Solar energy, the cycling of matter, and gravity sustain life on Earth. Ecosystems survive through energy flow and matter recycling. Water's unique properties, including its ability to dissolve compounds and change state, drive key Earth processes like the water and carbon cycles. The nitrogen cycle involves nitrogen fixation by bacteria, assimilation by plants, ammonification, nitrification, and denitrification, returning nitrogen to the atmosphere in a natural cyclic process.
1. What Sustains Life on Earth?
• Solar energy, the
cycling of matter,
and gravity
sustain the
earth’s life.
2. Two Secrets of Survival: Energy Flow
and Matter Recycle
• An ecosystem
survives by a
combination of
energy flow and
matter recycling.
3. 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.
4. • 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
5.
6. 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
9. 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
10. Nitrogen Cycle
• natural cyclic
process in the
course of which
atmospheric
nitrogen enters the
soil and becomes
part of living
organisms
12. Nitrogen Fixation
• nitrogen gas is converted into
inorganic nitrogen compounds. It is mostly
(90 percent) accomplished by free-living,
nitrogen-fixing bacteria.
13. 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
14. 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.
16. 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.
20. Nitrification
• a process carried out by nitrifying bacteria,
transforms soil ammonia into nitrates,
which plants can incorporate into their
own tissues.
