Chapter 54Ecosystems

Water cycle

Most of the water cycle occurs between the oceans and the atmosphere through evaporation and precipitation.

Water is essential to all living organisms. The main processes driving the water cycle are evaporation of liquid water by solar energy, condensation of water vapor into clouds, and precipitation.

Water cycle

Phosphorus cycle

Organisms require phosphorus as a major constituent of nucleic acids, phosphlipids and ATP and other energy storing moleculesand mineral constituent to bones and teeth.

Only relatively small amounts of phosphorus move through the atmosphere, ( dust or sea spray).

Weathering of rocks gradually adds phosphate to soil; some leaches into groundwater and surface water and may eventually find it’s way into the sea. Phosphate taken up by porducers and incorporated into biological molecules may be eaten by consumers and distributed through either decomposition of biomass or excretion by consumers.

Phosphorus Cycle

Nitrogen cycle

Nitrogen is a component of amino acids , prteins, and nucleic acids and is crucial and often limiting plant nutrient.

Major pathway for nitrogen to enter an ecosystem is nitrogen fixation, the conversion on N2 by bacteria to forms that can be used to synthesize nitrogenous organic compunds.

Ammonification- decomposes organic nitrogen in NH4 + .

Nitrification- NH4+ is converted to NO3- by nitrifying bacteria.

Denitrification- in anaerobic conditions dentrifying bacteria release N2 .

Nitrogen Cycle

Trophic levels

Trophic levels

Primary consumers eat the plants and use some of the energy.

Secondary consumers eat the primary consumers and gain the energy from them.

Detrivores are consumers that get their energy from detrius , which is nonliving organic material, such as remains of dead organisms. This is then absorbed by the producers and the cycle repeats.

This system of levels shows the way energy is

passed.

•The sun gives solar energy to the primary producers.(plants)•Primary producers convert the solar energy to chemical energy.

Productivity

Productivity is the flow of energy through an ecosystem.

Primary vs. Secondary- Primary the amount of light energy converted to chemical energy by the autotrophs (plants) of an ecosystem

Secondary- rate that an ecosystems consumers convert the chemical energy of the food they eat into their own new biomass.

Biomass

The dry weight of organic materials. Standing crop BiomassTotal biomass of photosynthetic autotrophs

present at a given time. AKA- the total amount of dry organic

materials at one time

Ecological efficiency of ecosystems

The percent of energy transferred from one trophic level to the next.

It means the amount of energy each trophic level gives to the next (Net Primary productivity)

Production efficiency= net secondary production

Assimilation of primary production

Pyramids of productivityThe pyramids of production show the loss of energy with each transfer in the food chain.

Pyramids of productivity

Pyramids of BiomassEach tier represents the standing crop biomass

( the total dry weight of all organisms) in one trophic

level .Most start with primary producers at the bottom except for some aquatic

ecosystems that are inverted.