Cnidarians (hydrozoa and scyphozoa) Flashcards
Cnidaria based on the roots words meaning __
like nettles
are cnidaria an ancient group?
yes, they have the longest fossil history dating back to more than 700 million years
where are cnidaria found?
found in both shallow marine and freshwater habitats
mostly __, some slow swimming species
sessile
characteristics of cnidarians
- exhibit primarily radial symmetry or biradial symmetry
- they exhibit two distinct body forms
- equipped with specialized cells: cnidocytes
- specialized cells used for stinging and capturing prey
- gastrovascular cavity- serving as both the digestive and circulatory system
- nerve net
some molluscs and fish feed on ___
cnidarians
mutualism- hermit crab and cnidarian
- the crab gets some protection from predation by the presence of cnidarians
- cnidarians get a free ride and bits of food from the crabs meal
characteristic of polyps
- tubular body with the mouth directed upward and surrounded by tentacles
- mouth leads into a blind gastrovascular cavity
- attach to substratum by pedal disc
- reproduce asexually by budding, fission, or pedal laceration
in colonial forms…
polyps may be specialized for feeding, reproduction, or defense
colonial polyps are permanently__
attached
hydra can glide on the __
pedal disc
most medusae can move __
freely
life cycles of polyps and medusae
zygote develops into motile planula larva, planula settles and metamorphoses into a polyp
A hydra moves using__
epitheliomuscular cells
Gastrovascular vascular acts as a___
stomach
how do cnidarians eat?
catch prey with tentacles and pass them to the gastrovascular cavity
gastrodermis
layer of cells lining gastrovascular cavity consists chiefly of large, ciliated, columnar epithelial cells:
- nutritive-muscular cells
-interstitial cells
-gland cells
water serves as a__
hydrostatic skeleton
epitheliomuscular cells
- form most of the epidermis and cause muscular contraction
- forms a layer of longitudinal muscle next to the mesogle
end of cnida is covered by a little lid called an
operculum
three functional types in hydras
penetrants, volvents, glutinants
what is the function of the basal or pedal disc in cnidarians?
movement
hydra reproduces asexually by__
budding
the class of cnidarians with the most conspicuous medusa stage is__
scyphozoa
nematocysts are stinging organelles contained inside cells called
cnidocyte
the cnidarian body type best adapted for floating or free swimming is the__
medusa
list the correct sequence of the life cycle of the jellyfish Aurelia
planula settles, scyphistoma, strobila
