Sci230 Week 7

Physiology Assignment
August 30, 2013
Lisa Miller

Jellyfish are sea dwelling organisms that can be very intimidating. They are extraordinary creatures that are both beautiful and mysterious. These creatures have adapted to life in the water.
Jellyfish are made up more than 90% of water, which helps them float in the water (Jellyfish Adaptations, 2013). They are composed of an outer layer called the epidermis. This body part covers and protects the external body of the organism. The inner layer called the gastrodermis lines the gut. A jellylike material can be found between these two layers, called the mesoglea. The jellyfish has one digestive cavity that is rather simple called the coelenterons. It does the job of the gullet, stomach and intestine. There is only one opening that is shared as the mouth and the anus. Jellyfish have four to eight tentacles that are used to transport food into the mouth. Jellyfish do not have brains instead they have a nerve net. This is used to detect and respond to light, smell and other stimuli (Jellyfish, 2010).
(Jellyfish Anatomy, 2013)

Jellyfish have no real control over horizontal its horizontal movement. Waves and current aid in horizontal movement while muscles found in the hood (bell) of the organism move the jellyfish vertically. Muscles found in the hood contract and relax pushing the jellyfish through the water. This pulsating rhythm can be very important because jellyfish are light sensitive. The pulsating movement allows the organism to dive deeper into the water allowing it to get away from the suns ray (Jellyfish, 2010).
Jellyfish have a special apparatus called a cnidoblast, a venomous mechanism used for defense and feeding. Inside the cnidoblast is a small structure called the nematocyst. This is adapted with a trigger and a stinging structure. Nematocysts consist of a hollow coiled thread with barbs that lines its length. These are found on the tentacles or the oral arms of the...