Lecture 3 - Biogeochemical Cycles Nutrient - substance an organism needs to live, grow or reproduce Macronutrients - nutrients needed in large amounts - make up > 95% of all organism’s mass - e.g., C, N, P, K, H, O

Micronutrients - the 30+ elements required by organisms in small amounts - e.g., iron, zinc Biogeochemical Cycles - literally “life-earth-chemical” cycle - also called nutrient cycles

Biogeochemical Cycles cont’d natural processes that recycle nutrients from the non-living environment to living organisms, then back to the non-living environment e.g., carbon, oxygen, nitrogen & hydrologic cycles

Carbon Cycle Carbon - basic building block of carbohydrates, fats, proteins and nucleic acids (such as DNA) - the main source of C for organisms is CO2 from the atmosphere or dissolved in surface water

Carbon Cycle cont’d the 3 largest reservoirs of C are : 1. Earth’s rocks 2. fossil fuels 3. ocean beds the C cycle is based on the carbon dioxide gas 0.036% of the atmosphere is carbon dioxide gas

The Carbon Cycle

Carbon Cycle cont’d if the C cycle removes too much CO2 then the Earth will cool if the C cycle generates too much CO2 then the Earth will get hotter slight changes in the C cycle can affect climate & thus the types of life that can exist on Earth

2 ways that humans have disturbed the C cycle: Carbon Cycle cont’d 2 ways that humans have disturbed the C cycle: Forest & brush clearing 2. Burning fossil fuels and wood

Nitrogen Cycle Nitrogen - organisms need N to make proteins, DNA and other nitrogen compounds - nitrogen gas, N2,makes up 78% of atmospheric volume - N2 cannot be used directly by plants or animals

Nitrogen Cycle cont’d Ways Humans Intervene in N Cycle: 1. Adding excess nitrate and ammonia to aquatic ecosystems in agricultural runoff and discharge of municipal sewage 2. Emitting large quantities of nitric oxide when fuel is burned

Phosphorus Cycle is the movement of P through water, earth’s crust and living organisms P, mainly in the form of phosphates, is an essential plant & animal nutrient P is found is essential to bones, teeth & plant and animal cell membranes

Phosphorus Cycle cont’d 2 chief ways humans intervene with the P cycle: Mining large quantities of phosphate rock to produce commercial inorganic fertilisers and detergents Adding excess phosphate to aquatic ecosystems in runoff or animal wastes from cropland, sewage discharge & livestock feedlots

Hydrologic Cycle describes the movement of H2O between oceans and land masses collects, purifies and distributes Earth’s fixed supply of water organisms are made up primarily of H2O

The Water Cycle

Hydrologic Cycle cont’d 2 main ways humans interfere in H2O cycle: Withdrawing large quantities of fresh water Clearing vegetation from land for agriculture, mining, roads, construction, etc.

Weather & Climate Weather - short-term changes in temperature, pressure, precipitation and other conditions in the atmosphere at a given place & time

Weather & Climate cont’d Climate - average weather of an area - taken over a period of at least 30 years - temperature & precipitation are the 2 most important factors that determine climate

Weather & Climate cont’d Precipitation - water in the form of rain, sleet, hail & snow that falls from the atmosphere onto the land and bodies of water