Flow of Matter in Ecosystems Flashcards
Biochemical cycling
The cycling of matter through living components (organisms) and non-living components (geosphere, hydrosphere, atmosphere) of an ecosystem
How is carbon cycled through Earth’s reservoirs?
§ Geosphere
□ Earth’s metal core
□ Solid rock
□ Molten rock
□ Soil
□ Sediments
§ Hydrosphere
□ All water in all forms
- Ice
- Vapour in the atmosphere
- Liquid in oceans, rivers, soil, groundwater
§ Atmosphere
□ All the gases surrounding the earth
§ Biosphere
□ The sum of all ecosystems around the earth
□ All places where life can be found
- In the atmosphere, biosphere and hydrosphere
The main forms of carbon in each reservoir
○ Geosphere
- Fossil fuels
- Methane in seafloor sediment
○ Hydrosphere
- Carbonic acid
○ Atmosphere
- Carbon dioxide gas
- Methane
○ Biosphere
- Glucose in producers
- Glucose, proteins, and fats in consumers
- Methane in cattle
Processes of the carbon cycle
○ Photosynthesis
- Carbon dioxide gas is absorbed from the atmosphere into autotrophs and transformed into high-energy carbon compounds (e.g. glucose)
○ Respiration
- Glucose is broken down and carbon dioxide gas is released back into the atmosphere
○ Consumption
- When consumers feed on a producer or another consumer, high-energy carbon compounds are ingested and broken down through respiration
○ Death
- Dead organisms will be decomposed
○ Decomposition
- Decomposers break down complex organic molecules into simpler inorganic forms and return carbon to the soil
- Makes nutrients available for living plants
- Releases carbon dioxide into the atmosphere
○ Diffusion
- Carbon dioxide diffuses in and out of the ocean
□ Carbon dioxide is used by producers in the ocean for photosynthesis
□ In the ocean carbon dioxide is turned into carbonic acid
○ Combustion
- Burning fossil fuels releases carbon back into the atmosphere in the form of carbon dioxide
○ Volcanic eruptions
- Carbon is released as carbon dioxide when volcanoes erupt
○ Weathering
- Carbon stored in rocks and soil is released when the rock breaks down or dissolves in water
Main forms of nitrogen
○ Atmosphere
- Nitrogen gas - 78% of atmosphere
○ Geosphere
- Nitrogen dioxide in soil
○ Biosphere
- DNA, RNA, proteins in animals
- Ammonium ions in bacteria and plants
- Nitrite and nitrate in bacteria
Nitrogen cycle
○ The nitrogen cycle is the biochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates through the atmosphere, geosphere, and biosphere
○ Nitrogen needs to change form to be useful
Nitrogen cycle processes
- Nitrogen-fixing
- Consumption
- Death
- Decomposition
- Ammonification
- Nitrification
- Denitrification
Nitrogen-fixing
§ Nitrogen removed from the atmosphere by
□ Lightning (small amount) N2 converted to NO2
□ Nitrogen fixers in soil (bacteria in the soil)
- Free-living - absorb nitrogen gas from air spaces in soil and build it into amino acids
□ Nitrogen fixers in nodule bacteria
- Specialised bacteria invade the fine root hairs of plants causing the formation of nodules
- This symbiotic relationship provides the bacteria with carbon, and the bacteria deliver additional nitrogen to the plants
Consumption
- Animals consume nitrogen in food (plants and animals)
□ Plants absorb nitrogen from the nitrogen-fixing stage
□ Absorbed nitrogen is converted into nucleic acids and proteins
Death
- Plants and animals die, which produces organic waste
Decomposition
- Decomposers break down dead organisms, urine, and faeces (excretion), returning nitrogen into the soil as ammonium (NH4+)
Ammonification
- Bacteria or fungi within the soil convert the organic matter back to ammonium (NH4+)
Nitrification
- ammonium -> nitrites -> nitrates
- Plants struggle to absorb nitrogen
- Nitrifying bacteria convert ammonium to nitrites
□ Nitrites cannot be absorbed by plants - Other nitrifying bacteria convert
□ Nitrates can be absorbed by plants
Denitrification
- Denitrifying bacteria turns nitrate (NO3-) into nitrogen gas (N2)
- The nitrogen gas is released back into the atmosphere
- Also releases oxygen which can be used by plants growing in waterlogged soils where oxygen is in short supply
