
A prezygotic barrier prevents (a) the union of egg and sperm (b) reproductive success by an interspecific hybrid (c) the development of the zygote into an embryo (d) allopolyploidy from occurring (e) changes in allometric growth

Introduction: The biological species concepts define species as the group of members which can interbreed among themselves and produce fertile offspring. It explains the integrity of a species is maintained by reproductive isolation. The prezygotic barriers are the important role players to prevent interspecies breeding.
Answer to Problem 1TYU
Correct answer: A prezygotic barriers prevent the fertilization process by the union of egg and sperm of two different species. Hence, the correct answer is option (a).
Explanation of Solution
Reason for correct answer:
The reproductive isolation by prezygotic barriers prevents the event of fertilization of the gametes of the gametes of two different species. The prezygotic barrier as its name suggests is the barrier having several mechanisms to discourage different species including closely related species to not to mate with each other and become reproductively isolated.
Option (a) is given as “the union of egg and sperm”.
The union of egg and sperm is prevented by the prezygotic barrier. Hence, the correct answer is option (a).
Reasons for incorrect answer:
Option (b) is given as, “reproductive success by an interspecific hybrid”.
The prezygotic barrier as the name suggests is a barrier which prevents the formation of zygote. Instead, the reproductive success of an interspecific hybrid is checked by the means of postzygotic barriers. Hence, option (b) is incorrect.
Option (c) is given as, “the development of the zygote into an embryo”.
The development of the zygote into an embryo is checked by the means of reproductive failure mechanism which is a part of postzygotic barriers instead of the prezygotic barrier. Hence, option (c) is incorrect.
Option (d) is given as, “allopolyploidy from occurring”.
The prezygotic barriers do not prevent allopolyploids instead of postzygotic barriers along with selection pressure checks allopolyploidy. Hence, option (d) is incorrect.
Option (e) is given as, “changes in allometric growth”.
The changes in allometric growth are a result of adaptive evolutionary modifications of pre-existing characters of the same species whereas prezygotic barriers prevent fertilization and mating between two different species. Hence, option (e) is incorrect.
Hence, the options (b), (c), (d), and (e) are incorrect.
A prezygotic barrier is an isolation mechanism which prevents fusion of male and female gametes (sperm and egg).
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Chapter 20 Solutions
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