Chapter 54

1. Chapter 54 Ecosystems

2. 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.

3. Water cycle

4. 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.

5. Phosphorus Cycle

6. 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 .

7. Nitrogen Cycle

8. Trophic levels

9. 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.

10. 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.

11. Biomass • The dry weight of organic materials. • Standing crop Biomass • Total biomass of photosynthetic autotrophs present at a given time. • AKA- the total amount of dry organic materials at one time

12. 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

13. Pyramids of productivity The pyramids of production show the loss of energy with each transfer in the food chain.

14. Pyramids of productivity Pyramids of Biomass Each 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.