The Biogeochemical Cycles

Chapter 5

5.1 How Chemicals Cycle

Biogeochemical Cycles

Chemical Reactions

5.2 Environmental Questions

Biological

Geological

Atmospheric

Hydrologic

5.3 Limiting Factors

Macronutrients are elements required in

large amounts by living things.

Micronutrients are elements required in

small amounts by living things.

Limiting factors are the single

requirement for growth available in the

least supply.

5.4 General Concepts

Some chemicals cycle quickly and are

readily available for biological activity.

(Oxygen)

Other chemicals are easily tied up in

relatively immobile forms and are

returned slowly. (Phosphorus)

5.4 General Concepts

Chemicals whose biogeochemical cycles

include a gas phase and that are stored

in the atmosphere tend to cycle quickly.

Since life evolved, it has greatly altered

biogeochemical cycles, and this has

changed the planet.

5.4 General Concepts

Biogeochemical cycles are essential to

life on Earth.

Through modern technology, we have

begun to transfer chemical elements

among air, water, and soil at rates

comparable to natural processes.

5.5 The Geologic Cycle

Tectonic Cycle involves the creation and

destruction of the solid outer layer of

Earth.

Hydrologic Cycle is the transfer of water

from the oceans to the atmosphere to the

land and back to the oceans.

5.5 The Geologic Cycle

The Rock Cycle consists of numerous

processes that produce rocks and soils.

5.6 Biogeochemical Cycling in Ecosystems

Involves living and nonliving things.

Metallic elements cycle differently than

nonmetallic elements.

Usually metallic elements cycle slower

because they do not have a gas phase.

Calcium Cycle

Sulfur Cycle

5.7 Major Global Chemical Cycles

Carbon Cycle

Nitrogen Cycle

Phosphorus Cycle

Carbon Cycle

Needed for carbohydrates, lipids, DNA,

and proteins.

Cycles through photosynthesis and

cellular respiration.

Missing Carbon from cycle...where did it

go? (Missing Carbon Sink)

Carbon Cycle

Carbon Cycle in a Lake

Global Flux of Carbon

Carbon Silicate Cycle

Nitrogen Cycle

Needed for proteins and DNA.

Free nitrogen (N2 ) is 80% of atmosphere, but

unusable by most organisms.

Plants, bacteria, algae take up NO3- (nitrate) or

NH4- (ammonium).

Converting N2 into ammonia or nitrate is called

nitrogen fixation. Converting back into N2 is

called denitrification.

Global Nitrogen Cycle

Phosphorus Cycle

Required for DNA.

Enters cycle by uptake of plants.

Passed on when organisms eat plants.

Global Phosphorus Cycle