00:00Jellyfish are some of the oldest creatures on Earth, having existed for over 500 million years.
00:07They are invertebrates, meaning they have no bones, no brain, and no heart.
00:13About 95% of their body is made up of water, which gives them a translucent, jelly-like appearance.
00:21Most jellyfish move through the water by pulsating their bell-shaped bodies,
00:25but they are largely carried by ocean currents.
00:28They have umbrella-like bodies with tentacles hanging down.
00:34These tentacles contain stinging cells used for capturing prey and for self-defense.
00:41Some species have venom that can be dangerous to humans.
00:45For instance, the box jellyfish is among the most venomous animals in the world.
00:51However, most jellyfish are harmless and may only cause mild skin irritation.
00:56Jellyfish usually feed on plankton, small fish, and other tiny sea creatures.
01:03They capture prey and bring it into their mouth opening, which also serves as an anus,
01:09a single opening for both ingestion and waste expulsion.
01:13Their reproduction is fascinating.
01:15Jellyfish go through both sexual and asexual stages.
01:20Their life cycle includes both a polyp and a medusa phase, allowing them to reproduce rapidly and spread widely.
01:28Today, climate change, overfishing, and warming oceans have led to jellyfish blooms in some areas,
01:35which can place stress on marine ecosystems.
01:37root
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