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THE CYCLING OF NUTRIENTS WITHIN ECOSYSTEMS
Biogeochemical Cycles
April 20, 2023Energy Flow in Ecosystems
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Life on Earth depends on recycling essential chemical elements.Biogeochemical cycles move elements between the atmosphere,
hydrosphere, lithosphere, and biosphere.Carbon is a necessary building block for most biomoleculesPhosphorus is necessary for DNA, RNA and the energy molecule
ATPNitrogen is a key component in proteins, DNA, RNA and many
enzymesWater is necessary for most chemical functions
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Energy Flow in Ecosystems
Biogeochemical Cycles
Nutrients cycle between abiotic and biotic components of the ecosystem
General Nutrient cycle model
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Energy Flow in Ecosystems
1. The water cycleWater is essential to all
living thingsTypically found in
oceans, lakes, rivers, ice caps, groundwater (small amount in atmosphere)
Cycles via sublimation, precipitation, evaporation, condensation, consumption, transpiration
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Energy Flow in Ecosystems
The Water cycle
April 20, 2023Energy Flow in Ecosystems
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Water is necessary for most chemical processes in living organisms.
The water cycle includes both biotic and abiotic processes. Water in oceans, rivers etc. evaporates into the atmosphere.
Clouds form when water vapour condenses and water falls back to the ground in the form of precipitation.
Water returns to the ocean etc. through runoff or returns to aquifers through seepage.
Plants take up water and return unused water to the atmosphere through transpiration.
Animals take up water and return it through perspiration, breathing, and elimination
The Water cycle
Precipitation over the sea (283)
Solar heat
Water vapour over the sea
Oceans
Net movement of water vapor by wind (36)
Evaporation from the sea (319)
Evaporation and transpiration (59)
Water vapor over the
land
Precipitation over the land (95)
Surfacewater and
groundwater
Flow of water from land to sea (36)
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Energy Flow in Ecosystems
2. The Carbon cycle
Carbon is essential to building organic molecules
Can be found in the atmosphere (CO2), plants, animals, fossil fuels, soils, sediments
Cycles via photosynthesis, respiration, combustion, consumption
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Energy Flow in Ecosystems
The Carbon Cycle
CO 2 in the atmosphere diffuses into the water.
Both land and aquatic plants take in CO 2 and produce carbohydrates and other biomolecules through photosynthesis.
2. Carbon Cycle
Producers: Plants take in CO2 and make sugar by photosynthesis.
Consumers: Animals eat plants to get energy (respiration) from sugar and make proteins from the carbon. Breath out CO2 as a waste product of respiration.
Animals die and dentritus (decomposers) break down the carbon and other elements back into the soil and air for plants to use again.
Human activities such as burning fossil fuels, and cutting and burning forests puts carbon back into the atmosphere.
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Energy Flow in Ecosystems
CO2 in atmosphere
Burning
Wood and fossil fuels
Cellular respiration
Higher-level consumers
Decomposition
Detritivores
Photosynthesis
Producers
Primary consumers
Detritus
The Carbon cycle
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Energy Flow in Ecosystems
3.The Nitrogen cycle
Found in the atmosphere (it is 80% N2), soils, sediments, water, organisms
Nitrogen is part of important biological molecules and limits plant growth
Nitrogen in nitrate forms are used by plants for production of amino acids and nucleic acids for protein synthesis and DNA
Animals get amino acids by eating plants or animals that have eaten plants.
N2 in the atmosphere is FIXED into ammonia (NH3) by nitrogen fixing bacteria in the soil.
a small amount is fixed during chemical reaction that occur during lightening storms.
April 20, 2023
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Energy Flow in Ecosystems
Nitrogen Fixation by bacteria
Plants need nitrogen but cannot take it in from the air.Bacteria in the soil on the roots of plants take in nitrogen (N2)
and make ammonia (NH4) which plants can then use to get nitrogen.
Ammonification is the breakdown of nitrogen products in waste and decomposing tissue to return it to the cycle.
Denitrification is the conversion of ammonia in the soil to free nitrogen by denitrifying bacteria.
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Energy Flow in Ecosystems
Denitrifying bacteria Assimilation
by plants
Nitrogen (N2) in atmosphere
Amino acids and
proteins in plants and animals
Detritus
Detritivores
Nitrogen-fixing bacteria in root
nodules of legumesDecomposition
Nitrogen fixation Nitrogen-
fixing bacteriain soil
Ammonium (NH4
+ )Nitrifying bacteria
Nitrates (NO3
– )
The Nitrogen cycle
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Energy Flow in Ecosystems
5. The Phosphorous cycle
Important component of many biological molecules (nucleic acids, ATP)
Found in rocks in great amount, some in soils and water
Cycles through weathering, taken up by organisms, sedimentation
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Energy Flow in Ecosystems
The Phosphorus Cycle
Phosphorus in the rocks leaches into the soil where it is taken up by plants.
Producers make nucleic acids and when they are eaten pass the phosphorus through the food chain to consumers.
Phosphorus reenters the soil through decomposition and waste.