Question

 19. Variation is important for evolution, because it provides the fitness differences upon which natural selection operates. Sexual reproduction is an important source of variation in plants and animals, but what about asexually reproducing organisms like bacteria? Where does their variation come from? (Concepts: sexual versus asexual reproduction, mechanisms generating allelic variation)

 20. The Phoenix Zoo kept the only remaining population of Arabian Oryx for ten years in captivity. Finally, when the captive population was high enough and the habitat was better protected in Arabia, some of these Oryx were shipped back to Arabia and released into the wild. In the wild most of the newly released Oryx died of starvation, overheating or were killed by predators. Why is this result not unexpected? (Concepts: relationships between genotype and phenotype, relationship between phenotype and natural selection)

 21. Do all domesticated dogs belong to the same species? Why or why not? (Concept: species)

 22. Differentiate between allopatric and sympatric speciation. (Concept: mechanisms of speciation)

Answer 1

19. Asexually reproducing organisms like bacteria generate variation in their genome via horizontal gene transfer (very common in prokaryotes) and mutation (presence of a high frequency of mutation in genome).

20. Bred in secured and stable captivity for a long time, the Oryx population lost the skills and behavioral adaptations needed to survive in the conditions of a harsh and wild natural environment. Due to extended unuse, their useful phenotypes changed and natural selection then acted against them.

21. All domesticated dogs belong to the same species. This is because they can interbreed and produce hybrid or intermediate dogs which are fertile. When two strains of organisms become reproductively isolated, then only they become a separate species, which is not the case for domesticated dogs.

22. Allopatric speciation involves occurrence of a geographical barrier, due to which an existing population gets physically separated, accumulates differences over time and becomes reproductively isolated. This form of speciation is quite common in nature.

Sympatric speciation happens from an ancestral species in a particular population living in a particular habitat without any geographical barriers. Polyploidy is one major way of sympatric speciation. It's commonly found in plants.