PowerPoint Presentation

(1)

(2)

The Biogeochemical Cycles

(3)

Fig 4.5 Periodic table of the elements.

(4)

D. T. Krohne, General Ecology

(5)

Fig 4.6 Idealized diagram of the

geologic cycle, which includes the tectonic, hydrologic, rock and biogeochemical cycles.

(6)

Modified from D. T. Krohne, General Ecology

15%/year

CO₂ & CH₄

(7)

(8)

The Carbon Cycle

(9)

Fig 4.14 The Carbon Cycle.

(10)

Fig 4.15 Idealized diagram illustrating photosynthesis for a green plant (tree) and generalized reaction.

(11)

(12)

Fig 4.17 Global flux of carbon, 1850-1990.

(13)

50% fertilizer

(Bacteria)

(14)

Microbial mediated processes in the nitrogen cycle

(15)

Nitrogen fixation

Cyanobacteria live everywhere in the aquatic environment

Nitrogen fixing bacteria in plant root nodules

Microbes fix nitrogen gas into ammonia that is

incorporated into plant

tissue

(16)

Ammonification (Mineralization)

Refers to the

breakdown of organic matter in order to

release the

organically bound nitrogen as inorganic (mineral) nitrogen in the form of ammonia Decomposition is the biological process that allows for the process

(17)

Nitrifying bacteria (Nitrosomonas and Nitrobacter)

(18)

Occurs in oxygen poor or anaerobic

environments usually deep in the soil or in muddy sediments

(19)

NO

₃^-

→ NO

₂^-

→ NO → N

₂

O → N

₂

gas

The complete denitrification process can be expressed as a redox

reaction

2NO

₃^-

+ 10e

^-

+ 12H

⁺

→ N

₂

+ 6H

₂

O

(20)

Mangrove swamps are areas where denitrification happens

(21)

From http://www.epa.gov/maia/html/nitrogen.html

(22)

Fig 4.19 The global nitrogen cycle.

(23)

Critical Thinking Issue – How are Human Activities Affecting the Nitrogen Cycle?

• Increased nitric acid in soil:

• Leaching of magnesium and potassium

• Increased aluminum levels

• Plant root damage

• Changes in microbe communities

• Fish kills

• Eutrophication of water bodies

• Nitrates in drinking water

• Global effects on plant based CO₂ uptake

Effects of increased use of nitrogen fertilizer:

(24)

D. T. Krohne, General Ecology D. T. Krohne, General Ecology

Gaseous phase

(25)

Phosphorous cycle in water

(26)

Fig 4.20 The global phosphorus cycle.

(27)

Ecosystems and the Gaia Hypothesis

(28)

Ecosystem defined:

a community of organisms and it’s corresponding abiotic

environment through which matter cycles and energy flows

• Wide variation in ecosystems

• Boarders can be well defined or vague

• Can be natural or artificial, managed or wild

• Wide range in scale

• Common to all ecosystems: energy flow and cycling of matter

(29)

(30)

Gaia Hypothesis(es)

• Life has greatly affected the planetary environment

• This alteration has allowed life to persist

• The Earth is a “super-organism” - Life controls the environment in a fashion that is equivalent to the way an organism controls its various systems

• Evolution?

(31)

(32)