Ch.33 Flashcards
invertebrates
animals that lack a back bone
-account for 95% of known animal species
-morphologically diverse
-all but one phylum are invertebrates
clade
groups organisms believed to have evolved from the same ancestor
Phylums
Porifera
Cnidaria
Platyhelminths
Rotifera
Lophophorates
Mollusca
Annelida
Nematoda
Anthropoda
Echinodermata
Chordata
Porifera (Phylum 1)
-sponges
-lack true tissues
-have choanocytes
Sponge
-sedentary
-live in marine and fresh water
-suspension feeders (capturing food in water and pass through body, drawn through spongocoel and out osculum)
-lack true tissues/organs
-hermaphodites
amoebocytes
found in mesohyl and play roles in digestion and structure in sponges
mesohyl
-gelatinous noncellular layer between 2 cell layers
-in sponge
Choanocytes
-flagellated collar cells
-generate water current through sponge and ingest suspended food
**Cnidaria **
Phylum 2
-one of oldest group in this clade (Eumetazoa, with true tissues)
-hydras
-jellies
-sea anemones
-corals
-radially symmetrical (diploblastic)
-unique stinging structures (nematocysts)
-housed in cnidocytes
-gastrovascular cavity w/ single opening
-carnivores
-4 major classes : Hydrozoa, Scyphozoa, cubozoa, anthozoa
medusa
bell-shaped body w/ its mouth on the underside
cnidocytes
-unique cells that function in defense/capture of prey
-on tentacles
polyp`
adheres to the substrate by the aboral end of its body
nematocytes
specialized organelles within cnidocytes that eject a stinging thread
hydrozoans (class of Cnidarians)
-alternate between polyp and medusa forms
-hydra: freshwater cnidarians, only in polyp form, asexual by budding
-hydra: in salt water too
-kinda look like a plant
Anthozoans (class of Cnidarians)
-corals (form symbioses w/ algae, secrete hard external skeleton)
-sea anemones
-occur only as polyps
cubozoans (class of Cnidarians)
-box jellies, sea wasps
-have highly toxic cnidocytes
scyphozoans
(class of Cnidarians)
- true jellies(medusae)
Lophotrochozoa
clade
-clade consist of phylums:
platyhelminths (flatworms)
rotifera
lophophorates
Mollusca
annelida
Platyhelminths
phylum 3
-plylum
-flat worms
-live in marine, freshwater, and damp terrestrial habitats
-unsegmented acoelomates (no body cavities)
-dorsoventrally flattened
-gastrovasuar cavity or no digestive tract
Flatworm
-divided into 2 lineages (catenulida (chain worms) and rhabditophora)
-platyhelminthes
-undergo triploblastic development
-acoelomates
-protonephridia
protonephridia
regulate osmotic balance
planarians
best known rhabditophorans
-live in fresh water
-prey on smaller animals
-light sensitive eyespots
-centralized nerve nets
-hermaphodites (sexually, asexual, fission)
-nervous system more complex than nerve nets in cnidarians
2 parasitic rhabditophorans (platyhelminths)
-trematodes: complex life cycles, alternate between sexual/asexual, produce proteins that manipulate host’s immune system, live in snail hosts (ones that parasitize humans)
-tapeworms (cestode, type of flatworm)
tapeworm
parasites of vertebrates
-lack digestive system
-absorb nutrients from host’s intestine
-sexual reproduction, leaves hosts in feces
-scolex contains suckers/hoods for attachment