OPTION C.6 NITROGEN & PHOSPHORUS CYCLES

Transcription

1 OPTION C.6 NITROGEN & PHOSPHORUS CYCLES

2 C.6 A Cycle

3 INTRO IB BIO C.6 3 The nitrogen cycle describes the movement of nitrogen within ecosystems. It involves several processes and stores.

4 INTRO IB BIO C.6 4 Cycle

5 IB BIO C.6 5 Understandings U1: fixing bacteria convert atmospheric nitrogen to ammonia. gas N 2 1 Ammonia NH 3 2 fixation is the assimilation of nitrogen gas by microbes into ammonia. Methods include: 1. Free-living Bacteria in the soil fix nitrogen without needing a host. Cycle Fixation 2. Mutualistic Bacteria that have formed a symbiotic relationship with a plant fix nitrogen.

6 IB BIO C.6 6 Understandings U2: Rhizobium associates with roots in a mutalistic relationship. Rhizobium are bacteria that convert N 2 into NH 4. They are typically not free-living and instead form mutualistic relationships with plants. Cycle Rhizobium They form root nodules and provide ammonia to the host plant. In exchange, it passes carbohydrates produced by photosynthesis.

7 IB BIO C.6 7 Understandings U3: In the absence of oxygen denitrifying bacteria reduce nitrate in the soil. Cycle Nitrification/ Denitrification gas N Ammonia NH 3 3 Nitrite NO 2 3 Nitrate NO 3 2 Nitrification is the oxidation of ammonia. 3. Nitrifying bacteria in the soil convert ammonia to nitrite and then nitrate. Denitrification is the reduction of nitrates, which produces N In the absence of oxygen, denitrifying bacteria in soil reduce nitrates and release N 2 back into the atmosphere.

8 IB BIO C.6 8 Skills S1: Drawing and labelling a diagram of the nitrogen cycle. Cycle Detritus 7 Animals 6 Plants gas N Ammonia NH 3 3 Nitrite NO 2 3 Nitrate NO Plants use ATP to actively pump the nitrates into their roots. 6. Plants use nitrates to make proteins. Animals feed on plants, digesting/rearranging the proteins to make their own. 7. When animals/plants die, their organic matter (detritus) is nitrogen rich.

9 IB BIO C.6 9 Skills S1: Drawing and labelling a diagram of the nitrogen cycle. Cycle Detritus 7 Animals 6 Plants gas N Ammonia NH 3 3 Nitrite NO 2 3 Nitrate NO Decomposers break down the detritus In the process, ammonium ions are produced. These ions are converted to nitrate by nitrifying bacteria (Step 3)

10 IB BIO C.6 10 Skills S1: Drawing and labelling a diagram of the nitrogen cycle. Detritus gas N 2 decomposition Ammonia NH 3 fixation NITROGEN CYCLE Cycle death Animals consumption uptake Plants denitrification Nitrite NO 2 Nitrate NO 3 nitrification nitrification

11 IB BIO C.6 11 Skills S1: Drawing and labelling a diagram of the nitrogen cycle. Cycle Cycle

12 IB BIO C.6 12 Applications A1: The impact of waterlogging on the nitrogen cycle. Waterlogging occurs when soil becomes saturated with water. This can occur due to flooding or poor drainage and results in decreased oxygen availability. Waterlogging

13 IB BIO C.6 13 Applications A1: The impact of waterlogging on the nitrogen cycle. The anaerobic environment promotes denitrification by Pseudomonas denitrificans, a denitrifying bacteria. This depletes nitrates in the soil, which significantly reduces plant growth. Waterlogging

14 IB BIO C.6 14 Applications A2: Insectivorous plants as an adaptation for low nitrogen availability in waterlogged soils. Areas that are waterlogged for long periods of time have nitrogen-deficient soils. Some plants have adapted to be carnivorous and obtain nitrogen by digesting animals. For example, some plants use pitfall traps to lure insects with nectar. Waterlogging Their inner lining is slippery, so insects fall in and are broken down by digestive enzymes.

15 IB BIO C.6 15 Applications A1: The impact of waterlogging on the nitrogen cycle. Waterlogging also affects the nitrogen cycle when water runs off. Water carries nutrients away from the soil into nearby water bodies. This excess of nutrients can result in eutrophication. Waterlogging

16 IB BIO C.6 16 Understandings U7: Leaching of mineral nutrients from agricultural land into rivers causes eutrophication and leads to increased BOD. Eutrophication is the excessive richness of mineral nutrients in a body of water that can occur near agricultural land. This results in excessive algal growth, leading to occurrences of algal blooms. Waterlogging Eutrophication

17 IB BIO C.6 17 Understandings U7: Leaching of mineral nutrients from agricultural land into rivers causes eutrophication and leads to increased BOD. Algal blooms block light to aquatic plants, preventing photosynthesis. When the algae die, they are decomposed by bacteria via respiration, increasing Biological Oxygen Demand (BOD) Waterlogging Eutrophication BOD Due to plant death, oxygen is used faster than it is added by photosynthetic organisms. Decreased oxygen levels limit the number and type species that can inhabit the environment.

18 REVIEW IB BIO C Define the nitrogen cycle. 2. Draw and label the nitrogen cycle. 3. Outline events in the nitrogen cycle that you drew. 4. Outline the effects of waterlogging on the nitrogen cycle, including environmental effects: - Eutrophication - BOD