Sunday, 28 April 2013

5.9 explain the methods which are used to farm large numbers of fish to provide a source of protein, including maintenance of water quality, control of intraspecific and interspecific predation, control of disease, removal of waste products, quality and frequency of feeding and the use of selective breeding.

Fish are a source of protein in many diets, humans consume a lot of fish for this reason. Fish farms are used to supply fish because: the fish's food safety standard is monitored; fresh water fish are declining; the deman for fish is increasing.

Fresh water fish may have come into contact with unclean water; containing sewage, waste, chemicals. In fish farming the water is filtered to make sure the fish don't come into contact with anything it would be unsafe to digest. Also if the water is cleaned regularly the spread of disease is minimised and the oxygen levels are high enough to maintain the respiration of the fish.

Intraspecific predation is the fish being bred eating each other, this can be stopped by: separating fish of different ages; separating fish of different genders; feeding fish regularly; giving fish adequate room.

Interspecific predation is the farmed fish being prayed on by other species, this can be prevented by: fencing the area the fish are in; putting nets around the area the fish are in; keeping the fish in inside tanks.

To minimise spread of disease, the water the fish are in should be changed regularly and their surroundings sterilised often. Also if small amounts of fish are kept together then disease can only contaminate a few fish.

Waste can be removed by changing the water in a tank, or changing the nets and location of fish kept outside.

Fish need to be fed often in small amounts, this is so they don't starve but they wont be able to over eat. It is important to feed fish food with nutrients in for growth.

Selective breeding can ensure that farmers produce fish with desired characteristics  by letting only the fish with the right characteristics breed and pass on the gene.

A useful source is:

5.8 interpret and label a diagram of an industrial fermenter and explain the need to provide suitable conditions in the fermenter, including aseptic precautions, nutrients, optimum temperature and pH, oxygenation and agitation, for the growth of micro-organisms

Here is a diagram of a fermenter, the key parts are labelled:
The motor (labelled here as stirrer) turns the blades, this evens out the mixture: making sure the temperature and concentration is the same through out; and increasing the contact between the micro-organisms and other components.

The cooling jacket (labelled here as water column) controls the temperature as the cool water conducts heat from within. The temperature and PH both need to be monitored so that they can be kept at the optimum level for the enzymes. If the enzymes are in their optimum conditions then they will react faster.

Inoculum is the starter culture; basically it helps the fermentation start.

The air inlet gets oxygen into the fermenter. Oxygen is needed for the micro-organisms to respire. A sparger/agitator makes the air into very small bubbles; this means they have a larger surface area and can dissolve easily, so there is better access to oxygen for micro-organisms.

Aseptic conditions are needed as if there were other microbes in the fermenter; firstly they would contaminate the product; secondly they would use up nutrients and oxygen.

Nutrients are needed in the fermenter so the micro-organism can grow.

Thursday, 25 April 2013

5.7 understand the role of bacteria (Lactobacillus) in the production of yoghurt

When Lactobacillus respire anaerobically, they make lactic acid: this acid clumps milk proteins together making yoghurt.

5.5 understand the role of yeast in the production of beer

Yeast converts sugar to ethanol and CO2 whe it respires anaerobically.
ethanol is alcohol...

5.4 understand the reasons for pest control and the advantages and disadvantages of using pesticides and biological control with crop plants Micro-organisms

Pests can eat crops or damage them so they can't be sold.

Pesticides are used to kill pests that reduce crop yield.
The assure that crops won't be damaged. Fast and accurate to apply. Instant results.
They can harm other wildlife.
Killing the pest may affect biodiversity.
Pesticides can leech into the soil and possibly pollute rivers or surrounding habitats.
Pests can become immune.

Biological control is introducing a predator into the environment with the crops to kill the pests.
Cheep. Self regulating.
The predator may enter the wild and effect the biodiversity.

5.3 understand the use of fertiliser to increase crop yield

Fertilisers contain minerals that plants require to grow; most of them are called NPK fertilisers, this means they contain nitrates, phosphates and potassium.

Nitrates are needed to make proteins- proteins are what plant cells are made of. If there is a lot of nitrate in the soil then plants have the ability to grow as much as they can.

Phosphates are involved in respiration and growth- both things are needed to sustain a plant.

Potassium must be present for enzymes to work- with out it the plant wouldn't be able to carry out reactions and so would die or have very limited growth.

5.2 understand the effects on crop yield of increased carbon dioxide and increased temperature in glasshouses

Glass houses and polythene tunnels increase the heat in the environment that crops are growing in. Reactions happen faster when there is more heat, for example photosynthesis. Given photosynthesis produces energy that the plant needs to grow, if there is more heat there is more growth and so higher yield.

Carbon dioxide is a reactant in photosynthesis. If there is a more than enough carbon dioxide, then every plant will be able to photosynthesise as best as it can. The more photosynthesis the more glucose, the more glucose the more energy, the more energy the more growth. Hence crop yield is increased.

5.1 describe how glasshouses and polythene tunnels can be used to increase the yield of certain crops

In glasshouses and polythene tunnels conditions can be controlled. This control means that all the limiting factors for plant growth can be set to the optimum conditions; this will result in more growth, so higher yield.

Sunday, 21 April 2013

4.17 understand the effects of deforestation, including leaching, soil erosion, disturbance of the water cycle and of the balance in atmospheric oxygen and carbon dioxide.

Leeching is basically loss of nutrient from soil. Normally nutrient is rained into the soil; absorbed by plants; shed in their leaves/when they die; digested by decomposers so its back in the soil. If you take away the vegetation you remove nutrients from the cycle. In addition to this the soil is not protected by plants and so when it rains there will be a higher rate of surface run off, this will take the nutrients from the soil with it. Soil erosion is also caused by the fact that without plants to protect the soil there is more surface run off, because soil is taken with it.

Plants absorb water from the soil and lose water from their leaves (through transpiration) in to the atmosphere which goes on to make clouds. If there are less plants then less water is evaporated into the atmosphere, this means there are less clouds; less clouds means less rain, which can mean drought.

Plants also convert carbon dioxide into oxygen when they photosynthesise. Forests carbon sinks, they use more carbon than they release: this means they help to make sure there aren't too high levels of CO2 in the atmosphere. When forests are cut down this process is lost and additionally the trees are usually burnt which releases CO2 into the atmosphere.

This article is explains some of the effects of deforestation nicely:

4.16 understand that eutrophication can result from leached minerals from fertiliser

Eutrophication is when there are excessive amounts of nutrients in a lake. The effects of this are that algae will bloom (grow quickly). Having a lot of algae will mean that there is not enough oxygen for other organisms, they will also struggle to find enough light as algae covers the surface. More organisms will die then usual- more algae to die/ less oxygen and light so fish die- so decomposers will thrive; these decomposers will also use a lot of oxygen from the water. In the end there will not be enough oxygen for fish.

Nutrient get leached into rivers from soil as rain water runs off land into rivers and lakes taking nutrient with it. If fertiliser has been put in the soil then the soil will be rich in certain nutrient, especially nitrogen: so rain water runs off fertilised soil it will bring high amounts of nutrient into surrounding rivers or lakes causing eutrophication.

4.14 understand how an increase in greenhouse gases results in an enhanced greenhouse effect and that this may lead to global warming and its consequences

The sun heats up the earth with infra-red waves that it emits, these waves travel from the sun through the earth atmosphere and warm it up. The earth emits its own rays so that it maintains its heat instead of just warming up forever! Many of these rays escape the earth's atmosphere- revealing it of heat- but some are absorbed by certain gasses- Greenhouse gasses- this means the heat is trapped within the earth's atmosphere. On a large scale this heats the earth, which we call global warming, and this can lead to climate change: the expected weather patterns reverse or exaggerate: this is thought to result in natural disaster (drought, floods).

4.13 understand how human activities contribute to greenhouse gases

Many of the processes that we carry out in homes and factories produce or release gasses with the greenhouse effect. Many things release greenhouse gasses when they are burned; reactions can create greenhouse gasses; some plants and animals that we keep a lot of naturally release greenhouse gasses. Processes that produce greenhouse gasses include burning fossil fuels and keeping large amounts of live stock.

4.12 understand that water vapour, carbon dioxide, nitrous oxide, methane and CFCs are greenhouse gases

A green house gas is one that absorbs heat reflected by the earth, this heat is then trapped in the earth's atmosphere warming the earth. In large quantities these gasses can change the climate by keeping in too much heat. Gasses that do this include: water vapour, carbon dioxide, nitrous oxide, methane and CFCs.

A CFC is a compound that contains only carbonchlorinehydrogen and fluorine.

4.11 understand the biological consequences of pollution of air by sulfur dioxide and by carbon monoxide

Sulfur dioxide and carbon monoxide are created by many processes we use in factories and homes. When in the atmosphere they can dissolve in rain water to create rain the is acidic. Acid rain corrodes metals and rocks like limestone which can damage buildings and statues. Acid rain can also change the PH in soil or rivers, this can mean that some species can not survive in that area.

Monday, 15 April 2013

4.10 describe the stages in the nitrogen cycle, including the roles of nitrogen fixing bacteria, decomposers, nitrifying bacteria and denitrifying bacteria

Nitrogen fixing bacteria turn nitrogen from N2 into ammonia.
Decomposers break down dead animals, urea and egested materials which releases nitrogen into the soil as ammonia.
Nitrifying bacteria convert nitrates into nitrogen.
Denitrifying bacteria break down nitrates into nitrogen which is then released into the atmosphere.

Here is a diagram to help explain:
File:Nitrogen Cycle.svg

This animation is very helpful:

4.9 describe the stages in the carbon cycle, including respiration, photosynthesis, decomposition and combustion

Respiration is carried out by animals and plants to release energy from glucose, the equation is:
C6H12O6 + 6O2    →    6CO2 + 6H2O . This means carbon is produced.

Photosynthesis is what plants do to create glucose the equation is:
6 CO2 + 12 H2 C6H12O6 + 6 O2 + 6 H2O. This means carbon is used.

Decomposition is happens when an animal dies, it is then eaten by a decomposer which releases the carbon in it back into the atmosphere.

Combustion is burning, if something with carbon is burnt it will release it into the atmosphere, e.g. a tree, fossil fuel.

This is one of many useful diagrams:

4.8 describe the stages in the water cycle, including evaporation, transpiration, condensation and precipitation

Evaporation is when water turns into steam due to being heated
Transpiration is when water is evaporated from leaves
Condensation is when water vapour turns into water due to being cooled, this forms clouds
Precipitation is when water is released from a cloud, e.g. rain, snow, hail

The best way to understand this is with a diagram: