1. By Chantele Dalmida AP Bio 09
Ecosystems
By Chantele Dalmida
AP Bio 09

2. 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

3. 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

4. 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.

5. 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

6. 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

7. 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

8. 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