Question

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Commercial bananas are grown as a monoculture, with all banana plants cloned from one original banana plant. The commercial strains of bananas are seedless, so each new banana plant has to be manually planted from a cutting of an existing banana root. In the 1950s, the Gros Michel banana strain, the dominant export banana at that time, was destroyed by the fungus Fusarium oxysporum. A new Fusarium resistant variety, the Cavendish banana, was developed and is currently the banana strain grown for export. Recently, a Fusarium strain that successfully attacks the Cavendish strain has been documented. Which of the following best provides reasoning supporting a method that would help protect commercial banana crops from infection by pathogenic organisms such as Fusarium fungi? (A) The commercial banana strains should be exposed to X-rays to encourage random mutations that will then be passed to offspring, producing resistance to pathogenic organisms. (B) The Cavendish banana plants should be exposed to pathogenic organisms under controlled conditions, so the plants can be encouraged to mutate and develop resistance to the pathogens. (C) The commercial banana strains should not be grown in monocultures, since many pathogenic organisms are able to evolve rapidly in response to a single selective pressure. (D) Growing the Cavendish strain under different conditions will allow natural selection to produce the variation needed to resist infection by pathogenic organisms.

I don't understand why it is C

Answer 1

Selection pressure is a force that causes a particular organism to evolve in a certain direction. In the case of antibiotic resistance, antibiotics cause a selective pressure by killing susceptible bacteria, and unfortunately allowing antibiotic-resistant bacteria to survive and multiply. A selective pressure might be a reason for organisms with certain phenotypes to have either a survival benefit or disadvantage. A selective pressure is a phenomenon that leads natural selection.  

Hence in monoculture possibility of adaption is high for bacteria. They can create resistance for particular selective pressure lead to rapid growth of bacteria. Thats why C is correct.