Download presentation
Presentation is loading. Please wait.
Published byChristian Watkins Modified over 9 years ago
1
Cnidaria
2
General Information Eumetazoans (true animals) all animals other than sponges-have both tissues and symmetry When eumetazoans develop-they develop three embryonic tissue types Ectoderm outer layer-gives rise to outer covering of body and nervous system Mesoderm middle layer-gives rise to skeleton and muscles Endoderm inner layer-gives rise to digestive organs
3
Cnidaria Characteristics Includes jellyfish, hydra, sea anemones, and corals All radially symmetrical All are carnivorous-capture prey with tentacles around the mouth Evolved a digestive cavity Two body forms Medusa (sexual) free floating, umbrella shape Polyp (asexual) cylindrical, attached to rocks
4
Cont… Single opening (mouth/anus) to gastrovascular cavity where food & water enter & wastes leave; called one-way digestive system Have a simple nerve net (only travels one way) to help with movement & senses
5
Reproductive Life Cycle Alternate generations between polyp and medusa form Planula (larval form) Polyp Medusa Egg Sperm Zygote + Asexual - budding Sexual
6
Stinging Cells Tentacles have stinging cells called cnidocytes Each cnidocyte has nematocyst that are barbed and are used to spear the prey
8
Feeding Use cnidocytes to stun or kill prey Tentacles contract to bring food to mouth Food is digested in gastrovascular cavity
9
Three Classes of Cnidaria Hydrozoa Polyp dominant which is larger than medusa Scyphozoa Medusa dominant and it is larger than polyp Anthozoa Only polyps no medusa forms
10
Hydrozoa Hydrozoans Have both medusa and polyp stages EX: Hydra freshwater- no medusa stage- solitary polyp- lives in quiet ponds, lakes, and streams- attaches to rocks with sticky basal disk EX: Portuguese Man of War marine-medusa and polyps- colony of organisms-gas filled balloon floats on surface and dangling below are the tentacles with stinging cells-prey is entangled in the tentacles
11
Hydrozoan Reproduction Most hydrozoan reproduce asexually by forming small buds on the outside of their bodies-these buds develop into miniature polyps- Hydrozoan can also reproduce sexually-the polyps produces male and female medusa that release egg and sperm in water-the egg and sperm form a larvae called a planulae the eventually settles to the bottom and forms a polyp. Bud
12
Colonization Some Hydrozoans produce colonies in which different polyps have a different specialization. Some specialized in feeding, reproduction, and protection
13
Scyphozoan Scyphozoan cup animal Jellyfish live most of their life as medusa Active predators-hunt food Sea wasp-deadly Reproduce much like hydrozoans but male and female medusa mate and form planulae which settles to bottom and forms polyp. Polyp grows it and buds off to form medusa
14
Anthozoans Anthozoans largest class of Cnidaria – name means flower animal-DO NOT form medusa – Show neoteny (sexual maturity during the larval stage) Sea Anemones soft bodied polyps-coastal- feed on fish-when touched they retract their tentacles-Symbiotic Corals live in colonies-polyp secretes a hard outer covering which make up coral reefs-
15
Three types of Reefs Fringing-close to beach-Florida Barrier-form in deeper water farther out from the shore-Great Barrier Reef in Australia Atoll-coral island that form far out at sea and grow into a ring shape with a lagoon in the center.
16
Homework 1.What are some differences between the three different classes discussed? 2.Why would it be of an advantage to switch from polyp to medusa for vise verse? 3.Why would it be of an advantage to have specialization in colonies?
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.