Exam 5 Material (Annelids: Group of Lophotrochozoans) Flashcards
How big is the annelid group?
second largest group of lophotrochozoans
What are annelids sister taxa to?
Mollusks
What are annelids often referred to as?
segmented worms (b/c they are broken up into segments—helps them with locomotion)
How can you describe annelids’ brains?
Simple (w/ group of ganglia)
where are annelids’ nerve cord located?
It is ventrally located (belly side)
What makes annelids different from molluksks?
They have a well-developed coelom
What makes annelids similar to cephalopod mollusks?
They have a closed circulatory system (no hemolymph dumped into the hemocoel)
what kind of digestive system do annelids have?
a complete digestive system
Do annelids do gas exchange? If so, how?
Yes (not through gills but through cutaneous respiration
What is being described?:
Annelids breathing through their skin (have structures metaphiridia—associated with water retention and osmotic pressure balance)
Cutaneous respiration
What are the three classes of annelids?
polychaeta, oligochaeta, and hirudinida
What is being described?:
Important for locomotion and gas exchange (in polychaeta: class of annelid) (creates extra surface area for gas exchange)
Parapodia
What is being described?:
Stiff bristle-like structures on the tips of the parapodia (in polychaeta)
Setae
Which group of annelid is being described?:
- Have a very well-formed head—have antennae and eyes—like the mollusks, they have free-swimming trochophores for larvae)
Polychaeta
Which group of annelid is being described?:
- Includes earthworms— oligo means little (refers to them having very little setae compared to Polychaeta) (chaeta refers to setae)—about 3100 species—unlike the polychaetas they do not have well-developed heads–they secrete, like a plant, from their epidermis, a thin cuticle (not waxy like a plant’s but helps w/ retention of water)—inside the earthworm, we see the segments being separated by septa—they have longitudinal and circular muscles in their body—they have a complete digestive tract (mouth, esophagus, pharynx, crop—stores food, gizzard—chops up food, intestine—digest nutrients)—they have dorsal and ventral blood vessels that pump hemolymph through their bodies—they have FIVE hearts that pump the hemolymph posteriorly on the ventral end and will join at the clitellum and exchange sperm—sperm from one worm will go to the other’s eggs and they store that sperm, fertilize the eggs and then they lay the eggs and release the sperm they stored into a shut off portion of the cuticle—creating a cacoon–traps moisture/keeps eggs moist until they hacth
Oligochaeta
Which Oligochaeta muscle is being described?:
will extend the length of the body, but when those muscles contract, their bodies shorten
Longitudinal muscle
Which Oligochaeta muscle is being described?:
will wrap around their body and when those muscles contract, the diameter of their body gets shorter/they get skinnier)
circular muscle
Which group of annelid are being described?:
- are not all bloodsuckers but 75% of them are bloodsucking parasites—most live in freshwater—some are predators (will go out looking for food)—they have muscular suckers—they produce a substance called hirudin (an anticoagulant—prevents blood from clotting—can store food in their body and can live off of stored food until they find a new host)
Hirudinea (leeches)
Which sucker is being described in Hirudinea (leeches)?:
- is NOT where the mouth is—it’s actually a tail)
Big sucker
Which sucker is being described in hirudinea (leeches)?
- is where the mouth is
little sucker
Which group of annelids are being described?:
- Bounces around from being lophotrochozoans and ecdysozoans—are teeny tiny—2,000 known species—most live in freshwater and they have a cuticle (why they are sometimes placed w/ ecdysozoans—they do not have a true coelom (have pseudocoelom)—have a crown of cilia near the mouth (makes it look like they’re rotating)—are the size of a protist—they have a constant cell count (have a set number of cells in their body—don’t grow new cells after a certain point)—can reproduce sexually and asexually
Rotifera
Which group of lophotrochozoans are being described?:
- have the lophophores (contributes to name of lophotrochozoans)—almost all of them are marine—use lophophores for suspension feeding (grabbing pieces of food out of the water)—they have no distinct head—phylogeny is still unknown (but DNA puts them w/ lophotrochozoans)
Lophophorates (brachiopods, phoronids, bryozoans)
Which subgroup of lophophores is being described?:
superficially resemble bivalve mollusks—referred to as lamp shells—325 species (extant)
Brachiopods
Which subgroup of lophophores is being described?:
- are a relatively small group—120 extant species—are worm-like and sessile—secrete a chitinous tube—fairly small
Phoronids
Which subgroup of lophophores is being described?:
- Superficially resemble corals—are microscopic—live in sessile colonies—reproduce through asexual budding—use their lophophores to pull out pieces of food from the water—about 4500 species
Bryozoans
Which group of protosomes is being described?:
- Is the second group of protosomes—are known for having a cuticle (non-cellular covering secreted by the epidermis)—will molt this cuticle (a process called ecdysis)
Ecdysozoa
