Unit III: Early branching Metazoa Flashcards
Ctenophora (comb jellies)
- Move via eight “combs” of cilia
- Capture food with sticky colloblast cells
- Decentralized nerve net
- Inner and outer tissue separated by jelly-like mesoglea
- Rotational symmetry
combs
groups of cilia Ctenophore use for swimming
colloblasts
Ctenophore cells that are sticky and adhere to prey
mesoglea
a middle layer of jelly-like material in ctenophora and cnidaria
How did Ctenophora develop?
- Embryos for most species are diploblasts
- Two types of germ layer tissues (Exo & Endo)
diploblasts
animals that have a nonliving middle layer between the endoderm and ectoderm
What are the defining traits of Ctenophora?
- “combs” of cilia
- Colloblasts
- Diploblastic
- Rotational symmetry
- Diffuse nerve net
Porifera (sponges)
- Larval stages swim, but adults are primarily sessile
- Lack germ layers, complex tissue, nerve cells, and muscle
- Have 2 different cell types
sessile
live permanently attached to substrate
What are the 2 cell types of Porifera?
- Choanocyte
- Pinacocyte
Choanocyte
functions to generate a water current and to trap and ingest food particles via phagocytosis
Pinacocyte
epithelial-like cell that forms the outermost layer and encloses a jelly-like substance called mesohyl
How was Porifera support achieved?
- Secreted exoskeleton (made of calcium carbonate)
- Spicules
- Spongin fibers
Spicules
small bone-like structures that support sponges, made of silica or calcium carbonate
Spongin
a modified type of collagen protein that forms the fibrous substance, also supports sponges
What are defining traits of Porifera?
- Choanocytes, pinacocytes
- Spicules, spongen
Cnidaria
Variety of mostly marine species :
- anemones
- corals
- hydrozoans
- jellyfish
- box jellies
Cnidocytes
Specialized stinging cell found in Cnidaria
– usually on tentacles or near cavity opening
Nematocyst
harpoon-like organelle within cnidocyte with pointed projectile and poison to stun and entangle prey
How do Cnidaria develop?
- Diploblast embryos
- Ectoderm and endoderm layers surround jelly-like mesoglea
- Single gastrovascular cavity with one opening
What are defining traits of Cnidaria?
- Cnidocytes and nematocyst
- Diplobastly
- Mesoglea
- Radial symmetry
- Diffuse nerve net
What is Cnidaria body plan?
2 main body plan with radial symmetry: Polyp & Medusa
- Some species have life cycle with both forms
Polyp
stalk-like sessile life form with mouth and tentacles facing upward, usually sessile but may be able to glide along surface
Medusa
free-floating body plan with mouth on underside and tentacles hanging down from a bell
