5.10 understand that plants with desired characteristics can be developed by selective breeding

Notes


Farmers can use selective breeding to increase plant yield

-> Example: Rice grains
The number of grains produced per plant (yield) is controlled by the genes of that specific plant.
The number of grains produced per plant in a crop field varies - this can be shown with a distribution curve which resembles the one below:

where the left, middle and right sections show the least, average and most number of grains produced in the crop field respectively. Supposing a farmer had three plants - which yielded 6, 8 and 10 grains respectively - to increase crop yield, the farmer would:
-> Harvest the two plants which produced only 6 and 8 grains
-> Re-plant the grains from the 10 grain plant (as these will share the same genes)
-> This would cause the next generation of plants to have 8, 10 and 12 grains respectively instead

Selective breeding (in plants) can be used to shift the distribution curve so that the median percentile of plants produces the desired characteristics, therefore increasing crop yield.
NOTE: The distribution curve shifts - simply because a 10 grain plant seed is re-planted does not guarantee ALL plants will produce 10 seeds (hence, a curve).