18. Which of the following examples best illustrates sexual reproduction?
Answer: B
B: A bee transfers pollen between the flowers of different plants of the same species.
This example best illustrates sexual reproduction, as it involves the transfer of genetic material between two different plants, leading to the fertilization of ovules and the production of seeds.
A) A single bacterium increases in size and divides into two bacteria.
This option describes asexual reproduction, specifically binary fission, where a single organism replicates its genetic material and divides into two identical organisms. This process does not involve the combination of genetic material from two different organisms.
B) A bee transfers pollen between the flowers of different plants of the same species.
This option exemplifies sexual reproduction because it entails the transfer of pollen (male gametes) to the stigma of a different flower (female gametes), resulting in fertilization. This genetic exchange is essential for creating genetic diversity in the offspring.
C) A small bud forms on a yeast cell, slowly grows, and separates from the original cell.
This choice also represents a form of asexual reproduction known as budding, where a new organism develops from an outgrowth or bud on the parent organism. This process does not involve the mixing of genetic material from two different individuals.
D) A flatworm's body fragments into different parts, which all become fully formed adults.
This example illustrates asexual reproduction through fragmentation. Each fragment can develop into a new organism, but again, this process does not involve sexual reproduction or the exchange of genetic material.
Conclusion
Option B is definitively correct as it showcases the essential elements of sexual reproduction, involving the exchange of genetic material between distinct individuals. In contrast, options A, C, and D all describe various forms of asexual reproduction, which do not involve the genetic recombination necessary for sexual reproduction. Thus, only option B accurately represents the concept being tested.