Ecological Cycles

Nitrogen, Carbon-Oxygen, Phosphorus, Sulfur

The Nitrogen cycle

The Nitrogen Cycle

Nitrogen is used by living organisms to produce a number of complex organic molecules like amino acids, proteins, and nucleic acids.

78% of the world’s atmosphere is nitrogen Despite its abundance in the atmosphere,

nitrogen is often the most limiting nutrient for plant growth. This problem occurs because most plants can only take up nitrogen in two solid forms: ammonium ion (NH4+ ) and the ion nitrate (NO3- ) and CONNOT use raw atmospheric nitrogen

Four processes participate in the cycling of nitrogen through the biosphere:

nitrogen fixation atmospheric fixation by lightning biological fixation by certain microbes industrial fixation – making ammonia

decay (ammonification) – bacteria convert dead matter and wastes into ammonia

nitrification – bacteria convert ammonia into nitrates and nitrites

denitrification – bacteria return nitrogen to the atmosphere

Human Influence on Nitrogen Cycle

artificial nitrogen fertilization planting of nitrogen fixing crops N2O has risen in the atmosphere as a

result of agricultural fertilization, biomass burning, cattle and feedlots, and other industrial sources (N2O also destroys ozone)

eutrophication

Water Cycle

Water Cycle – Man’s Influence

Tropical Rain Forest – deforestationLess trees = less tramsiration = less water

in atmosphere = less rainOlalla Reservoir

Huge groundwater store in central U.S.Being depleted faster than replenished

Carbon Cycle

Carbon Cycle

O.03 carbon dioxide in atmospherePlants take in CO2 and release O2 in

PHOTOSYNTHEISAnimals take in O2 and release CO2 in

CELLULAR RESPIRATIONDecay also release CO2 into the

atmosphere

Man’s Influence on Carbon Cycle

Burning fossil fuels releases CO2 into atmosphere

Cellulose in dead plant material is hard to breakdown (too big)

Accumulates undecomposed over time forming peat

Peat over time and under pressure forms fossil fuels

When fossil fuels are burned – releases carbon

Sulfur Cycle

SulfurComponent of proteinsComponent of vitamins

Most sulfur is in rock and mineral slatsReleased naturally into atmosphere from

volcanoes and decomposition in wetlands

In atmosphere, SO2 reacts with water to produce sulfuric acid

Man’s Influence

We release excess SO2 into the atmosphere by:

Burning fossil fuelsRefining petroleum productsMining processes

Chemosynthesis

Ocean vents in trenchesBacteria use hydrogen sulfide H2S as

energy source

Phosphorus Cycle

Phosphorus important inDNA moleculesATPCell membranesBonesTeethshells

Slow cycleNot much in atmosphere – but in soil,

rock, and waterBig water component

Phosphorus Cycle