Jellyfish have drifted through the world's oceans for more than five hundred million years, making them among the oldest animals on Earth. Jellyfish have drifted through the world's oceans for more than five hundred million years, making them among the oldest animals on Earth. This book offers a clear, structured introduction to their biology, behavior, and ecological role. You will learn about their basic anatomy, how they move and feed without a brain or heart, and how they reproduce through complex life cycles. The book also covers the diversity of species, from the tiny box jellyfish to the large lion's mane, and examines their place in marine food webs, their interactions with humans, and their surprising resilience in changing ocean conditions. Written and generated with the aid of artificial intelligence, this guide is intended as an accessible starting point for readers curious about these ancient, understated creatures. Jellyfish have drifted through the world's oceans for more than five hundred million years, making them among the oldest animals on Earth. This book offers a clear, structured introduction to their biology, behavior, and ecological role. You will learn about their basic anatomy, how they move and feed without a brain or heart, and how they reproduce through complex life cycles. The book also covers the diversity of species, from the tiny box jellyfish to the large lion's mane, and examines their place in marine food webs, their interactions with humans, and their surprising resilience in changing ocean conditions. Written and generated with the aid of artificial intelligence, this guide is intended as an accessible starting point for readers curious about these ancient, understated creatures.