1. What is speciation? 2. What is a “hybrid zone”? 3. What postzygotic barriers are often found in hybrid zones that result in a lack of species fusion? 4. What are the differences among the three possible outcomes for hybrids over time: reinforcement, fusion, and stability?

explain the following : 1. Does chromosome structure differ between humans and their closest relative among the apes. 2.How can natural selection promote reproductive isolation in allopatric populations

What do you mean by subspecies categories?

Q5. Which of the following is FALSE? If a genetic disease reduces fertility and the allele that causes the disease offers no other advantage, the allele will likely eventually disappear, due to natural selection. Natural selection does not favor individuals who are homozygous for the sickle-cell allele, because these individuals typically die before they are old enough to reproduce. Individuals who are heterozygous HbA/HbS are protected from malaria, and this is why sickle-cell anemia persists in wetter, mosquito-prone regions in Africa. O In regions where malaria does not occur, individuals who are heterozygous HbA/HbS have a selective advantage over those who are homozygous for the normal hemoglobin allele (HbA).

1. In island radiations we often see the following pattern: similar forms found in different species living in similar habitats on different islands. This pattern raises the question: did the form evolve once on a single island in a single species and then spread to multiple islands by dispersal (let’s call this the “dispersal model”)? Or did a single species first disperse to different islands, then ecologically adapt to the many different environments on each (let’s call this the “convergence model”)? A phylogeny can help us identify which of these processes is at play. Considering the three traits shown on this tree, which model appears to have more support: the dispersal model or the convergence model? Explain how you arrived at this conclusion.

1. Anagenesis (non-branching speciation), in which the ancestral and descendant populations do not co- exist in time, but might have occupied the same geographic area, is thought to have occurred in the case: A. of the evolution of several Hawaiian honeycreepers from a single Asian migratory species B. of the evolution of the polar bear Ursus arctos maritimus from the brown bear in Kamchatka C. of the evolution of 13 Galapagos finches from a single South American migratory species D. of the evolution of the proto-horse Merychippus from the near-horse Parahippus on prairies E. of the evolution of the arctic fox from the swift fox in tundra regions of North America

20. Savanna giraffes are thought to have evolved from okapi-like ancestors as the climate became more arid in Africa (20 MYA). Since savanna giraffes and okapis occupied different geographic areas and habitats then, as they do today (grassland for giraffes, mountain forest for okapis), they represent: A. one of the best examples of speciation by cladogenesis due to stabilizing selection B. one of the best examples of speciation by anagenesis due to directional selection C. one of the best examples of sympatric speciation due to stabilizing selection D. one of the best examples of speciation by anagenesis due to stabilizing selection E. one of the best examples of speciation by cladogenesis due to disruptive selection

Researchers use a technique call RNA interference to knock down (i.e. not completely gone) the Bcl-2 gene in the amygdala of lab animals. What cellular response would you expect to occur?   Question 1 options:   A)  An increase in apoptosis; many cells in the area would die   B)  An increase in axon regrowth after injury   C)  A decrease in cytochrome c levels released from the mitochondria   D)  A decrease in glial cell infiltration after injury

Swordtails, platyfish and Poecilia species are incapable of interbreeding with each other but swordtail species 1 can produce viable hybrids with swordtail species 2. In addition, both Poecilla fish, platyfish, and swordtails can all be distinguished genetically, but swortail species 1 and 2 cannot be genetically distinguished. Using this information indicate how many distinct 1) Biological, 2) morphological, and 3) phylogenetic species would be found in this group of fish. If you cannot determine this for any of the 3 species categories, state what you would need to know in order to do so. Edit View Insert Format Tools Table 12pt v Paragraph v BIUAv er Tv: 1. There are four 2.

What are factors which causes two hybrid populations not to change? Reinforcement Fusion Stability