Q: Which formula best represents the prezygotic isolation index as described in the study materials?

$$\text{Prezygotic isolation index} = 1 - \text{Interspecific mating probability}$$

Question 1

Which of the following best describes the concept of 'reinforcement' in the evolution of reproductive isolation?

Accepted Answer

Natural selection favors alleles that confer mating discrimination, reducing hybridization in areas of sympatry.

Question 2

According to Haldane’s Rule, which sex is most likely to exhibit sterility or inviability in hybrids between Drosophila species?

Accepted Answer

The heterogametic sex (XY or ZW)

Question 3

In Coyne & Orr’s studies, what is the relationship between genetic distance ($$D) $$and prezygotic isolation in allopatric taxa?

Accepted Answer

Prezygotic isolation increases as genetic distance increases.

Question 4

Which experimental result supports the rapid evolution of assortative mating in Drosophila pseudoobscura?

Accepted Answer

Flies reared on the same substrate showed strong evidence for assortative mating after 25 generations.

Question 5

Which of the following is a premating barrier to reproductive isolation?

Accepted Answer

Ecological isolation, such as breeding at different times or places

Question 6

What is the significance of the Nup96 gene in the context of hybrid incompatibility between Drosophila melanogaster and D. simulans?

Accepted Answer

Nup96 is essential for cytonuclear transport and its divergence causes hybrid inviability.

Question 7

Which formula best represents the prezygotic isolation index as described in the study materials?

Accepted Answer

$$	ext{Prezygotic isolation index} = 1 - 	ext{Interspecific mating probability}$$

Question 8

What is the 'Snowball effect' in the context of reproductive isolation?

Accepted Answer

Hybrid incompatibilities accumulate exponentially as genetic divergence increases.

Question 9

Which scenario best illustrates reinforcement in Drosophila pseudoobscura and D. persimilis?

Accepted Answer

Females from sympatric populations avoid mating with hybrid males, while allopatric females do not.

Question 10

Which of the following is a plausible explanation for Haldane’s Rule based on the study materials?

Accepted Answer

Sterility and inviability are pleiotropic effects of recessive alleles exposed in the heterogametic sex in hybrids.

Question 11

If a Drosophila population is split by a mountain range, and each population evolves independently, which type of reproductive isolation is most likely to evolve first?

Accepted Answer

Prezygotic isolation due to ecological or behavioral differences

Question 12

Which experimental approach did Presgraves et al. (2003) use to investigate hybrid incompatibility in Drosophila?

Accepted Answer

Crossing D. melanogaster females with D. simulans males and mapping lethal regions using chromosomal deletions and balancer chromosomes.

Question 13

Which of the following is NOT a postzygotic barrier to reproductive isolation?

Accepted Answer

Ecological isolation

Question 14

In the context of Drosophila speciation, what does the term 'intrinsic reproductive isolation' refer to?

Accepted Answer

Isolation due to genetic incompatibilities that reduce hybrid fitness.

Question 15

Which gene was mapped by Presgraves et al. (2003) as responsible for hybrid inviability in Drosophila?

Accepted Answer

Nup96

Question 16

If the prezygotic isolation index between two Drosophila species is 0.8, what is the probability of interspecific mating?

Accepted Answer

$$0.2$$

Question 17

Which of the following best explains why hybrid males between D. melanogaster and D. simulans die at the pupal/larval transition?

Accepted Answer

Hybrid males express incompatible alleles from both parents, leading to lethal cytonuclear interactions.

Question 18

Which scenario would most likely lead to reinforcement of reproductive isolation?

Accepted Answer

Two populations come into secondary contact and hybrids have reduced fitness.

Question 19

Which of the following is a real-world example of a premating barrier in plants?

Accepted Answer

Specialized pollinators that only visit certain species

Lec 38

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