C4.2 - nutrient cycling in ecosystems (4g) Flashcards
what is the recycling of chemical elements in ecosystems like, including the roles of organisms?
- all elements used by living organisms, not just carbon, are recycled in ecosystems
- producers obtain inorganic nutrients for the abiotic environment
- decomposers play a key role in this recycling by breaking down organic matter, releasing the nutrients trapped in the biomass of dead organisms, and returning the nutrients to the soil
- nutrients are not lost but transformed into different compounds
what are carbon sources?
there is a net release of carbon dioxide, when the rate of respiration exceeds that of photosynthesis
what are carbon sinks?
there is a net uptake of carbon dioxide, when the rate of photosynthesis exceeds that of respiration
what is the relationship between photosynthesis and carbon sink size?
the higher the relative rate of photosynthesis, the larger the carbon sink that is formed
what are examples of carbon sinks?
carbon sinks include: limestone, oceans, permafrost in frozen tundra, and trees
what is the role of combustion?
combustion of fuels release carbon dioxide into the atmosphere
what are examples of combustible carbon sinks?
biomass, peat and fossil fuels are combustible carbon sinks
how can combustion occur naturally?
combustion can occur naturally from lightning strikes and lava flows
what is primary production?
primary production is the accumulation of carbon compounds in biomass by autotrophs
how is biomass accumulated in primary production?
this occurs through fixation of carbon through photosynthesis
what can be observed when biomass accumulates?
biomass accumulates when autotrophs and heterotrophs grow or reproduce
what is biomass?
what are the units?
biomass is the mass of all living organisms
- measured in mass of carbon, per unit area, per unit time (g m-2 yr-1)
what is a biome?
a large community of plants and animals
- biomes vary in their capacity to accumulate biomass
what is the relationship between photosynthesis and biomass production?
factors increasing the rate of photosynthesis relative to respiration should increase biomass production
what is secondary production?
secondary production is the accumulation of carbon compounds in biomass by heterotrophs
- carbon compounds (eg, proteins and lipids) are ingested during feeding, the large molecules are digested to form small soluble molecules that are absorbed
- the heterotroph then assimilates these small molecules to form its own carbon compounds
why is secondary production lower than primary production?
secondary production is lower than primary production in an ecosystem because biomass is lost when:
- carbon compounds are converted to carbon dioxide and water in cell respiration
- waste products (eg, urea) are excreted
how are respiration and photosynthesis dependent on each other?
aerobic respiration requires atmospheric oxygen produced by photosynthesis, whilst photosynthesis requires atmospheric carbon dioxide produced by respiration
what interaction is there between autotrophs and heterotrophs?
the fluxes involved per year are huge, in the region of 200 gigatonnes of carbon per year, so this is a major interaction between autotrophs and heterotrophs
what are carbon fluxes?
carbon fluxes are movement of carbon between stores
why is photosynthesis a negative flux?
photosynthesis is a negative flux because it removes carbon dioxide from the atmosphere
why is respiration a positive flux?
respiration is a positive flux because it adds carbon dioxide to the atmosphere
what is the keeling curve?
a daily record of global atmospheric carbon dioxide concentration from the Mauna Loa Observatory, in Hawaii, started in 1958 by Keeling
what is the annual fluctuation analysis of the keeling curve?
- during the summer and autumn, when greater day lengths and light intensity plus a larger biomass of plant increases the rate of photosynthesis, the rate of photosynthesis exceeds the rate of carbon dioxide production (eg, from respiration and combustion) there is a decrease in the carbon dioxide concentration
- during winter and spring, when there is a relatively low rate of photosynthesis, the carbon dioxide fixation by photosynthesis is slower than its production so there is an increase in carbon dioxide concentration
what is the long-term analysis of the keeling curve?
there is an increase in carbon dioxide concentration over time because over the course of each year more carbon dioxide is released into the atmosphere by respiration, combustion and weathering, than is fixed from the atmosphere by photosynthesis
what is the carbon cycle, including the roles of photosynthesis, feeding and respiration?
photosynthesis: absorption of carbon dioxide from the atmosphere or water by autotrophs, which use photosynthesis to fix carbon dioxide and form carbohydrates
- thus plants act as carbon sinks
- humans use plant products for making cloth/household items/building/arts creating a reservoir for carbon
feeding: plants are eaten by consumers (moving carbon in the food chain)
- carbon compounds are transferred through food chains, for example as protein
respiration: in plants and animals converts carbohydrates to carbon dioxide and releases it into the atmosphere/water
respiration: saprotrophs and detritivores digest dead plants releasing carbon dioxide, in the process of decomposition
peat forms when decomposition of dead plant matter is incomplete, storing carbon in a carbon sink
- peat forms when organic matter is not fully decomposed because of acidic and/or anaerobic conditions in waterlogged soils
fossilization of carbon stores it as coal, oil, or natural gas, as a carbon sink
carbon dioxide dissolves in aquatic ecosystems, forming carbonic acid
- reef-building corals and molluscs use calcium carbonate to build shells and exoskeletons
- hard parts, shells and exoskeletons precipitation of calcium carbonate to form limestone and creating a carbon sink
methane is produced from organic matter in anaerobic conditions (by methanogenic archea)
- some methane diffuses into the atmosphere and some accumulates in the ground
- methane is oxidized to carbon dioxide (and water) in the atmosphere
