12 Questions
What does the term 'biogeochemical' indicate in the context of substance cycling?
Biological, geological, and chemical factors are involved
Which term describes the cycling pathway by which chemical elements required by life moves through both biotic and abiotic compartments of Earth?
Biogeochemical cycle
Which elements are mentioned as part of the chemical nutrients that cycle through biotic and abiotic compartments?
Carbon, Oxygen, Nitrogen, Phosphorous, Sulphur
In which type of cycle do elements move through the atmosphere?
Gas cycle
What is a common feature of the Carbon cycle, nitrogen cycle, and oxygen cycle mentioned in the text?
They are examples of Gas cycles
Why can't plants and animals use nitrogen directly in its elemental form from the atmosphere?
Nitrogen in its elemental form is not chemically reactive for utilization
During nitrogen fixation, which process converts free nitrogen of the atmosphere into a biologically available form of nitrogen?
Ammonification
Which type of fixation involves the conversion of atmospheric nitrogen into nitrites and nitrates by free-living bacteria and blue-green algae?
Physiochemical fixation
How do free-living bacteria like Azobacter and Clostridium fix nitrogen from the atmosphere?
By breaking down nitrogen into smaller molecules
What is the final product of the physiochemical fixation process that occurs during lightning and electric discharge in clouds?
Nitrites
Which step in the nitrogen cycle involves the conversion of ammonia into nitrates and nitrites?
Denitrification
What happens to the nitrogen cycle when denitrification occurs?
Nitrates are converted into ammonia
Study Notes
Biogeochemical Cycles
- A biogeochemical cycle is the pathway by which chemical elements required by life move through both biotic and abiotic compartments of Earth.
- The term "biogeochemical" indicates the involvement of biological, geological, and chemical factors.
Cycles of Substances
- Chemical elements such as Carbon, Oxygen, Nitrogen, Phosphorous, Sulphur, and Water cycle through the environment.
- Elements can cycle in either gas cycles or sedimentary cycles.
- Gas cycles involve the movement of elements through the atmosphere.
- Sedimentary cycles involve the movement of elements from land to water to sediment.
Nitrogen Cycle
- Nitrogen is a crucial element, making up 78% of Earth's atmosphere, and is a component of amino acids, proteins, vitamins, DNA, and RNA.
- Plants and animals cannot use atmospheric nitrogen directly and require it in a biologically available form.
- The nitrogen cycle consists of various steps: nitrogen fixation, nitrogen assimilation, ammonification, nitrification, denitrification, and sedimentation.
Nitrogen Fixation
- Nitrogen fixation is the process by which atmospheric nitrogen is converted into biologically available nitrogen.
- There are four ways of nitrogen fixation:
- Physiochemical fixation: occurs during lightning and electric discharge in clouds, producing nitrogen oxides that dissolve in water to form nitrates and other nitrogenous compounds.
- Biological nitrogen fixation: occurs through free-living bacteria, symbiotic bacteria, and blue-green algae, which convert atmospheric nitrogen into nitrites and nitrates.
Biological Nitrogen Fixation
- Free-living bacteria, such as Azobacter and Clostridium, fix atmospheric nitrogen in the soil by combining gaseous nitrogen with hydrogen from the respiratory pathway to form ammonia.
Test your knowledge on the cycling of chemical elements through the biosphere, lithosphere, atmosphere, and hydrosphere. Explore how biological, geological, and chemical factors play a role in these essential cycles.
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