Phylum Platyhelminthes Flashcards
bilateral symmetry
having two well-formed sides
scavengers
to feed off dead animals
hermaphrodites
having both male and female reproductive organs
flukes
class Trematoda
Platyhelminthes
flatworm
fission
reproduction by splitting in half
cephalization
having a head
pharynx
muscular tube for drawing in food near the mouth
proglottids
segment of tapeworms body
acoelomates
lacking a body cavity, without coelom, digestive cavity is lined with endoderm.
class Cestoda
tapeworm
diffusion
mechanisms for respiration, exception and circulation
flatworm
soft bodied, few millimetres thick, have tissues and internal organs, three embryonic germ layers. bilateral symmetry.
feeding
single opening for mouth and anus. near the mouth is a muscular tube called the pharynx, pharynx extends out of the mouth to pump into digestive cavity. digestion and absorption takes place in the gut. nutrients diffuse to other parts of the body.
carnivores
preying on aquatic animals
parasitic worms
feed on blood, tissue fluids or pieces of cells. feed on already a digested food, simple digestive system.
respiration, exception and circulation
rely on diffusion to transport oxygen and nutrients throughout. rely on diffusion to remove waste products and Co2, lacks gills or other respiratory organs. lack heart, blood vessels and blood. flames cells are found in flat worms. for excretion of excess water. they are joined in a. network of tubes that empties to outside environment through pores in skin.
response
head encloses several ganglia which controls nervous system. has two longitudinal nerve cords along length of body connected by several shorter longitudinal Neve cords across the body. many flatworms have eyespots that detect changes in amount of light. also have specialized cells for detecting other external stimuli scattered throughout body located food and find dark hiding places.
movement
movement via cilia on epidermal cells facilitating gliding through waters and over surfaces. muscle cells enable turning and twisting.
reproduction
most free living flatworms are hermaphrodites meaning they have both male and female sex organs. during reproduction, two worms join to exchange sperm with one another. asexual reproduction occurs with fission, splitting in two. some species of worms “fall in pieces” with each smaller piece regenerating to become new individuals.
group of flatworms, three groups include:
turbellarians, flukes and tapeworms.
turbellarians
free-living flatworms, live in marine or freshwater, bottom dwellers in sand or mud under stones or shells. most familiar are planarians -> cross-eyed freshwater flatworm
flukes
class Trematoda, parasitic flatworm found in any internal organs or blood of host. some are may be external parasites found on skin, mouth, gills or other outside body parts.
tapeworms
class Cestoda, long, flat. parasitic worm found in intestines of host. digested food of host is absorbed directly into body of tapeworm.
structure of a tapeworm
head has scolex which contains suckers or suckers for anchoring onto hosts intestinal walls. behind scolex is a narrow region that divides into proglottids segments of the tapeworms body. tapeworms can fertilize their own eggs or other individuals eggs.
planaria
class turbelleria
ganglia
collection of nerve cells
cyst
dormant larval stage of tapeworm
parasite
obtaining nutrients from a host
