Transcript 09.02.11 Cycling of Materials in Ecosystems

Cycling of Materials in
Ecosystems
Cycles within an Ecosystem
Water Cycle
Carbon Cycle
Phosphorous and Nitrogen Cycle
Cycles within Ecosystems
• Almost everything within an ecosystem
is recycled.
• Water, carbon, nitrogen & phosphorus
pass from the nonliving environment to
living organisms & then back to the
environment.
Water Cycle
• Water is the most important, nonliving component of the ecosystem.
• Nonliving cycle: involves
condensation, precipitation, &
evaporation.
• Living cycle: involves plants in a
process called transpiration.
Water Cycle
• Nonliving portion:
– Water vapor, as it cools, condenses in the
form of clouds and falls to the Earth’s
surface as precipitation (as rain, snow, etc)
– Then water evaporates (turning from a
liquid to a gas) and re-enters the
atmosphere
• Living portion:
– Water is absorbed by roots of plants
– After passing through the plant, the water
evaporates from the leaves in a process
called transpiration
Carbon Cycle
– Carbon dioxide in the air (or dissolved
water) is used by photosynthesizing plants,
algae and bacteria as raw material to build
organic molecules.
– What does that mean? Autotrophs take in
carbon dioxide to help make food in order
to grow and survive
– Involves:
• Respiration (breathing where CO2 is a
by product)
• Combustion (burning)
• Erosion (limestone)
Phosphorous and Nitrogen
Cycle
• You need phosphorous and nitrogen to build
proteins and nucleic acids (part of DNA)
• Since more organisms are unable to use
nitrogen gas (N2), nitrogen fixing bacteria
bind nitrogen with hydrogen to form
ammonia (NH3)
• What does that mean? We need nitrogen, but
we can’t use pure nitrogen gas (N2) so
certain bacteria convert N2 into a usable
forms (ammonia)
Phosphorous and Nitrogen
Cycle
• Stages:
– Assimilation (absorption of nitrogen gas,N2, by
plants)
– Ammonification (production of ammonia, NH3,
by bacteria during organism decay)
– Nitrification (production of nitrate from
ammonia)
– Denitrification (conversion of nitrate to N2)