 Although energy is essential for life, organisms need much more  Over 95% of most living organisms are made up of just 4 elements 1.Oxygen 2.Carbon 3.Hydrogen 4.Nitrogen  These elements must be available in a form so organisms can take them in for cellular functions

 Matter flows through an ecosystem differently than energy ◦ Instead of a one way flow like energy, matter is recycled within and between ecosystems  Biogeochemical Cycles – the passing of elements, chemical compounds and other forms of matter from one organism to another from part of the biosphere to another ◦ Connects biological, chemical and geological aspects of the biosphere

 When an organism uses energy, the amount of energy remaining to the next trophic level is reduced (remember the energy pyramids…)  Unlike energy, matter is not used up, but transformed in the biosphere ◦ Matter can be assembled as tissue or passed as waste ◦ Ex) plant takes in CO2 and performs photosynthesis, plant releases O2, we inhale, we exhale CO2 (and the process goes on)

 Living things require water to survive  Where does the water come from?  The water cycle shows how water moves between bodies of water, air and land

1. Turning water from liquid to a gas ◦ Evaporation – the process by which water changes from a liquid to a gas ◦ Transpiration – the evaporation of water from the leaves of plants 2. Turning water back into a liquid ◦ Condensation – the formation of clouds ◦ Precipitation – when water returns to the earth in some form (rain, snow, sleet or hail)  These 2 steps happen over and over again

 Nutrients – all the chemical substances that an organism needs to sustain life ◦ Producers obtain them from sunlight or chemical bonds of inorganic compounds ◦ Consumers obtain them by eating other organisms  Every living organism needs nutrients to build tissues and carry out essential life functions  Like water, nutrients are passed between organisms and the environment through biogeochemical cycles

 How does carbon move through the environment 1.Biological Processes – photosynthesis, respiration 2.Geochemical Processes – erosion, volcanos 3.Biogeochemical Processes – decomposition (which makes fossil fuels) 4.Human Activities – mining, cutting forests, burning wood and fossil fuels

 All organisms require nitrogen to make amino acids and build proteins  Nitrogen Fixation – the ability to convert nitrogen gas into usable nitrogen (nitrates) for other organisms ◦ Done by bacteria that live on the roots of legumes (beans)  Denitrification – the ability to convert nitrates (usable nitrogen) into nitrogen gas ◦ Done by decomposers and return nitrogen to the atmosphere

 Phosphorus is essential to living organisms to make up molecules like DNA and RNA  it does not enter the atmosphere like C, O and N ◦ remains mostly on land in rock and soil minerals or in ocean sediment  Phosphorus is contained in rocks and sediment and is released as they wear down and can be dissolved into water ◦ Some phosphorus can be washed onto land and seep into soil where it then cycles between producers and consumers

 Ecologists are interested in primary productivity of an ecosystem ◦ The rate at which organic matter is created by producers  If a nutrient is in short supply in an ecosystem, it could limit an organisms growth ◦ Limiting Nutrient – a substance within an ecosystem that is scarce or cycles very slowly ◦ Can have adverse effects in an ecosystem if not corrected  ex. Placing fertilizer on fields to enhance crop growth