2.6: cycling of Matter in Ecosystems
pg. 48
Key Concepts:
4. Human activities influence biogeochemical cycles such as the water and carbon cycles.
Evidence of Learning: Students can …
- describe the main pathways of the water cycle.
- explain how the carbon cycle is related to energy flow in an ecosystem.
- understand how the carbon cycle and the water cycle affect atmosphere temperatures.
Biogeochemical Cycle
Biogeochemical Cycle: the movement of matter through the biotic and abiotic
environment.
- All things are made up of matter.
- All living things require water and are made up of water.
- Matter can not be created or destroyed.
- Chemicals (nutrients) are continuously consumed, rearranged, stored, used, and released
by organisms.
- This movement of chemicals (nutrients) are known as cycles.
Water Cycle
Water Cycle: the series of processes that cycle water through the environment.
- Most water is cycled through the abiotic environment.
- Water is evaporated from lakes, rivers, streams, oceans, and the ground, and appears as
water vapour in the atmosphere.
- Water condenses and falls from the sky as rain, snow, hail or sleet.
- Plants and other organism will use the water as needed, Plants lose water through
transpiration and enters the atmosphere again.
Figure 3: The Water Cycle
The Carbon Cycle
Carbon Cycle: the biogeochemical cycle in which carbon is cycled through the
lithosphere, atmosphere, hydrosphere, and biosphere.
- Carbon is cycled between abiotic and biotic parts of the ecosystem.
- Carbon dioxide from the air is used by plants during photosynthesis, and returned back
to the atmosphere during cellular respiration.
- Animals obtain carbon from the food they eat and return carbon dioxide to the
atmosphere also by cellular respiration.
- A large quantity of carbon is not cycled but trapped in rich deposits, forming fossil fuels,
such as; oil, gas, and coal.
- As organisms die the carbon which make up their bodies is trapped in the ground as
they decompose.
- Aquatic organism with shell made up of carbon (chitin) sinks to the bottom of the ocean,
trap for millions of years.
Figure 5: The carbon cycle results in the long-term and short-term storage of carbon.
- Humans have a negative affect on the carbon cycle.
- Since the industrial revolution, human have released large quantities of carbon back into
the atmosphere.
- The burning of fossil fuels has increase Carbon atmosphere concentration, causing
global climate change, and disrupting ecosystems.
- Deforestation decreases the ability to take carbon out of the atmosphere.
The Nitrogen Cycle
Nitrogen Cycle: the series of processes in which nitrogen compounds are moved through
the biotic and abiotic environment.
- The atmosphere is 72% nitrogen, but this is not usable by organisms.
- Lightning and ultraviolet light can convert nitrogen gas into nitrate and nitrites.
- Bacteria can take nitrogen out of the atmosphere by nitrogen fixation, creating nitrates
nitrites, and ammonia, which can be used by plants.
- Animals eat plants and obtain nitrogen compounds required for life.
- Decomposers break down dead organic matter, releasing nitrogen back into the
environment. Denitrifying bacteria release nitrogen gas back into the atmosphere.
Figure 6: The nitrogen cycle
Check Your Learning
Questions 1 – 10, page 51
Summary:
- Matter is cycled through ecosystems via biogeochemical cycles.
- Water can occur in all states (solid, liquid, and gas) as it moves through the water cycle.
- Carbon moves between the abiotic and biotic components of the ecosystem via
photosynthesis and cellular respiration.
- Nitrogen is removed from the atmosphere by soil micro-organisms undergoing nitrogen
fixation and returned to the atmosphere by denitrifying bacteria.
- Carbon, oxygen, and hydrogen are readily available to living organisms, but nitrogen is
more difficult to obtain.
- Human activities disrupt biogeochemical cycles.