Cnidaria Hanna, Monica and Maddy
Kingdom • They are the first to show tissue level organization • Have no organs. • The adult forms are derived from two distinct embryonic germ layers, the ectoderm and the endoderm • Higher phyla are triploblastic
Animalia • Radially symmetric • The end of the organism which contains the mouth is the oral end
Characteristics • Members of this phylum live in both fresh and salt water, have tissues and a simple nervous system, and have stinging cells called nematocysts. • They display radial symmetry and have two embryonic cell layers.
Classification • The three classes are grouped according to body plan. • Members of the class Hydrozoa have both the polyp and medusa stage in their life cycle. • Members of the class Anthozoa have only the polyp stage in their life cycle and are slightly more complex than hydrozoans. • Members of the class Scyphozoa have only the medusa stage in their life cycle. They are the most large and complex members of this phylum.
Jellyfish do not have a specialized circulatory system. • They are able to digest with the help of the gastrodermis that lines the gastrovascular cavity where nutrients from their food is absorbed.
They do not need a respiratory system since their skin is thin enough that air can diffuse in and out of their body
Jellyfish have long tentacles with a number of nematocysts inside the cnidoblast which have a trigger and a stinging apparatus. • When tentacles make contact with a fish, the thousands of nematocysts fire paralyzing toxins into their prey. When the prey is paralyzed, the tentacles move together to push it into the mouth of the jellyfish.
The jellyfish squeeze their bodies in order to push the streams of water into a direction. • They use the velocity of their bodies as well as the weight of the water when pressure is applied to propel them.
The cells of the gastro dermis distributes digestive acids that pour into a main cavity. The enzymes within the digestive acids begin the process of digestion, which is completed within the vacuoles when the prey is broken down and engulfed by the cells of the gastro dermis. Food digestion
Food is excreted by diffusing through the top of the gastro vascular cavity which is also commonly known as the mouth, after the nutrients is absorbed within the body. Excretion
Interesting Facts • Cnidarians are radially symmetrical • Cnidarians have tentacles that encircle their mouth. • To treat a box jellyfish sting, you have to pour vinegar over the effected area. If left untreated, the venom can impair the heart and can cause death of children within 3 minutes. • Cnidaria have no brains or even central nervous systems
Changes In Classification • Cnidarians were grouped with Ctenophores in the phylum Coelenterata, however their differences caused them to be placed in separate phyla. Cnidarians are classified into four main groups: sessile Anthozoa(sea anemones)(sea pens) swimming Scyphozoa (jellyfish) Cubozoa(box jellies) • Staurozoa are now a class in their own rather than a sub-group of Scyphozoa.
References • http://sicb.org/meetings/2010/symposia/cnidaria.php • http://www.google.ca/imgres?q=cnidaria+phylogenetic+tree&um=1&safe=active&sa=N&rls=com.microsoft:en-ca&hl=en&tbm=isch&tbnid=vq9C83M9uZc39M:&imgrefurl=http://www.unige.ch/cyberdocuments/theses2001/KaloulisK/these_body.html&docid=PdsYdfzt32QHJM&imgurl=http://www.unige.ch/cyberdocuments/theses2001/KaloulisK/images/image002.jpg&w=392&h=382&ei=4ExxUbymGK7b4AP-84CgBA&zoom=1&biw=1024&bih=585&iact=rc&dur=172&page=1&tbnh=139&tbnw=152&start=0&ndsp=15&ved=1t:429,r:7,s:0,i:104&tx=76&ty=24 • http://www.darwinsgalapagos.com/animals/cnidaria_jellyfish_coral_sea_anemone.htm • http://www.google.ca/search?rls=com.microsoft:en-ca&q=who%20belongs%20in%20the%20cnidaria%20family&biw=1024&bih=585&safe=active&surl=1&um=1&ie=UTF-8&hl=en&tbm=isch&source=og&sa=N&tab=wi&ei=ZVFxUaKIJpGn4APXloGQBA • http://animaldiversity.ummz.umich.edu/accounts/Renilla/classification/ • http://en.wikipedia.org/wiki/Fire_coral • http://animaldiversity.ummz.umich.edu/accounts/Pelagia/classification/