Abyssal zone is the bottom zone in marine ecosystem.These zones are dark and cold throughout the year. Photosynthetic activity is absent.Deep sea animals are mostly predators and scavengers. The larger forms have wider mouth and huge curved teeth which prevent escape of any prey.Absence of skeleton, flattened bodies are some characteristics observed. Some also have special structures that produce light on their bellies, around their eyes and at the sides of their bodies. Some animals show bio luminescence. Hope this helps you
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