2.3 Flows of Energy and Matter

The sun is 4.5 billion years old and ½ way through its lifespan.It has burned up ½ of its hydrogen in nuclear fusion to make helium and release energy.

The energy is in the form of packets called photons and it takes 8 minutes for a photon to reach Earth.

The energy leaving the sun is about 63 million Jules per second per square meter.(Js-1 m-2)

The solar energy reaching the top of the atmosphere of Earth is 1,400 J s-1 m-2

This is Earth’s solar constant

The only way in which life can turn solar energy into food is through photosynthesis by green plants.

Energy transfer and transformation in an ecosystem• Light from the sun is the source of energy for life on our planet

• Less than 1% of the sun’s energy is available to plants

WHY SO LITTLE?

Energy transfer and transformation in an ecosystem• Less than 0.05% of light energy falling on the Earth is captured by

plants and converted to glucose from photosynthesis

WHY SO LITTLE?

BECAUSE….

• Reflection: Some light is reflected from the surface of the leaves or it passes through w/o being captured

BECAUSE….

• Wavelength: chlorophyll only captures certain wavelengths of light for use during photosynthesis• Greenlight reflected and not absorbed

• Red and blue are the most effective for photosynthesis

BECAUSE….

• Efficiency: Photosynthesis is limited by factors such as temperature, light, water, and CO2 concentrations, and the rate at which enzyme catalyst can work.

BECAUSE….• Not absorbed: Light that does enter the leaves may not strike the

chloroplast

Energy transfer and transformation in an ecosystem• Some of the glucose from photosynthesis is respired and the energy

used to keep the plant alive

• The remainder is converted into other compounds like starch and protein to be stored in the plant

• This is what is available to the next trophic level

PRODUCTIVITY

GPP/NPP/GSP/NSP

Gross vs. Net

•Gross = everything being made (All the $ you bring in at food fair)

•Net = what is leftover after your losses($ you are left with after you pat for costs of food fair supplies)

Gross Primary Productivity (GPP)•GPP – The total gain in energy or biomass per unit area per unit time fixed by photosynthesis in green plants.

Basically: The total energy converted by photosynthesis in plants.

GPP = NPP + R

Net Primary Productivity (NPP)•NPP – The gain by producers in energy or biomass per unit area per unit time remaining after allowing for respiratory losses (R). This is potentially available to consumers in an ecosystem.

Basically: gain by producers in energy minus the losses of energy from respiration

NPP = GPP - R

Gross Secondary Productivity (GSP)•GSP – The total gain by consumers in energy or biomass per unit area per unit time through absorption.

Basically: GSP is the food eaten – food lost in feces (food that wasn’t absorbed)

GSP = food eaten – fecal loss

Net Secondary Productivity (NSP)

•NSP – The gain by consumers in energy or biomass per unit area per unit time remaining after allowing for respiratory losses (R).

Basically: food eaten – fecal loss – respiration

NSP = GSP - R

Plants can only absorb 40% of the energy that hits a leaf.

5% is reflected 50% lost and 5% passes straight through the leaf.

Plants only use red and blue wavelengths.(That’s why the plant looks green)

Of the 40% absorbed only 9% can be used. This is the GPP of the plant. Just under ½ of this is required in respiration to stay alive so 5.5% of the energy hitting the leaf becomes NPP.

• Decomposer food chains are important in energy transfer

• Fungi break down detritus and make food available for other decomposers

• This releases valuable nutrients back into the soil

The biogeochemical cycles.

The biogeochemical cycles.

• Movement of nutrients and energy through the ecosystem is quite different.

• Energy travels from the sun, through food webs and is eventual lost to space as heat.

• Nutrients are recycled and reused. (Via the decomposer food chain)

• Organisms die and are decomposed

• Nutrients are released

• Eventually become parts of living things again, when they are taken up by plants

• The origin of all the energy in an ecosystem is the sun and the fate of the energy is eventually to be released as heat

Nitrogen Cycle

• 78% of the atmosphere is nitrogen

• Nitrogen is a key chemical element for all organisms. It is needed to build proteins

• Atmospheric nitrogen is not useable to plants unless it goes through a transformation

• There are only a few ways nitrogen can be altered from the atmosphere.

The enormous energy of lightningbreaks nitrogen molecules and enables their atoms to combine with oxygen in the air forming nitrogen oxides. These dissolve in rain, forming nitrates, that are carried to the earth. Atmospheric nitrogen fixation probably contributes some 5– 8% of the total nitrogen fixed.

Nitrogen fixing bacteria live in nodules on the rots of plants called legumes

DecomposersDecomposers convert the nitrogen found in other organisms into ammonia and return it to the soil. A few of these type of bacteria return nitrogen to the atmosphere by a process called denitrification, however this amount is small.

Carbon Cycle

• Energy flows from one compartment to another. E.g. a food chain. But when one organism eats another organism the energy that moves between them is in the form of stored chemical energy: Flesh

• Energy Flows through an ecosystems in the form of carbon–carbon bonds within organic compounds. These bonds ae broken during respiration when carbon joins with oxygen to produce carbon dioxide. Respiration releases enrgy that is either used by organisms (life processes) or is lost as heat.

• The balance between Photosynthesis, Respiration and incorporation into the lithosphere

• Carbon is an essential element in living systems, providing the chemical framework to form molecules that make up living organisms. Carbon makes up around 0.03% of the atmosphere as carbon dioxide, and is present in the Oceans as carbonate and bicarbonates and in rocks such as limestone and coal.

• Carbon cycles between living (biotic) and non-living (abiotic) chemical cycles: carbon is fixed by photosynthesis and released back to the atmosphere through respiration. Carbon is also released back to the atmosphere through combustion, including fossil fuels and biomass.

• Carbon can remain locked in either cycle for long periods of time. ie in the wood of trees or as coal and oil.

• Human activity has disrupted the balance of the global carbon cycle (carbon budget) through increased combustion, land use changes and deforestation