ECOLOGY Part 2 - Chapter 3.4 Cycles

How energy flows . . . Sun - main source of energy Autotrophs / producers… can make own food Heterotrophs / consumers… must eat Decomposers / saprophytes… fungi & bacteria break down dead materials

Biogeochemical Cycles Within Ecosystems: Chapter 2.3, pg. 45 - 49 Water cycle – precipitation, evaporation and condensation Carbon cycle – increasing carbon dioxide traps more heat and causes the “greenhouse effect.” Phosphorus cycle – cycles between organisms and the land. Nitrogen cycle – converts atmospheric nitrogen (N2) to a form useable by organisms.

Water Cycle Processes: Evaporation – liquid changes to a gas (Transpiration – occurs from plants) Condensation – gas changes to a liquid (clouds form) Precipitation – temperature dependent a. re-evaporates b. surface runoff – rivers, streams, ocean c. stored as ground water - collection

Water Cycle

Carbon/Oxygen Cycle The basis of this is the reciprocal process of photosynthesis and respiration.

Carbon/Oxygen Cycle Cell respiration by animals and bacterial decomposers adds carbon dioxide to the air and removes oxygen.

Carbon/Oxygen Cycle The burning of fossil fuels adds carbon dioxide to the air. Photosynthesis removes carbon dioxide from the air and adds oxygen.

Nitrogen cycle Very little nitrogen enters the ecosystems directly from the air. Most of it enters an ecosystem by way of bacterial processes.

Nitrogen Cycle

Nitrogen cycle Nitrogen fixation is the conversion of… “N2” into usable organic compounds by bacteria “N2” from decaying organisms into ammonia

Nitrogen Cycle

Nitrogen Cycle N2 fixing bacteria live in the roots of legumes and convert free N2 into the ammonium ion (NH4+).

Nitrogen Cycle Nitrifying bacteria converts the ammonium ion (NH4+) into nitrites (NO2-): 2NH4+ +3O2  2NO2- + 4H+ + energy and then into Nitrates: 2NO2- + O2  2NO3- + energy

Nitrogen Cycle

Nitrogen Cycle Denitrifying bacteria convert nitrates (NO3-) into free atmospheric nitrogen (N2) “N2” is released from organisms that are being decomposed.

Phosphorus Cycle Phosphorus is essential to living organisms because it forms a part of vital molecules such as DNA and RNA. It’s not abundant in the biosphere. Phosphorus in the form of inorganic phosphate remains mostly on land (rocks, soil minerals, oceans, sediments)

Phosphorus Cycle Phosphate is gradually released during weathering, cycling between organisms and the soil. Plants bind phosphate into organic compounds and cycles through the food web from producers to consumers.

Phosphorus Cycle Some phosphate washes into rivers and streams and dissolves ending up in the oceans. Marine organisms process and incorporate it into biological compounds. Phosphorus is taken up by primary producers, reused by consumers, and released by excretion and decomposing matter.

Nutrient Limitations How does nutrient availability relate to the primary productivity of an ecosystems? Ample sunlight & water availability are basic requirements Availability of nutrients may be a limiting factor Limiting nutrient – single essential nutrient that limits productivity in an ecosystem

Nutrient Limitations in Soil Fertilizers supply missing nutrients Usually contain large amounts of nitrogen, phosphorus, & potassium Micronutrients – calcium, magnesium, sulfur, iron & manganese needed in smaller amounts

Nutrient Limitation in Aquatic Ecosystems Compared to land the ocean is nutrient-poor Nitrogen is often the limiting nutrient in oceans Phosphorus in streams, lakes and freshwater environments Runoff – algae blooms disrupt ecosystems

The End! . Go and Recycle!