bilateria: helminthes and annelids Flashcards
all organisms in the clade bilateria have?
bilateral symmetry
the different organisms have different degrees of?
cephalization (differention of the head region)
all of the nervous systems of bilateria is concentrated at what end?
the anterior
are bilateria diploblastic or triploblastic?
triploblastic
what are some characteristics of the clade lophotrochozoa?
range from morphologically very simple (worm) to morphologically and behaviorally complex (octopus)
the relationships among lophotrochozoan phyla is unclear, which creates a?
polytomy
what does the phylum platyhelminthes refer to?
flatworms: top and bottom flat (think bacon)
what are flatworms?
acoelomates - triploblastic with a gastrovascular cavity (gut) but no fluid filled body cavity
how do flatworms breathe?
diffusion due to the high surface area the volume ratio and flatness
do platyhelminthes have a complete digestive system?
no! they have one common opening ‘mouth’ and no anus
what are some characteristics of the class turbellaria in the phylum platyhelminthes?
- free living flatworms
- mostly predatory - use eye spot on their head to navigate their environment
- have a ganglia - bundle of nerve tissue
- the surface of their body is covered in cilia - movement
- not a complete digestive system
what are some characteristics of the class cestodia in the phylum platyhelminthes?
- tapeworms
- endoparasites - parasites that live inside the host/digestive system of other animals
- have an invertebrate host and intermediate host
- lack a digestive system
- no mouth or gastrovascular cavity
- absorb nutrients through thin body wall
cestodiea’s have a scolex, what is it?
when the front end of the body is modified for holding onto the host’s gut (suckers or hooks)
tapeworms have a long chain of units devoted to reproduction from their posterior to scolex, what is this called?
proglottids
tapeworms have a complex life cycle; this means they need _ hosts to complete their lifecycle?
2 or more
what is the tapeworms intermediate host?
where the eggs are initially consumed and develop into larvae; parasite undergoes asexual reproduction
what is the tapeworms definitive host?
where the intermediate host is eaten, and the larvae develop into an adult tapeworm in the gut; parasite undergoes sexual reproduction
what are the stages of a tapeworm’s life cycle?
- eggs consumed by the intermediate host
- develop into larvae that encyst in the tissue of the intermediate host
- intermediate host is eaten by the definitive host
- larvae develop into the adult tapeworm in the gut of the definitive host
what are some characteristics of the class trematoda in the phylum platyhelminthes?
- dorso-ventrally flattened
- no body cavity
- ‘flukes’ with two large suckers for attachment
- mouth is near the sucker, which feeds on host tissue and blood
- not a complete digestive system - no anus
- simultaneous hermaphrodites
- complex life cycle
what does the phylum annelida refer to?
segmented worms or round worms
what are some of the feeding behaviors of annelida?
predatory, suspension feeder, deposit feeders
what are the two clades (not classes anymore) of annelida?
errantians and sedentarians
what are some characteristics of annelids?
- segmented - each piece of their body is a repeating unit and separated by internal septa
- clitellum - thickened area of earthworm
- eucoelomate - body cavity lined with mesodermal tissue
- closed circulatory system - blood is contained in vessels
- gas exchange through skin diffusion
- complete digestive system with a mouth and anus
does the clade errantia have cephalization?
yes! they have a clearly differentiated head
are errantians sessile?
no! they are mobile, very active and mostly predatory
how do errantians move around?
body segments with fleshy lobe like feet called parapodia gives them grip and traction with helps them with locomotion
how do sedentarians differ from erratians?
they are less mobile and their parapodia is reduced
how do sedentarians undergo gas exchange and filter feed?
they have gills or tentacles
how do sedentarians reproduce?
they are free-spawning; eggs and sperm are released into the water and fertilization occurs outside the body of the parent
what are two common types (animal) of sedentarians?
earthworms and leeches
what are some characteristics of earthworms?
- lack parapodia
- lack a well-developed head
- terrestrial and freshwater
- simultaneous hermaphrodite - both male and female at the same time
- direct development - eggs hatch and look like small adult worms
how do earthworms feed?
ingesting substrate and digesting matter
sedentarian earthworms are morphologically and ecologically much less diverse then?
polychaetes
how do earthworms reproduce?
- each worm in a pair act both as male and female
- transfer sperm by copulation - deposits sperm into partner’s seminal receptacle
- produces gelatinous cocoon secretions from clitellum
- deposits eggs in cocoon, slides cocoon forwards, deposits stored sperm
what are some characteristics of leeches?
mostly freshwater
lack parapodia
have clitellum
lack chatae
how do leeches move?
they have two suckers
what do leeches feed on?
some on the blood of vertebrates (mammals and turtles) and the rest of soft bodied invertebrates
