What is an example of a prezygotic barrier in speciation?
A) Different mating seasons
B) Hybrid infertility
C) Hybrid breakdown
D) Reduced hybrid viability
The correct answer and explanation is:
The correct answer is A) Different mating seasons.
In the process of speciation, prezygotic barriers are factors that prevent mating or fertilization between different species. These barriers occur before the formation of a zygote, hence the term “prezygotic.” One example of a prezygotic barrier is different mating seasons, which prevents species from interbreeding due to the timing of their reproductive cycles. When two species breed at different times of the year or in different seasons, they never have the opportunity to mate, thus preventing gene flow between them. This temporal isolation leads to reproductive isolation, which is a key driver in speciation.
This barrier is particularly relevant in species where mating is highly seasonal, such as certain types of frogs or birds. For instance, if one species of frog mates in the spring and another in the summer, even though they may inhabit the same environment, their reproductive timing prevents interbreeding.
Other examples of prezygotic barriers include behavioral isolation, where species do not recognize each other’s mating behaviors, and mechanical isolation, where the physical structures required for mating differ between species, preventing successful copulation.
The other options listed are examples of postzygotic barriers, which occur after fertilization:
- Hybrid infertility (B) refers to when offspring are produced but are sterile, such as in the case of mules (the hybrid offspring of horses and donkeys).
- Hybrid breakdown (C) occurs when the first generation of hybrids is viable and fertile, but subsequent generations suffer from genetic problems.
- Reduced hybrid viability (D) means that hybrids do not develop properly or are not able to survive to reproductive age.
These postzygotic barriers typically prevent the gene flow from continuing across generations, further contributing to speciation.