Marine Biology Phylum Snidaria

1. Phylum Cnidaria

2. General Characteristics
• They are ________ symmetrical;
oral end terminates in a ________
surrounded by __________
• They have 2 tissue layers
• Outer layer of cells - the
_____________
• Inner __________________,
which lines the gut cavity or
______________________
cavity (gastrodermis secretes
digestive juices into the
gastrovascular cavity)
• In between these tissue layers is a
noncellular jelly-like material called
________________

3. Cnidarian Body Plans
_________________ form
• Tubular body, with the mouth directed ______________
• Around the mouth are a whorl of feeding ________________
• Only have a small amount of __________________
• _______________
_________________ form
• ________________ or umbrella shaped body, and the mouth is directed
___________________.
• Small tentacles, directed
downward.
• Possess a large amount
of ____________
• _______, move by weak
contractions of body

4. Soft Coral
Polyp
Worm
Anterior end with brain, eyes, etc.

5. Conditions for growth
• Requires a temperature of 70-85 F degrees
to grow.
• Water movement ___________ the supply
of ___________ and of __________.
• Clarity allows _____________ for critical
plankton growth.
• Ocean water is a source of __________ for
their skeleton development.

6. Movement
• Both the epidermis and the gastrodermis possess ____________
arranged in a loose network - nerve net (plexus), which innervate
primitively developed muscle fibers that extend from the epidermal
and gastrodermal cells
• ______________ in one part will spread across the whole body via
the network

7. Nutrition
• Cnidarians are ________________ (hydras and corals eat
_____________ and sea anenomes can eat ______________
• Tentacles capture ________ and direct it toward the mouth so that
it can be digested in the ___________________ via secretions from
gland cells (extracellular digestion); some food is phagocytized by
special cells and digestion occurs ________cellularly
• The gastrovascular cavity exists as ________________ for food
intake and the elimination of waste
• There is no system of internal transport, gas exchange or
excretion; all these processes take place via _________________

8. Stinging Organelles
• Prey is captured by stinging cells called
____________ located in the outer epidermis.
• The cnidocyte is armed with a stinging
structure called a ______________.
• The nematocyst is a long coiled thread that
is _________ to release by touch or chemicals
• Some entangle the prey; others harpoon prey
and inject a paralyzing _____________

10. Reproduction
•Some ________________ lost parts
• Asexual reproduction is common with new
individuals being produced by ______________
• They are _________________
(sexually distinct as males and females)
• Fertilization is ______________, with the
zygote becoming a elongated, ciliated, radially
symmetrical larva - __________________
•The Larva is ____________________
(plankton for a while) until it drops to the ocean
floor and grows into a ____________
Planula larva

11. Class ____________________
• Includes the solitary freshwater _____; most are colonial and marine
• Typical life cycle may include both asexual polyps and sexual
medusa stages
Solitary Hydras
• Freshwater hydras are found in ponds and
streams on the underside of vegetation
•Mouth opens to the gastrovascular cavity
• The life cycle is simple: eggs and sperm are
shed into the water and form fertilized _____;
____________ is passed and hatches into
young hydras
• Asexual reproduction via ____________

12. Colonial Hydrozoans - e.g., Obelia
•All polyps in the colony are usually
__________________________
• Two different kinds of individuals that
comprise the colony:
- __________ polyps or gastrozooids (C)
and - - ______________ polyps or
gonozooids (B)

13. Class Hydrozoa cont.
Other Hydrozoans
•____________________:
Single gas-filled float with
tentacles
•______________ house
the polyps and modified
medusae of the colony
• _________________

14. Class __________________
_______________
• The medusae are
_______________ and contain
massive amounts of mesoglea
•Possess four ____________
pouches lined with ____________;
these are connected with the mouth
and the gastrovascular system

15. • Gametes develop in
gastrodermis of gastric
pouches; eggs and sperm are
shed through mouth
• Fertilized eggs develop into a
___________; settles on
substrate and develops into a
___________
• The polyp releases free
swimming _________ jellyfish
•The jellyfish make _______
and continue the cycle
Scyphozoan Life Cycle - Aurelia

16. Class __________________
• Exclusively ____________; there is no _______________ stage
• At end of the mouth is a ciliated groove that generates a water current and
brings food to the gastrovascular cavity
• Possess a well developed ________________
•The gastrovascular cavity is large and petitioned by septa or
mesenteries that increase the surface area for digestion or support

17. Class Anthozoa cont.
• Most anthozoans are ____________
(e.g. corals) and secrete external
skeletons composed of
_____________________________
• Corals obtain much of their energy
from microscopic photosynthetic
green algae (________________) or
dinoflagellates that live
__________________ inside the
cells of the coral
•Why live together?
•Coral?
•Zooxanthellae?

18. Ctenophora – _______________
• 100 species up to
_______________!
• Swim with eight rows of
______ that beat in waves.
• ____________ with big
appetites eating fish larvae
and ______________.