B6.2 Feeding The Human Race

Question 1

Factors affecting food security:

Answer 1

Increasing human population
Changing diets
Climate change- increase in C02 may lead to increasing yields of some crops
New pests and pathogens may evolve

Question 2

How to increase food production:

Answer 2

Maximising photosynthesis
Using fertilisers- helps land remain fertile
Removing competition and pests
Planting varieties of crops that are pest resistant

Question 3

Organic farming

Answer 3

Using natural methods of producing crops and rearing animals avoiding the use of artificial chemicals. Yields are generals smaller, so products may be more expensive.

Question 4

Intensive farming

Answer 4

Using fertilisers and pesticides to aid plant growth
Maximising animal growth rates
Minimising labour inputs by using machinery

Question 5

What is sustainable food production

Answer 5

Producing food in ways that can be continued indefinitely such as fish farming

Question 6

Features of fish farming

Answer 6

Fishing quotas- provide limits on the numbers and types of fish that may be caught in an area so that they can maintain their population

Mesh size of nets- bigger holes mean that younger, less developed fish can escape through the holes

Question 7

How to reduce the use of fertilisers

Answer 7

• replace soil nutrients by spreading manure instead of using fertilisers
• crop rotation, different crops require different nutrients
• biological control, use natural predators to kill crop pests which are often present in intensive farming

Question 8

What is a hydroponic system

Answer 8

Growing a plant in water containing dissolved minerals to ensure it receives the mineral it needs, enables crops to grow quickly

Question 9

What is selective breeding

Answer 9

Purposely breeding plants or animals which have desirable features

Question 10

How does a farmer selectively breed organisms

Answer 10

Decide which characteristics of a species is desirable and select parents with high levels of this characteristic. Breed from these individuals. Then select the best offspring and breed again- repeat for many generations.

Question 11

How has selective breeding changed wheat

Answer 11

• it’s made it easier to harvest and produces higher yields

Question 12

Differences between wild and modern wheat plants

Answer 12

Modern: stalks grow at same length, large ears with many seeds, stronger stalks, ears ripen at same time
Wild: small ears with few seeds, brittle stalks that ears often fall off, ears ripen at different time, stalks grow at different lengths

Question 13

Disadvantages of selective breeding

Answer 13

• it reduces variation meaning that if a disease were to come, it would wipe out a lot of the population due to a reduced gene pool of the species, species may become extinct
• increases the chance of inheriting a genetic disease

Question 14

What is genetic engineering

Answer 14

Altering an organisms genome to produce an organism with desired characteristics. It can occur in one generation and single genes can be targeted.

Question 15

Benefits of using genetic engineering in agriculture. List examples.

Answer 15

Cotton- increase crop yield from same area of land
Corn- to produce toxins that kill insects making the plant more resistance to pest, meaning less pesticide is needed
Bacteria- to produce medical drugs such as insulin

Question 16

Risks of genetic engineering

Answer 16

• eating genetically engineered organisms may lead to health problems e.g. may introduce new allergens that may cause some people to allergic to the organism
• genetically engineered crops may cross pollinate with wild plants, introducing a new gene to wild plants which could disrupt the balance of the ecosystem

Question 17

What problems to some people have with genetic engineering?

Answer 17

• it can be viewed as unethical as altering an organisms genome is seen as science interfering with nature
• some people don’t like the idea of eating genetically engineered organisms

Question 18

How are organisms genetically engineered?

Answer 18

1) identify genes that code for the desired characteristics
2) remove the gene from the donor organism
3) insert the gene into the host organism, often a bacterium

Question 19

Summarise genetic engineering

Answer 19

Using enzymes to move a gene between genomes

Question 20

Restriction enzymes

Answer 20

They cut the donor at a specific base sequence. They make a staggered cut, leaving a few exposed, unpaired DNA strands called sticky ends. The same restriction enzyme is used to cut the bacterial plasmid DNA to create complementary sticky ends.

Question 21

Ligase enzymes

Answer 21

They rejoin DNA strands at sticky ends. As both the host and the donor have the same sticky ends, the new gene is joined into the plasmid DNA.

Question 22

Cloning vs Genetic Engineering

Answer 22

Cloning: produces exact genetic copies, genes copied within the same species
Genetic Engineering: produces unique set of genes, genes transferred between species

Question 23

How is golden rice genetically modified?

Answer 23

A gene taken from a daffodil is placed into rice which makes the rice produce beta carotene, which the body uses to make vitamin A

Question 24

Problems with using pesticides

Answer 24

• are often harmful to humans, so must be used in low levels
• can harm animals which aren’t pests which can affect the food chain negatively

Question 25

Advantages of using biological control instead of pesticides

Answer 25

• does use chemicals so there is less pollution and chemicals don’t get passed along food chains
• biological control can have longer lasting effects on the pest population than chemical pesticides
• less harmful to wildlife

Question 26

Why might a farmer choose to grow crops that have been genetically modified to be herbicide -resistant?

Answer 26

So they could spray his crops with herbicides to kill weeds without affecting the crop itself. This could increase crop yield.

Question 27

Disadvantages of using hydroponics

Answer 27

• you need to add lots of fertiliser to the nutrient solution
• the cost of setting up hydroponics can be very high

Question 28

How to test if your genetic engineering is successful

Answer 28

Insert a gene which codes for antibiotic resistance (a marker gene) into the plasmid at the same time as the gene for the desired characteristic. Then grow the host bacteria on a special plate containing antibiotics. Only the bacteria containing the marker gene will be able to survive and reproduce (antibiotics will kill the rest).

Question 29

How to genetically engineer a bacteria.

Answer 29

Use a restriction enzyme to cut out the useful gene from the human DNA. Use the same enzyme to cut open the plasmid, leaving both the plasmid and human DNA with complementary sticky ends. Then use ligase enzymes to join the two pieces or DNA together. These plasmid vectors containing the new DNA are then inserted into the host bacteria.

Question 30

What does crop rotation do?

Answer 30

• Different crops take different nutrients from the soil
• It gives soil a chance to recover, and maximises plant growth
• It also prevents building up a population of a particular crop pest.