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