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 Runoff Water 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 CycleDriven by biological forces:photosynthesis and respiration
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
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.
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.