Biological Productivity and Energy Flow

Central African Republic: Violence Increases Hunger Risk, U.N. Warns

http://www.nytimes.com/2012/09/16/business/world-hunger-the-problem-left-behind-economic-view.html

http://www.nytimes.com/2014/04/02/business/energy-environment/a-200-year-old-forecast-for-food-scarcity-may-yet-come-true.html

1. How many bushels of wheat can a farmer produce in a field in a year?

2. What is the upper limit of food that can be produced for all the people on Earth?

What is the limit on the number of whales in the ocean?

What is the maximum production that we can expect of forests?

The ultimate limit on production of organic matter is energy flow.

Total amount of organic matter = biomass Measured in amount per unit area(g/m2) Increased through growth Change over time = net production The capture of usable energy to produce

organic compounds where that energy is stored = biological production

1. Primary – autotrophs a. photo b. chemo 2. Secondary – heterotrophs- Organic matter may be used for: a. Moving b. Making new compounds c. Growing d. Reproducing e. Storage- Energy is made available through respiration

Gross Primary Production, GPP, is the total amount of CO2 that is fixed by the plant in photosynthesis.

Respiration, R, is the amount of CO2 that is lost from an organism or system from metabolic activity.

Net Primary Production, NPP, is the net amount of primary production after the costs of plant respiration are included. Therefore, NPP = GPP - R

http://quizlet.com/31560822/test

• All life requires energy. – The ability to do work • Ecosystem energy flow - the movement of

energy through an ecosystem from the abiotic environment through a series of organisms (biotic) and back to the abiotic part of the environment.

Energy enters an ecosystem by two pathways.

– 1. Energy fixed by organisms (photosynthesis)

– 2. Transfer of heat energy by air, water, soil, and warm living things.

• First law = Law of conservation of energy – In any physical or chemical change,

energy is neither created nor destroyed but merely changed from one form to another.

• Second law = Law of Entropy – Energy is always increasing level of chaos (becoming less useful).

• As energy flows through a food web, it is degraded, and less and less is useable. • Energy efficiency- the ratio of output to input – The amount of useful work obtained from

some amount of available energy

Trophic-level efficiency- the ratio of production of one trophic level to the production of the next trophic level.

– Never very high – 1-3% in natural ecosystems – 10% may be maximum efficiency! – 90% of all energy lost as heat