Selective breeding

Genetically modified (GM) crops have been developed over the last 30 years.

Explain what is meant by the term genetically modified.

Farmers have been growing GM soybean and corn for a number of years. The table shows data for soybean and corn grown in the USA from 1996 to 2014. It shows the percentage of each crop that is GM.

Plot a line graph of the data on the grid. Use a ruler to join the points with straight lines.

Describe the changes in the use of GM soybean and corn from 1996 to 2014.

Herbicides are chemicals that kill plants. Crops can be genetically modified to be herbicide resistant. Suggest why farmers may want to grow crops that are herbicide resistant.

Farmers also grow GM crops that are resistant to other factors. Name one of these factors.

Selective breeding is another way of improving crop production. Describe how selective breeding could be used to improve seed size in wheat.

The photograph shows a chicken with feathers.

Scientists can use selective breeding to produce chickens with no feathers. Explain how a chicken with no feathers can be produced by selective breeding.

Selective breeding is also used to breed chickens for egg production and chickens for meat production. The graph shows how age affects the average (mean) number of eggs produced per chicken per year. The graph shows this information for chickens bred for egg production and for chickens bred for meat production.

Describe how age affects the number of eggs produced by each group of chickens.

Chickens in factory farms are kept in cages inside buildings rather than being kept outdoors. Suggest how factory farming can affect egg production.

Flies lay their eggs in the urine and faeces that sticks to the wool on sheep. The eggs hatch and the larvae damage the skin of the sheep leading to infection. To reduce this problem, farmers in New Zealand have been developing sheep that have no wool growth on their legs, their backside or on the underside of their abdomen.

Suggest why flies are attracted to urine and faeces.

Farmers have crossed different breeds of sheep to produce offspring with desired characteristics. The characteristics of different breeds of sheep are shown in the

Describe how farmers could use selective breeding to develop sheep with bare legs and bare backsides.

Describe two differences between selective breeding and natural selection.

Farmers sometimes use pesticides to prevent flies attacking sheep. Give two problems with the use of chemical pesticides.

The table describes four different geographical regions. It also gives the amount of energy converted into plant biomass each year in each region.

Plot a bar graph on the grid to show the amount of energy converted into plant biomass each year in each region.

The amount of energy converted into plant biomass each year depends on the effect that abiotic (non-living) factors have on the rate of photosynthesis. Carbon dioxide is one of these abiotic factors. Name three other abiotic factors likely to affect the rate of photosynthesis.

Regions C and D have the same climate. Plants grown in region D have more energy converted into plant biomass than plants grown in region C. One reason for this is the use of selective breeding to produce high yielding crops.

Suggest two other reasons for more energy being converted into plant biomass in region D.

What is meant by the term selective breeding ?

Describe how you could use a quadrat to estimate the plant biomass in one of the regions.

Describe the stages that are used to genetically modify a bacterium that is able to manufacture human growth hormone.

BST is a hormone that increases milk yield in cows.

Explain what is meant by the term hormone.

In some countries BST from genetically modified bacteria has been injected into cows to improve milk production. In other countries selective breeding has been used to improve milk production. Describe how selective breeding could be used to increase milk production.