Nutrient Cycles Flashcards
What is a nutrient cycle?
The process(es) by which certain nutrients pass through all three elements of the biosphere
What are the four main nutrient cycles?
Water
Oxygen
Nitrogen
Carbon
What is precipitation?
Any process which causes water to move from the atmosphere to the earth
What are examples of precipitation?
Rain Snow Fog Hail Dew Frost
What is hygroscopic water?
The layer of water that adheres tightly around soil particles
What is capillary water?
Water that is found between soil particles
What kind of soil water is easily absorbed by plant roots?
Capillary water
What three things can happen to water that falls to the earth’s surface?
Absorbed by the upper layers of soil
Infiltration
Water run-off
What happens to water that is absorbed by the upper layers of soil?
Forms hygroscopic and capillary water
What is infiltration?
The process by which water is absorbed by the soil
What happens during infiltration?
Some water filters through the upper layers of soil to the water table
What is gravitational water?
The water that filters through to the water table
What occurs during water run-off?
Some of the water runs off above ground and forms streams and rivers
What do streams and rivers do?
They flow into lakes and oceans
What is the water table?
The upper surface of the saturated layer of groundwater
It is in the deeper layers of the soil
What are springs?
Groundwater that has reached the surface again
In what two ways can water reach the atmosphere?
Through evaporation
Through transpiration
What is evaporation?
The process whereby water particles les change to gas, but only on the surface of water (not boiling, can occur at any temperature)
How does transpiration allow water to enter the atmosphere?
When plants transpire they lose water to the atmosphere in the form of water vapour
What happens to water vapour in the atmosphere?
It condenses to form clouds
How would you summarise the water cycle?
Precipitation Surface run-off, capillary water and infiltration Springs (optional) Evaporation and transpiration Condemnation Precipitation
What are wetlands?
Semi-aquatic ecosystems
What sort of habitats are included in wetlands?
A wide range of inland and coastal habitats
Lagoons
Marshes
Estuaries
How are wetlands linked?
By rivers and streams
How do wetlands improve the environment?
Regular water supply
It is filtered naturally by vegetation
The effects of floods and droughts are reduced
They have a great biodiversity
What are some characteristics of wetlands?
They have a high water table
The soil has a high water-holding capacity
Hydrophytes are abundant
What are examples of plants that are commonly found in wetlands?
Bulrushes (Typha capensis)
Arum lily (Zantedeschia aethiopica)
Red-hot poker (Kniphofia caulescens)
What are the four main areas where oxygen occurs?
Atmosphere
Water masses
Rocks
Living organisms
What is the main source of oxygen on earth?
Photosynthetic organisms
What are photosynthetic organisms?
Plant life on land
Green algae
Phytoplankton
What substances are used and formed during photosynthesis?
Carbon dioxide
Carbohydrates and oxygen
What substances are used and formed during respiration?
Oxygen and carbohydrates
Carbon dioxide and water
Why do decomposers need oxygen?
They need it to break down organic matter and release CO2
How is oxygen responsible for surface weathering of rocks?
It combines with silicon (forms silicates) and iron (forms rust). These compounds then break away from the rocks
What does lichen do?
Break down rocks and release oxygen and nutrients for living organisms
How is oxygen transferred from the atmosphere to the rocks?
Through surface weathering
How is oxygen transferred from the rocks to living organisms?
Through weathering
How is oxygen transferred from living organisms to water masses?
Photosynthesis
How is oxygen transferred from water masses to living organisms?
Through respiration and decomposition
How is oxygen transferred from living organisms to the atmosphere?
Through photosynthesis
How is oxygen transferred from the atmosphere to living organisms?
Through respiration and decomposition
Why is Nitrogen essential for living organisms?
They need it to form amino acids, which are the building blocks of proteins
In what form is Nitrogen found in the atmosphere?
As “free” N2
What is the only form of Nitrogen that plants can absorb?
Nitrates (NO3-)
What are the two ways in which N2 is converted into NO3-?
Electrical fixation
Nitrogen-fixing bacteria
What is electrical fixation?
It is when lightning and rain convert N2 into NO3- through a chemical reaction (induced by the heat of the lightning)
What are the two types of nitrogen-fixing bacteria?
Free-living soil bacteria
Mutualistic nodule bacteria
What are free-living soil bacteria?
Bacteria that exist in the spaces between soil particles
They absorb the Nitrogen in these spaces and convert it into NO3-
What are mutualistic nodule bacteria?
Bacteria that live on the roots of legumes
They convert free Nitrogen into nitrates for the plant
In return, the plant provides food and a secure habitat for the bacteria
What is assimilation?
The process whereby plant roots absorb Nitrogen in the form of nitrates
What is Nitrogen used for in plants?
To form plant proteins
How do animals obtain Nitrogen?
By eating the plants
What happens to the Nitrogen in plants and animals when they die?
The proteins in their bodies are broken down into ammonia by decomposition bacteria
What is ammonification?
The process whereby proteins are broken down into ammonia by decomposition bacteria
What is another way in which Nitrogen becomes ammonia?
Through the excretion of urea by animals
This is then converted into ammonia (NH3)
What happens to ammonia in the soil?
It is converted into nitrites by nitrifying bacteria
What happens to nitrites in the soil?
It is converted to nitrates by nitrification by nitrifying bacteria
What is nitrification?
The process whereby ammonia is converted into nitrates by nitrifying bacteria
What two things can happen to nitrates in the soil?
Can be absorbed by plants
Can be converted into N2 by denitrifying bacteria
What is denitrification?
The process whereby nitrates are converted to N2 by denitrifying bacteria
Summarise the Nitrogen cycle, mentioning the origin, the destination, the process, the form in which Nitrogen is being transferred, and the cause at every step
- Atmosphere to soil, N2 to NO3-, fixation, lightning or bacteria
2a. Soil to plant, NO3- to plant proteins, assimilation, plant roots
2b. Soil to atmosphere, NO3- to N2, denitrification, denitrifying bacteria
3a. Plants to animals, plant proteins to amino acids, eating, animals
3b. Plant to dead organic material, plant proteins, death, cause varies
4a. Animals to dead organic material, animal proteins, death, cause varies
4b. Animals to ammonia, amino acids to urea to ammonia, excretion, metabolism - Dead organic material to ammonia, proteins to NH3, decomposition, decomposition bacteria
- Ammonia to nitrites, NH3 to NO2-, nitrification, nitrifying bacteria
- Nitrites to nitrates, NO2- to NO3-, nitrification, nitrifying bacteria
Why is carbon essential for life?
It is an important component of organic compounds: carbohydrates, proteins, lipids, nucleic acids and vitamins
In what form does carbon occur in the atmosphere?
Carbon dioxide
CO2
What are the five main places where carbon can be found?
Atmosphere Plants Animals Dead organic material Fossil fuels
How do plants obtain Carbon?
Through photosynthesis
How do animals acquire carbon?
By eating plants
How is carbon transferred to the soil?
When plants and animals die
What can sometimes happen to dead organic material?
It can form fossil fuels
How are fossil fuels formed?
Through fossilisation
What happens during fossilisation?
Dead organic material is compressed to form fossil fuels
What are examples of fossil fuels?
Coal
Oil
How many ways are there for carbon dioxide to return to the atmosphere?
Three
What are the three ways in which CO2 returns to the atmosphere?
Cellular respiration
Decomposition
Combustion
How does cellular respiration cause CO2 to be released into the atmosphere?
During cellular respiration, organic compounds are broken down in the presence of oxygen and energy, water and CO2 are released
How does decomposition cause CO2 to be released into the atmosphere?
Decomposers break down the organic compounds in dead plants and animals and release carbon in the form of CO2
What is combustion?
Burning
How does combustion cause CO2 to be released into the atmosphere?
Wood and fossil fuels release CO2 during combustion
Summarise the carbon cycle, stating origin, destination and the process by which it is transferred
Atmosphere to plants through photosynthesis
Plants to atmosphere through respiration and combustion
Plants to animals through eating
Animals to atmosphere through respiration
Plants and animals to dead organic matter through death
Dead organic matter to atmosphere through decomposition
Dead organic matter to fossil fuels through fossilisation
Fossil fuels to atmosphere through combustion
What happens when nutrient cycles do not function correctly?
It leads to negative consequences
Give an example of a negative consequence caused by a nutrient cycle imbalance
Climate change
How is climate change causes by a nutrient cycle imbalance?
Too many greenhouse gases (incl. carbon dioxide) in the atmosphere
Why is an excess of greenhouse gases a bad thing?
They trap the heat of the earth’s atmosphere and cause the earth’s temperature to rise
What has caused this carbon cycle imbalance?
Human activities
What human activities have caused this carbon cycle imbalance?
The burning of fossil fuels has increased the amount of CO2 in the atmosphere
Deforestation has decreased photosynthesis
What are some possible solutions to the carbon cycle imbalance?
Reduce the use of fossil fuels
Control industrial gas emissions
Cooperation to reduce the release of greenhouse gases
How do you reduce the use of fossil fuels?
By using alternative energy sources
Give some examples of alternative energy sources
Solar energy
Wave energy
Wind energy
