Three key nutrient cycles - water, carbon, and nitrogen - allow organisms to obtain needed nutrients. The water cycle is driven by the sun and involves evaporation from bodies of water and transpiration from plants, condensation in the atmosphere, and precipitation back to the ground. The carbon cycle moves carbon between living things and the atmosphere, with photosynthesis fixing carbon and respiration releasing it. Nitrogen gas makes up 80% of the atmosphere but is not directly usable, so bacteria play a crucial role in nitrogen fixation, making nitrogen bioavailable to plants through processes like nitrification and ammonification.

1. How do organisms
obtain nutrients?
Although energy moves through
ecosystems in a one-way direction,
nutrients are recycled.
Three basic nutrient cycles are
present in all ecosystems allowing
organisms to obtain needed
nutrients to function effectively.

2. Water Cycle
Driving force is the sun.
Consists of the alternation between
evaporation and condensation.
Most water returned to the
atmosphere comes from evaporation
from the oceans.

3. Water Cycle

4. Water Cycle
Terminology
Water vapor- gaseous form of water in
atmosphere
Evaporation- liquid water from bodies of
water becomes gas returned to
atmosphere.
Transpiration- loss of water by land plants
Condensation- process which water
molecules gather in atmosphere “change
from gas to liquid” when cooled.
Precipitation- water falls from atmosphere
to ground (rain, snow, sleet, or hail)

5. Why is the water cycle
important?
Water is the most important
nonliving (abiotic) component of an
ecosystem.
Water essentially determines what
organisms we find in an ecosystem.
What is the major difference
between the tropical rainforest and
the desert? Why?

6. Carbon Cycle
Carbon cycles between the living
organisms and the non-living
components of ecosystem.
Carbon exists in the atmosphere as
carbon dioxide (CO2)
Why do living things need carbon?

7. Carbon Cycle

8. Carbon Cycle
Terminology
Photosynthesis- process where sunlight,
CO2 and H2O is used to make food
Respiration- process by which animals
take in O2 given off by plants and give off
CO2
***THE OPPOSITE OF
PHOTOSYNTHESIS!
Fossil fuels- formed by pressure applied
to dead organisms that are buried in
sediment. They are carbon and release
CO2 when burned.
Combustion- burning of fossil fuels

9. Why is the carbon cycle
important?
Energy for living organisms
(carbohydrates).
***Humans in the United States are
altering this cycle.
Burning of too many fossil fuels is
releasing extra CO2 into the
atmosphere creating “global
warming” due to increased
greenhouse effect.

10. Nitrogen Cycle
The atmosphere contains 80%
nitrogen gas (N2).
However, this nitrogen can not be
used by most living things.
Bacteria are the only organisms that
are use nitrogen directly from the
environment.
They can fix nitrogen for plants to
use

11. Nitrogen Cycle

12. Nitrogen Cycle
Terminology
Nitrogen fixation- nitrogen gas in
atmosphere to ammonia (bacteria in
soil, lightning)
Nitrification- ammonia to nitrate
(bacteria in soil)
Assimilation- absorption of ammonia
and nitrate by plants
Ammonification- break down of dead
organisms returns nitrogen to soil
(bacteria and fungi) as ammonia.
Denitrification- conversion of
ammonia back to nitrogen gas
(decomposers).

13. Why is the nitrogen
cycle important?
Why is nitrogen important to
living things?
How do plants obtain nitrogen?
Why are bacteria SO important
to the nitrogen cycle?
How do we obtain nitrogen?