herbivores, carnivores, omnivores, decomposers primary, secondary and tertiary consumers

Feeding relationships Trophic levels - represent feeding levels in a food chain Energy transfer - not efficient plants use 1% of light energy each link in chain 10% energy available for next level 90% used by previous organism (heat energy, respiration, undigested waste, movement Range of efficiencies 5 - 20% depends on ecosystem

Representations of productivity Pyramids of numbers biomass productivity

Pyramid of numbers exceptions include when a tree is supporting many insects and birds numbers of organisms counted and grouped into trophic levels

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 Primary productivity = the biomass of vegetation added to an ecosystem per unit area in a certain time (e.g. g/m2/year) Gross primary productivity is the total yield of organic matter from photosynthesis. Net primary productivity is the biomass after respiration energy is taken into account.

Decomposers Ultimate loss of energy is as heat from respiration, as organic materials are broken down by decomposers into inorganic materials to be reused