Phylum Cnidaria and Bilateria Clade

Question 1

What are 4 major characteristics that define phylum Cnidaria?

Answer 1

1. Eumetazoa: have true, differentiated tissues
2. Diploblastic = two layers (ecto and endoderm)
3. Has organs
4. Has radial symmetry

Question 2

What are organs?

Answer 2

they are collections of tissues specialized for different tasks

Question 3

What species does phylum cnidaria consist of?

Answer 3

all marine: jellyfish, hydras, sea anemones, and corals

Question 4

What are the two basic body forms of cnidaria?

Answer 4

The polyp, which is the sessile form (kind of like a stalk) and the oral end is upwards attached to a substrate. Within the stalk theres tenticles and gastrovascular cavity. Mouth and anus are the same hole

• The type is the Medusa, this is the motile form of cnidaria such as jellyfish. They have their oral/anal end downwards and move freely through the water via hydrostatic skeleton

Question 5

What is the method of movement in Medusa type structures in phylum cnidaria?

Answer 5

They move via hydrostatic pressure which water pushes against the cells and the cells push against their cavity and it creates a pulse-like motion of movement

Question 6

What do carnivorous cnidarians use to feed and capture their prey?

Answer 6

They contain unique cells called Cnidocytes, each cnidocyte contains very complex endocellular structure called a nematocyst (specialized organelle)

Question 7

What are nematocysts?

Answer 7

they are released by the cnidarians, and they contain sticky parts that may contain toxins to capture prey and use for defence. They are triggered by touch and can shoot out poisons, barbs or sticky substances

Question 8

What are some motile forms of cnidaria (aka Medusa)?

Answer 8

1. Hydrozoa
2. Scyphozoa
3. Cubozoa

Question 9

What are some non-motile forms of cnidaria (aka Polyp)?

Answer 9

They are called anthozoa

Question 10

What are some of the ecology and importance of Cnidarians?

Answer 10

they are predatory in general

• house symbiotic algae called zooxanthellae
• important predators of zooplankton and larval fish
• Toxins they produce and release from nematocysts can be very dangerous for humans
• reefs that are made by corals house and shelter many marine species
• Negative: run off from farms are causing threats to coral reefs.
• Coral bleaching occurs due to loss of zooxanthellae (photosynthetic algae)
• human tourism

Question 11

What is the “portuguese man o’war”

Answer 11

its a floating hydrozoan (medusa) colony that can sting

Question 12

What is the life cycle of the hydrozoan Obelia?

Answer 12

THIS IS NOT THE SAME GROUP AS JELLYFISH

• one species releases an egg and the other releases the sperm into the water
• fertilization occurs
• then the zygote grows into a planula (larva)
• the planula forms into a developing polyp
• the polyp reproduces via asexual reproduction (budding)
• forms a portion of the colony of polyps and grows two distinct parts: a feeding polyp and a reproductive polyp

Question 13

What are some characteristics of polyps?

Answer 13

• they are motile in their larval stage
• they can produce asexually and sexually in one term (reproduce sexually first then asexually by budding)
• they live in colonies and each polyp in the colony has different specialization

Question 14

What are 5 characteristics on the clade Bilateria?

Answer 14

• they have bilateral symmetry
• they have varying degrees of cephalization (their head region is differentiated)
• they have a high concentration of arterior neural ganglia (which is the brain)
• reduced number of non-motile (sedentary animals)
• Triploblastic (they have a endo, ecto and mesoderm!)