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Question 1

How can greenhouses and polythene tunnels be used to increase the yield of crops?(4)

Answer 1

The transparent walls of greenhouses allow natural light for photosynthesis, and additional lighting in the winter substitute as a ‘longer day’.
Short wavelength infrared radiation cannot space through the glass because it is re-radiated as longer wavelength radiation, so the glasshouse heats up.
If extra heaters use fossil fuels such as gas, the carbon dioxide produced would be used as a raw material of photosynthesis. The water vapour produced would also maintain a moist atmosphere - reducing transpiration.
If the plants are also grown in a hydroponic culture, the exact right balance of mineral ions will be provided for a particular crop.

Question 2

How can fertiliser increase crop yield?(4)

Answer 2

Organic fertilisers, made of animal faeces mixed with straw, will return a portion of lost nitrogen to the soil.
Inorganic fertilisers will apply a calculated amount of nitrate or other ion, when applied correctly.
From these facts it would appear that inorganic fertilisers are more useful, but they also lead to pollution problems. An alternative to fertilisers, is growing a legume crop in a field.
Legumes have nitrogen fixing bacteria on their roots, which convert nitrogen gas to ammonium ions. This can then be passed to plants to make proteins.

Question 3

What are some disadvantages and advantages of pesticides and biological control?(4)

Answer 3

Pesticides are very easy to use and are cheap, however they can harm other wildlife and are temporary.
Biological control introduces other organisms into an ecosystem. This has a longer effect than pesticides, and does not damage wildlife as much. However, it is unreliable and can cause new problems; new species can become pests themselves.

Question 4

How is yeast important in production of beer?(4)

Answer 4

Beer is made from barley.
After allowing the barley seeds to germinate they produce amylase.
This amylase breaks down starch into the sugar maltose.
Later the maltose from the seeds is fermented by yeast in a large open vat.

Question 5

How is bacteria important in the production of yogurt?(4)

Answer 5

The equipment is sterilised to kill off unwanted microorganisms, then the milk is pasteurised and cooled.
Lactobacillus bacteria are added and the mixture is incubated in a fermenter.
Lactic acid causes milk to clot, and solidify into yoghurt.
Lastly, flavours and colours are added and the yoghurt is packaged.

Question 6

How is yeast important in the production of bread?(5)

Answer 6

Bread dough is mixed with yeast as well as other ingredients and then left to warm.
Enzymes break down the carbohydrates in the flour into sugars.
Carbon dioxide is produced from aerobic respiration, when the oxygen runs out anaerobic respiration produces carbon dioxide again and ethanol.
The CO2 is trapped in bubbles in the dough which causes the dough to rise.
Finally, the temperature rises to eventually kill the yeast and boil away any alcohol produced.

Question 7

How are conditions in an industrial fermenter kept suitable?(4)

Answer 7

Stirring paddles, mix up the contents and keep microorganisms in suspension in the liquid; more exposure to nutrients.
If the microorganisms respire aerobically, filtered air is supplied through an inlet. Hot steam is also used to sterilise all the tanks, and pipes in between uses. This further prevents contamination and prevents reduction of yield; these methods are called aseptic precautions.
Temperature and pH probes are both present, and will be kept constant(pH for example by adding acid or alkali).
There is a water jacket and cold water inlet, outlet. This prevents the contents from overheating - cold water constantly circulates.

Question 8

How are conditions in fish farming kept suitable?(3)

Answer 8

Water quality is controlled: temperature, O2 levels, water clarity, and chlorophyll levels are all measured. Filtered air can be pumped into enclosures to increase the amount of oxygen dissolved in the water.
Diet of the fish is carefully monitored, when they feed and what to feed them.
Enclosing the fish protects them against predators, pesticides are also used to kill parasites. If fish start eating smaller fish, they are moved into different cages, sorted by size.

Question 9

What are disadvantages of fish farming?(3)

Answer 9

Antibiotics are regularly used to treat disease in fish farms, but these may not have degraded by the time they are eaten by humans. This adds to the problem of antibiotic resistance in bacteria.
Fish farms also create a pollution problem - the organic material from the animals faeces can contaminate waters outside a fish farm and cause eutrophication.
Carnivorous salmon and sea bass are fed with pellets made from other fish; a few kilos of wild fish are required to produce 1 kilo of farmed fish.

Question 10

Define selective breeding.

Answer 10

Selective breeding is best described as the breeding of only those individuals with desirable features.

Question 11

What are some examples of successful selective breeding in modern plants?(3)

Answer 11

Brassica is a genus of cabbage-like plants that was selectively bred to give several strains.
These include Brussel sprouts, Kohlrabi, Kale, Broccoli, Cauliflower and Cabbage.
The most common example of a selectively bred plant however is wheat, which is a strain of grass.

Question 12

What do farmers look for when selectively breeding for animals and plants?(6)

Answer 12

In plants; Give a higher yield, ie more wheat on a single wheat strand,
Resistance to certain insect pest damage, as well as resistance to certain diseases,
Better balance of nutrients in the crop and hardier structure so that they might survive floods etc.
In animals; Produce more meat, milk or eggs,
Produce more fur or better quality fur or feathers,
Produce more offspring as well as showing resistance to disease and parasites.

Question 13

Describe and explain the first processes of micropropagation?(3)

Answer 13

Begins by taking tips of the stems and side shoots of a plant to be cloned. These parts are labelled the explants.
The explants are trimmed(0.5 - 1mm) and sterilised on their surface to kill any microorganisms.
They are placed in a sterile agar medium for growth, while the explants with shoots are transferred to another culture medium with hormone balance to encourage root formation.
After the explants grow roots, they are transferred to greenhouses, transplanted into compost.

Question 14

Describe and explain the final processes of micropropagation?(3)

Answer 14

After the explants are transferred to a greenhouse, they gradually acclimatise to normal growing conditions.
The atmosphere of the greenhouse is kept very moist to reduce water loss.
There is such an amount of water vapour in these greenhouses they are called fogging greenhouses.

Question 15

What are the advantages of using micropropagation to clone plants?(3)

Answer 15

Large numbers of genetically identical plants can be produced rapidly and they can be produced in this number anytime of the year.
Species difficult to grow from seed or cuttings can be cloned through this method.
They are easy to store in large numbers, and genetic modifications can be introduced into large numbers of plants quickly.

Question 16

How was the first successful animal cloned?(3)

Answer 16

The mammary gland of the parent sheep was removed and cultured, and a mammary gland cell was electrically fused with a cell from an unfertilised egg with no nucleus,
The cell then developed into an embryo and was transferred into a surrogate mother.
A lamb was born genetically identical(although with some defects) as the parents sheep.

Question 17

What is a transgenic organism?(2)

Answer 17

Recombinant DNA is DNA that has been cut out of the DNA of one species and inserted into the DNA of another.
An organism that receives the gene from a different species is a transgenic organism.

Question 18

Describe and explain how to produce a transgenic bacterium?(5)

Answer 18

First, plasmids that contain DNA in bacteria are isolated from a bacterium. The plasmid is called a vector.
These plasmids are then opened with a specific restriction enzyme.
The gene to be transferred from the donor is cut using the same restriction enzyme.
The isolated plasmid and isolated gene are mixed with a DNA ligase enzyme to create recombinant plasmids.
Bacteria are incubated with the recombinant plasmids, some of these bacteria will take up the plasmids.

Question 19

How can large amounts of human insulin be manufactured from GM bacteria?(2)

Answer 19

Human insulin is required by people suffering from diabetes. The alternative to this was pig insulin which lead to diabetics having a lower life expectancy.
Bacteria are easy to be cultured on a mass scale using industrial fermenters.

Question 20

What is the advantage of genetically modified plants?(3)

Answer 20

Genetically modified food, such as ‘golden rice’, provides increased resistance against pests and pathogens, increased heat and drought resistance.
Increased salt tolerance, better balance of proteins, carbohydrates, lipids, vitamins and minerals.
The example golden rice, has increased vitamin A for the diet, which a lot of children in less economically developed countries lack.

Question 21

How can cloned transgenic animals be used to produce human proteins?(3)

Answer 21

Upon producing a transgenic animal, this can be cloned in large numbers - all genetically identical. Therefore these animals could be used for production of human proteins.
AAT, alpha -1- antitrypsin, is involved in the immune response; it is produced by phagocytes as a counter measure to trypsin.
However, some people carry a mutagen that means they do not produce enough AAT, hence the trypsin damages liver and lungs.