10.2 Energy transfer through ecosystems

How is energy transferred between trophic levels?

• Only a small amount of the energy available to an organism is transferred to the next trophic level

• Some is never taken in, some is lost before being transferred

What is meant by net & gross primary productivity?

• Gross primary productivity = Energy is taken in by primary consumers

• Net primary productivity = energy transferred into biomass (available to the next trophic level)

Why is some energy never taken in at each trophic level?

• Some parts of food aren’t eaten

• Some parts of food are indigestible

• Plants can’t use all light energy as some is in the wrong wavelength

Why is some energy lost at each trophic level?

Respiration - it is lost as heat

How are nutrients recycled within an ecosystem?

By microorganisms

Outline the roles of microorganisms in the nitrogen cycle

• Nitrogen-fixing bacteria in roots/soil convert gaseous nitrogen into ammonia

• Saprobionts decompose nitrogenous waste into ammonium compounds

• Nitrifying bacteria convert ammonium compounds into nitrates and nitrites