Marine ecosystems are among the most complex and biologically significant systems on the planet, supporting an extraordinary range of species whose interactions maintain global ecological stability. From coral reefs that function as biodiversity hotspots to deep‑sea environments that host organisms adapted to extreme pressure and darkness, marine life demonstrates remarkable evolutionary innovation. These ecosystems regulate climate through carbon cycling, sustain global fisheries, and influence weather patterns that affect human populations worldwide. Yet their resilience is increasingly compromised by anthropogenic pressures such as ocean acidification, plastic pollution, and habitat destruction. Understanding the biological mechanisms that allow marine organisms to survive — and how those mechanisms are disrupted — is essential for developing effective conservation strategies and ensuring the long‑term health of Earth’s oceans.