What Sustains Life on Earth?

• Solar energy, the cycling of matter, and gravity sustain the earth’s life.

Two Secrets of Survival: Energy Flow and Matter Recycle

• An ecosystem survives by a combination of energy flow and matter recycling.

Water’ Unique Properties• There are strong forces of attraction

between molecules of water.• Water exists as a liquid over a wide

temperature range. • Liquid water changes temperature

slowly.• It takes a large amount of energy for

water to evaporate.• Liquid water can dissolve a variety of

compounds.• Water expands when it freezes.

• Water moves through the biotic and abiotic factors in the environment

• Ways water can move:– Precipitation

• water moves from the atmosphere to the land in the form of snow, rain, sleet and hail.

• During evaporation and transpiration (evaporation from plants and through skin) water cools and condenses, precipitation forms

• About 91% falls into oceans. The rest falls on land to replenish the fresh water supply – Evaporation• Water moves from the land to the

atmosphere• Ground Water – when precipitation seeps

into the ground and becomes part of the water table

RunoffWater that flows on top of the ground

The Carbon Cycle• All living things have carbon in them• All carbon that is on earth has been here

since the earth was formed• Photosynthesis – carbon gets taken out of

the air and used by producers to make food• Respiration- carbon gets put back into the

air by animals when they exhale• Decomposition – breakdown of dead

materials by bacteria and fungi• Combustion – carbon in fossil fuels is

released while burning

The Carbon Cycle

Driven by biological forces:photosynthesis and respiration

15%/year

CO2 & CH4

The Nitrogen Cycle

• 78% of the earth’s atmosphere is nitrogen• Organisms cannot use nitrogen directly from

atmosphere• Nitrogen fixation- when bacteria in the soil

change atmospheric nitrogen gas into usable nitrogen

• Lightening can also fix nitrogen• Denitrification-different bacteria change

usable nitrogen into atmospheric nitrogen gas

Nitrogen Cycle• natural cyclic

process in the course of which atmospheric nitrogen enters the soil and becomes part of living organisms

Steps of Nitrogen Cycle• Nitrogen Fixation• Nitrogen Assimilation• Ammonification• Nitrification• Denitrification

Nitrogen Fixation• nitrogen gas is converted into

inorganic nitrogen compounds. It is mostly (90 percent) accomplished by free-living, nitrogen-fixing bacteria.

Nitrogen-Fixing Bacteria• symbiotic bacteria living on the

roots of plants (mostly legumes and alders)

• cyanobacteria (formerly known as blue-green algae)

• archaebacteria (also known as archaea) in deep-sea hydrothermal vents

Nitrogen Fixation by Lightning• The high energies provided by

lightning and cosmic radiation serve to combine atmospheric nitrogen and oxygen into nitrates, which are carried to the Earth’s surface in precipitation.

Steps of Nitrogen Cycle• Nitrogen Fixation• Nitrogen Assimilation• Ammonification• Nitrification• Denitrification

Nitrogen Assimilation• are assimilation of nitrates and

ammonia resulting from nitrogen fixation into the specific tissue compounds of algae and higher plants. Animals then ingest these algae and plants, converting them into their own body compounds.

Steps of Nitrogen Cycle• Nitrogen Fixation• Nitrogen Assimilation• Ammonification• Nitrification• Denitrification

Ammonification• The remains of all living things—

and their waste products—are decomposed by microorganisms which yields ammonia.

Steps of Nitrogen Cycle• Nitrogen Fixation• Nitrogen Assimilation• Ammonification• Nitrification• Denitrification

Nitrification• a process carried out by nitrifying

bacteria, transforms soil ammonia into nitrates, which plants can incorporate into their own tissues.

Steps of Nitrogen Cycle• Nitrogen Fixation• Nitrogen Assimilation• Ammonification• Nitrification• Denitrification

Denitrification• The process where nitrates are

metabolized by denitrifying bacteria to free nitrogen and returned to the atmosphere

Oxygen Cycle:

oxygen

respiration

carbondioxide

photosynthesis