A new species of hawk that preys on rabbits is introduced to the habitatThe hawks have more success in catching rabbits with white fur because they are easier to see in the habitatThe rabbits´ white fur mutate so their fur is tan or brownThe next generation of rabbits has a higher proportion of individuals with tan and brown fur.
Explanation:
Natural selection is an evolutive force that can act favoring an allele or against it, according to how it affects the fitness of individuals. Natural selection selects beneficial alleles and increases their frequency in the population.
When many organisms in a population sharing the same trait die, it is because they did not have good fitness, so they were not adapted to the environment and its pressures. The alleles coding for that trait were not good for the fitness of the animals, so they do not get to survive.
These individuals die before reproducing, so they could not transfer their genetic charge to the following generation. Eventually, the alleles coding for the trait will decrease in the population, probably near zero. Natural selection is acting against this phenotype. Other alleles will be beneficiated, and their frequency in the population will increase.
This change in alleles frequency is what we call adaptation.
Natural selection results in adaptation, which means the increase of the aptitude phenotype. Aptitude is the contribution of each genotype to the next generation.
In many cases, adaptations can be correlated to environmental factors or selective pressures applied by other organisms or habitats.
Let us remember that a mutation is a change or alteration in DNI sequences that introduce new variants. Many of these are eliminated, but some of them might succeed and be incorporated into each individual. These mutations are the ones that have been selected by natural selection.
So, in the exposed example, we are focussing on rabbits populations.
•The selective pressure or modeling environmental factor is predation by the introduced hawk.
•The rabbits´ response to predation is the survival of only those that carry mutations ⇒ tan or brown fur
•Natural selection benefits these mutations.
•Tan or brown rabbits survive and increase their fitness.
