Field Weeds per m2 Soya yield / t per ha ordinary soya, not sprayed 42 2.1 ordinary soya, sprayed 5 1.4 GM soya, sprayed 4 3.2 Some crop plants have been ge...

This question uses trial data on herbicide-resistant GM soya to test the idea of genetic modification, competition, and a percentage-change calculation.

(a) A genetically modified organism is one whose genetic material (DNA) has been changed [1], usually by inserting a gene from another organism [1]. [2]

(b) Comparing the sprayed fields, spraying kills the weeds in the GM field (only 4 remain) [1] but does not damage the GM crop [1]; in contrast, spraying ordinary soya damages the crop and lowers its yield (from 2.1 to 1.4 t per ha) [1]. [3]

(c) The sprayed GM soya yields most because there are far fewer weeds, so there is less competition with the crop [1] for light, water, mineral ions and space [1]; and because the herbicide does not harm the resistant GM crop, more soya can grow [1]. [3]

(d) \[ \text{percentage decrease} = \frac{42-4}{42}\times100 = \frac{38}{42}\times100 \approx 90.5\% \] So the number of weeds falls by about 90.5% (accept 90-91%). [2, 1 method + 1 answer]

(e) Any two disadvantages [3, max 3]: weeds may themselves become resistant to the herbicide over time [1]; loss of biodiversity as fewer wild plants and the animals depending on them survive [1]; GM seed is expensive and farmers become dependent on the seed company [1].

(f) The enzyme used to cut the resistance gene out of another organism's DNA is a restriction enzyme. [1]