Flashcards
5B: Nutrient Cycles
Cards in this deck (36)
- 1WHAT IS A NATURAL ECOSYSTEM?One that hasn't been changed by human activity
Nutrients such a nitrogen and phosphorus are recycled through food webs - 2WHAT DO SAPROBIONTS DO?They feed on the remains of dead plants and animals and on their waste products, breaking them down. This makes saprobionts a type of decomposer and it allows important chemical elements in the remains and waste to be recycled.
They secrete enzymes and digest their food externally, then absorb the nutrients they need (extracellular digestion). During this process, organic molecules are broken down into inorganic ions - 3WHAT IS SAPROBIONTIC NUTRITION?Obtaining nutrients from dead organic matter and animal waste using extracellular digestion
- 4WHAT ARE MYCORRHIZAE?The symbiotic relationships formed by some fungi with the roots of plants
- 5WHAT ARE HYPHAE?Long, thin strands which make up the fungi that connect to the plant's roots
They greatly increase the surface area of the plant's root system, helping the plant to absorb ions from the soil that are usually scarce
Hyphae also increase the uptake of water by the plant.
The fungi obtain organic compounds, such as glucose, from the plant. - 6WHY DO PLANTS AND ANIMALS NEED NITROGEN?To make proteins and nucleic acids (DNA and RNA)
- 7IN WHAT FORM CAN PLANTS AND ANIMALS USE NITROGEN?Nitrogen containing compounds
The atmosphere is made up of 78% nitrogen gas, but plants and animals can't use it in that form - they need bacteria to convert it into nitrogen containing compounds - 8WHAT IS NITROGEN FIXATION?When nitrogen gas in the atmosphere is turned into nitrogen containing compounds.
Biological nitrogen fixation is carried out by bacteria such as Rhizobium
It turns nitrogen into ammonia, which goes on to form ammonium ions in solution that can be used by plants - 9WHERE IS RHIZOBIUM FOUND? WHAT RELATIONSHIP IS FORMED?Inside root nodules of leguminous plants
e.g. peas, beans, clover
They form a mutualistic relationship with the plants - they provide the plant with nitrogen compounds and the plant provides them with carbohydrates - 10WHAT IS A MUTUALISTIC RELATIONSHIP?A type of symbiotic relationship where both species benefit
- 11WHERE ARE OTHER NITROGEN FIXING BACTERIA FOUND?In the soil
- 12WHAT IS AMMONIFICATION?When nitrogen compounds from dead organisms or animal waste are turned into ammonia by saprobionts, which goes on to form ammonium ions.
- 13WHAT IS NITRIFICATION?When ammonium ions in the soil are changed into nitrogen compounds that can then be used by plants (nitrates)
First, nitrifying bacteria called Nitrosomonas change ammonium ions into nitrites
Then, other nitrifying bacteria called Nitrobacter change nitrites into nitrates - 14WHAT IS DENITRIFICATION?When nitrates in the soil are converted into nitrogen gas by denitrifying bacteria - they use nitrates in the soil to carry out respiration and produce nitrogen gas, under anaerobic conditions
- 15WHAT ARE THE OTHER WAYS THAT NITROGEN CAN GET INTO AN ECOSYSTEM?By lightning - fixes atmospheric nitrogen into nitrogen oxides
By artificial fertilisers - produced from atmospheric nitrogen on an industrial scale in the Haber process - 16WHY DO PLANTS AND ANIMALS NEED PHOSPHORUS?To make biological molecules
- phospholipids - cell membranes
- DNA
- ATP - 17WHERE IS PHOSPHORUS FOUND?In rocks and dissolved in the oceans in the form of phosphate ions
Phosphate ions dissolved in water can be assimilated by plants and other producers - 18WHAT DOES 'ASSIMILATED' MEAN?Absorbed and then used to make more complex molecules
- 19THE PHOSPHORUS CYCLE: STAGE 1Phosphate ions in rocks are released into the soil by weathering
- 20THE PHOSPHORUS CYCLE: STAGE 2Phosphate ions are taken into the plants through the roots
Mycorrhizae greatly increases the rate at which phosphorus can be assimilated - 21THE PHOSPHORUS CYCLE: STAGE 3Phosphate ions are transferred through the food chain as animals eat the plants and are in turn eaten by other animals
- 22THE PHOSPHORUS CYCLE: STAGE 4Phosphate ions are lost from the animals in waste products
- 23THE PHOSPHORUS CYCLE: STAGE 5When plants and animals die, saprobionts are involved in breaking down the organic compounds, releasing phosphate ions into the soil for assimilation by plants.
These microorganisms release the phosphate ions from urine and faeces - 24THE PHOSPHORUS CYCLE: STAGE 6Weathering of rocks releases phosphate ions into seas, lakes and rivers
This is taken up by aquatic producers, such as algae, and passed along the food chain to birds - 25THE PHOSPHORUS CYCLE: STAGE 7The waste produced by sea birds (guano) contains a high proportion of phosphate ions
Guano returns a significant amount of phosphate ions to soils (particularly in coastal areas)
It is often used as a natural fertiliser - 26LOSS OF NUTRIENTSCrops take in minerals from the soil as they grow and use them to build their own tissues.
When crops are harvested, they're removed from the field where they're grown rather than being allowing to die and decompose there. This means the mineral ions that they contain are not returned to the soil by decomposers in the nitrogen or phosphorus cycles - 27HOW ELSE ARE PHOSPHATES AND NITRATES LOST FROM THE SYSTEM?When animals or animal products are removed from the land
Animals eat grass and other plants, taking in their nutrients
When they are taken elsewhere for slaughter or taken to a different field, the nutrients aren't replaced through their remains or waste products. - 28WHY ARE FERTILISERS USED?Adding fertilisers replaces the lost minerals, so more energy from the ecosystem can be used for growth, increasing the efficiency or energy transfer
- 29WHAT ARE ARTIFICIAL FERTILISERS?Inorganic
They contain pure chemicals (e.g. ammonium nitrate) as powder or pellets - 30WHAT ARE NATURAL FERTILISERS?Organic matter
Include manure, composted vegetables, crop residues and sewage sludge - 31WHY CAN THE USE OF FERTILISERS LEAD TO ENVIRONMENTAL ISSUES?If more fertiliser is applied than the plants need it can lead to the fertilisers leaching into waterways. This can lead to eutrophication.
The inorganic ions in chemical fertilisers are relatively soluble, so the excess minerals not used immediately are more likely to leach. Leaching is also more likely if the fertiliser is applied before heavy rainfall - 32WHAT IS LEACHING?When water soluble compounds in the soil are washed away
e.g. by rain or irrigation systems
They're often washed into nearby ponds and rivers - 33WHY IS LEACHING LESS LIKELY WITH NATURAL FERTILISERS?The nitrogen and phosphorus are still contained in organic molecules that need to be decomposed by microorganisms before they can be absorbed by plants
This means that their release into the soil for uptake by plants is more controlled - 34WHY IS THE LEACHING OF PHOSPHATES LESS LIKELY THAN THE LEACHING OF NITRATES?Phosphates are less soluble in water
- 35WHAT IS EUTROPHICATION?The process whereby nutrients build up in water, leading to the growth of large quantities of algae. This results in the death of plants, and the decomposition of dead plant matter causes the oxygen content of the water to fall, killing aquatic organisms.
- 36THE PROCESS OF EUTROPHICATION1. Mineral ions leached from fertilised field stimulate the rapid growth of algae in ponds and rivers
2. Large amounts of algae block light from reaching the plants below
3. The plants die because they're unable to photosynthesise enough
4. Bacteria feed on the dead plant matter. The increased numbers of bacteria reduce the oxygen concentration in the water by carrying out aerobic respiration
5. Fish and other aquatic organisms die because there isn't enough oxygen
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- A-Level Biology (UNIT 5) Flashcards on 5B: Nutrient Cycles, created by Beth Tonks on 03/01/2017.
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