•Biogeochemical Cycles•Biomes

•Succession•Natural Selection

Terrestrial EcologyPart Two

Biogeochemical CyclesThe carbon, phosphorous, nitrogen and sulfur cycles

illustrate the law of conservation of matter the 1st law of thermodynamics- energy Is neither

created nor destroyed by it may be converted from one form to another

Fig. 3-7, p. 55

Nitrogencycle

Biosphere

Heat in the environment

Heat Heat Heat

Phosphoruscycle

Carboncycle

Oxygencycle

Watercycle

Biogeochemical CyclesCarbon

Is an atmospheric cycle but can be found in all three spheres- air, land and water

Carbon is required for formation of organic compounds in living things.

Carbon is taken out of the air by plants during photosynthesis and is returned to the air by cellular respiration.

Largest reservoir of carbon - sedimentary rocks (limestone) Second largest reservoir of carbon - ocean (dissolved

carbon dioxide), living things in ocean.

The Carbon Cycle:Part of Nature’s Thermostat

Figure 3-27Figure 3-27

Biogeochemical CyclesCarbon Cycle1. C in carbon dioxide in atmosphere and in water is moved to C in

glucose by photosynthesis by producers. 2. C in glucose is moved to C in carbon dioxide by cellular

respiration. 3. C in glucose is moved to C in organic molecules by synthesis

reactions in living things. 4. C in organic molecules is moved to C in carbon dioxide by

combustion. 5. C in organic molecules in organisms is moved to C in fossil fuels

over millions of years by pressure, heat, and bacterial action. 6. C in limestone (CaCO3) is released slowly to C in carbon dioxide

when exposed to oxygen and/or water.

Biogeochemical CyclesCarbon Cycle- Human

ImpactsWe alter the carbon cycle

by adding excess CO2 to the atmosphere through:Burning fossil fuels.Clearing vegetation

faster than it is replaced.

Biogeochemical CyclesPhosphorous-Phosphorus is required in the form of phosphate ions for

nucleic acids, ATP, phospholipids in cell membranes, bones, teeth, shells of animals.

Does not contain a gaseous phaseIs a sedimentary cycle - does not include the atmosphere.

Recycled only if the wastes containing it are deposited in the ecosystem from which it cameLimiting factor for plants

Biogeochemical CyclesThe phosphorus cycle is slow and phosphorus is

usually found in rock formations and ocean sediments.

Phosphorus is found in fertilizers because most soil is deficient in it and plants need it.

Phosphorus is usually insoluble in water and is not naturally found in most aquatic environments.

Biogeochemical CyclesPhosphate on land and in ocean sediment released by

weathering into water and taken up by plants. Can be limiting factor for plant growth - is present in

artificial fertilizer. Animals get phosphorus by eating plants or other animals. Decomposition changes organic molecules with

phosphorus back into phosphate which dissolves in water which returns the phosphorus to ocean sediment or deposited as rocks.

The Phosphorous Cycle

Figure 3-31Figure 3-31

Biogeochemical CyclesPhosphorous and Human Impact

Mining of phosphate for fertilizers and soap causes disruption to ecosystems.

Removal of phosphorus from ecosystems by cutting down of vegetation. Most of phosphorus is taken up as biomass.

Excessive phosphate in runoff from fertilizer, discharge of sewage, farm waste causes growth of algae, etc. (same problem as nitrogen).

Biogeochemical CyclesNitrogenIs an atmospheric cycle. Plants and animals cannot use free nitrogen gas in the

atmosphere. They must have nitrogen in "fixed" form. Nitrogen is required for proteins, nucleic acids in living things.

Nitrogen is often limiting factor in plant growth because ammonia, ammonium ion, nitrate are water-soluble: can be leached from soil.

The main reservoir of nitrogen is in the air78% nitrogen gas

You need phosphorous and nitrogen to build proteins and nucleic acids (part of DNA)

Since more organisms are unable to use nitrogen gas (N2), nitrogen fixing bacteria bind nitrogen with hydrogen to form ammonia (NH3)

Biogeochemical CyclesStages:

Nitrogen fixation (atmospheric nitrogen, N2, is converted to a more usable form by bacteria)

Assimilation (absorption of nitrates/ammonia,

by plants)Ammonification (production of ammonia,

NH3, by bacteria during organism decay)Nitrification (production of nitrate from

ammonia)Denitrification (conversion of nitrate to N2)

Fundamental Aspects

Nitrogen Cycle

Biogeochemical CyclesComplicated versionFree N2 in atmosphere is "fixed" by nitrogen-fixing bacteria to NH3

(ammonia) Nitrogen fixing bacteria live in nodules on the roots of leguminous plants

(soybeans, peas, clover, and alfalfa.) Water in the soil reacts with ammonia to form NH4+ (ammonium ion) Another species of bacteria can perform nitrification once ammonium

has formed Assimilation - absorption of ammonia, ammonium ion, nitrate for use by

plants to make nucleic acids, proteins Animals get fixed nitrogen by eating plants or other animals. Plants and animals are broken down by still other bacteria that convert

nitrogen-containing organic molecules in organisms to an inorganic form of nitrogen (ammonia or ammonium ion) = ammonification

Once this ammonia has formed, still another group of bacteria can perform denitrification

The Nitrogen Cycle: Bacteria in Action

Figure 3-29Figure 3-29

Biogeochemical Cycles

Nitrogen and Human ImpactWe alter the nitrogen cycle by:

Adding gases that contribute to acid rain.Adding nitrous oxide to the atmosphere through farming

practices which can warm the atmosphere and deplete ozone.

Contaminating ground water from nitrate ions in inorganic fertilizers.

Releasing nitrogen into the troposphere through deforestation.

Planting many legume cropsAccelerates the normal rate of nitrogen fixation

Human activities such as production of fertilizers now fix more nitrogen than all natural sources combined.

Figure 3-30Figure 3-30

Biogeochemical CyclesSulfur CycleIs an atmospheric cycle. H2S (hydrogen sulfide) and SO2 (sulfur dioxide)

released into atmosphere from natural (volcanoes) and non-natural sources.

Biogeochemical CyclesSulfur and the Human ImpactWe add sulfur dioxide to the atmosphere by:

Burning coal and oilRefining sulfur containing petroleum.Convert sulfur-containing metallic ores into free metals

such as copper, lead, and zinc releasing sulfur dioxide into the environment.

BiomesBiomes

Temperature and precipitation define a biomeAs you move from Arctic to equator, generally speaking,

there is an increase in mean annual temp and mean annual precipitation

Biomes tend to converge around latitude lines on the globe.

Separated by physical barriersOcean, mountains, etc

BiomesTerrestrial Biomes-

DesertTemperate GrasslandWoodlandChaparralTundraTropical Forests Temperate rainforestsTemperate deciduous forestsConiferous ForestsTaigas/Boreal Forest

You need to study the difference between these biomes

BIOMESHuman Impacts on Terrestrial Biomes Human activities have damaged or disturbed more than

half of the world’s terrestrial ecosystems. Humans have had a number of specific harmful effects on

the world’s deserts, grasslands, forests, and mountains. Remember HIPPO? It applies here as well

BiomesAquatic Biomes-

Lakes and PondsStreams and RiversWetlandsEstuariesCoastal OceansOpen Oceans

SuccessionSuccessionTransition of one biotic community to the nextNew environmental conditions allow one group of

species in a community to replace other groups.Ecological succession: the gradual change in species

composition of a given areaPrimary succession: the gradual establishment of biotic

communities in lifeless areas where there is no soil or sediment.

Secondary succession: series of communities develop in places containing soil or sediment.

SuccessionPrimary Succession:

Starting from ScratchPrimary succession begins with

an essentially lifeless are where there is no soil in a terrestrial ecosystem

Examples:- Lichen growing on a bare rock- Glaciers recede and expose

uninhabited soil- Abandoned parking lot- An area after a volcanic

eruption where lava covered and hardened over the soil

Figure 7-11Figure 7-11

SuccessionPioneer species-

First organisms to live in a new community

Usually brought in by wind or animals

Examples-Moss, weeds, lichen,

opportunistic species

SuccessionPrimary SuccessionMosses invade an area

and provide a place for soil to accumulate.

Larger plants germinate in the new soil layer resulting in additional soil formation.

Eventually shrubs and trees will invade the area.

Succession Secondary Succession:

Starting Over with Some Help

Secondary succession begins in an area where the natural community has been disturbed.

Figure 7-12Figure 7-12

SuccessionSecondary

Usually takes place after a land clearanceFire, landslide, forest clearing

Soil is already thereMore rapid than primary

One Year Later…

Thirteen Years Later…

SuccessionEach successive (new) community is more favorable for new

speciesChanges in stages until a climax community is established

The area is dominated by a few, long lived plant speciesNothing can “succeed” the plants in this community unless

some sort of natural disaster/act of mother nature occurs

SuccessionAquatic Succession

When a body of water is taken over by vegetationWater becomes shallow, less water volume and more fertile

Aquatic Succession

This used to be a lake!