Chapter 11 - Manipulation Of Food Species

Question 1

Describe asexual reproduction in plants

Answer 1

• the offspring develop from the parent plant rather than from seeds, for example, strawberry plant ‘runners’
  -artificial asexual reproduction involves cutting where new plants are produced from sections to leaf, stem or root tissue from the parent plant
  ✅ offspring are genetically identical to the parent plant, so their characteristics are predictable
  ✅ the survival rate is high because the parent plant is adapted to the area
  ❌ there is no genetic variation in the offspring so their characteristics cannot be improved
  ❌ fewer offspring are produced than by sexual reproduction

Question 2

Describe asexual reproduction in animals

Answer 2

-cloning is an artificial asexual reproduction technique for livestock that is still being develope.
- aim is to produce offspring that are genetically identical to a selected individual with desirable characteristic
- method: cells are removed from the donor and grown in culture. An egg is removed from a female, nucleus of the egg is removed and replaced by the nucleus from one of the donor cells . The egg is implanted into a surrogate female where it develops during a normal pregnancy

Question 3

Describe selective breeding

Answer 3

• involves the production of offspring from parents that were chosen because of their genetic characteristics.
• breeding between genetically similar individuals may produce offspring with similar characteristics, but there is an increased risk of inbreeding

Question 4

Describe cross breeding

Answer 4

• crossbreeding between two different parents breeds may produce a combination of desirable characteristics with ‘hybrid vigour’ and a lower risk of inbreeding

Question 5

Give an example of cross breeding

Answer 5

-Zebu cattle are reared in areas with a hot climate. They tolerate the heat well but give a low milk yield.
- Ayrshire cattle from Scotland give a very high milk yield but they are not heat tolerant.
- crossbreeding between zebu and Ayrshire cattle has produced cattle that can tolerate the heat and have a high milk yield

Question 6

Describe genetic engineering/ transgenics / GM

Answer 6

• conventional selective breeding programmes can only introduce characteristics that exist within the gene pool of the species or other species that are very closely related and can produce fertile hybrid offspring
• GM allows the introduction of single characteristics from one species to another, or between varieties or breeds of the same species

Question 7

Give an example of a GM crop

Answer 7

Golden rice:
- a diet that’s deficient in Vitamin A causes about 500,000 new cases of blindness each year
- rice contains vitamin A, but it’s in the husk that’s normally removed so that the rice grains can be stored
- genes have been transferred from the daffodil and a soil bacterium so that vitamin A is produced within rice grains.

Question 8

What are some advantages of GM crops

Answer 8

✅ individual desirable characteristics can be introduced without associated unwanted characteristics
✅ genes may be introduced from other species that could never have been achieved by normal selective breeding
✅ GM techniques can increase pathogen resistance reducing disease in a crop

Question 9

What are some disadvantages of GM production ?

Answer 9

❌ it’s been claimed that GM food can increase food allergies
❌ potential gene transfer from GM foods to cells of the body
❌ increased costs to farmers especially in LEDCs as many GM crops require new seeds to be purchased each year rather than harvesting seeds from an existing crop
❌ concerns in LEDCs that GM crops will reduce the local indigenous crop diversity including the successful seed saving practices

Question 10

How can stocking / crop densities be manipulated to increase productivity?

Answer 10

• increasing the population density can increase the total yield, although yield per individual may be reduced due to inter species competition
• a high population can increase the risk of rapid spread of disease

Question 11

How can monocultures be manipulated to increase productivity?

Answer 11

• involves cultivating a single species, often over a large area. This can ,ale cultivation easier by allowing the use of larger machinery.
• but pests and disease spread rapidly if they colonise the field