Lecture 7 - platyhelminthes

Question 1

what are xenacoelomorpha

Answer 1

very simple animals which look like platyhelminthes - base of the tree for bilateral animals

Question 2

how many body layers and do they have a body cavity

Answer 2

3 - triploblastic - acoelomate - no cavity

Question 3

symmetry

Answer 3

bilaterally symmetrical

Question 4

what have they developed because they a more active

Answer 4

cephalisation - concentration of sense organs forming a brain

Question 5

do they have blood

Answer 5

organs but no blood - diffusion for gas exchange

Question 6

excretory system

Answer 6

gut has one opening and simple excretory system with protonephridia that connect with the outside of the body with flagella that waft waste out

Question 7

key feature

Answer 7

dorso ventrally flattened

Question 8

free living flatworms

Answer 8

turbellarians

Question 9

how do turbellarians feed

Answer 9

insert pharynx into food and release enzymes making a broth to suck up

Question 10

how do turbellarians move

Answer 10

longitudinal and circular muscle fibres, some have cilia

Question 11

turbellarians sensory organs

Answer 11

simple eyes - detect if light is present

auricles - detect chemicals

Question 12

what sex organs are present

Answer 12

hermaphrodites

Question 13

how can flat worms regenerate

Answer 13

they have loads of pluripotent cells - can even regenerate brain

Question 14

reproduction

Answer 14

sexual - pair up and exchange sperm

Question 15

what is penis fencing

Answer 15

its more costly to produce the fertilised eggs than just pass sperm so they fight to be the male

Question 16

what are the 2 parasitic forms of flatworms

Answer 16

1) flukes (trematodes)

2) tapeworms (cestoidea)

Question 17

6 adaptations of parasitic forms

Answer 17

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

Question 18

what is a flukes protective barrier called

Answer 18

tegument

Question 19

generalised fluke lifecycle

Answer 19

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

Question 20

describe a blood fluke

Answer 20

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

Question 21

describe co-operative trematodes

Answer 21

form groups with soldier forms and reproductive forms - soldier forms protect colony against other parasites

Question 22

tape worms have strobila what are they?

Answer 22

repeated segments full of reproductive tissue

Question 23

describe a beef tapeworm

Answer 23

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