By Chantele Dalmida AP Bio 09 Ecosystems By Chantele Dalmida AP Bio 09

Trophic Levels A trophic level is an organisms position in the food chain It is a display of energy lost at each level The first and largest block represents the sum The second block which is smaller than the first represents primary producers The third and fourth blocks represent secondary and tertiary consumers respectively At each level 10% of the energy consumed is lost At the tertiary level there is very little energy available to the consumer, which is why most trophic pyramids stop at four steps

About Ecosystems Consists of all the organisms in a community and all the abiotic factors that they interact with Energy passes from the sun to primary producers then primary consumers to secondary consumers and then to tertiary consumers Detritivores like fungi and bacteria break down chemical elements by decomposing organic materials and returning them to the soil According to the Green World hypothesis herbivores consume a small portion of vegetation because of predation, disease, symbiosis, and other factors

Physical and Chemical Factors Limit Primary Production Primary producers use light energy to synthesize energy rich organic molecules which are then broken down to make ATP Gross primary production (GPP) is the amount of light energy that is converted into chemical energy by photosynthesis Net primary production is GPP- R (the energy used in respiration) Light limitation affects aquatic ecosystems because light drives photosynthesis and if light cannot reach producers then no energy is produced. Light is only absorbed in the first meter of water. Nutrient limitation affects ecosystems because low levels of nitrogen and phosphorus limit plankton growth whereas high levels of these elements are found in deep oceans where no photosynthesis takes place.

Water Cycle Begins with evaporation of water from the land by the sun Then the condensation of water vapor into the clouds Followed by precipitation (rain, sleet, snow) Transpiration in plants (the releasing of water by the open stomata of plants) also expels water

Carbon Cycle Photosynthesis by primary producers removes CO2 from the air and is used as food Primary consumers eat the plants and take in CO2 and release it by respiration When plants and animals die the CO2 is absorbed into the ground by the soil and leaves decaying CO2 also gets absorbed into oceans and bodies of water Humans also affect the carbon cycle by burning fossil fuels which release carbon dioxide gas

Nitrogen Cycle Nitrogen is taken in through the soil by plants in the form of NO3- (nitrate ion) or NH4+ (ammonium ion) Animals consume plants and take in nitrogen When the animal dies nitrogen re enters the nitrogen cycle by decomposition. The nitrogen is released when the body breaks down Decomposers breakdown the decaying body and change the ammonia into NH4+ this is called mineralization (used by plants, fungi, and some bacteria) Nitrification is the oxidation (adding of oxygen) of ammonium to nitrite and nitrite to nitrate Denitrification converts the nitrates in nitrous oxide (N2O) or nitrous gas (N2), these gases then get released into the atmosphere

Phosphorus Cycle The weathering of rocks releases phosphorus into the atmosphere as phosphate ions Plants then take up the phosphate ions through water because the ions are soluble and use them as fertilizer Animals that eat the plants also take in some of the phosphate When plants and animals decay the phosphate is released back into the environment for reuse