........The jellyfish are marine invertebrates. Jellyfish can be found in any ocean anywhere. They can be found in only some fresh waters. The name jellyfish is an ordinary name but they have no relationship with fish that have vertebrates. Jellyfish are from a class called the Scyphozoa. The word jellyfish is also used for other relatives of the Scyphozons and some are the Hydroza and the Cubozoa. The jelly kind of material that is around a jellyfish’s body is called ectoplasm because it’s out of the jellyfish’s body. The ectoplasm has amounts of protein granules and other organic things. Those are smaller amounts than its cytoplasm, which is in it. It is also called endoplasm. Endo means inner and ecto means outer.

.....The body of the jellyfish is bell shaped. It also encloses its inner body and that’s where its
tentacles come out. Cnidocytes are cells that are on the jellyfish’s tentacles. The cells make them able to kill other animals. When jellyfish catch their prey, they use the cells to make sure they can eat the prey. Some other jellyfish like the ones from the Rhizostomae class don’t even have tentacles so they can’t sting. Jellyfish also use the cells for defense when attacking. They don’t have organs to use to sense with and they don’t have a brain. But their nervous system helps them know where there is light or odors. It also helps them to do things they need to do fast. They eat small fish and also things smaller than that like zooplankton. They catch it in their tentacles.
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...... Jellyfish are docile and slow swimmers. The shape of their body makes a current that forces the prey to be in a spot where the jellyfish can get the prey. The way they do that is by opening and closing its bell shape on its body several times. They have a digestive system that is not complete. The body of a jellyfish is mostly water - 94%-98% of its body is made up of water. The bell on its body has layers of these 3 things: Epidermis, Gastrodermis and Mesoglea (thick and makes most of the jelly).

.....They have a nervous system called the nerve net, which helps them know if something is touching them. The nerve net is in the layer of epidermis. Its touches a stimuli is connected by nerve rings and it goes through its rhopalial lappet and that part is around the jellyfish's body to the nerve cells. They have fragile organs that are light and are called ocelli. They are used to tell which way is up and which way is down. That's how they respond to the sunlight when it shines on the water, which is up so that’s how they know which way is up and down. The jellyfish has a circulatory system that is not specialized. They use the gastrodermal lining of gastrovascular cavity and that’s where they absorb food or nutrients and they also use that to digest. Since their skin is really thin and their body is oxygenated by diffusion, they do not need this system called a respiratory system. They only have little control over their motion, mostly a motion called free-float. They can move vertically by using their hydrostatic skeleton of the water pouch and also because the motion goes through pulsations of its body that looks like a disc.

... Jellyfish group up into hundreds of jellyfish. They form groups depending on how the ocean currents are, food, climate, and ambient oxygen concentrations. When they are in groups, they sometimes breed a lot. When there is lots of jellyfish some people may say that there is a jellyfish outbreak. Jellyfish are eaten in China and other Asian countries. The life cycle of a jellyfish is like this:

1. An egg
2. Larva
3. Polyp
4. A polyp transforming
5. A young medusa
6. An adult medusa

The male and female jellyfish mate and then the female has an egg and it grows to be a jellyfish.

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