2.2 Nutrient Cycles in Ecosystems p.68-91 Chapter 2 2.2 Nutrient Cycles in Ecosystems p.68-91 Words to Know: cellular respiration photosynthesis denitrification sedimentation nitrification weathering Nutrients (c) McGraw Hill Ryerson 2007

2.2 Nutrient Cycles in Ecosystems Nutrients - chemicals needed for plant and animal growth. Nutrient cycles – the flow of nutrients IN and OUT of the land, ocean, atmosphere and deep rock. The health of our ecosystems depends on the balance of: Carbon, Nitrogen, Phosphorous, Hydrogen and Oxygen C N P H O (c) McGraw Hill Ryerson 2007

Nutrient Cycle Diagram (c) McGraw Hill Ryerson 2007

Nutrient Cycles: The Carbon Cycle A. Carbon Facts Carbon is an element found in the molecules of all living and dead things. It is important for plant growth. Places carbon is found are called stores or sinks. Short-term Stores Long-term Stores living things in water and on land underground (oil, gas, natural rotting tissue of plants and animals gas and coal) atmosphere (air) sedimentary rock (limestone) ocean (dissolved in the water) ocean floor (old shells) (c) McGraw Hill Ryerson 2007

How Carbon Changes Form 1. Photosynthesis (in plants, algae and cyanobacteria) CO2 + H2O + sunlight  C6H12O6 + O2 2. Cellular respiration (in cells of all living things) C6H12O6 + O2  CO2 + H2O + ENERGY (energy is used for growth, repair etc.) Decomposition (rotting) cellulose  CO2 Only done by bacteria and fungi (c) McGraw Hill Ryerson 2007

Ocean mixing moves CO2 around the world Ocean Processes: Ocean mixing moves CO2 around the world CO2 sinks in cold ocean waters  flows to the warm equator and evaporates into the air. (c) McGraw Hill Ryerson 2007

Combustion: (burning, engines, volcanoes, forest fires) fossil fuels + O2  CO2 + H2O + ENERGY (oil, gas, natural gas, coal) (c) McGraw Hill Ryerson 2007

CARBON CYCLE DIAGRAM See page 76 (c) McGraw Hill Ryerson 2007

Nutrient Cycles: The Carbon Cycle (continued) Human Activities Have Increased CO2 in the atmosphere. Burning Fossil Fuels. CO2 in atmosphere has increased 30% in past 160 years (since Industrial Revolution began). In the 160,000 years before that, it only increased 1-3%. Carbon is being removed from long-term storage more quickly than it naturally would as we mine coal and drill for oil and gas. CO2 is also a greenhouse gas, which traps heat in the atmosphere. See page 77 (c) McGraw Hill Ryerson 2007

Crops that replace the trees don’t remove as much CO2 Removing Trees. Large trees and shrubs absorb CO2 from the atmosphere, so when they are cut down, there is more CO2 in the air. Crops that replace the trees don’t remove as much CO2 (c) McGraw Hill Ryerson 2007

Nutrient Cycles: The Nitrogen Cycle Nitrogen Facts Makes up DNA and proteins (muscle function). Help plants grow. Where Nitrogen is Found: Atmosphere (78% is N2) Oceans Organic matter in soil Lakes, marshes, organisms See page 78 (c) McGraw Hill Ryerson 2007

How Nitrogen Changes Form. N2 is not usable by plants or animals, so it has to be converted to other forms. Plants can use NO3- (nitrate) and NH4+ (ammonium) Nitrogen Fixation Lightning changes N2 (nitrogen gas)  NO3- (nitrate). Rain washes nitrate into soil. This only fixes a tiny amount of nitrogen. Bacteria in soil (rhizobium) and cyanobacteria in water change N2 (nitrogen gas)  NH4+ (ammonium). This processes fixes most nitrogen. Rhizobium live on the roots of legumes (peas, alfalfa, beans) and alder trees. (c) McGraw Hill Ryerson 2007

Nutrient Cycles: The Nitrogen Cycle (continued) Nitrification NH4+ (ammonium)  NO2- (nitrite)  NO3- (nitrate) This is done by nitrifying bacteria. Uptake NO3- is sucked into plants and used for growth. Herbivores eat the plants and use the Nitrogen for making proteins and DNA. Denitrification NO3-  N2 done by denitrifying bacteria N2 is also returned to the atmosphere through volcanic eruptions. See pages 78 - 79 (c) McGraw Hill Ryerson 2007

Nitrogen Cycle See page 81 (c) McGraw Hill Ryerson 2007

Nutrient Cycles: The Nitrogen Cycle (continued) Human activities affect the nitrogen cycle. The amount of nitrogen in the ecosystem has doubled in the last 50 years due to: Burning fossil fuels and sewage treatment. NO and NO2 are byproducts Land-clearing by burning. acid rain is formed which contains nitric acid (HNO3). Overfertilization excess NH4+ and NO3- leach into the soil and waterways. This promotes huge growth in aquatic algae = eutrophication These algal blooms use up all CO2 and O2 and block sunlight, killing many aquatic organisms. The algal blooms can also produce neurotoxins that poison animals. (c) McGraw Hill Ryerson 2007

Nutrient Cycles: The Phosphorous Cycle Phosphorous Facts Phosphorous is a part of the molecule that carries energy in cells (ATP). Phosphorous helps root growth, stem strength and seed production. In animals, phosphorous is important for strong bones. Where Phosphorous is Found: Not in atmosphere, but in phosphate rocks (PO43–, HPO42–, H2PO4) and sediments on the ocean floor. See pages 83 - 84 (c) McGraw Hill Ryerson 2007

How Phosphorous Changes Form. 1. Weathering (breaking down rock into smaller pieces). a) Chemical weathering acid rain or lichens releases phosphates (PO43- ) b) Physical weathering wind, water and freezing release the phosphates. Uptake plants suck up PO43- for growth, then are eaten by animals. (c) McGraw Hill Ryerson 2007

Decomposition (rotting) Bacteria break down dead plants and animals and phosphorous is returned to soil. Geologic Uplift when rocks under the ground are pushed up  mountains  weathering. (c) McGraw Hill Ryerson 2007

The Phosphorous Cycle (c) McGraw Hill Ryerson 2007

C. Human activities affect the Phosphorous Cycle. 1. Mining Increases P in ecosystems quickly. Natural stores are not replaced. 2. Slash-and-burn forest practices. Turns P into ash, which runs into waterways. (c) McGraw Hill Ryerson 2007

How Changes in Nutrient Cycles Affect Biodiversity To Review: Any significant changes to any of these nutrients (C, H, O, N or P) can greatly impact biodiversity. Carbon cycle changes  climate change and global warming. Too much nitrogen can allow certain plant species to out-compete other species. Decreased levels of phosphorous  slow growth of algae (important producers). Take the Section 2.2 Quiz (c) McGraw Hill Ryerson 2007