Cnidarians, Cnetophores Flashcards
What are the main types of cnidarians?
Anemones, corals, jellyfish, hydroids
These organisms are part of the phylum Cnidaria.
How many species of cnidarians are there approximately?
Over 10,000 species
Describe the body structure of cnidarians.
Bag shaped body with a single opening – mouth and anus
What is the gut cavity in cnidarians called?
Coelenteron
What are nematocysts?
Tentacles with stinging cells
How many cell layers do cnidarians have?
Two cell layers – endoderm and ectoderm
What is found between the endoderm and ectoderm in cnidarians?
Mesoglea
What are the two stages in the life cycle of cnidarians?
Mobile medusa and sessile polyp
What type of symmetry do cnidarians exhibit?
Radial symmetry
True or False: Cnidarians have a head and brain.
False
What is the primary feeding strategy of cnidarians?
Predatory carnivores
What is the function of nematocysts in cnidarians?
Used for defence and protection
Describe the structure of a nematocyst.
Barbed dart borne on a coiled thread with toxin
How do nematocysts fire?
Independently based on chemical and mechanical stimuli
Which group of cnidarians has no medusa stage?
Anthozoa
What are the two subtypes of Anthozoa?
Alcyonaria (soft corals) and zoantharian (anemones and reef-building corals)
What is a defining feature of Cubozoa?
Box jellyfish and voracious fish predators
What type of eyes do Cubozoa have?
Well-developed eyes
What is the polyp stage like in Scyphozoa?
Transient
What is the main body composition of jellyfish in Scyphozoa?
Extensive mesoglea
What is unique about Hydrozoa in terms of life stages?
They have both polyps and medusae
How do zoantharian anthozoans contribute to coral reefs?
Nearly all colonial – form large structures
What do polyps of zoantharian anthozoans secrete?
Calcium carbonate around themselves
What role do symbiotic algae play for coral reefs?
Produces nutrients and O2, removes CO2 – promotes deposition of calcium carbonate
