A farmer has 1000 chickens. A disease is introduced into the population that infects almost
A farmer has 1000 chickens. A disease is introduced into the population that infects almost all of the chickens. The farmer loses 500 chickens to this disease. The chickens that were infected but didn't die produce fewer eggs than the chickens that were never sick, so generations later, there are more chickens that are immune to the disease than chickens who can be infected with the disease. A few generations of chickens later, the genetic diversity of the chickens is drastically reduced. What evolutionary processes are at play?
- A. Natural selection and population bottleneck.
- B. Natural selection and mutation.
- C. Natural selection and genetic drift.
- D. Mutation and genetic drift
Correct Answer: A. Natural selection and population bottleneck.
Explanation
We see natural selection because those chickens that are entirely immune to the disease produce more offspring than those chickens who were infected but survive. The gene(s) that offers protection against contracting the disease is retained at a greater rate than the gene(s) that protects the chicken from dying of the disease. If the genetic diversity of the population is reduced generations later, this suggests that the chickens experienced a population bottleneck when the population number dropped to half of its original number.