food production, selective breeding, genetic modification and cloning

Question 1

how do glasshouses and polythene tunnels increase crop yield?

Answer 1

1. keeping plants enclosed in a glasshouse reduces the risk of pests and diseases.
2. easier to control water supplied to the crops
3. artificial light gives plants more time to photosynthesise
4. can increase CO2 concentration through burning fossil fuels
5. heaters can be used

Question 2

what is the effect of increasing CO2 concentration on crop yield?

Answer 2

Increasing CO2 concentration provides a higher level of substrate for photosynthesis, which increases the crop yield. This only increases the rate of photosynthesis if CO2 is not in excess.

Question 3

what is the effect of increasing temperature on crop yield?

Answer 3

Increasing the temperature gives the reactants more kinetic energy so there are more successful collisions, the rate of photosynthesis increases and the crop yield increases. Once the optimum temperature is exceeded, the enzymes will denature and so photosynthesis will stop.

Question 4

how does the use of fertiliser increase crop yield?

Answer 4

Plants need certain minerals (e.g nitrates for proteins, phosphates for DNA and potassium for enzymes) to grow. Farmers use fertilisers to increase the amount of these minerals in the soil, which increases the crop yield of plants.

Question 5

what are the advantages of using pesticides over biological pest control?

Answer 5

1. pesticides are quicker
2. no risk that the introduced organisms would eat other organisms that weren’t pests
3. no risk that the introduced organisms wouldn’t adapt to the new environment
4. no risk that the introduced organisms would become pests themselves

Question 6

what are the advantages of biological pest control over using pesticides?

Answer 6

1. no pollution
2. no resistance
3. can target specific species
4. long lasting
5. doesn’t need to be repeatedly applied

Question 7

what is pesticide pollution?

Answer 7

1. This is when pesticides that remain on plants are eaten, which results in a build up of that pesticide in the organism’s fat stores. This is called bioaccumulation.
2. The concentration of the pesticide increases over time as each consumer eats the preceding organisms. This is called biomagnification.
3. An example of this is DDT.

Question 8

describe how pesticide resistance occurs?

Answer 8

1. Due to random mutations, there is variation and some pests will develop resistance to a pesticide.
2. These pests will have a selective advantage because they are less likely to be killed by the pesticide.
3. This means they are more likely to survive and reproduce, passing their alleles onto their offspring.
4. Over many generations, the proportion of pests with resistance to the pesticide increase within a population.

Question 9

Describe the role of yeast in the production of bread

Answer 9

1. A bread dough is made by mixing yeast, flour, water and some sugar together. The dough is then left to rise.
2. The enzymes in yeast respire aerobically to produce carbon dioxide from glucose.
3. Once the oxygen has run out, the yeast respires anaerobically to produce carbon dioxide and ethanol from glucose.
4. The carbon dioxide gas is trapped in bubbles in the dough.
5. These pockets of air expand which causes the dough to rise.
6. When the dough is baked in the oven, the yeast continues to ferment until the temperature is high enough to kill the yeast. Also, any ethanol is boiled away.

Question 10

Describe an experiment to investigate the rate of respiration of yeast at different temperatures

Answer 10

1. Make a mixture of yeast, sugar and distilled water and add it to a test tube.
2. Add a layer of oil to the test tube to create anaerobic conditions.
3. Add a bung to the test tube and connect it to a separate test tube containing water.
4. Place the test tube containing the yeast mixture in a water bath.
5. Leave the tube to warm up for 2 minutes and then count how many bubbles are produced in a 5 minute period.
6. Calculate the rate of respiration by dividing the number of bubbles by the time period.
7. Repeat the experiment at different temperatures.

Question 11

what is the role of lactobacillus in yogurt production?

Answer 11

1. Milk is pasteurised at 85-95 degrees for 15-30 minutes to kill off any micro-organisms.
2. Milk is cooled to 40-45 degrees and a starter culture of lactobacillus is added.
3. Milk is incubated at this temperature for several hours while lactobacillus digests milk proteins and ferments lactose into lactic acid.
4. The thickened yogurt is stirred and cooled to 5 degrees.
5. Colourants, flavourings and fruits are added.

Question 12

why are nutrients needed in a fermenter and how are they provided?

Answer 12

For the growth of the microorganisms and they are provided in the liquid culture medium.

Question 13

why are aseptic precautions taken in a fermenter?

Answer 13

To kill unwanted microbes. This helps increase the product yield because the microorganisms aren’t competing with other organisms and also the product doesn’t get contaminated.

Question 14

why is the PH and temperature controlled in a fermenter?

Answer 14

This is so that the PH and temperature are at optimum level for the microorganisms’ enzymes to work efficiently. This increases the rate of reaction thus product yield.

Question 15

what is the use of oxygenation and agitation in a fermenter?

Answer 15

1. Sterile air is pumped into the fermenter (oxygenation) so that the microorganisms can always respire and produce energy for growth.
2. Microorganisms are kept in contact with fresh medium by paddles that circulate so that they can always access the nutrients needed for growth.

Question 16

what are the advantages of fish farming over wild fishing?

Answer 16

1. ability to selectively breed
2. fish can be protected against predators
3. water quality can be controlled
4. feeding can be controlled, which ensures rapid growth

Question 17

what are intraspecific and interspecific predation?

Answer 17

Interspecific predation is the predation between different species.
Intraspecific predation is the predation within the same species.

Question 18

how are intraspecific and interspecific predation prevented?

Answer 18

Intraspecific predation is prevented by separating fish by age and size so that they don’t eat each other or fight.
Interspecific predation is prevented by separating different species of fish by fences, nets or tanks.

Question 19

Why is water quality controlled?

Answer 19

So that the temperature , PH and oxygen level are okay for the fish.

Question 20

why are waste products removed?

Answer 20

Because there are bacteria in the waste that may be harmful to the fish. Also, a high oxygen level in the water needs to be maintained so CO2 needs to be removed.

Question 21

how is feeding of fish controlled?

Answer 21

The fish are fed a diet of food pellets that is carefully controlled to maximise the amount of energy they get. Better food quality means fish grow bigger more quickly.
Also, fish are fed frequently but in small amounts so that they don’t overeat or start eating each other.

Question 22

what is selective breeding?

Answer 22

improving a particular crop plant or domestic animal by breeding organisms with desired characteristics

Question 23

how is selective breeding carried out?

Answer 23

1. humans select the organisms which display the desired characteristics
2. they breed these organisms together to produce offspring with these characteristics
3. the offspring which best display these traits are then selected and allowed to breed.
4. this is repeated over may generations

Question 24

what is a vector?

Answer 24

something that is used to transfer DNA into a cell (either plasmids or viruses)

Question 25

what is a plasmid?

Answer 25

a small, circular molecule of DNA that can be transferred between bacteria

Question 26

how are viruses used as vectors?

Answer 26

they insert DNA into the organisms they infect

Question 27

describe how genetic modification is used in the large- scale production of insulin

Answer 27

1. a restriction enzyme recognises the specific sequence of DNA that codes for the production of insulin and cuts it out
2. the DNA of a plasmid is also cut by a restriction enzyme
3. a ligase enzyme attaches the insulin gene to the vector DNA (the DNA is now recombinant)
4. the plasmid is taken in by a bacteria cell
5. the bacteria is now transgenic
6. the bacteria is placed in a fermenter to grow rapidly
7. the insulin produced by the bacteria is collected and purified

Question 28

how can genetically modified plants be used to improve food production?

Answer 28

Crops can be genetically modified to be resistant to insects or herbicides. This increases crop yield as plants are less likely to be eaten or killed.

Question 29

describe the process of micropropagation

Answer 29

1. Small pieces are cut from the tip of a shoot or side stem of a plant with desirable characteristics.
2. These removed pieces are called explants.
3. They are placed in a sterile nutrient agar medium containing glucose, vitamins, minerals and growth regulators which help the plants grow into small plants.
4. Once the small plants have grown roots, they are transferred to a glasshouse.
5. they will develop into larger plants that are genetically identical so also have desirable characteristics.

Question 30

describe how mammals can be cloned?

Answer 30

1. the nucleus of a mammal’s egg cell is removed, creating an enucleated cell
2. a diploid nucleus from a mature cell is inserted into the enucleated egg cell
3. the zygote is stimulated by an electric shock so it starts diving by mitosis to develop into an embryo
4. the embryo is implanted into the uterus of a surrogate mother

Question 31

how can cloned, transgenic animals be used to produce proteins?

Answer 31

1. transfer human genes into the DNA of cows
2. they then produce human proteins in their milk
3. clone these transgenic animals to that their alleles are passed on and the clone has identical genetic characteristics