Question

7. Suppose that the natural ranges of horses and donkeys were to overlap. Which of the following statements best describes what would likely happen to the populations over time?

a. The hybrid offspring (mules) would become widespread and mate with members of both populations.

b. The hybrid offspring would mate with other hybrid offspring to produce viable offspring.

c. The hybrid offspring would be less reproductively fit and reinforcement would strengthen postzygotic barriers.

d. Eventually all members of both populations would be hybrids.

e. The hybrid offspring would be less reproductively fit and reinforcement would strengthen prezygotic barriers.

Answer 1

Answer 7: C. The hybrid offspring would be less reproductively fit and reinforcement would strengthen postzygotic barriers.

Comments: The group of organism that can interbreed to produce viable, fertile offspring are recognised as species. Mule comes with the mating of the female horse with a male donkey. Mules are infertile and do not have their own offspring’s. Both horse and mule are two separate species so they do not interbreed to produce healthy and fertile offspring’s due to prezygotic and postzygotic reproductive barriers.

Prezygotic barriers: prevent the members of different species from mating to produce embryo due to

• Habitat isolation
• Temporal isolation
• Behavioural isolation
• Gametic isolation etc.

Postzygotic barriers: The hybrid embryo generated after mating of the members of two different species which may not match up correctly or carry a correct set of information. The mismatch of the chromosome is sometimes lethal for embryo if embryo survives that are unhealthy or infertile because it can't split its mismatched chromosomes evenly into eggs and sperm. This type of mismatch is responsible for the formation of mules (sterile).