Cnidarian Reproduction
and Life Cycle
Ms. Springstroh
Sources:
http://www.hartnell.edu/faculty/nwheat/13.%20Radiate%20Animals.ppt
http://web.campbell.edu/faculty/bartlett/chapt13%20cnidarians%20final2.ppt
http://teacher.edmonds.wednet.edu/mths/jtong/documents/sponges__cnidarians.ppt
http://www.dtmag.com/Stories/Marine%20Life/04-01-feature-1.htm
Mrs. Gallegos
Two methods of reproduction
• Asexual
– Typically used by polyps
(especially hydrozoans)
• Sexual
– Typically used by medusae
Asexual Reproduction
In some species, new
individuals simply grow
and split off from the
body of another. In this
case, the new animal is
genetically identical to
its “parent”.
This is called “budding.”
Here is a budding
Hydra.
Advantages to budding?
Disadvantages to budding?
Sexual Reproduction in Jellyfish
• Step 1: Male medusae release sperm, female medusae
release eggs into the water. Sperm and egg join together
in a process called ________.
• Step 2: When sperm and
egg fertilize one another,
a ________ results. The
zygote turns into a
planula (larva), which
settles on a substrate and
grows into a polyp.
• Step 3: The polyp
then produces
tiny ______ by
asexual means
(typically by
budding). Voila,
we have more
medusae! Then,
Step 1 begins
again.
Advantages of sexual reproduction?
• Genetic diversity
• Can move around/disperse
• Parent does not have to share nutrients w/
offspring
Disadvantages of sexual reproduction?
• Have to find a mate
• Low sperm count can lead to a lack of
fertilization
• Sperm or eggs can be eaten
Some types of cnidarians, like the anemone,
have completely lost the medusa stage. The
zygote (fertilized egg) of an anemone
becomes a baby polyp, and forever remains
a polyp.
Others, like many jellyfish, have lost the polyp
stage. In this case, the zygote develops into
a tiny medusa.
Phylum Cnidaria Life Cycle
Animation
• http://bcs.whfreeman.com/thelifewire/conte
nt/chp32/32020.html
Microscopes
• Look at a slide of Obelia.
• Draw what you see on your paper. Your
drawing should be within a circle,
representing your “field of view”.
• Label each drawing as a polyp or a
medusa.
• Which class of cnidarians do you think
Obelia is found under? Be prepared to
justify your answer!