BIOGEOCHEMICAL CYCLES - PowerPoint Presentation

Slide1

BIOGEOCHEMICAL CYCLESSlide2

Biogeochemical Cycle

: the cycling of chemical elements required by life between the living and nonliving parts of the environment. Some examples of these chemical elements are H2O, P, S, N2, O2 and C.

These elements cycle in either

1)a

gas cycle or

2)a

sedimentary cycle;

3)some

cycle as both a gas and sediment.Slide3

In a

gas cycle

elements move through the atmosphere. Main reservoirs are the atmosphere and the ocean.

In a

sedimentary cycle

elements move from land to water to sediment. Main reservoirs are the soil and sedimentary rocks. Slide4

Gas Cycles:

Sedimentary

Cycles:

Carbon  

Phosphorus

Nitrogen

Sulfur

Oxygen

  Slide5

CARBON CYCLE

    Slide6

Facts:

                - Carbon (C) enters the biosphere during photosynthesis:

CO2 + H2O ---> C6H12O6 + O2 + H2O

- Carbon is returned to the biosphere in cellular respiration:

O2 +H2O + C6H12O6 ---> CO2 +H2O + energy Slide7

Amount

of CO2 during the year:

-

Every year there is a measurable difference in

the

concentration of atmospheric CO2 in phase with the seasons.

            e

.g.

in winter there is almost no

photosynthesis therefore

there is a high concentration of CO2. Slide8

- During the growing season there is a measurable

difference

in the

concentration

of atmospheric CO2  over parts of each day.

e.g. At sunrise

photosynthesis begins with the uptake of CO2,

by

afternoon plant respiration increases, at sunset photosynthesis

stops

so the concentration of CO2 in the atmosphere increases. Slide9

Human induced changes in the global carbon cycle:

- The Earth is getting warmer.

-

The 20th century has been the warmest in the last

600

years

.

  - This century is about 1 degree Fahrenheit warmer than last century.   - The balance of evidence suggests that burning of fossil

fuel

(

eg

. coal, oil, natural gas), which emits CO2 as a waste, is

the

cause.

- CO2 is a "Green House" gas - it traps heat at the Earth's surface

.

(H2O vapor and methane are also examples of green house gases) Slide10

Signs that the climate is warming:

- Plants start blooming 8 days earlier in spring than 11 years ago

.

  - Birds from the United

Kingom

lay eggs earlier.

-

Buds on trees appear earlier and leaves fall later in the Northern

Hemisphere. - Alaska, North West Canada, and Siberia have warmed up as much as 5 degrees Fahrenheit in the last 30 years.

  Slide11

NITROGEN

CYCLESlide12

Facts:

                - Nitrogen (N) is an essential constituent of protein, DNA,

                RNA, and chlorophyll.

                     - N is the most abundant gas in the atmosphere, but it must

                be fixed or converted into a usable form. Slide13

Nitrogen Fixation Methods:

1) High energy fixation- a small amount of atmospheric nitrogen is fixed by lightening. The high energy combines N and H2O resulting in ammonia (NH3) and nitrates (NO3). These forms

  are carried to Earth in precipitation.

2) Biological fixation: achieves 90% of the nitrogen

fixation. Atmospheric nitrogen (N2) is split and combined with hydrogen (H) atoms to form ammonia (NH3). Slide14

Who performs nitrogen fixation?

               - symbiotic bacteria (

eg

.

Rhizobium

spp.) living in association with leguminous ( plants in the pea family), and root-

noduled

non- leguminous plants (

eg

.

Alnus

spp.).                    - free-living anaerobic bacteria                    - blue-green algae (cyanobacteria

)

ia

                ammonium ion (NH4), or without it to form NO3. NH4+ and

                NO3 are readily absorbed by plants.

  Slide15

OXYGEN CYCLE Slide16

Facts:

Sources of Oxygen:

1)

photodisassociation

of H2O vapor

                            2) photosynthesis

Slide17

Since oxygen is so reactive its cycling is complex:

       1) As a constituent of CO2 it circulates freely

       throughout the biosphere.

       2) Some CO2 combines with Ca to form carbonates.

       3) O2 combines with nitrogen compounds to form nitrates.

      4) O2 combines with iron compounds to form ferric oxides.

       5) Photosynthesis and respiration

       6) O2 in the troposphere is reduced to O3 (ozone). Ground level O3 is a pollutant which damages lungs.

  Slide18

SULFUR CYCLE

           Slide19

PHOSPHORUS CYCLE

  Slide20

Facts:

- Component of protein

  - Cycles in both a gas and sedimentary cycle.

  - The source of Sulfur is the lithosphere(earth's crust.

  - Sulfur (S) enters the atmosphere as  hydrogen

sulfide (H2S) during fossil fuel combustion, volcanic eruptions, gas exchange at ocean surfaces, and decomposition.

   - H2S is immediately oxidized to sulfur dioxide (SO2)    - SO2 and water vapor makes H2SO4 ( a weak sulfuric acid), which is then carried to Earth in rainfall.

   - Sulfur in soluble form is taken up by plant roots and incorporated into amino acids such as

cysteine

. It then travels through the food chain and is eventually release through decomposition.

Slide21

Facts:

- Component of DNA, RNA, ATP, proteins and enzymes

  - Cycles in a sedimentary

cylce

  - A good example of how a mineral element becomes part of an organism.

The source of Phosphorus (P) is rock.

- It is released into the

cylce

through erosion or mining

- It is soluble in H2O as phosphate (PO4)

It is taken up by plant roots, then travels through food chains.

- It is returned to sediment Slide22