Final answer:
The inability to complete meiosis would prevent sexual reproduction, leading to no offspring and potential species extinction. It would also result in chromosome disorders, reducing genetic diversity and adaptive potential.
Step-by-step explanation:
If an organism could not complete meiosis, it would have profound effects on its ability to reproduce sexually. Since meiosis is the process by which gametes, or sex cells, are produced, failure to complete meiosis would result in the absence of viable sperm or eggs. This would prevent the organism from producing offspring, eventually leading to population decline or even species extinction. Moreover, chromosome disorders like nondisjunction can cause developmental issues, and any mistakes during meiosis can result in gametes with an abnormal number of chromosomes. For example, in humans, such errors can lead to conditions like Down syndrome, where there are three copies of chromosome 21, or to the loss of a pregnancy.
Sexual reproduction is highly valued in evolutionary terms for the genetic variation it introduces, which is vital for the adaptation and survival of populations. Meiosis contributes to this variation by reshuffling genes through crossovers during prophase I and random assortment at metaphase I. In sexually reproducing organisms, the alternation between fertilization and meiosis is essential for maintaining the correct chromosome number across generations. Without meiosis, there would be no reduction in chromosome number, causing a potential imbalance upon fertilization and making adaptation through genetic diversity much harder.