Nutrient Cycles Flashcards
What is the role of pathobionts?
- They feed on dead organic matter or waste products and break them down so they can be recycled.
- They secrete enzymes and digest their food externally. They then take in the nutrients they need and leave the rest in the soil that can be used for the growth of plants.
What is a mycorrhizae relationship?
Fungi are made up of long, thin strands that attach to the roots of plants and increase their surface area. The increase in surface area increases the uptake of water and mineral ions by the roots. It also allows the fungi to get important biological molecules from the plant.
What do plants need nitrogen for?
To make proteins and nucleic acids.
Why does the nitrogen cycle need to occur?
Plants can’t use the nitrogen from the air, so they need it to be converted to nitrogen-containing compounds in the soil.
What are the four stages of the nutrient cycle?
- Nitrogen fixation
- Ammonification
- Nitrification
- Denitrification
What happens in nitrogen fixation?
Nitrogen-fixing bacteria turn nitrogen in the air into ammonia which becomes ammonium ions in the soil.
What happens in ammonification?
Saprobionts break down dead organic matter or waste products that contain nitrogen. This releases ammonia and they become ammonium ions in the soil.
What happens in nitrification?
Nitrifying bacteria turn the ammonium ions into nitrites. Then they turn the nitrites into nitrates.
What happens in denitrification?
Denitrifying bacteria turn the nitrogen-containing compounds back into nitrogen in the air.
Why are fertilizers needed?
The crops are removed so the dead organic matter can’t be broken down by decomposers. The nutrients are not returned to the soil.
What are artificial fertilizers?
They are made up of pure chemicals in the form of powders and pellets.
What are natural fertilizers?
They include manure, compost and other organic matter.
How does leaching occur?
If more fertiliser is applied than the crops can use, the fertilisers can dissolve in rainwater and leak into water sources.
How does eutrophication occur?
- Fertilisers leak into water sources and cause the formation of an algae bloom.
- This stops the plants beneath it from photosynthesing and they die.
- The bacteria have more food so they increase in number.
- Many bacteria are respiring aerobically, so the water can become anoxic.
- This leads to the death of aquatic animals.
Why is the leaching of artificial fertilisers more likely compared to natural fertilisers?
The inorganic ions in the artificial fertilisers are very soluble in water. The ones in natural fertilisers are still contained in organic molecules so they must be broken down before the ions can dissolve in water.
