7. Eumetazoa Intro: Cnidaria Flashcards
(63 cards)
The clade Eumetazoa is characterized by phyla with ‘true tissues’, which are clearly derived from what?
embryonic ectoderm and endoderm layers
If ctenophora is more basal than placozoa and/or porifera, what’s implied about the evolution of true tissues?
either true tissues evolved more than once OR true tissues evolved once at the base of the metazoa (& were lost in porifera and placozoa)
T/F
Where ctenophores belong in the tree of metazoa is extremely contentious
true
we’ll stick to brusca 3rd ed: origin of ctenophora after porifera and placozoa
T/F
Eumetazoa= a POTENTIALLY real clade, united by the presence of true tissues derived from embryonic germ layers, and Brusca’s features 7-12 (synapomorphies)
true
potentially real, depending on where ctenophora truly belongs
List the 6 features Brusca et al. have identified as synapomorphies of Eumetazoa
- gap junctions
- gonads
- synaptic nervous system
- epithelium-lined gut
- primary larva
- presence of particular opsins
gap junctions=
a particular type of intercellular junction
- protein tubes that allow dissolved substances to pass from one cell to the next without having to go through cell membranes
- synapomorphy of eumetazoa
The synaptic nervous system of eumetazoa is derived from ___ ____.
What does ‘synaptic’ refer to?
embryonic ectoderm
the arrangement of cells that permits a neuron to pass an electrical or chemical signal to another neuron or to some other target cell
The epithelium-lined gut of eumetazoa has ____ enzymes, and is derived from the embryonic ______
- synapomorphy of eumetazoa
digestive
endoderm
In eumetazoa,
- synaptic nervous system is derived from _________
- epithelium-lined gut is derived from ______
ectoderm –> nervous system
endoderm –> gut
The primary larva is a synapomorphy of eumetazoa. Describe what it is.
= a ciliated larva bearing a sensory apical organ (called a primary larva)
The presence of particular opsins are a synapomorphy of eumetazoa. Describe what opsins are
= proteins that bind to light-reactive chemicals
associated with vision, phototaxis, etc
Phylum Cnidaria includes ~____ extant species and many fossil ones (mainly corals)
13,300
T/F
Species in phylum cnidaria are mostly freshwater
false
mostly marine, with ~100 freshwater spp and no terrestrial spp
List the 3 subphyla of phylum cnidaria
- Anthozoa
- Medusozoa
- Endocnidozoa
How many class(es) are in subphylum Anthozoa? Give 2 examples of Anthozoans
1 class
corals, sea anemones
How many classes are in subphylum Medusozoa?
Give an example of a medusozoa
4
true jellyfish
How many classes are in subphylum Endocnidozoa?
These are morphologically ____. Are they symbionts or parasites?
2
reduced
completely parasitic
Cnidaria have 2 main body forms. Give & describe them
Polyps: benthic (lives on the bottom of the water body)
- asexual reproduction
Medusa: pelagic (swims in open water)
- sexual reproduction
- many spp alternate b/w the 2 forms, some have only 1 form in their life cycles
T/F
Free-living cnidarians often do not show clear polyp or medusa forms
false
In free-living spp, there are 2 main body forms (medusa and polyp)
PARASITIC cnidarians often do not show clear polyp or medusa forms
What is the primary body axis of free-living cnidarians?
oral to aboral
What symmetry to most free-living cnidarians have?
they’re roughly radially symmetrical
- rarely perfect
- often have 4-, 6-, or 8- fold radial symmetry
How many openings does the gut of most free-living cnidarians have?
1 opening
- mouth only, no anus
Cnidarians have tentacles, but they’re not just a cnidarian feature; many invertebrate taxa have tentacles.
Give the general definition of a tentacle.
What do cnidarians use them for?
tentacle= a general term for a long, thin, flexible appendage that is often sticky
Cnidarians use tentacles to capture prey & move food to their mouth
T/F
Cnidarians do not have specialized gas-exchange, excretory, or circulatory systems
true!
these roles are performed by the gastrovascular cavity
