Cnidaria and Ctenophores Flashcards
(22 cards)
What types of animals are included in the phylum Cnidaria?
Hydras, jellyfish, sea anemones, and corals.
What kind of body symmetry and germ layers do cnidarians have?
Radial symmetry and diploblastic with ectoderm and endoderm separated by jelly-like mesoglea.
What is the gastrovascular cavity in cnidarians?
A central digestive cavity with one opening serving both digestion and circulation.
What are cnidocytes and nematocysts?
Specialized stinging cells (cnidocytes) containing capsules with long threads (nematocysts) that discharge to entangle or inject toxin into prey
Where are nematocysts mostly located in cnidarians?
In the epidermis of tentacles, around the mouth, and lining the gastrovascular cavity.
How do cnidarians respond to stimuli without a brain?
They have a nerve net (plexus) that allows simple movement towards or away from stimuli.
What is the difference between the polyp and medusa body forms?
- Polyp: sessile, cylindrical, mouth upwards, attached at aboral end.
- Medusa: free-swimming, bell-shaped, mouth downward, tentacles hanging from oral surface.
What is the lifecycle of Hydrozoa like?
Usually alternate between asexual polyp and sexual medusa stages; some lack one stage; often colonial.
What distinguishes Scyphozoa (true jellyfish)?
Prominent medusa stage, bell with tentacles, no velum, larvae called planula develop into sessile polyps (scyphistoma) which strobilate to produce ephyra (juvenile medusae).
What makes Cubozoa (box jellyfish) unique and dangerous?
Square bell shape, potent venomous nematocysts causing human fatalities, strong swimmers, and complex eyes.
What is coral bleaching and what causes it?
Expulsion of symbiotic dinoflagellates from corals due to stress (temperature rise, salinity changes, starvation, solar irradiance) causing coral death.
How do ctenophores move?
Using eight rows of cilia called combs.
Do ctenophores have nematocysts?
No, instead they have adhesive cells called colloblasts.
What are some characteristics of ctenophores?
Fragile, transparent, bioluminescent, carnivorous on plankton.
What is cephalisation?
The evolutionary trend of developing sensory structures concentrated at the anterior end.
What are some key traits of nemerteans?
Mostly marine, dorsoventrally flattened and ciliated, have an eversible proboscis for prey capture, complete digestive tract with mouth and anus.
Describe the body and digestion of flatworms.
Dorsoventrally flattened, unsegmented, with a gastrovascular cavity that has only one opening.
How do flatworms respire and excrete?
Gas exchange via diffusion; excretion via protonephridia (simple tubular system).
What are the four classes of flatworms?
Turbellaria, Monogenea, Trematoda, and Cestoda.
What distinguishes Turbellaria?
Mostly free-living, swim or crawl on mucus, use a mid-ventral mouth to feed, some stab prey with a hardened stylet.
What are Monogenea and Trematoda commonly called?
Flukes; Monogenea mostly ectoparasites on aquatic vertebrates; Trematoda mostly endoparasites with complex life cycles.
Describe cestodes (tapeworms).
Endoparasites in vertebrate intestines, have a scolex with hooks/suckers, segmented body (strobila) made of reproductive proglottids.
