Polyploidy, the duplication of entire genomes, is a common phenomenon in both prokaryotic and eukaryotic organisms, occurring in somatic and germ cells. While often considered an evolutionary dead end, polyploidy has short-term adaptive potential, especially in response to environmental stress. The retention of duplicated genes following whole-genome duplication (WGD) can lead to long-term evolutionary transitions and increased biological complexity. Ancient WGD events are increasingly recognized as significant in evolutionary history, with evidence showing that many WGDs occurred during key evolutionary periods, such as vertebrate evolution and the divergence of teleosts. However, the number of ancient WGDs is much smaller than the number of current polyploid species, suggesting that polyploidy is often an evolutionary dead end, except under specific conditions. Polyploidy can enhance survival and adaptation through increased genetic variation, changes in metabolism, and improved resistance to environmental stress. It also plays a role in speciation and ecological niche shifts. In plants, polyploidy is common and often associated with increased tolerance to environmental stress. In animals, polyploidy is less common but has been observed in various species. Polyploidy can also contribute to cancer development and resistance to targeted therapy. In prokaryotes, polyploidy is not uncommon and may provide mutational robustness and increased genetic variation. Overall, polyploidy has significant implications for evolution, ecology, and adaptation, and its study is crucial for understanding biodiversity and addressing challenges such as climate change and cancer.Polyploidy, the duplication of entire genomes, is a common phenomenon in both prokaryotic and eukaryotic organisms, occurring in somatic and germ cells. While often considered an evolutionary dead end, polyploidy has short-term adaptive potential, especially in response to environmental stress. The retention of duplicated genes following whole-genome duplication (WGD) can lead to long-term evolutionary transitions and increased biological complexity. Ancient WGD events are increasingly recognized as significant in evolutionary history, with evidence showing that many WGDs occurred during key evolutionary periods, such as vertebrate evolution and the divergence of teleosts. However, the number of ancient WGDs is much smaller than the number of current polyploid species, suggesting that polyploidy is often an evolutionary dead end, except under specific conditions. Polyploidy can enhance survival and adaptation through increased genetic variation, changes in metabolism, and improved resistance to environmental stress. It also plays a role in speciation and ecological niche shifts. In plants, polyploidy is common and often associated with increased tolerance to environmental stress. In animals, polyploidy is less common but has been observed in various species. Polyploidy can also contribute to cancer development and resistance to targeted therapy. In prokaryotes, polyploidy is not uncommon and may provide mutational robustness and increased genetic variation. Overall, polyploidy has significant implications for evolution, ecology, and adaptation, and its study is crucial for understanding biodiversity and addressing challenges such as climate change and cancer.