What do these animals have in common?

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What do these animals have in common?
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Phylum Cnidaria the jellies
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What is a cnidarian?

• invertebrates
• more than 9000 species
• jellyfishes, corals, sea anemones, and hydras.

• worldwide
• all but a few are marine

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• two distinct body forms during their life cycles
  

Medusa
Polyp
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• polyp sessile form
• mouth surrounded by tentacles.

- sea anemones, corals, and hydras.

• medusa free-swimming form
• - jellyfish

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Body Form
The Medusa

• an umbrella-shaped,
• floating body a bell, with mouth on underside.

Tentacles
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Body Form
mouth
The Polyp Attached to substrate, mouth on top
surrounded by tentacles
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Body form
One body form may be more often seen than the
other.
In jellyfishes, the medusa form is usually
observed.
In hydras, polyp form is most common form of
hydras.
http//www.microscope-microscope.org/gallery/Mark-
Simmons/pages/hydra2.htm
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Body form
Most cnidarians undergo a change in body form
during their life cycles.
Medusa
Polyp
At some point, most Cnidarians exist as both a
polyp and a medusa.
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Body structure
Mouth
Tentacle

• radially symmetrical
• one body opening
• two cell layers
• How is this similar to sponges?

Cavity
Inner cell layer
Jellylike layer
Bud
Outer cell layer
Disc
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Body structure

• cell layers are organized into tissues with
  specific functions
• - true tissues

Mouth
Tentacle
Cavity
Inner cell layer
- inner layer mainly assists in digestion
-surrounds the GASTROVASCULAR CAVITY
Jellylike layer
Bud
Outer cell layer
Disc
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Body structure

• two cells layers allows easy diffusion of

- Oxygen - dissolved in water, it can diffuse
directly into body cells.
- Carbon dioxide /other wastes - moves out of
the body cells directly into the surrounding
water.
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Reproduction in cnidarians

• sexual and asexual reproduction

• Sexual reproduction
• occurs in only in the Medusa phase if it has
  both forms in life cycle

IF there is NO medusa stage, then the polyp can
reproduce sexually.
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Sexual Reproduction in Cnidarians
Both the medusae and polyps are diploid (2n)
animals. Diploid 2 full sets of chromosomes
Per body cell
Female
Male
Eggs
Fertilization
Asexual Reproduction
Blastula
Larva
Bud
Polyp
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Nematocyst before discharge
Nematocyst after discharge
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Digestion in cnidarians

• Predators
• - capture or poison prey using nematocysts

- a capsule that contains a coiled, threadlike
tube.
-tube may be sticky or barbed, and may
contain toxins
- located in stinging cells that are on tentacles
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Digestion in cnidarians
Once captured by nematocysts, prey is brought
to the mouth by contraction of the tentacles.
Mouth
Gastrovascular cavity
Polyp
Mouth
Medusa
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• Food enters gastrovascular cavity

• digestive cells release enzymes to break down
  prey
• undigested materials are ejected back out
  through the mouth.

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Diversity of Cnidarians
There are four classes of cnidarians

• Hydrozoa
• Anthozoa
• Scyphozoa
• Cubozoa

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Class Hydrozoa

• 2 groups
• - hydroids (hydra)
• - siphonophores (Portuguese man-of-war)

• marine animals
• Most hydrazoans go through both stages
• Hydra - polyp stage only
• reproduce by budding
• found attached to piers, shells, and other
  surfaces.

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budding
daphnia
development
Sea monkey
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Class Hydrozoa
The siphonophores - floating colonies
-drift about on oceans surface.
The Portuguese man-of-war, Physalia, is an
example of a siphonophore hydrozoan
colony Different functions for different
individuals
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Class Anthozoa

• exhibit only the polyp form.

• Corals
• Sea anemones
• Sea fans

Sea apple feeding
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Corals

• live in colonies of polyps in warm ocean waters
  around the world.

• secrete protective, cuplike calcium carbonate
  shelters around their soft bodies.

• Colonies of many coral species build the coral
  reefs
• provide food and shelter for many other marine
  species.

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Corals
Corals that form reefs are hard corals.

• soft corals do not build calcium carbonate
  structures not reef builders.

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Corals

• Living portion of a coral reef is a thin,
  fragile layer
• grows on top of the shelters left behind by
  previous generations.

• Often found in
• shallow,
• nutrient-poor waters,
• thrive because of symbiotic relationship with
  microscopic, photosynthetic protists called
  zooxanthellae.

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Bleaching Worldwide
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• Zooxanthellae
• produce oxygen and food that corals use,
• Uses carbon dioxide and waste materials produced
  by the corals
• cause bright colors found in coral reefs.
• free-swimming, sometimes leave the corals
• Caused by warming ocean temperatures and
• Increasing acidity due to increased CO2 in
  atmosphere
• Corals die without them bleaching
• 70 bleached in 20-30 yrs 35 million acres so
  far

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• Coral reefs provide habitat for 25 of marine
  fish
• About 1 billion people rely on fish as their
  primary food source

• Tourism over a billion dollars is spent every
  year in the Caribbean, Australia (3.9
  billion/year), and the Pacific Islands
• 1.2 Billion in Florida each year
• Most diverse ecosystem Ocean Rainforest
• 4000 species of fish, 800 species of coral

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• Corals are used for pharmaceuticals
• Chemical extracts from corals have helped create
  drugs to treat AIDS, Cancer, Arthritis,
  Inflammatory disorders, and pain killers
• Beneficial for patients with heart, kidney, and
  liver transplants.

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Class Scyphozoa jellyfish

• Fragile
• sometimes luminescent bodies

• Some are transparent
• May be pink, blue, or orange.

Medusa form is the dominant stage in this
class.
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Class Scyphozoa

• muscle-like cells in outer cell layer can
  contract
• When these cells contract , the bell contracts
• propels the animal through the water.

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Class Cubozoa

• Box jellyfish
• Originally included in Class Scyphozoa.
• Differences
• Their bells are square-shaped, instead of round
• They have primitive brians
• They have eyes
• They swim, not float
• They sleep

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Class Cubozoa

• The Irukandji in Australia is one of the most
  dangerous animals
• It is very small, only 2.5 cm from bell to
  tentacles

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Giant Jellyfish

• Japan has been invaded by Nomuras jellyfish
  the giant jellyfish.

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Research

• What are Nomuras Jellyfish?
• Where are they found? Just Japan?
• What causes them to get so big?
• Are they dangerous?
• Are they new? Or are they only now getting
  noticed?

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Giant Jellyfish

• 6.5 ft wide and 450 lbs
• More common in China and Korea
• Only recently in Japan

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Giant Jellyfish

• Not much is known, Japan studying
  mating/migration habits
• Choking fishing nets
• Possible warmer seas (global warming) causes
  increase in population
• http//video.google.com/videoplay?docid2208948115
  892996006qgiantjellyfishtotal103start0num
  10so0typesearchplindex0

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Where did they come from?
The earliest known cnidarians also date to the
Precambrian, about 630 million years ago.
The earliest coral species were not reef
builders, so reefs cannot be used to date early
cnidarians.
The larval form of cnidarians resembles
protists, and because of this, scientists
consider cnidarians to have evolved from
protists.
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