Question

20. A "zony" is a cross between a female pony (2n=64) and a male zebra (2n = 44). Zonies are and have a normal lifespan but the different number of chromosomes between the two parent species means they are unable to produce offspring of their own. Zonies are an example of: hybrid inviability hybrid sterility hybrid breakdown autopolyploidy meiotic error 21. Which of the following would best be described as a case of speciation in sympatry? a. A population of lizards is subdivided by a natural barrier and subsequently diverges to form two species that cannot interbreed. b. Speciation cannot take place in sympatry - only in allopatry, where geography poses a barrier to gene flow. c. A new, isolated population of fruit flies is founded by a small group of colonists, which then diverge from the ancestral source population. d. An individual hermaphroditic plant undergoes meiotic failure, producing diploid pollen and ovules; these self-fertilize, germinate, and grow into several fully fertile tetraploid plants.

Answer 1

Sol. 20

Zonies are an example of hybrid sterility.

Hybrid breakdown

Hybrid breakdown is a type of reproductive failure that appears after the F2 generation of crosses between different species or sub-species. It is caused by incompatibility between interacting genes.

So, option (c) is incorrect.

Hybrid sterility

Hybrid zygotes sometimes develops into adults, such as zonies, but the adults fail to develop functional gametes and are sterile.

So, option (b) is the correct answer for this question.

Hybrid inviability

Hybrid inviability is a post zygotic barrier, which reduces a hybrid's capacity to mature into a healthy, fit adult.

So, option (a) is incorrect.

Autopolyploidy

Autopolyploidy refers to a type of polyploidy in which the chromosome complement consists of more than two copies of homologous chromosomes. It occurs by the fusion of gametes of the same parent.

So, option (d) is incorrect.

Meiotic error

Errors during meiosis can lead to mutations in gametes. Defective gametes that undergo fertilization may result in miscarriages or ultimately lead to genetic disorders. The most likely mistake to occur during meiosis is chromosomal non-disjunction , which results in the wrong number of chromosomes in a sex cell.

So, option (e) is incorrect.

Hence, option (b) is the correct answer for this question.