Biogeochemical Cycles: Natural Cycles of Elements

1. Biogeochemical Cycles:
Natural Cycles of Elements
Water, Nitrogen and Carbon

2. Cycles of Elements
Nutrients (water, nitrogen, carbon) are cycled through
the Earth in cycles called the BIOGEOCHEMICAL
CYCLES.
Law of Conservation of Mass
Matter cannot be created or destroyed in chemical
reactions it simply changes forms
No new sources of matter on Earth instead it continuously
cycles through
Matter simply changes in the way that the elements are
bonded together

3. I. Water Cycle

4. 5 Main Processes of the Water
Cycle
1) Evaporation: Water turning from a
liquid into a gas.
Liquid water from
oceans, lakes or other
bodies of water,
changes into water
vapor (gas) and is
released in the
Water Cycle

5. 2) Transpiration:
when liquid water in
plants changes into
water vapor (gas) and
is released into the
atmosphere
Part of photosynthesis
3) Condensation:
water vapor (gas)
changes into liquid
•Ex. Cloud formation,
dew

6. 4) Precipitation: when
water returns to the
Earth’s surface
Water droplets get too
large, they fall out of the
air.
Ex. Rain, snow, hail
5)Runoff- water moving
from a higher elevation
(mountains, etc.) to a
lower elevation (oceans,
lakes, seas, etc.)

7. The Water Cycle
Transpiration
Evaporation
Precipitation
Condensation
Runoff

8. II. Nitrogen Cycle
Nitrogen gas (N2) is naturally found
in the atmosphere
It is the most abundant gas in our
atmosphere.
N2 is
unusable to
most living
things

9. Some bacteria and lightning are able to
change nitrogen gas (N2) into chemicals
called nitrates (NO3), which are usable by
plants.

10. Nitrogen (NO3) in plants is passed on to
an organism when it is eaten

11. Nitrogen (NO3) is returned to the soil by
excretion from animals

12. Or when the animal dies…

13. The nitrogen (NO3) in the soil is changed
back into nitrogen gas (N2) by bacteria that
live in the soil

15. III. Carbon Cycle

16. Carbon is found in the atmosphere as
Carbon Dioxide (CO2)
CO2 is used by plants during
photosynthesis to make food and give
off O2.

17. Animals eat food (plants) for energy.
During cellular respiration (that takes place
in plants and animals), the organism takes in
O2 gives off CO2.
This releases the CO2 back into the
atmosphere (respiration).

18. Some carbon is trapped in dead creatures
and changed into a fossil fuel (coal or oil).
The decomposition of dead organisms
releases carbon back to the atmosphere.

19. Burning of plant material or fossil
fuels, also returns carbon as CO2
back to the atmosphere.

20. The Carbon Cycle

21. Greenhouse Effect
Naturally occurring gasses in the Earth’s
atmosphere that trap heat. They keep the Earth’s
temperature about 60° warmer than it would be
otherwise.
Human Impact:
Change: Increased level of greenhouse gases (such
as CO2, methane, & water vapor)
Cause: Burning of fossil fuels and deforestation
Effect: Global warming

23. Ozone Layer
The ozone layer is a naturally occurring layer of the
stratosphere that absorbs large amounts of
ultraviolet rays.
Human Impact:
Change: Reduction of ozone (O3) detected near
poles
Cause: Release of chlorofluorocarbons (CFC) that
catalyze reactions with ozone molecules
Effect: Increased ultraviolet radiation at the Earth’s
surface