Transcript File
(Write these down) Nitrogen Cycle summary questions 1.Nitrogen is available to plants generally in which two chemical forms? 2.Which two things perform the process of nitrogen fixation? 3.Describe the process of nitrogen fixation. 4.Denitrification is a chemical process that does what? 5.What kinds of organisms perform denitrification? 6.What kind of ecosystem accounts for more than half of terrestrial denitrification? The playa’s Lightning Nitrogen-fixing bacteria Legumes Decomposers Denitrifying bacteria Why Nitrogen is important It’s a major component of Proteins! It’s a major component of DNA ! The movement of nitrogen between different groups of organisms and between the different molecular types is known as the nitrogen cycle Here’s a problem… Organisms can die of a Nitrogen deficiency while being completely surrounded by it. Remember, N2 is _______% of the atmosphere Unfortunately Putting N2 into a plant or animal is like trying to fit a square peg into a round hole Bottom line…N2 has to be changed Lightning!! The high energy in lightning can take atmospheric Nitrogen, N2, and convert it in mid air to Nitrates If not lightning… The only other natural way to get N2 into a usable form, is to have a certain bacteria Bacteria These bacteria are called Rhizobium Rhizobium So Mr. Irvine, my tomatoes died this year because of a Nitrogen deficiency. Could Rhizobium help my garden? Well Fiddy, here’s what you do… Clover Peas Beans Alfalfa These plants have a symbiotic relationship with the Rhizobium and will give your soil these special bacteria. Nice… Plants like NH4+ and NO3- How do plants use the Nitrate and Ammonium? “Assimilation” •Plants will build their biological molecules such as Proteins and DNA… Pretty important stuff! Now to the Animals… So how do consumers get their Nitrogen for Proteins and DNA? “Assimilation” Death becomes it Or Death becomes a PART of the plant or animal “For you are dust, And to dust you shall return.” Ammonification Decomposers break apart the organic molecules and return some of it back into the soils, or water as inorganic ammonia (NH3) It can now be used again by the producers… What if plants don’t get to these Nitrates? Then they’re OURS! Denitrifying Bacteria These guys convert Nitrates and nitrites into Nitrogen Gas Yeah, were pretty gassy! Conditions for Denitrification: Anaerobic conditions… aka no oxygen Waterlogged fields High clay soils Swampy ecosystems Over half! Over half of the worlds Denitrifying bacteria are found in anaerobic (no oxygen) ecosystems like swamps and bogs Yuk… so many denitrifying bacteria in here Summary: • Either Nitrogen-fixing bacteria or ____________ remove nitrogen gas (N2 ) from the atmosphere and convert it to _________. • ___________ take in nitrates and use them to build biological molecules. • _____________ disassemble nitrogen-containing molecules in plants and animals and release ammonium back into the soils. • ____________ bacteria convert nitrates into nitrogen gas which is released back into the _______________. Free response: 1. Nitrogen is critical for sustaining life in both terrestrial and aquatic ecosystems. a) Draw a fully labeled diagram of the nitrogen cycle (4 points) b) Describe the following steps in the nitrogen cycle i. Nitrogen fixation (1 point) ii. Ammonification (1 point) iii. Denitrification (1 point) c) Describe one reason why nitrogen is crucial for sustaining life on Earth (1 point) d) Describe one way that the nitrogen cycle can be disrupted by human activities. (1 point) Now… •Humans are altering some of the cycle. Your job is to look at page 85, under “How are human activities affecting the Nitrogen Cycle?” Look at the fourth cause and write a few notes on the subject.