**Step-by-Step Solution:**
1. **Understanding Gametogenesis**: In vertebrate animals, gametogenesis refers to the formation of gametes (sperms and eggs). The male process is called spermatogenesis, while the female process is called oogenesis.
2. **Initiation of Processes**: Oogenesis begins during intrauterine life in females, meaning it starts before birth. In contrast, spermatogenesis begins at puberty in males, which is the onset of sexual maturity.
3. **Outcome of Gametogenesis**: Oogenesis typically produces one functional ovum and three polar bodies (which are non-functional), resulting in a total of four cells, but only one is viable. Spermatogenesis, on the other hand, results in four functional sperm cells from one spermatogonium.
4. **Cytokinesis Differences**: In oogenesis, cytokinesis (the division of cytoplasm during cell division) is unequal. This means that during the division of the primary oocyte, one cell (the secondary oocyte) receives most of the cytoplasm, while the other (the polar body) receives very little. In contrast, cytokinesis in spermatogenesis is equal, resulting in four sperm cells of equal size.
5. **Duration of Processes**: Oogenesis ends at menopause in females, which is a natural cessation of reproductive capability. Spermatogenesis, however, continues throughout a male's reproductive life and does not have a definitive end point like menopause.
6. **Conclusion**: The main differences between spermatogenesis and oogenesis include the timing of initiation, the number of functional gametes produced, the nature of cytokinesis, and the duration of the processes.
**Final Answer**: The correct statement about the differences between spermatogenesis and oogenesis is that cytokinesis is unequal in oogenesis, while it is equal in spermatogenesis.
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