ch. 33 triploblastic acoelomates Flashcards
phylum of triploblastic acoelomates
- phylum platyhelminthes
- phylum nemertea
classes of phylum platyhelminthes
- class turbellaria
- class monogenea
- class trematoda
- class cestoda
phylum platyhelminthes characteristics
- acoelomates
- flatworms
- lack specialized respiratory/circulatory system
- respire by diffusion
- bilaterally symmetrical w/ head
platy
flat
helminth
parasitic worm
digestive system of phylum platyhelminthes
incomplete - one opening for mouth/anus
excretory system for phylum platyhelminthes
distinct with protonephridia and flame cells
eyes in phylum platyhelminthes
light sensitive eyespots (ocelli)
nervous system in phylum platyhelminthes
- cerebral ganglia receive input
- more centralized nervous system
reproduction in phylum platyhelminthes
sexual or asexual
- most hermaphroditic but don’t self-fertilize
class turbellaria
- planarians
- live in fresh water and prey on smaller animals
- ocelli and centralized nerve nets
- hermaphrodites - sexual reproduction or fission
class trematoda
- parasitize wide range of hosts
- those that parasitize humans spend part of lives in snails
- produce surface proteins that mimic host
- release molecules that manipulate host’s immune system
class cestoda
- tapeworms or parasitic worms
- head = scolex w/ several suckers
- suckers attach to intestine walls of host and absorb food as it is digested
- doesn’t kill host but causes weight loss
length of human tapeworms
18 meters
what is the body of a tapeworm divided into?
sections called proglottids
proglottids of tapeworms in class Cestoda
- contain male and female reproductive organs
- sperm fertilizes egg in proglottids
- fertilized eggs related when mature proglottids break off and burst open
how many eggs can a proglottid contain?
100,000
what happens when cows, pigs, of fish consume food or water contaminated with tapeworm eggs
- eggs enter intermediate host and hatch into larva
- larva burrow into muscle of host and form protective dormant cysts
- human eats raw/uncooked meat, and larvae become active within human host
phylum nemertea characteristics
- mostly marine, few fresh water
- some active swimmers, others burrow in sand
- simple circulatory system (not heart)
- complete digestive tract
size of organisms in phylum nemertea
less than 1 mm to more than 30 mm
ex. of organism from phylum nemertea
proboscis worms
