Which of the following is an example of a prezygotic reproductive isolating mechanism?

• A. Hybrid breakdown, where hybrids have reduced fitness in subsequent generations
• B. Temporal isolation, where species breed at different times
• C. Hybrid inviability, where hybrids fail to develop properly
• D. Hybrid sterility, where offspring are infertile

Answer: (B)

Verified step by step guidance

1. Understand the concept of reproductive isolating mechanisms: These are biological features that prevent different species from interbreeding. They are categorized into prezygotic (before fertilization) and postzygotic (after fertilization) mechanisms.
2. Review the definition of prezygotic isolating mechanisms: These mechanisms prevent the formation of a zygote by hindering mating or fertilization. Examples include temporal isolation, behavioral isolation, mechanical isolation, gametic isolation, and habitat isolation.
3. Analyze the provided options: Identify which mechanisms occur before fertilization (prezygotic) and which occur after fertilization (postzygotic).
4. Focus on the option 'Temporal isolation': Temporal isolation is a prezygotic mechanism where species reproduce at different times (e.g., different seasons or times of day), preventing interbreeding.
5. Conclude that the other options (hybrid breakdown, hybrid inviability, and hybrid sterility) are postzygotic mechanisms because they involve issues that arise after fertilization, such as reduced fitness, failure to develop, or infertility in offspring.