| Common features of nutrient cycles | - The nutrient is taken up by producers as simple, inorganic mols
- The producer converts nutrient into complex organic mols
- Consumer eats producer
- Passes along food chain when these animals are eaten
- When producers + consumers die, their complex molecules are broken down by saprobiontic microorganisms
- They release the nutrient in its simple form |
| What does it do | - Shows how nitrogen is converted into a usable form + passed on between different living organisms
- Nitrogen cycle includes food chains |
| Purpose of the nitrogen cycle | - Plants + animals need nitrogen to make proteins + nucleic acids
- The atmosphere's made up of 78% nitrogen gas, but plants + animals cant use it in that form
- They need bacteria to convert it into nitrogen-containing compounds first |
| Key steps in the nitrogen cycle | - Nitrogen fixation
- Ammonification
- Nitrification
- Denitrification |
| Nitrogen fixation | - The fixing of inorganic atmospheric nitrogen to ammonium ions which are converted to amino acids
- Carried out by aerobic bacteria (N2 fixing bacteria)
- Can be found in root nodules of leguminous plants (forms mutualistic relationship), can also be free in soil |
| Ammonification | - The breakdown of organic compounds into ammonium ions
- Carried out by saprobiontic aerobic bacteria
- The waste product is ammonia this reacts with H ions from h20 to produce ammonium ions |
| Nitrification | - The conversion of ammonium ions into nitrite then nitrate by aerobic nitrifying bacteria
- These are oxidation reaction - release energy |
| Denitrification | - Conversion of nitrates to organic atmospheric nitrogen by anaerobic denitrifying bacteria
- BOOOO! farmers dont like this |
| Assimilated meaning | - Absorbed + then used to make more complex molecules |
| Purpose of the phosphorous cycle | - Plants + animals need phosphorous to make biological mols like phospholipids
- Phosphorus is found in rocks + dissolved in the oceans in the form of phosphate ions
- Phosphate ions dissolved in water in the soil can be assimilated by plants + other producers |
| Process of the phosphorous cycle (1) | - Phosphate ions in rocks are released into the soil by weathering
- Phosphate ions are taken into plants through roots |
| Process of the phosphorous cycle (2) | - Mycorrhizae greatly increase rate at which phosphate can be assimilated
- Phosphate ions are transferred through the food chain as animals eat the plants + are in turn eaten by other animals |
| Process of the phosphorous cycle (3) | - Phosphate ions are lost form the animals in waste products
- When plants + animal die, saprobionts break down organic compounds, releasing phosphate ions into the soil for assimilation by plants |
| Process of the phosphorous cycle (4) | - These microorganisms also release the phosphate ions form urine + faeces
- Weathering of rocks also releases phosphate ions into seas, lakes, rivers |
| Process of the phosphorous cycle (5) | - This is taken up by aquatic producers, like algae, and passed along the food chain to birds
- The waste produced by sea birds is known as guano + contains a high proportion of phosphate ions |
| Process of the phosphorous cycle (6) | - Guano returns a significant amount of phosphate ions to soils
- It is often used as a natural fertiliser |
| The importance of fungi and bacteria (mycorrhizae) in nutrient cycles | - Relationship between certain types of fungi + roots of plants
- Fungi act like extensions of the plant's roots system + vastly increase SA for absorption of water + minerals
- The mycorrhizae acts like a sponge so holds water + minerals in the neighborhood of the roots
- Plant now better at resisting drought + takes up inorganic ions more readily
- The mycorrhizae plays a part in nutrient cycle by improving the uptake of relatively scarce ions like phosphates ions |
