Lecture 7 - platyhelminthes Flashcards
what are xenacoelomorpha
very simple animals which look like platyhelminthes - base of the tree for bilateral animals
how many body layers and do they have a body cavity
3 - triploblastic - acoelomate - no cavity
symmetry
bilaterally symmetrical
what have they developed because they a more active
cephalisation - concentration of sense organs forming a brain
do they have blood
organs but no blood - diffusion for gas exchange
excretory system
gut has one opening and simple excretory system with protonephridia that connect with the outside of the body with flagella that waft waste out
key feature
dorso ventrally flattened
free living flatworms
turbellarians
how do turbellarians feed
insert pharynx into food and release enzymes making a broth to suck up
how do turbellarians move
longitudinal and circular muscle fibres, some have cilia
turbellarians sensory organs
simple eyes - detect if light is present
auricles - detect chemicals
what sex organs are present
hermaphrodites
how can flat worms regenerate
they have loads of pluripotent cells - can even regenerate brain
reproduction
sexual - pair up and exchange sperm
what is penis fencing
its more costly to produce the fertilised eggs than just pass sperm so they fight to be the male
what are the 2 parasitic forms of flatworms
1) flukes (trematodes)
2) tapeworms (cestoidea)
6 adaptations of parasitic forms
loss of unwanted organs e.g. live in a gut dont need own gut penetration devices attachment devices e.g. suckers protective devices e.g. coverings transmission via a vector large production of eggs
what is a flukes protective barrier called
tegument
generalised fluke lifecycle
egg gets eaten by 1st intermediate host and develops into cercaria which gets released from host and taken up by second intermediate host - 2nd intermediate host gets eaten by a definitive host were reproduction of parasite takes place
describe a blood fluke
separate sexes - live in veins of bladder or intestine - eggs released in faeces or urine - makes way into snail - cercacia stage released from snail and borrow through human skin - mature in veins
describe co-operative trematodes
form groups with soldier forms and reproductive forms - soldier forms protect colony against other parasites
tape worms have strobila what are they?
repeated segments full of reproductive tissue
describe a beef tapeworm
humans = definitive host
faeces containing egg on pasture
cows = intermediate host
borrow into gut and go in blood to muscle
bladderworm forms in meat and is ingested by humans
