Cycles of Nutrients

Carbon

Essential element in all living organisms; used for structure and energy storage and the main form of carbon in the atmosphere is carbon dioxide

Role of carbon in organisms

Structural component of organic molecules and chemical energy storage

Greenhouse gas and Carbon dioxide

Gas that traps heat in the atmosphere and carbon dioxide traps heat and prevents Earth from freezing but excess causes global warming

Anthropogenic activity

Human activities that increase carbon dioxide in the atmosphere

Fossil fuels

Formed from dead plants buried over millions of years and burning them release carbon dioxide into the atmosphere

Carbon cycle

Movement of carbon between biotic and abiotic environments

Photosynthesis

Process that removes carbon dioxide and forms carbohydrates

Carbon fixation

Removal of carbon dioxide during photosynthesis

Photosynthesis equation and the energy source.

6CO2 + 6H2O → C6H12O6 + 6O2, energy source - sunlight

Respiration

Process that returns carbon dioxide to the atmosphere

Aerobic respiration

Breakdown of glucose using oxygen to release energy and carbon dioxide

Respiration equation

C6H12O6 + 6O2 → 6CO2 + 6H2O

Combustion

Burning of fuels that releases carbon dioxide

Natural combustion

Forest fires and natural events

Human combustion

Transport, cooking and industry

CO2 in water reaction

CO2 + H2O → HCO3- + H+

Ocean carbon storage

Oceans act as carbon sinks

Weathering & Sedimentation

Breakdown of rocks releasing or storing carbon | Removal of carbon into rocks and sediments

Limestone formation

Formed from skeletal remains of organisms

Chalk formation

Formed from calcium carbonate deposits

Calcium carbonate

CaCO3 found in limestone and chalk

Termites and their role

Break down cellulose and release carbon dioxide Return carbon to ecosystem

Fungi and their role

Decompose dead organic matter, release carbon dioxide and methane during decomposition

Methane

Gas released during decomposition that later forms carbon dioxide

Fungal decomposition

Recycles nutrients and carbon

Dung beetles and their role

Recycle carbon and nutrients from animal waste, Return carbon to soil and food chain

Dung pats

Source of carbon and nutrients for soil organisms

Soil microflora

Fungi, bacteria, protozoa and earthworms

Human impact on carbon cycle

Burning fossil fuels increases CO2

Effect of human activity

Global warming and air pollution

Carbon sinks

Oceans, forests and soil that store carbon

Global warming

Increase in Earth's temperature due to greenhouse gases

Air pollution

Increase in harmful gases in atmosphere

Alternative energy

Solar, wind and hydropower

Solar energy, wind energy and hydropower

Energy from sunlight, Energy from moving air, energy from moving water

Benefit of alternative energy

Reduces carbon dioxide and pollution

Nitrogen and the role of nitrogen in organisms

Essential element for amino acids, peptides, polypeptides, and proteins.Used by plants to build proteins, which are then eaten by consumers

Nitrogen forms and Nitrogen Availability

Elemental nitrogen (N2), ammonia (NH3), nitrate (NO3-), amino acids, nucleic acids. Primary producers can use nitrogen only after it is converted from N2 to NH3

Nitrogen scarcity

Nitrogen is abundant in the atmosphere but largely inaccessible, limiting primary productivity

Nitrogen fixation

Process that reduces nitrogen to ammonium ions (NH4+) or ammonia; catalyzed by nitrogenase

Nitrogenase

Enzyme that catalyzes nitrogen fixation

Nitrogen-fixing bacteria

Free-living (Azotobacter), symbiotic (Rhizobium), cyanobacteria (Nostoc)

Nitrogen fixation in legumes

Bacteria in root nodules convert atmospheric nitrogen to usable forms

Lightning fixation

High-energy lightning converts nitrogen and oxygen into nitrogen oxides (NO, NO2) that dissolve in rainwater

Nitrogen fixation by lightning

Equation: N2 + O2 → 2NO

Nitrification

Series of oxidations converting ammonium compounds to nitrates, releasing energy

Nitrite-forming bacteria

Equation: NH4+ + O2 → NO2- + energy (Nitrosomonas)

Nitrate-forming bacteria

Equation: NO2- + O2 → NO3- + energy (Nitrobacter)

Plant absorption of nitrates

Nitrates absorbed by roots and converted to NH4+, then amino acids, peptides, proteins

Denitrification

Process where denitrifying bacteria break down nitrates into N2 and N2O

Denitrifying bacteria

Examples: Pseudomonas, Thiobacillus

Denitrification equations

2NO3- → 2NO2- → N2 + O2 or N2 + N2O

Denitrification conditions

Prevalent in waterlogged soils with low oxygen and decomposable organic matter

Ammonification

Decomposition of organic nitrogen into ammonium ions (NH4+)

Human impact on nitrogen cycle

Addition: fertilisers, leguminous crops; Removal: overharvesting, pollution

Fertilizers effect

Add nitrogen compounds to soil, increasing nitrogen fixation

Leguminous crops effect

Increase nitrogen-fixing microorganisms in soil

Fossil fuel burning effect

Increases atmospheric N2O, NH3, NO

Aquatic pollution

Nitrate runoff from fertilisers causes eutrophication and pollution in water bodies

Eutrophication

Excess nutrients lead to algae blooms, oxygen depletion, and harm to aquatic life

Nitrogen cycle diagram key

N2 in atmosphere → nitrogen fixation → NH3/NH4+ → nitrification → NO2-/NO3- → assimilation by plants → amino acids/proteins → denitrification back to N2

Importance of nitrogen transformations

Supports productivity in biosphere; depends on microbial activity

Phosphorus

Essential element in energy transfer, DNA, RNA, bones, and teeth

ATP (Adenosine Triphosphate)

Energy-rich phosphate-containing compound important in cellular energy transfer

Role of phosphorus in plants

Used to form nucleic acids and incorporated into plant tissues

Role of phosphorus in animals

About 80% found in teeth and bones; essential for vertebrates

Phosphorus as a limiting factor

In aquatic ecosystems, limits primary productivity

Excess phosphorus effect

Leads to algal blooms and eutrophication in aquatic systems

Phosphorus cycle type

Sedimentary biogeochemical cycle; no gaseous phase

Largest phosphorus reservoir

Sedimentary rocks

Phosphate transport

Removed from rocks by weathering and enters soil and water

Phosphate movement to waterbodies

Occurs via erosion rather than leaching

River transport of phosphates

Rivers and streams carry phosphates to oceans

Ocean phosphate storage

Accumulation in deep ocean sediments and continental shelves

Plant uptake of phosphates

Plants absorb phosphate ions from soil

Animal uptake of phosphates

Phosphates move to animals when herbivores eat plants; carnivores eat herbivores

Return of phosphates to soil

Through animal waste and decomposition of organic matter by bacteria

Aquatic phosphorus cycle

Phosphate sinks in sediments; phosphates re-enter water when sediments stir

Fertilizer runoff effect

Excess phosphates enter waterways, causing eutrophication

Eutrophication problem

Causes algal blooms, oxygen depletion, and harms aquatic life

Dissolved oxygen depletion

Death and decomposition of algae by bacteria consume oxygen

Formation of foul gases

H₂S, NH3, thioalcohols produced in anoxic water

Ammonia forms

Un-ionised ammonia (NH3, toxic) and ionised ammonium (NH4+, less toxic)

Ammonia toxicity

Un-ionised NH3 predominates at high pH and is lethal to fish

Ammonium ion (NH4+)

Predominates at low pH and is non-toxic at normal concentrations

Effects of eutrophication

Anoxia, fish kills, algal blooms, decreased productivity, increased turbidity, toxic substances, species composition changes

Human activities impacting phosphorus

Use of commercial synthetic fertilizers, mining calcium phosphate, superphosphate production

Agricultural runoff effect

Large quantities of phosphates enter aquatic systems

Deforestation effect

Cutting tropical rainforests affects phosphorus cycling

Detergents effect

Contribute phosphates to waterways

Phosphorus in soil

Absorbed by plants, incorporated into plant tissue

Phosphorus in animal tissue

Returned to soil via urine, feces, decomposition

Geologic uplift effect

Sedimentary rocks re-exposed on land, continuing the cycle

Water

Covers about 70% of Earth's surface; essential for life and ecosystem functions

Water cycle

Also called the hydrologic cycle; describes movement of water through Earth’s spheres

Phases of water in cycle

Solid, liquid, gas

Spheres in water cycle

Atmosphere, lithosphere, hydrosphere, biosphere

Evaporation

Water changes from liquid to gas; includes evapotranspiration from plants

Driving force of evaporation

Sun provides energy to heat water for evaporation

Condensation

Water vapor cools in atmosphere forming clouds and fog