The jellies Flashcards
what is meant by the term Radiata
animals with radial symmetry
what is the phylum Cnidaria
marine diploblastic species which possess a gastrovascular cavity and have two basic body plans
give an example of species in the phylum Cnidaria
hydra
jellyfish
sea anemones
corals
what are the two basic body plans of cnidaria
1) polyp
2) medusa
outline the differences between the polyp and medusa body plans
1) sessile with an oral end direct upwards with mouth and tentacles for prey capture = asexual
2) free-living with a bell shape with an oral end concave pointed down and tentacles which hang from it = sexual
where are the medusoid forms found
in all cnidarian classes exepct anthoza
what are the stinging cells called in cnidarians
cnidocytes
outline how cnidocyte cells work
contain a trigger mechanisms called a nematocysts which contains along thread within a capsule which when discharged is thrown out and penetrate prey and release a toxin
outline how cnidaria can move
a fluid filled gastrovascular cavity can be used as a hydrostatic skeleton allowing simple movement
what are the different classes of the cnidaria phylum
1) hydrozoa
2) scyphozoa
3) cubozoa
4) staurozoa
5) anthozoa
what are the 2 genera of pleustonic hydroids
1) porpita
2) velella
what are siphonophores
1 order of hydrozoa = are colonies of medusoid individuals which float and swim, they drift beneath the surface e.g. portugaese man of war
outline the symbiotic relationship between hermit crabs and hydroza
hydrozoa lives on the shell of the grab providing protection using the stinging cells, in return the crab removes debris and moves fresh water over it
outline some characteristics of the class of jellyfish, scyphozoa
polyp stage as a larval form
body composed of translucent mesoglea with tentacles haing from bell margin
oral arms= 4 manubruim
no velum
outline sexual reproduction in scyphozoa
1) planula larvae develop after fertilisation
2) they settle as scyphistoma at the ocean floor
3) they feed and produce more scyphistome by budding
4) produce young jellyfish medusae by budding off at oral end and stacking in plates
5) released as young jelly fish
what is strobilation
the process which releases strobila (stacked jellyfish medusae) as young jellyfish, ephyra
outline the characteristics of box jellyfish
tranverse section the bell is square with tentacles at each corner
scyphistoma dont produce strovila
- strong swimmers
- predators
- lethal to humans
what does positively photoactic mean
move towards the light e.g. cubozoa jellyfish
outline the characteristic of the class staurozoa
stalked jellfish which dont alternate between polyp and medusa life cycles
the medusa is attached
found in colder waters
outline the characteristics of the class anthozoa
no medusae life cycle
all marine
poylps contracticle
= corals and anemones
what are the three subclasses of anthozoa
1) octocorallia - polyps have 8 pinnate tentacles some have sclerites
2) hexacorallia = 12 tentacles in 2 cycles and not pinnate
3) ceriantipatharia
how do anemones reproduce asexually
1) pedal laceration
2) fragmentation
3) longitudinal fission
what causes coral bleaching
- increasing water temp
- starvation
- changes in salinity
- changes in solar irradiance
what are the two classes in the phylum ctenophora
1) tentaculata
2) nuda
what is the key differences between ctenophora and cnidaria
instead of stinging cells they have adhesive cells called colloblasts
bioluminescence
what is cephalisation
an evolutionary trend towards developing sensory structures at the anterior end (the head)
what is the difference between radiata and bilateria
radiata= two germ cell layers (diploblastic)
bi = three germ layers (triploblastic)
what is an acoelomate
translates to without hollow
the area is filled with mesoderm cells so no true cavity
what are the two phyla of acoelomates
1) nemertea
2) platyhelminthes
outline the characteristics of nemertea phyla
- ribbon worms
- free living
- dorsoventrally flattened
- complete digestive tract with mouth and anus
outline the characteristics of the phylum platelminthes
flatworms
- body dorsoventrally flattened
- gas exchange via diffusion
- no circulatory organs
what is a protonephridium
a simple tubular excretory system
