Identify the heritable variation and selection pressure, then trace how differential survival and reproduction increase an advantageous allele over generations.
Aquaculture is the controlled cultivation of aquatic organisms such as fish, shellfish and plants. It is an important source of food in many countries of the world. The photograph shows freshwater aquaculture ponds in Africa.
Vibrio are bacteria that are common in aquatic habitats. They cause diarrhoea and cholera and are also pathogenic to shellfish. The resistance of Vibrio to antibiotics and to heavy metals in aquaculture ponds in Nigeria was investigated.
The samples of Vibrio taken from each pond were spread on agar containing different antibiotics.
The scientists expected the percentage of resistant bacteria to be higher in the samples of Vibrio taken from the ponds previously treated with antibiotics. Explain why the scientists expected this difference.