Explain the term selective pressure as it relates to changes in populations

Selection pressures are external agents which affect an organism's ability to survive in a given environment. Selection pressures can be negative (decreases the occurrence of a trait) or positive (increases the proportion of a trait)

Selection pressure are external agents which affect an organism ability to survive in a given environment, selection pressures can be negative ( decreases to occurrence of a trait) or positive ( increases the proportion of a trait)

in the year 2850, humans successfully colonized mars. the martian modules that were constructed could hold only a small population of people. it is now a century later, and the population on mars has grown to 600 people. of the current mars population, 45 people express the recessive phenotype for phenylketon- uria (pku) syndrome (pp genotype).

explanation: