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Cnidarians
AP Biology Lab Test
24
Biology
Undergraduate 1
11/22/2009

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Term
Cnidarian Clades/Subkingdoms
Definition

Parazoa
  -Sponges
 - “beside the animals”
 -no true tissues


Eumetazoa
  -All other animals
 -“true animals”
  - animals with true tissues
 

Term
Phylum Cnidaria
Definition

-Kingdom Animalia, subkingdom eumetazoa

• Most primitive Eumetazoan
 • Radial symmetry
 • All members have nematocytes (cnidocytes)
 • specialized cells for capturing prey
 • contain organelles called nematocysts (cnidocysts)
 • eject barbed thread tipped with toxins
 • Carnivorous
 • nematocyst studded tentacles to capture prey larger
and more complex than themselves

-Stinging cells, Contain nematocyst

 

Term
Cnidarian Nematocye (Cnidocyte) Anatomy
Definition
[image]
Term
Cnidarian Specialized Cell Types
Definition

        5 Specialized Cell Types

  1.  nerve cells- sensory
  2. gland cells- ex. endodermal gland cells for digestion
  3.  nematocytes- make toxins
  4.  muscle cells- for movement
  5.  interstitial cells- undifferentiated, can become any cell type
Term
Cnidarian True Tissues
Definition
• cells act together to perform a function
 
• evolutionary step above Porifera’s cellular level of
organization
Term
Cnidarian 2 Main Body Forms
Definition
sessile polyp (hydra) vs. free-swimming medusa (jellyfish)
 [image]
Term
3 Cell Layers of a Hydra
Definition
ectoderm
• outer cell layer
• protective epithelium
• nerve tissue
endoderm
• inner cell layer
• lines gastrovascular cavity
mesoglea
• jelly-like layer
• between outer/inner cell layer
Term
Cell Layer Anatomy of a Hydra
Definition

Asexual reproduction by budding

Sexual reproduction via gonads that make egg and sperm

[image]

Term
Anatomy of a Hydra
Definition
[image]
Term
Cnidarian Gastrovascular (GV) Cavity
Definition
• gastro- digestive function
• vascular- circulatory function
• continuous with outside environment
• single opening is mouth and anus
Term
Cnidarian Digestion
Definition
• can eat animals larger than its individual cells
• starts extracellular
• food brought into mouth by tentacles
• gland cells secrete digestive enzymes into gastrovascular cavity
• ends intracellular
• gastroendodermal cells engulf partially digested food by
phagocytosis
• digestion completed in food vacuoles
Term
Cnidarian Excretion
Definition
• excrete metabolic wastes by diffusion
• between cell layers
• out through mouth
• excrete salt into gastrovascular cavity
• regulate water balance
Term
Cnidarian Circulation
Definition
• flagellated cells circulate in GV cavity circulate
materials
Term
Cnidarian Nervous System
Definition
 cephalization- not much
• nerve cells scattered around mouth
• no organization or brain
 nerve net cells and sensory cells
• sensitive to chemicals & touch
• coordinate muscle fiber action
• hormone glutathione produces feeding response
Term
Cnidarian Life Cycle Alternates Between
Definition
polyp (hydra)
• tubular body with tentacles
• sessile (attaches to substrate)
• asexual form
• some species have distinct feeding and
reproductive polyps
free-swimming medusa (jellyfish)
• cup-like jelly body
• tube containing mouth hangs from center
• sexual form
Term
Cnidarian: Polyp vs. Medusa (Picture #2)
Definition
[image]
Term
Cnidarian Reproduction
Definition
Asexual
• bud forms & falls off parent polyp to
become new polyp
Sexual
• medusa releases egg & sperm into
water
• fertilization in water to form zygote
•  zygote develops into larva called
planula
• planula develops into polyp
• polyp develops to new medusa
Term
Cnidarian Reproduction Stages
Definition
[image]
Term
Cnidarian Reproduction Diagram
Definition
[image]
Term
Cnidarian Classes
Definition

Anthozoa- sea anemones, most corals, sea fans, all marine
• no medusa stage
• many are colonial
• many corals have symbiotic relationship with
photosynthetic algae (dinoflagellates)
Scyphozoa- jellies, sea nettles, all marine

Cubozoa- box jellies, sea wasps, all marine
• medusa is box-shaped
• complex eyes

Hydrozoa- hydra, Portuguese man-of-war, Obelia, some corals

Term
Cnidarian Locomotion
Definition
• larva is ciliated and free-swimming
 • adult
 • polyps mostly sessile, attached to substrate
 • move in place
 • can detach & swim to escape predator
 • medusa is free-swimming
 • contractile fibers work together to coordinate movement
Term
Cnidarians: Symmetry, segmetation, mesoderm, type of body cavity, ciliated larva, protostome
Definition
Symmetry- radial; benefits sessile organism so can explore
entire environment
Segmentation- N/A
Mesoderm present- None.  Only 2 embryonic cell layers
(diploblastic).  Adult has epidermis (from ectoderm) and
gastrodermus (from endoderm) separated by jelly-like
mesoglea
Type of body cavity- None b/c only 2 cell layers.  Need 3
cell layers to have a body cavity
Ciliated larva- Planula
Protostome- N/A
Term
Cnidarian cleavage, nervous system, respiratory system, digestive system, excretory system
Definition
Cleavage/cells- Determinant
Nervous system- None.  Has nerve net.  No central
control and little coordination.
Respiratory system- No complex system.  Gas exchange
by diffusion through the outer and inner cell layers.
Digestive system- Gastrovascular cavity open to outside
through mouth.  Digestion is extracellular using enzymes
secreted by gland cells and intracellular by flagellated cells
within food vacuoles.
Excretory system- Excrete metabolic wastes by diffusion
through the inner and outer cell layers and out through
mouth.
Term
Cnidarian reproductive system, circulatory system, members, habitat and relationship to other phyla
Definition
Reproductive system- Asexual:  regeneration and budding. 
Sexual: most sessile organisms are hermaphrodites but do
get cross-fertilization.
Circulatory system- Gastrovascular cavity:  water is
circulated by beating flagella to create current to bring in
oxygen and food.
Members- Hydrozoa (hydra, Obelia); Scyphozoa (jellies);
Cubuzoa (cube jellies);  Anthozoa (sea anemones, corals)
Habitat- Aquatic and mostly marine.  Hydra are fresh
water.
Relationship to other phyla- N/A
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