Part 1 of Essay
Mankind has selectively bred plants for thousands of years with the aim of improving their quality. Experimenting with cereal crops, breeders have aimed to enhance their yield of grain, the quality of their flour, and their resistance to disease and drought. With other plants, breeders have tried to improve the perfume a ....

Part 2 of Essay
.... of 67 million acres was planted with the hybrid variety, yielding twice as much corn. Plant breeders have a definite advantage over animal breeders, because they can often produce fertile varieties - indeed, new species - by crossbreeding between species. This is because hybrids are often polypoid. Polyploidy, as we know, can occur naturally in the wild. Some species of cotton that we grow are polypodies that probably arose originally by accidental crosses between different species of cotton. ....