Objectives
• Describe how matter cycles between the living
and nonliving parts of an ecosystem.
• Explain why nutrients are important in living
systems.
• Describe how the availability of nutrients affects
the productivity of ecosystems.
Vocabulary
• Biogeochemical Cycle
• Evaporation
• Transpiration
• Nutrients
• Nitrogen Fixation
• Denitrification
• Primary Productivity
• Limiting Nutrient
• Algal Bloom
Recycling in the Biosphere
Unlike the one-way flow of energy, matter is
recycled within and between ecosystems.
Matter can be recycled, because biological systems do
not use up matter, they only change it from one form to
another.
The Water Cycle
The water cycle involves the movement of water
between the ocean, atmosphere, and land.
Evaporation is process by which water changes
from liquid form to atmospheric gas.
Transpiration is the process of water entering
the atmosphere by evaporating from the leaves of
plants.
The Water Cycle
Most of the water on Earth is held in the ocean.
The sun causes the water to evaporate. As the
water vapor cools it condenses into droplets.
When the droplets become large enough they
return to the Earth’s surface. On land, much of
the precipitation runs along the surface until it
enters a river or stream that carries the runoff
back to an ocean or lake. Water can enter plants
through their roots. The water cycle begins all
over again.
Nutrient Cycles
Nutrients include all the chemical substances
that an organism requires to live. Every organism
needs nutrients to grow and carry out essential
life functions. Like water nutrients are passed
between organisms through cycles.
The three nutrient cycles that play especially
prominent roles in the biosphere are the carbon
cycle, the nitrogen cycle, and the phosphorus cycle.
The Carbon Cycle
Carbon is the key ingredient in all living
organisms. Carbon is also found in the oceans, in
the air, and in certain types of rocks.
Scientists believe the Earth contains approximately
49,000 gigatons of carbon. However, less than 1
percent actively circulates within the biosphere. 71% is
in the oceans, 22% in fossils, 3% in dead organic
matter, and 3% in terrestrial ecosystems.
Carbon Cycle
There are four different kinds of processes involved
in the carbon cycle…
1. Biological
2. Geochemical
3. Biogeochemical
4. Human Impact
Biological Processes
Carbon in the atmosphere is carbon dioxide.
Plants take in carbon dioxide and use the carbon
to build carbohydrates during photosynthesis.
The carbohydrates are passed along the food
web to the consumers.
The carbohydrates are broken down by animals
during respiration and returned to the atmosphere
as carbon dioxide.
Biogeochemical Processes
These are caused by the burial of carbon-rich
remains of organisms and their conversion into
coal and petroleum (fossil fuels) by the pressure
of the overlying earth.
Human Impact
Humans affect the carbon cycle by mining,
burning fossil fuels, and destroying forests.
Nitrogen Cycle
All organisms require nitrogen to make amino acids,
which in turn are used to build proteins.
Nitrogen gas (N2) makes up 78% of our atmosphere.
Nitrogen-containing substances such as ammonia (NH3),
nitrates (NO3-), and nitrites (NO2
-) are found in dead and
decaying organic matter.
Humans add nitrogen to the biosphere in the form of
nitrate - a major component of plant fertilizers.
Nitrogen Cycle
Only certain types of nitrogen-fixing bacteria can use the
gasseous form of nitrogen (N2).
Nitrogen Fixation is when nitrogen-fixing bacteria
convert atmospheric nitrogen into ammonia.
Nitrogen-fixing bacteria live in the soil, and on the
roots of plants called legumes (bean plants).
Nitrogen Cycle
Producers can use the nitrogen in the soil to
make proteins. Consumers eat the producers
and reuse the nitrogen to make their own
proteins. When organisms die decomposers
return nitrogen to the soil as ammonia. Some of
the ammonia will be taken up again by producers.
Denitrification, other soil bacteria will convert the
nitrates into nitrogen gas (N2) returning it to the
atmosphere.
Phosphorus Cycle
Phosphorus is essential to living organisms
because it forms part of important life-sustaining
molecules DNA and RNA.
Inorganic phosphate makes up the the backbone of
DNA and RNA, the molecules of heredity.
Phosphorus Cycle
Phosphorus does not enter the atmosphere. It
remains mostly in the rocks, soil and the ocean
as its inorganic form (Pi).
Phosphorus Cycle
When plants absorb phosphate from the soil or
from water, the plants bind the phosphate into
organic compounds. Organic phosphate travels
through the food web.
Organic compounds are defined as compounds that
contain carbon.
Nutrient Limitation
Primary Productivity is the rate at which organicmatter is created by producers.
A Limiting Nutrient when a nutrient is in shortsupply and it limits the growth of the ecosystem.
Algal Bloom when an aquatic ecosystemreceives a large input of a limiting nutrient itresults in a rapid growth of algae.